Nanomaterials

18 pages, 1855 KiB

Open AccessArticle

Free-Standing Carbon Nanofiber Films with Supported Cobalt Phosphide Nanoparticles as Cathodes for Hydrogen Evolution Reaction in a Microbial Electrolysis Cell

by Gerard Pérez-Pi, Jorge Luque-Rueda, Pau Bosch-Jimenez, Eduard Borràs Camps and Sandra Martínez-Crespiera

Nanomaterials 2024, 14(22), 1849; https://doi.org/10.3390/nano14221849 (registering DOI) - 19 Nov 2024

Abstract

High-performance and cost-efficient electrocatalysts and electrodes are needed to improve the hydrogen evolution reaction (HER) for the hydrogen (H₂) generation in electrolysers, including microbial electrolysis cells (MECs). In this study, free-standing carbon nanofiber (CNF) films with supported cobalt phosphide nanoparticles have [...] Read more.

High-performance and cost-efficient electrocatalysts and electrodes are needed to improve the hydrogen evolution reaction (HER) for the hydrogen (H₂) generation in electrolysers, including microbial electrolysis cells (MECs). In this study, free-standing carbon nanofiber (CNF) films with supported cobalt phosphide nanoparticles have been prepared by means of an up-scalable electrospinning process followed by a thermal treatment under controlled conditions. The produced cobalt phosphide-supported CNF films show to be nanoporous (pore volume up to 0.33 cm³ g⁻¹) with a high surface area (up to 502 m² g⁻¹) and with a suitable catalyst mass loading (up to 0.49 mg cm⁻²). Values of overpotential less than 140 mV at 10 mA cm⁻² have been reached for the HER in alkaline media (1 M KOH), which demonstrates a high activity. The high electrical conductivity together with the mechanical stability of the free-standing CNF films allowed their direct use as cathodes in a MEC reactor, resulting in an exceptionally low voltage operation (0.75 V) with a current density demand of 5.4 A m⁻². This enabled the production of H₂ with an energy consumption below 30 kWh kg⁻¹ H₂, which is highly efficient. Full article

(This article belongs to the Special Issue Hydrogen Production and Evolution Based on Nanocatalysts)

25 pages, 10477 KiB

Open AccessArticle

Portable Homemade Magnetic Hyperthermia Apparatus: Preliminary Results

by Teresa Castelo-Grande, Paulo A. Augusto, Lobinho Gomes, Eduardo Calvo and Domingos Barbosa

Nanomaterials 2024, 14(22), 1848; https://doi.org/10.3390/nano14221848 (registering DOI) - 19 Nov 2024

Abstract

This study aims to describe and evaluate the performance of a new device for magnetic hyperthermia that can produce an alternating magnetic field with adjustable frequency without the need to change capacitors from the resonant bank, as required by other commercial devices. This [...] Read more.

This study aims to describe and evaluate the performance of a new device for magnetic hyperthermia that can produce an alternating magnetic field with adjustable frequency without the need to change capacitors from the resonant bank, as required by other commercial devices. This innovation, among others, is based on using a capacitator bank that dynamically adjusts the frequency. To validate the novel system, a series of experiments were conducted using commercial magnetic nanoparticles (MNPs) demonstrating the device’s effectiveness and allowing us to identify new challenges associated with the design of more powerful devices. A computational model was also used to validate the device and to allow us to determine the best system configuration. The results obtained are consistent with those from other studies using the same MNPs but with magnetic hyperthermia commercial equipment, confirming the good performance of the developed device (e.g., consistent SAR values between 1.37 and 10.80 W/gMNP were obtained, and experiments reaching temperatures above 43 °C were also obtained). This equipment offers additional advantages, including being economical, user-friendly, and portable. Full article

(This article belongs to the Special Issue New Insights into the Therapeutic Efficacy of Nanomaterials)

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28 pages, 1948 KiB

Open AccessReview

Nanomaterial-Enhanced Hybrid Disinfection: A Solution to Combat Multidrug-Resistant Bacteria and Antibiotic Resistance Genes in Wastewater

by Tapas Kumar Mandal

Nanomaterials 2024, 14(22), 1847; https://doi.org/10.3390/nano14221847 - 19 Nov 2024

Abstract

This review explores the potential of nanomaterial-enhanced hybrid disinfection methods as effective strategies for addressing the growing challenge of multidrug-resistant (MDR) bacteria and antibiotic resistance genes (ARGs) in wastewater treatment. By integrating hybrid nanocomposites and nanomaterials, natural biocides such as terpenes, and ultrasonication, [...] Read more.

This review explores the potential of nanomaterial-enhanced hybrid disinfection methods as effective strategies for addressing the growing challenge of multidrug-resistant (MDR) bacteria and antibiotic resistance genes (ARGs) in wastewater treatment. By integrating hybrid nanocomposites and nanomaterials, natural biocides such as terpenes, and ultrasonication, this approach significantly enhances disinfection efficiency compared to conventional methods. The review highlights the mechanisms through which hybrid nanocomposites and nanomaterials generate reactive oxygen species (ROS) under blue LED irradiation, effectively disrupting MDR bacteria while improving the efficacy of natural biocides through synergistic interactions. Additionally, the review examines critical operational parameters—such as light intensity, catalyst dosage, and ultrasonication power—that optimize treatment outcomes and ensure the reusability of hybrid nanocomposites and other nanomaterials without significant loss of photocatalytic activity. Furthermore, this hybrid method shows promise in degrading ARGs, thereby addressing both microbial and genetic pollution. Overall, this review underscores the need for innovative wastewater treatment solutions that are efficient, sustainable, and scalable, contributing to the global fight against antimicrobial resistance. Full article

(This article belongs to the Special Issue Multifunctional Nanomaterials: Innovations in Energy Harvesting, Biological Applications, and Environmental Remediation)

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16 pages, 4681 KiB

Open AccessArticle

M-Doped (M = Zn, Mn, Ni) Co-MOF-Derived Transition Metal Oxide Nanosheets on Carbon Fibers for Energy Storage Applications

by Andrés González-Banciella, David Martinez-Diaz, Adrián de Hita, María Sánchez and Alejandro Ureña

Nanomaterials 2024, 14(22), 1846; https://doi.org/10.3390/nano14221846 - 19 Nov 2024

Abstract

Carbon fiber, with its strong mechanical properties and electrical conductivity, is ideal as a fiber electrode in wearable or structural energy storage devices. However, its energy storage capacity is limited, and coatings like transition metal oxides (TMOs) enhance its electrochemical performance. Metal–organic frameworks [...] Read more.

Carbon fiber, with its strong mechanical properties and electrical conductivity, is ideal as a fiber electrode in wearable or structural energy storage devices. However, its energy storage capacity is limited, and coatings like transition metal oxides (TMOs) enhance its electrochemical performance. Metal–organic frameworks (MOFs) are commonly used to grow TMOs on carbon fibers, increasing the surface area for better energy storage. Despite this, TMOs have limited electrical conductivity, so ion exchange is often used to dope them with additional cations, improving both conductivity and energy storage capacity. This study compares different ion-exchange cations in ZIF-L-derived TMO coatings on carbon fiber. Testing both supercapacitor and Li-ion battery applications, Ni-doped samples showed superior results, attributed to their higher exchange ratio with cobalt. As a supercapacitor electrode, the Ni-doped material achieved 13.3 F/g at 50 mA/g—66% higher than undoped samples. For Li-ion battery anodes, it reached a specific capacity of 410.5 mAh/g at 25 mA/g, outperforming undoped samples by 21.4%. Full article

(This article belongs to the Special Issue Metal Organic Framework (MOF)-Based Micro/Nanoscale Materials)

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SEM images of ZIF-L coating on carbon fiber fabric at (a) lower magnification and (b) higher magnification, (c) undoped TMO sample, (d) Zn-doped TMO sample, (e) Mn-doped TMO sample, and (f) Ni-doped TMO sample. Full article ">Figure 2
(a) XPS surveys. (b) XPS Co 2p core level of the undoped sample. (c) XPS Zn 2p core level of Zn-doped sample. (d) XPS Mn 2p core level of Mn-doped sample. (e) XPS Ni 2p core level of Ni-doped sample. (f) The atomic percentage of each cation in each sample. (g) XRD spectra of TMO powder samples. Full article ">Figure 3
TEM images of undoped TMO samples at (a) lower and (b) higher magnification. Full article ">Figure 4
(a) CV curves at a scan rate of 20 mV/s. (b) Specific capacitance values are calculated from CV at 20 mV/s. (c) GCD test discharges at 50 mA/g. (d) Specific capacitance calculated from GCD tests at different current densities. Full article ">Figure 5
(a) CV curve of Ni-doped sample at different scan rates and (b) calculated b value in the inset. (c) Diffusion and capacitive-controlled processes contribute to different scan rates for Ni-doped samples. (d) Specific capacitance and coulombic efficiency of Ni-doped sample after 5000 GCD cycles at 150 mA/g. Full article ">Figure 6
(a) Normalized third-cycle CV of the samples. (b) GCD curves at 25 mA/g of the samples. (c) GCD calculated capacities at different current densities. (d) Nyquist plots of the samples. Full article ">Figure 7
(a) Ni-doped sample CV at different scan rates and calculated b value in the inset. (b) Percentage of each contribution at different scan rates in the Ni-doped sample. (c) Specific capacity of Ni-doped sample after 100 GCD cycles at 100 mA/g. (d) Nyquist plot of Ni-doped sample after several number of cycles. Full article ">

5 pages, 198 KiB

Open AccessEditorial

Micro- and Nanostructured Biomaterials for Biomedical Applications and Regenerative Medicine

by Michele Bianchi and Gianluca Carnevale

Nanomaterials 2024, 14(22), 1845; https://doi.org/10.3390/nano14221845 - 18 Nov 2024

Viewed by 328

Abstract

Over the past two decades, research on innovative micro- and nano-biomaterials has seen a significant surge in the bioengineering, biomedicine, and regenerative medicine fields [...] Full article

(This article belongs to the Special Issue Micro- and Nanostructured Biomaterials for Biomedical Applications and Regenerative Medicine)

13 pages, 3286 KiB

Open AccessArticle

Improving the NO₂ Gas Sensing Performances at Room Temperature Based on TiO₂ NTs/rGO Heterojunction Nanocomposites

by Yan Ling, Yunjiang Yu, Canxin Tian and Changwei Zou

Nanomaterials 2024, 14(22), 1844; https://doi.org/10.3390/nano14221844 - 18 Nov 2024

Viewed by 323

Abstract

The development of energy-efficient, sensitive, and reliable gas sensors for monitoring NO₂ concentrations has garnered considerable attention in recent years. In this manuscript, TiO₂ nanotube arrays/reduced graphene oxide nanocomposites with varying rGO contents (TiO₂ NTs/rGO) were synthesized via a two-step [...] Read more.

The development of energy-efficient, sensitive, and reliable gas sensors for monitoring NO₂ concentrations has garnered considerable attention in recent years. In this manuscript, TiO₂ nanotube arrays/reduced graphene oxide nanocomposites with varying rGO contents (TiO₂ NTs/rGO) were synthesized via a two-step method for room temperature NO₂ gas detection. From SEM and TEM images, it is evident that the rGO sheets not only partially surround the TiO₂ nanotubes but also establish interconnection bridges between adjacent nanotubes, which is anticipated to enhance electron–hole separation by facilitating electron transfer. The optimized TiO₂ NTs/rGO sensor demonstrated a sensitive response of 19.1 to 1 ppm of NO₂, a 5.26-fold improvement over the undoped TiO₂ sensor. Additionally, rGO doping significantly enhanced the sensor’s response/recovery times, reducing them from 24 s/42 s to 18 s/33 s with just 1 wt.% rGO. These enhancements are attributed to the increased specific surface area, higher concentration of chemisorbed oxygen species, and the formation of p-n heterojunctions between TiO₂ and rGO within the nanocomposites. This study provides valuable insights for the development of TiO₂/graphene-based gas sensors for detecting oxidizing gases at room temperature. Full article

(This article belongs to the Special Issue Design and Applications of Heterogeneous Nanostructured Materials)

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12 pages, 5364 KiB

Open AccessArticle

Controlled Formation of Silicon-Vacancy Centers in High-Pressure Nanodiamonds Produced from an “Adamantane + Detonation Nanodiamond” Mixture

by Dmitrii G. Pasternak, Rustem H. Bagramov, Alexey M. Romshin, Igor P. Zibrov, Vladimir P. Filonenko and Igor I. Vlasov

Nanomaterials 2024, 14(22), 1843; https://doi.org/10.3390/nano14221843 - 18 Nov 2024

Viewed by 338

Abstract

Despite progress in the high-pressure synthesis of nanodiamonds from hydrocarbons, the problem of controlled formation of fluorescent impurity centers in them still remains unresolved. In our work, we explore the potential of a new precursor composition, a mixture of adamantane with detonation nanodiamond, [...] Read more.

Despite progress in the high-pressure synthesis of nanodiamonds from hydrocarbons, the problem of controlled formation of fluorescent impurity centers in them still remains unresolved. In our work, we explore the potential of a new precursor composition, a mixture of adamantane with detonation nanodiamond, both in the synthesis of nanodiamonds and in the controlled formation of negatively charged silicon-vacancy centers in such nanodiamonds. Using different adamantane/detonation nanodiamond weight ratios, a series of samples was synthesized at a pressure of 7.5 GPa in the temperature range of 1200–1500 °C. It was found that temperature around 1350 °C, is optimal for the high-yield synthesis of nanodiamonds <50 nm in size. For the first time, controlled formation of negatively charged silicon-vacancy centers in such small nanodiamonds was demonstrated by varying the atomic ratios of silicon/carbon in the precursor in the range of 0.01–1%. Full article

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13 pages, 2793 KiB

Open AccessArticle

Nature of the Pits on the Lattice-Matched InAlAs Layer Surface Grown on the (001) InP Substrate

by Dmitrii V. Gulyaev, Demid S. Abramkin, Dmitriy V. Dmitriev, Alexander I. Toropov, Eugeniy A. Kolosovsky, Sergey A. Ponomarev, Nina N. Kurus, Ilya A. Milekhin and Konstantin S. Zhuravlev

Nanomaterials 2024, 14(22), 1842; https://doi.org/10.3390/nano14221842 - 18 Nov 2024

Viewed by 282

Abstract

The structural properties of lattice-matched InAlAs/InP layers grown by molecular beam epitaxy have been studied using atomic force microscopy, scanning electron microscopy and micro-photoluminescence spectroscopy. The formation of the surface pits with lateral sizes in the micron range and a depth of about [...] Read more.

The structural properties of lattice-matched InAlAs/InP layers grown by molecular beam epitaxy have been studied using atomic force microscopy, scanning electron microscopy and micro-photoluminescence spectroscopy. The formation of the surface pits with lateral sizes in the micron range and a depth of about 2 ÷ 10 nm has been detected. The InP substrate annealing temperature and value of InAlAs alloy composition deviation from the lattice-matched In_xAl_1−xAs/InP case (x = 0.52) control the density of pits ranging from 5 × 10⁵ cm⁻² ÷ 10⁸ cm⁻². The pit sizes are controlled by the InAlAs layer thickness and growth temperature. The correlation between the surface pits and threading dislocations has been detected. Moreover, the InAlAs surface is characterized by composition inhomogeneity with a magnitude of 0.7% with the cluster lateral sizes and density close to these parameters for surface pits. The experimental data allow us to suggest a model where the formation of surface pits and composition clusters is caused by the influence of a local strain field in the threading dislocation core vicinity on In adatoms incorporating kinetic. Full article

(This article belongs to the Section Nanophotonics Materials and Devices)

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Scheme of structures with InxAl1−xAs layer with thickness D grown at TS. The preparation of the InP substrate was performed at TA. The InAsP layer, formed during the substrate preparation, is marked as «InAsP». Full article ">Figure 2
AFM images of 1 μm thick InAlAs layers lattice-matched with the substrate. TA = 485 °C and TS = 485 °C for (A) and TA = 535 °C, TS = 525 °C for (B). Total layer thickness is 1000 nm for both structures. Relief profiles are presented in the insets. Full article ">Figure 3
(a) The dependence of the pit density on the substrate annealing temperature for the lattice-matched layer (x = 0.52, black dots) and on the layer composition deviation from the lattice-matched value (red dots). (b) The dependence of the lateral size of the pits on the InAlAs layer thickness for x = 0.52 (black dots) and x = 0.51 (red dots). (c) The dependence of the depth of the pits on the thickness of the InAlAs layer with x = 0.52 grown at the temperature of 505 °C. (d) The dependence of the depth of the pits on the growth temperature for the InAlAs layer with x = 0.52 grown at the total layer thickness of 1 μm. Full article ">Figure 4
The SEM cross-sectional image of the heterostructure grown at TA = 535 °C, TS = 525 °C and D = 1000 nm, with the alloy composition deviation of 0.5%. The vertical arrows at the top panel point to the surface pits. The bottom panel shows the same area of the SEM image but with the dislocations indicated by thin white lines for better clarity. Full article ">Figure 5
(A) A typical map of the position of the PL peak of the InAlAs layer with pits. (B) Micro-PL spectra from the InAlAs layer measured (1) inside and (outside) the cluster. The annealing temperature of the substrate/growth is 535/505 °C. Full article ">Figure 6
Experimental and calculated temperature dependencies of the pit depth (black square) and In depletion (red circle) for lattice-matched 1 μm thick InAlAs layers. Full article ">

11 pages, 2655 KiB

Open AccessArticle

Enhanced Optical and Electrical Properties of IGZO/Ag/IGZO for Solar Cell Application via Post-Rapid Thermal Annealing

by Chanmin Hwang, Taegi Kim, Yuseong Jang, Doowon Lee and Hee-Dong Kim

Nanomaterials 2024, 14(22), 1841; https://doi.org/10.3390/nano14221841 - 18 Nov 2024

Viewed by 295

Abstract

In this paper, we optimized IGZO/Ag/IGZO (IAI) multilayer films by post-rapid thermal annealing (RTA) to enhance the electrical conductivity and optical transmittance in visible wavelengths for solar cell applications. Our optimized device showed an average transmittance of 85% in the visible range, with [...] Read more.

In this paper, we optimized IGZO/Ag/IGZO (IAI) multilayer films by post-rapid thermal annealing (RTA) to enhance the electrical conductivity and optical transmittance in visible wavelengths for solar cell applications. Our optimized device showed an average transmittance of 85% in the visible range, with a lowest sheet resistance of 6.03 Ω/□ when annealed at 500 °C for 60 s. Based on these results, we assessed our device with photo-generated short circuit current density (J_SC) using a solar cell simulator to confirm its applicability in the solar cell. IAI multilayer RTA at 500 °C for 60 s showed a highest J_SC of 40.73 mA/cm². These results show that our proposed IAI multilayer film, which showed a high optical transparency and electrical conductivity optimized with post RTA, seems to be excellent transparent electrode for solar cell applications. Full article

(This article belongs to the Special Issue Nanostructured Materials for Electric Applications)

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The RTA process for the IGZO/Ag/IGZO multilayer, and the right diagram describes the generated oxygen vacancies from the IGZO inside by RTA. Full article ">Figure 2
AFM topology images of IGZO/Ag/IGZO after RTA, (a) RT, (b) 300, (c) 400, and (d) 500 °C for 60 s. Full article ">Figure 3
The sheet resistance of (a) IGZO and (b) IGZO/Ag/IGZO multilayers after varying temperature conditions. Full article ">Figure 4
(a) Impedance of IGZO/Ag/IGZO after RTA RT to 500 °C for 60 s and (b) equivalent circuit of IGZO/Ag/IGZO. Full article ">Figure 5
(a) Transmittance, (b) reflectivity, and (c) absorption coefficient of IGZO/Ag/IGZO after RTA RT to 500 °C for 60 s, and each inset depicts the transmittance and reflectivity at 500 nm wavelength with varying annealing temperature. Full article ">Figure 6
(a) Schematic structure of IGZO/Ag/IGZO-based solar cell and (b) the photo-generated short circuit current of IGZO/Ag/IGZO-based solar cell as a function of annealing temperature. Full article ">

18 pages, 2873 KiB

Open AccessArticle

Improving Resistive Heating, Electrical and Thermal Properties of Graphene-Based Poly(Vinylidene Fluoride) Nanocomposites by Controlled 3D Printing

by Rumiana Kotsilkova, Vladimir Georgiev, Mariya Aleksandrova, Todor Batakliev, Evgeni Ivanov, Giovanni Spinelli, Rade Tomov and Tsvetozar Tsanev

Nanomaterials 2024, 14(22), 1840; https://doi.org/10.3390/nano14221840 - 17 Nov 2024

Viewed by 517

Abstract

This study developed a novel 3D-printable poly(vinylidene fluoride) (PVDF)-based nanocomposite incorporating 6 wt% graphene nanoplatelets (GNPs) with programmable characteristics for resistive heating applications. The results highlighted the significant effect of a controlled printing direction (longitudinal, diagonal, and transverse) on the electrical, thermal, Joule [...] Read more.

This study developed a novel 3D-printable poly(vinylidene fluoride) (PVDF)-based nanocomposite incorporating 6 wt% graphene nanoplatelets (GNPs) with programmable characteristics for resistive heating applications. The results highlighted the significant effect of a controlled printing direction (longitudinal, diagonal, and transverse) on the electrical, thermal, Joule heating, and thermo-resistive properties of the printed structures. The 6 wt% GNP/PVDF nanocomposite exhibited a high electrical conductivity of 112 S·m⁻¹ when printed in a longitudinal direction, which decreased significantly in other directions. The Joule heating tests confirmed the material’s efficiency in resistive heating, with the maximum temperature reaching up to 65 °C under an applied low voltage of 2 V at a raster angle of printing of 0°, while the heating T_max decreased stepwise with 10 °C at the 45° and the 90° printing directions. The repeatability of the Joule heating performance was verified through multiple heating and cooling cycles, demonstrating consistent maximum temperatures across several tests. The effect of sample thickness, controlled by the number of printed layers, was investigated, and the results underscore the advantages of programmable 3D printing orientation in thin layers for enhanced thermal stability, tailored electrical conductivity, and efficient Joule heating capabilities of 6 wt% GNP/PVDF composites, positioning them as promising candidates for next-generation 3D-printed electronic devices and self-heating applications. Full article

(This article belongs to the Special Issue Hybrid Nano Polymer Composites (2nd Edition))

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45 pages, 11195 KiB

Open AccessReview

Exploring Plasmonic Standalone Surface-Enhanced Raman Scattering Nanoprobes for Multifaceted Applications in Biomedical, Food, and Environmental Fields

by Valentina Rojas Martínez, Eunseo Lee and Jeong-Wook Oh

Nanomaterials 2024, 14(22), 1839; https://doi.org/10.3390/nano14221839 - 17 Nov 2024

Viewed by 330

Abstract

Surface-enhanced Raman scattering (SERS) is an innovative spectroscopic technique that amplifies the Raman signals of molecules adsorbed on rough metal surfaces, making it pivotal for single-molecule detection in complex biological and environmental matrices. This review aims to elucidate the design strategies and recent [...] Read more.

Surface-enhanced Raman scattering (SERS) is an innovative spectroscopic technique that amplifies the Raman signals of molecules adsorbed on rough metal surfaces, making it pivotal for single-molecule detection in complex biological and environmental matrices. This review aims to elucidate the design strategies and recent advancements in the application of standalone SERS nanoprobes, with a special focus on quantifiable SERS tags. We conducted a comprehensive analysis of the recent literature, focusing on the development of SERS nanoprobes that employ novel nanostructuring techniques to enhance signal reliability and quantification. Standalone SERS nanoprobes exhibit significant enhancements in sensitivity and specificity due to optimized hot spot generation and improved reporter molecule interactions. Recent innovations include the development of nanogap and core–satellite structures that enhance electromagnetic fields, which are crucial for SERS applications. Standalone SERS nanoprobes, particularly those utilizing indirect detection mechanisms, represent a significant advancement in the field. They hold potential for wide-ranging applications, from disease diagnostics to environmental monitoring, owing to their enhanced sensitivity and ability to operate under complex sample conditions. Full article

(This article belongs to the Special Issue Versatile Plasmonic Nanostructures for Biomedical Applications)

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12 pages, 5559 KiB

Open AccessArticle

Potassium-Based Solid Sorbents for CO₂ Adsorption: Key Role of Interconnected Pores

by Yuan Zhao, Jiangbo Huo, Xuefei Wang and Shunwei Ma

Nanomaterials 2024, 14(22), 1838; https://doi.org/10.3390/nano14221838 - 17 Nov 2024

Viewed by 287

Abstract

Industrial CO₂ emissions contribute to pollution and greenhouse effects, highlighting the importance of carbon capture. Potassium carbonate (K₂CO₃) is an effective CO₂ absorbent, yet its liquid-phase absorption faces issues like diffusion resistance and corrosion risks. In this [...] Read more.

Industrial CO₂ emissions contribute to pollution and greenhouse effects, highlighting the importance of carbon capture. Potassium carbonate (K₂CO₃) is an effective CO₂ absorbent, yet its liquid-phase absorption faces issues like diffusion resistance and corrosion risks. In this work, the solid adsorbents were developed with K₂CO₃ immobilized on the selected porous supports. Al₂O₃ had an optimum CO₂ adsorption capacity of 0.82 mmol g⁻¹. After further optimization of its pore structure, the self-prepared support Al₂O₃-2, which has an average pore diameter of 11.89 nm and a pore volume of 0.59 cm³ g⁻¹, achieved a maximum CO₂ adsorption capacity of 1.12 mmol g⁻¹ following K₂CO₃ impregnation. Additionally, the relationship between support structure and CO₂ adsorption efficiency was also analyzed. The connectivity of the pores and the large pore diameter of the support may play a key role in enhancing CO₂ adsorption performance. During 10 cycles of testing, the K₂CO₃-based adsorbents demonstrated consistent high CO₂ adsorption capacity with negligible degradation. Full article

(This article belongs to the Topic Removing Challenging Pollutants from Wastewater: Effective Approaches)

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20 pages, 6771 KiB

Open AccessArticle

Enhancement of the Physical and Mechanical Properties of Cellulose Nanofibril-Reinforced Lignocellulosic Foams for Packaging and Building Applications

by Mara Paulette Alonso, Rakibul Hossain, Maryam El Hajam and Mehdi Tajvidi

Nanomaterials 2024, 14(22), 1837; https://doi.org/10.3390/nano14221837 - 17 Nov 2024

Viewed by 462

Abstract

Biobased foams have the potential to serve as eco-friendly alternatives to petroleum-based foams, provided they achieve comparable thermomechanical and physical properties. We propose a facile approach to fabricate eco-friendly cellulose nanofibril (CNF)-reinforced thermomechanical pulp (TMP) fiber-based foams via an oven-drying process with thermal [...] Read more.

Biobased foams have the potential to serve as eco-friendly alternatives to petroleum-based foams, provided they achieve comparable thermomechanical and physical properties. We propose a facile approach to fabricate eco-friendly cellulose nanofibril (CNF)-reinforced thermomechanical pulp (TMP) fiber-based foams via an oven-drying process with thermal conductivity as low as 0.036 W/(m·K) at a 34.4 kg/m³ density. Acrodur^®, iron chloride (FeCl₃), and cationic polyacrylamide (CPAM) were used to improve the foam properties. Acrodur^® did not have any significant effect on the foamability and density of the foams. Mechanical, thermal, cushioning, and water absorption properties of the foams were dependent on the density and interactions of the additives with the fibers. Due to their high density, foams with CPAM and FeCl₃ at a 1% additive dosage had significantly higher compressive properties at the expense of slightly higher thermal conductivity. There was slight increase in compressive properties with the addition of Acrodur^®. All additives improved the water stability of the foams, rendering them stable even after 24 h of water absorption. Full article

(This article belongs to the Special Issue Advanced Porous Nanomaterials: Synthesis, Properties, and Application (Second Edition))

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15 pages, 3359 KiB

Open AccessArticle

Improvement in Curcumin’s Stability and Release by Formulation in Flexible Nano-Liposomes

by Hua-Wei Chen, Su-Der Chen, Hung-Ta Wu, Chun-Hung Cheng, Chyow-San Chiou and Wei-Ting Chen

Nanomaterials 2024, 14(22), 1836; https://doi.org/10.3390/nano14221836 - 17 Nov 2024

Viewed by 300

Abstract

Curcumin is utilized extensively as Chinese medicine in Asia due to its antioxidant, antimicrobial, and inflammatory activities. However, its use has the challenges of low oral bioavailability and high heat sensitivity. The aim of this research was to produce flexible nano-liposomes containing curcumin [...] Read more.

Curcumin is utilized extensively as Chinese medicine in Asia due to its antioxidant, antimicrobial, and inflammatory activities. However, its use has the challenges of low oral bioavailability and high heat sensitivity. The aim of this research was to produce flexible nano-liposomes containing curcumin using an innovative approach of ethanol injection and Tween 80 to enhance the stability and preservation of curcumin. The mean particle size, encapsulation efficiency, thermal degradation, storage stability, and curcumin release in flexible nano-liposomes were also investigated. We found that the mean particle size of curcumin-loaded flexible nano-liposome decreased from 278 nm to 27.6 nm. At the same time, the Tween 80 concentration increased from 0 to 0.15 wt%, which corresponded with the results of transmission electron microscopy (TEM) morphology analyses, and particle size decreased with an enhancement in Tween 80 concentration. Further, pure curcumin was quickly released within one hour at 37 °C, and first-order kinetics matched with its release curve. However, curcumin encapsulated in flexible nano-liposomes showed a slow release of 71.24% within 12 h, and a slower release pattern matched with the Higuchi model over 24 h, ultimately reaching 84.63% release. Hence, flexible nano-liposomes of curcumin made by a combination of ethanol injection and Tween 80 addition prevented the thermal degradation of curcumin, and enhanced its storage stability and preservation for future drug delivery applications. Full article

(This article belongs to the Special Issue Green Nanoparticles for Topical Administration of Drugs)

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17 pages, 3778 KiB

Open AccessArticle

High-Performance Ammonia QCM Sensor Based on SnO₂ Quantum Dots/Ti₃C₂T_x MXene Composites at Room Temperature

by Chong Li, Ran Tao, Jinqiao Hou, Huanming Wang, Chen Fu and Jingting Luo

Nanomaterials 2024, 14(22), 1835; https://doi.org/10.3390/nano14221835 - 16 Nov 2024

Viewed by 410

Abstract

Ammonia (NH₃) gas is prevalent in industrial production as a health hazardous gas. Consequently, it is essential to develop a straightforward, reliable, and stable NH₃ sensor capable of operating at room temperature. This paper presents an innovative approach to modifying [...] Read more.

Ammonia (NH₃) gas is prevalent in industrial production as a health hazardous gas. Consequently, it is essential to develop a straightforward, reliable, and stable NH₃ sensor capable of operating at room temperature. This paper presents an innovative approach to modifying SnO₂ colloidal quantum dots (CQDs) on the surface of Ti₃C₂T_x MXene to form a heterojunction, which introduces a significant number of adsorption sites and enhances the response of the sensor. Zero-dimensional (0D) SnO₂ quantum dots and two-dimensional (2D) Ti₃C₂T_x MXene were prepared by solvothermal and in situ etching methods, respectively. The impact of the mass ratio between two materials on the performance was assessed. The sensor based on 12 wt% Ti₃C₂T_x MXene/SnO₂ composites demonstrates excellent performance in terms of sensitivity and response/recovery speed. Upon exposure to 50 ppm NH₃, the frequency shift in the sensor is −1140 Hz, which is 5.6 times larger than that of pure Ti₃C₂T_x MXene and 2.8 times higher than that of SnO₂ CQDs. The response/recovery time of the sensor for 10 ppm NH₃ was 36/54 s, respectively. The sensor exhibited a theoretical detection limit of 73 ppb and good repeatability. Furthermore, a stable sensing performance can be maintained after 30 days. The enhanced sensor performance can be attributed to the abundant active sites provided by the accumulation/depletion layer in the Ti₃C₂T_x/SnO₂ heterojunction, which facilitates the adsorption of oxygen molecules. This work promotes the gas sensing application of MXenes and provides a way to improve gas sensing performance. Full article

(This article belongs to the Special Issue Synthesis, Chemical-Physical Properties and Applications of Quantum Dots Nanocrystals)

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15 pages, 5249 KiB

Open AccessArticle

A Comprehensive Microstructure-Aware Electromigration Modeling Framework; Investigation of the Impact of Trench Dimensions in Damascene Copper Interconnects

by Ahmed Sobhi Saleh, Kristof Croes, Hajdin Ceric, Ingrid De Wolf and Houman Zahedmanesh

Nanomaterials 2024, 14(22), 1834; https://doi.org/10.3390/nano14221834 - 16 Nov 2024

Viewed by 291

Abstract

As electronic devices continue to shrink in size and increase in complexity, the current densities in interconnects drastically increase, intensifying the effects of electromigration (EM). This renders the understanding of EM crucial, due to its significant implications for device reliability and longevity. This [...] Read more.

As electronic devices continue to shrink in size and increase in complexity, the current densities in interconnects drastically increase, intensifying the effects of electromigration (EM). This renders the understanding of EM crucial, due to its significant implications for device reliability and longevity. This paper presents a comprehensive simulation framework for the investigation of EM in nano-interconnects, with a primary focus on unravelling the influential role of microstructure, by considering the impact of diffusion heterogeneity through the metal texture and interfaces. As such, the resulting atomic flux and stress distribution within nano-interconnects could be investigated. To this end, a novel approach to generate microstructures of the conductor metal is presented, whereby a predefined statistical distribution of grain sizes obtained from experimental texture analyses can be incorporated into the presented model, making the model predictive under various scales and working conditions with no need for continuous calibration. Additionally, the study advances beyond the state-of-the-art by comprehensively simulating all stages of electromigration including stress evolution, void nucleation, and void dynamics. The model was employed to study the impact of trench dimensions on the dual damascene copper texture and its impact on electromigration aging, where the model findings were corroborated by comparing them to the available experimental findings. A nearly linear increase in normalized time to nucleation was detected as the interconnect became wider with a fixed height for aspect ratios beyond 1. However, a saturation was detected with a further increase in width for lines of aspect ratios below 1, with no effective enhancement in time to nucleation. An aspect ratio of 1 seems to maximize the EM lifetime for a fixed cross-sectional area by fostering a bamboo-like structure, where about a 2-fold of increase was estimated when going from aspect ratio 2 to 1. Full article

(This article belongs to the Special Issue Mechanical and Thermal Properties of Nanomaterials)

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21 pages, 2882 KiB

Open AccessReview

Gold Nanoprobes for Robust Colorimetric Detection of Nucleic Acid Sequences Related to Disease Diagnostics

by Maria Enea, Andreia Leite, Ricardo Franco and Eulália Pereira

Nanomaterials 2024, 14(22), 1833; https://doi.org/10.3390/nano14221833 - 16 Nov 2024

Viewed by 335

Abstract

Gold nanoparticles (AuNPs) are highly attractive for applications in the field of biosensing, particularly for colorimetric nucleic acid detection. Their unique optical properties, which are highly sensitive to changes in their environment, make them ideal candidates for developing simple, rapid, and cost-effective assays. [...] Read more.

Gold nanoparticles (AuNPs) are highly attractive for applications in the field of biosensing, particularly for colorimetric nucleic acid detection. Their unique optical properties, which are highly sensitive to changes in their environment, make them ideal candidates for developing simple, rapid, and cost-effective assays. When functionalized with oligonucleotides (Au-nanoprobes), they can undergo aggregation or dispersion in the presence of complementary sequences, leading to distinct color changes that serve as a visual signal for detection. Aggregation-based assays offer significant advantages over other homogeneous assays, such as fluorescence-based methods, namely, label-free protocols, rapid interactions in homogeneous solutions, and detection by the naked eye or using low-cost instruments. Despite promising results, the application of Au-nanoprobe-based colorimetric assays in complex biological matrices faces several challenges. The most significant are related to the colloidal stability and oligonucleotide functionalization of the Au-nanoprobes but also to the mode of detection. The type of functionalization method, type of spacer, the oligo–AuNPs ratio, changes in pH, temperature, or ionic strength influence the Au-nanoprobe colloidal stability and thus the performance of the assay. This review elucidates characteristics of the Au-nanoprobes that are determined for colorimetric gold nanoparticles (AuNPs)-based nucleic acid detection, and how they influence the sensitivity and specificity of the colorimetric assay. These characteristics of the assay are fundamental to developing low-cost, robust biomedical sensors that perform effectively in biological fluids. Full article

(This article belongs to the Special Issue Noble Metal-Based Nanostructures: Optical Properties and Applications)

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Timeline of AuNPs use for nucleic acid detection. Full article ">Figure 2
Dependence of LSPR on spherical gold nanoparticles diameter and aggregation state. Full article ">Figure 3
Colorimetric detection methods using spherical AuNPs: (Top panel) Cross-linking assay—a color change occurs as nucleic acid sequence strands specifically hybridize with complementary sequences, reducing the distance between particles, and resulting in a blue solution (positive test). In the absence of complementary sequences, the solution stays red (negative test). (Middle panel) Non-cross-linking assay—an increase in ionic strength induces AuNP aggregation, resulting in a blue solution (negative test). When complementary targets are present, the solution stays red (positive test). (Bottom panel) Colorimetric assay using unmodified AuNPs: In the absence of complementary sequences, only single-stranded DNA (ssDNA) is present, stabilizing AuNPs against salt-induced aggregation, and the solution stays red (negative result). Conversely, when hybridization occurs in the presence of a complementary sequence, double-stranded DNA (dsDNA) forms, and aggregation occurs (blue solution is a positive result). UV/vis spectra and Nanoparticle Tracking analysis (NTA) profiles are shown with blue lines corresponding to aggregated AuNPs samples and red lines to non-aggregated ones. Also indicated are the positive (green check) and negative (red cross) results for each test. Full article ">Figure 4
Published successful functionalization methods of AuNPs with HS-oligos, resulting in Au-nanoprobes. Full article ">Figure 5
Examples of Au nanoparticle interaction with (i) ssDNA, (ii) PolyA-ssDNA and PolyT-ssDNA, (iii) PEG-ssDNA, and (iv) thiolated-(CH2)6-ssDNA. Full article ">

20 pages, 5333 KiB

Open AccessArticle

Green Synthesis of Fe₂O₃ Nanoparticles Using Eucalyptus globulus Leaf Extract on Pinus radiata Sawdust for Cationic Dye Adsorption

by Pablo Salgado, Eduardo Aedo and Gladys Vidal

Nanomaterials 2024, 14(22), 1832; https://doi.org/10.3390/nano14221832 - 16 Nov 2024

Viewed by 427

Abstract

The present study reports the synthesis of Fe₂O₃ nanoparticles on Pinus radiata sawdust (Fe₂O₃@PS) using a Eucalyptus globulus leaf extract. The morphology and structure of Fe₂O₃@PS were characterized using scanning electron microscopy [...] Read more.

The present study reports the synthesis of Fe₂O₃ nanoparticles on Pinus radiata sawdust (Fe₂O₃@PS) using a Eucalyptus globulus leaf extract. The morphology and structure of Fe₂O₃@PS were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and UV–Vis diffuse reflectance. The adsorption capacity of the system was evaluated by testing its ability to remove the Rhodamine B (RhB) dye. The optimization of the system was carried out using the Plackett–Burman design (PBD) and the response surface methodology (steepest ascent and the Box–Behnken design), which provided information on the main parameters affecting the adsorption process. The PBD results showed that the most important parameters for the removal of RhB using Fe₂O₃@PS were the removal time, the RhB concentration, and the initial pH of the system. The reusability of Fe₂O₃@PS under optimal conditions was tested and it was found to maintain its efficiency after five cycles of use. The efficiency and rate of RhB removal observed at pH values near 7.0 were found to be predominantly influenced by electrostatic interactions. In contrast, the analyses conducted at pH values near 8.3 exhibited reduced influence from electrostatic attractions, with π–π interactions and hydrogen bonds emerging as dominant forces. At pH values exceeding 8.3, all potential interactions between RhB and Fe₂O₃@PS exhibited diminished strength. This research provides valuable information on the formation of eco-friendly nanoparticles immobilized on a forest residue such as sawdust, which can effectively remove organic pollutants like RhB. This contributes to the valorization of resources and the search for solutions to water pollution. Full article

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13 pages, 7273 KiB

Open AccessArticle

Catalytic Methane Decomposition on In Situ Reduced FeCo Alloy Catalysts Derived from Layered Double Hydroxides

by Dianfeng Cao, Yuwen Li, Chao Lv, Yongtao An, Jiangfeng Song, Mingcan Li and Xin Zhang

Nanomaterials 2024, 14(22), 1831; https://doi.org/10.3390/nano14221831 - 15 Nov 2024

Viewed by 284

Abstract

Catalytic methane decomposition (CMD) reaction is considered a promising process for converting greenhouse gas CH₄ into hydrogen and high-value-added carbon materials. In this work, a series of Al₂O₃-supported FeCo alloy catalysts were successfully prepared in the CMD process. [...] Read more.

Catalytic methane decomposition (CMD) reaction is considered a promising process for converting greenhouse gas CH₄ into hydrogen and high-value-added carbon materials. In this work, a series of Al₂O₃-supported FeCo alloy catalysts were successfully prepared in the CMD process. Compared to the pre-reduced catalysts, the in situ reduced FeCo alloy catalysts showed higher methane conversion rates, with the highest reaching 83% at 700 °C, due to the finer active nanoparticle size and greater exposure of active site. Furthermore, the time-on-stream tests demonstrated that the catalytic activity of in situ reduced FeCo alloy catalysts could remain above 92.3% of the highest catalytic activity after 10 h. In addition, TEM analyses of the carbon products from the CMD in situ reduced catalysts revealed the production of carbon nanofibers and nanotubes several microns in length after the reaction. This indicates that the in situ reduced FeCo alloy catalysts more effectively promoted the growth of carbon nanofibers. These results could provide a viable strategy for future methane decomposition development aimed at producing hydrogen and high-value carbon. Full article

(This article belongs to the Special Issue Nanomaterials for Sustainable Green Energy)

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(a) XRD patterns of FeCoAl-LDH-x and (b) XRD patterns of FeCo/Al2O3-x. Full article ">Figure 2
TEM images of (a–c) FeCoAl-LDH-x (x = 1–3). (d–f) TEM images of FeCo/Al2O3-x (x = 1–3). (g–i) Statistical distribution graphs of the particle size of FeCo/Al2O3-x (x = 1–3). Full article ">Figure 3
(a) TG analysis of the FeCoAl-LDH-x, (b) the differential curves of TG about FeCoAl-LDH-x, (c) TG analysis of the FeCo/Al2O3-x, and (d) the differential curves of TG about FeCo/Al2O3-x. Full article ">Figure 4
The relationship between methane conversion and temperature in the TPSR test at 5 °C/min to 800 °C for (a) FeCoAl-LDH-x and (b) FeCo/Al2O3-x, and the relationship between methane conversion and temperature in the TOS test at 5 °C/min to 700 °C for insulation of (c) FeCoAl-LDH-x and (d) FeCo/Al2O3-x. Full article ">Figure 5
XRD patterns of methane decomposition reaction products catalyzed by (a) FeCoAl-LDH-x and (b) FeCo/Al2O3-x. Full article ">Figure 6
TEM images of carbon products created by (a,b) FeCoAl-LDH-1, (c,d) FeCoAl-LDH-2, (e,f) and FeCoAl-LDH-3. Full article ">Figure 7
TEM images of TG products created by (a) FeCo/Al2O3-1, (b) FeCo/Al2O3-2, and (c) FeCo/Al2O3-3. Full article ">Figure 8
Raman spectra of (a) spent FeCoAl-LDHs-x (x = 1–3) and (b) FeCo/Al2O3-x (x = 1–3) catalysts after TG. Full article ">

14 pages, 7597 KiB

Open AccessArticle

Magnetic Field/Ultrasound-Responsive Fe₃O₄ Microbubbles for Targeted Mechanical/Catalytic Removal of Bacterial Biofilms

by Liang Lu, Yuan Liu, Xiaolong Chen, Fengjiao Xu, Qi Zhang, Zhaowei Yin and Lihui Yuwen

Nanomaterials 2024, 14(22), 1830; https://doi.org/10.3390/nano14221830 - 15 Nov 2024

Viewed by 336

Abstract

Conventional antibiotics are limited by drug resistance, poor penetration, and inadequate targeting in the treatment of bacterial biofilm-associated infections. Microbubble-based ultrasound (US)-responsive drug delivery systems can disrupt biofilm structures and enhance antibiotic penetration through cavitation effects. However, currently developed US-responsive microbubbles still depend [...] Read more.

Conventional antibiotics are limited by drug resistance, poor penetration, and inadequate targeting in the treatment of bacterial biofilm-associated infections. Microbubble-based ultrasound (US)-responsive drug delivery systems can disrupt biofilm structures and enhance antibiotic penetration through cavitation effects. However, currently developed US-responsive microbubbles still depend on antibiotics and lack targeting capability. In this work, magnetic field/ultrasound (MF/US)-responsive Fe₃O₄ microbubbles (FMB) were constructed based on Fe₃O₄ nanoparticles (NPs) with superparamagnetic and peroxidase-like catalytic properties. In vitro experiments demonstrated that FMB can be targeted to methicillin-resistant Staphylococcus aureus (MRSA) biofilms by the direction of MF. Upon US irradiation, FMB collapse due to inertial cavitation and generate mechanical forces to disrupt the structure of MRSA biofilms and releases Fe₃O₄ NPs, which catalyze the generation of reactive oxygen species (ROS) from H₂O₂ in the biofilm microenvironment and kill the bacteria within the biofilm. In a mouse biofilm infection model, FMB efficiently destroyed MRSA biofilms grown in subcutaneous catheters with the MF and US. Magnetic-targeted mechanical/catalytic therapy based on FMB provides a promising strategy for effectively combating bacterial biofilm infection. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanomaterials for Imaging and Therapy)

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3 pages, 2535 KiB

Open AccessCorrection

Correction: Arbi et al. Polypyrrole-Assisted Ag Doping Strategy to Boost Co(OH)₂ Nanosheets on Ni Foam as a Novel Electrode for High-Performance Hybrid Supercapacitors. Nanomaterials 2022, 12, 3982

by Hammad Mueen Arbi, Anuja A. Yadav, Yedluri Anil Kumar, Md Moniruzzaman, Salem Alzahmi and Ihab M. Obaidat

Nanomaterials 2024, 14(22), 1829; https://doi.org/10.3390/nano14221829 - 15 Nov 2024

Viewed by 182

Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Nanostructured Materials for Energy Applications)

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34 pages, 4568 KiB

Open AccessReview

Nanothermodynamics: There’s Plenty of Room on the Inside

by Ralph V. Chamberlin and Stuart M. Lindsay

Nanomaterials 2024, 14(22), 1828; https://doi.org/10.3390/nano14221828 - 15 Nov 2024

Viewed by 385

Abstract

Nanothermodynamics provides the theoretical foundation for understanding stable distributions of statistically independent subsystems inside larger systems. In this review, it is emphasized that extending ideas from nanothermodynamics to simplistic models improves agreement with the measured properties of many materials. Examples include non-classical critical [...] Read more.

Nanothermodynamics provides the theoretical foundation for understanding stable distributions of statistically independent subsystems inside larger systems. In this review, it is emphasized that extending ideas from nanothermodynamics to simplistic models improves agreement with the measured properties of many materials. Examples include non-classical critical scaling near ferromagnetic transitions, thermal and dynamic behavior near liquid–glass transitions, and the 1/f-like noise in metal films and qubits. A key feature in several models is to allow separate time steps for distinct conservation laws: one type of step conserves energy and the other conserves momentum (e.g., dipole alignment). This “orthogonal dynamics” explains how the relaxation of a single parameter can exhibit multiple responses such as primary, secondary, and microscopic peaks in the dielectric loss of supercooled liquids, and the crossover in thermal fluctuations from Johnson–Nyquist (white) noise at high frequencies to 1/f-like noise at low frequencies. Nanothermodynamics also provides new insight into three basic questions. First, it gives a novel solution to Gibbs’ paradox for the entropy of the semi-classical ideal gas. Second, it yields the stable equilibrium of Ising’s original model for finite-sized chains of interacting binary degrees of freedom (“spins”). Third, it confronts Loschmidt’s paradox for the arrow of time, showing that an intrinsically irreversible step is required for maximum entropy and the second law of thermodynamics, not only in the thermodynamic limit but also in systems as small as

N = 2

particles. Full article

(This article belongs to the Section Synthesis, Interfaces and Nanostructures)

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15 pages, 4260 KiB

Open AccessArticle

Microwave-Assisted Synthesis of N, S Co-Doped Carbon Quantum Dots for Fluorescent Sensing of Fe(III) and Hydroquinone in Water and Cell Imaging

by Zhaochuan Yu, Chao Deng, Wenhui Ma, Yuqian Liu, Chao Liu, Tingwei Zhang and Huining Xiao

Nanomaterials 2024, 14(22), 1827; https://doi.org/10.3390/nano14221827 - 14 Nov 2024

Viewed by 503

Abstract

The detection of heavy metal ions and organic pollutants from water sources remains critical challenges due to their detrimental effects on human health and the environment. Herein, a nitrogen and sulfur co-doped carbon quantum dot (NS-CQDs) fluorescent sensor was developed using a microwave-assisted [...] Read more.

The detection of heavy metal ions and organic pollutants from water sources remains critical challenges due to their detrimental effects on human health and the environment. Herein, a nitrogen and sulfur co-doped carbon quantum dot (NS-CQDs) fluorescent sensor was developed using a microwave-assisted carbonization method for the detection of Fe³⁺ ions and hydroquinone (HQ) in aqueous solutions. NS-CQDs exhibit excellent optical properties, enabling sensitive detection of Fe³⁺ and HQ, with detection limits as low as 3.40 and 0.96 μM. Notably, with the alternating introduction of Fe³⁺ and HQ, NS-CQDs exhibit significant fluorescence (FL) quenching and recovery properties. Based on this property, a reliable “on-off-on” detection mechanism was established, enabling continuous and reversible detection of Fe³⁺ and HQ. Furthermore, the low cytotoxicity of NS-CQDs was confirmed through successful imaging of HeLa cells, indicating their potential for real-time intracellular detection of Fe³⁺ and HQ. This work not only provides a green and rapid synthesis strategy for CQDs but also highlights their versatility as fluorescent probes for environmental monitoring and bioimaging applications. Full article

(This article belongs to the Special Issue Nanomaterials in Electrochemical Electrode and Electrochemical Sensor)

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Figure 1
Synthesis and characterization of NS-CQDs. (a) HRTEM image of NS-CQDs (the inset shows its lattice fringes). (b) Diameter distribution analysis, (c) XRD, (d) AFM image, (e) height distribution analysis, and (f) Raman spectroscopy of NS-CQDs. Full article ">Figure 2
Chemical composition analysis of NS-CQDs. (a) FTIR and (b) XPS spectra of NS-CQDs. (c–f) High-resolution XPS of C 1s, N 1s, S 2p, and O 1s, respectively. Full article ">Figure 3
Evaluation of FL properties of NS-MQDs. (a) UV-vis absorption spectra and FL excitation (Ex) and FL emission (Em) spectra of NS-MQDs in aqueous solution. (b) FL emission spectra of NS-MQDs at different excitation wavelengths (320–480 nm). Full article ">Figure 4
“On-off-on” detection performance of NS-CQDs for Fe3+ and HQ. (a) The concentration-dependent emission spectra of NS-CQDs at different concentrations of Fe3+ (0–833.3 μM). (b) Stern-Volmer plot of F/F0 versus Fe3+ concentration for NS-CQDs. (c) FL intensity change profiles of NS-CQDs in the presence of potential competing ions (green) and Fe3+ upon addition of competing anions (3-fold excess, purple) in DI water. (d) The concentration-dependent emission spectra of (NS-CQDs+Fe3+) for different concentrations of HQ (0–1333.3 μM). (e) Stern-Volmer plot of F/F0 versus HQ concentration for (NS-CQDs+Fe3+). (f) FL intensity change profiles of NS-CQDs in the presence of potential competing ions (green) and HQ upon addition of competing anions (3-fold excess, purple) in DI water. Full article ">Figure 5
Fluorescence “on-off-on” principle of NS-CQDs. (a) UV-vis absorption spectrum and (b) FL decay curves of NS-CQDs before and after the addition of Fe3+. (c) FL spectrum of NS-CQDs, NS-CQDs+HQ, NS-CQDs+Fe3+, NS-CQDs Fe2+, and NS-CQDs+Fe3++HQ. (d) Schematic of the proposed “on-off-on” mechanism for the detection of Fe3+ and HQ using NS-CQDs. Full article ">Figure 6
Confocal FL images of living HeLa cells. The images after incubating NS-CQDs at 37 °C for 4 h are as follows: (a) bright field, (d) FL, and (g) merged image. The images of HeLa cells stained with NS-CQDs after treatment with Fe3+ (300 μM) for 4 h are: (b) bright field, (e) FL, and (h) merged image. The images of HeLa cells stained with NS-CQDs after treatment with Fe3+ (300 μM) followed by HQ (300 μM) for 4 h are: (c) bright field, (f) FL, and (i) merged image. Full article ">Scheme 1
Schematic of the fabrication of co-doped NS-CQDs and its applications. Full article ">

11 pages, 4207 KiB

Open AccessArticle

Respiration Monitoring Using Humidity Sensor Based on Hydrothermally Synthesized Two-Dimensional MoS₂

by Gwangsik Hong, Mi Eun Kim, Jun Sik Lee, Ja-Yeon Kim and Min-Ki Kwon

Nanomaterials 2024, 14(22), 1826; https://doi.org/10.3390/nano14221826 - 14 Nov 2024

Viewed by 494

Abstract

Breathing is the process of exchanging gases between the human body and the surrounding environment. It plays a vital role in maintaining human health, sustaining life, and supporting various bodily functions. Unfortunately, current methods for monitoring respiration are impractical for medical applications because [...] Read more.

Breathing is the process of exchanging gases between the human body and the surrounding environment. It plays a vital role in maintaining human health, sustaining life, and supporting various bodily functions. Unfortunately, current methods for monitoring respiration are impractical for medical applications because of their high costs and need for bulky equipment. When measuring changes in moisture during respiration, we observed a slow response time for 2D nanomaterial-based resistance measurement methods used in respiration sensors. Through thermal annealing, the crystal structure of MoS₂ is transformed from 1T@2H to 2H, allowing the measurement of respiration at more than 30 cycles per minute and enabling analysis of the response. This study highlights the potential of two-dimensional nanomaterials for the development of low-cost and highly sensitive humidity and respiration sensors for various applications. Full article

(This article belongs to the Special Issue 2D Materials for Advanced Sensors: Fabrication and Applications)

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2 pages, 170 KiB

Open AccessEditorial

Semiconductor Quantum Dots: Synthesis, Properties and Applications

by Donghai Feng, Guofeng Zhang and Yang Li

Nanomaterials 2024, 14(22), 1825; https://doi.org/10.3390/nano14221825 - 14 Nov 2024

Viewed by 510

Abstract

Semiconductor nanoparticles of sizes smaller than exciton Bohr diameters undergo quantum confinement and are called quantum dots (QDs), which exhibit size-dependent physicochemical properties [...] Full article

(This article belongs to the Special Issue Semiconductor Quantum Dots: Synthesis, Properties and Applications)

18 pages, 5175 KiB

Open AccessArticle

Co-Activating Lattice Oxygen of TiO₂-NT and SnO₂ Nanoparticles on Superhydrophilic Graphite Felt for Boosting Electrocatalytic Oxidation of Glyphosate

by Wenyan He, Sheng Bai, Kaijie Ye, Siyan Xu, Yinuo Dan, Moli Chen and Kuo Fang

Nanomaterials 2024, 14(22), 1824; https://doi.org/10.3390/nano14221824 - 14 Nov 2024

Viewed by 267

Abstract

Glyphosate (GH) wastewater potentially poses hazards to human health and the aquatic environment, due to its persistence and toxicity. A highly superhydrophilic and stable graphite felt (GF)/polydopamine (PDA)/titanium dioxide nanotubes (TiO₂-NT)/SnO₂/Ru anode was fabricated and characterized for the degradation [...] Read more.

Glyphosate (GH) wastewater potentially poses hazards to human health and the aquatic environment, due to its persistence and toxicity. A highly superhydrophilic and stable graphite felt (GF)/polydopamine (PDA)/titanium dioxide nanotubes (TiO₂-NT)/SnO₂/Ru anode was fabricated and characterized for the degradation of glyphosate wastewater. Compared to control anodes, the GF/PDA/TiO₂-NT/SnO₂/Ru anode exhibited the highest removal efficiency (near to 100%) and a yield of phosphate ions of 76.51%, with the lowest energy consumption (0.088 Wh/L) for degrading 0.59 mM glyphosate (GH) at 7 mA/cm² in 30 min. The exceptional activity of the anode may be attributed to the co-activation of lattice oxygen in TiO₂-NT and SnO₂ by coupled Ru, resulting in a significant amount of •O₂⁻ and oxygen vacancies as active sites for glyphosate degradation. After electrolysis, small molecular acids and inorganic ions were obtained, with hydroxylation and dephosphorization as the main degradation pathways. Eight cycles of experiments confirmed that Ru doping prominently enhanced the stability of the GF/PDA/TiO₂-NT/SnO₂/Ru anode due to its high oxygenophilicity and electron-rich ability, which promoted the generation and utilization efficiency of active free radicals and defects-associated oxygen. Therefore, this study introduces an effective strategy for efficiently co-activating lattice oxygen in SnO₂ and TiO₂-NT on graphite felt to eliminate persistent organophosphorus pesticides. Full article

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11 pages, 3198 KiB

Open AccessArticle

Mo₂TiAlC₂ as a Saturable Absorber for a Passively Q-Switched Tm:YAlO₃ Laser

by Chen Wang, Tianjie Chen, Zhe Meng, Sujian Niu, Zhaoxue Li and Xining Yang

Nanomaterials 2024, 14(22), 1823; https://doi.org/10.3390/nano14221823 - 14 Nov 2024

Viewed by 324

Abstract

Owing to their remarkable characteristics, two-dimensional (2D) layered, MAX phase materials have garnered significant attention in the field of optoelectronics in recent years. Herein, a novel MAX phase ceramic material (Mo₂TiAlC₂) was prepared into a saturable absorber (SA) by [...] Read more.

Owing to their remarkable characteristics, two-dimensional (2D) layered, MAX phase materials have garnered significant attention in the field of optoelectronics in recent years. Herein, a novel MAX phase ceramic material (Mo₂TiAlC₂) was prepared into a saturable absorber (SA) by the spin-coating method for passively Q-switching (PQS), and its nonlinear optical absorption properties were characterized with a Tm:YAlO₃ (Tm:YAP) nanosecond laser. The structure characteristics and composition analysis revealed that the Mo₂TiAlC₂ material exhibits a well-defined and stable structure, with a uniform thin film successfully obtained through spin coating. In this study of a PQS laser by employing a Mo₂TiAlC₂-based SA, an average output power of 292 mW was achieved when the absorbed pump power was approximately 4.59 W, corresponding to a central output wavelength of 1931.2 nm. Meanwhile, a stable pulse with a duration down to 242.9 ns was observed at a repetition frequency of 47.07 kHz, which is the narrowest pulse width recorded among PQS solid-state lasers using MAX phase materials as SAs. Our findings indicate that the Mo₂TiAlC₂ MAX phase ceramic material is an excellent modulator and has promising potential for ultrafast nonlinear photonic applications. Full article

(This article belongs to the Special Issue Linear and Nonlinear Optical Properties of Nanomaterials)

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Illustration of the preparation process for the Mo2TiAlC2-based SA. Full article ">Figure 2
Morphological characterization of the Mo2TiAlC2 powder. (a–c) SEM images of the Mo2TiAlC2 powder at different magnifications; (d,e) EDS images of the Mo2TiAlC2 powder. Full article ">Figure 3
(a–c) TEM images of the Mo2TiAlC2 powder at different magnifications. Full article ">Figure 4
Structural and linear absorption characterization of Mo2TiAlC2 material. (a) XRD image of Mo2TiAlC2 powder; (b) Raman spectrum of Mo2TiAlC2 powder; (c) AFM image of Mo2TiAlC2-based SA; and (d) linear absorption properties of Mo2TiAlC2-based SA. Full article ">Figure 5
The experimental setup of the PQS Tm:YAP laser with the Mo2TiAlC2-based SA. Full article ">Figure 6
Output performances of PQS Tm:YAP laser. (a) Output power varies with absorbed pump power; (b) pulse width and repetition frequency as a function of absorbed pump power; (c) stable pulse trains of T = 5% (2.5, 100 μs/div, and 1 ms/div); and (d) output spectrum of laser in CW and PQS modes. Full article ">Figure 7
(a) The beam quality of the PQS Tm:YAP laser with T = 5%; (b) output power stability of the PQS Tm:YAP laser. Full article ">

12 pages, 1170 KiB

Open AccessArticle

An Evaluation of Moderate-Refractive-Index Nanoantennas for Enhancing the Photoluminescence Signal of Quantum Dots

by Rafael Ramos Uña, Braulio García Cámara and Ángela I. Barreda

Nanomaterials 2024, 14(22), 1822; https://doi.org/10.3390/nano14221822 - 14 Nov 2024

Viewed by 328

Abstract

The use of nanostructures to enhance the emission of single-photon sources has attracted some attention in the last decade due to the development of quantum technologies. In particular, the use of metallic and high-refractive-index dielectric materials has been proposed. However, the utility of [...] Read more.

The use of nanostructures to enhance the emission of single-photon sources has attracted some attention in the last decade due to the development of quantum technologies. In particular, the use of metallic and high-refractive-index dielectric materials has been proposed. However, the utility of moderate-refractive-index dielectric nanostructures to achieve more efficient single-photon sources remains unexplored. Here, a systematic comparison of various metallic, high-refractive-index and moderate-refractive-index dielectric nanostructures was performed to optimize the excitation and emission of a CdSe/ZnS single quantum dot in the visible spectral region. Several geometries were evaluated in terms of electric field enhancement and Purcell factor, considering the combination of metallic, high-refractive-index and moderate-refractive-index dielectric materials conforming to homogeneous and hybrid nanoparticle dimers. Our results demonstrate that moderate-refractive-index dielectric nanoparticles can enhance the photoluminescence signal of quantum emitters due to their broader electric and magnetic dipolar resonances compared to high-refractive-index dielectric nanoparticles. However, hybrid combinations of metallic and high-refractive-index dielectric nanostructures offer the largest intensity enhancement and Purcell factors at the excitation and emission wavelengths of the quantum emitter, respectively. The results of this work may find applications in the development of single-photon sources. Full article

(This article belongs to the Section Nanophotonics Materials and Devices)

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Figure 1

Figure 1
(a) A scheme of the illumination of the dimer by a plane wave propagating along the negative direction of the z-axis, i.e., from the air to the substrate, and linearly polarized parallel to the dimer orientation (x-axis). (b) A scheme of the dimer when it is excited by an electric dipole oscillating in the x-direction, representing the QD, located in the middle of the gap and 5 nm above the substrate to take into account the QD size. Full article ">Figure 2
Scheme of all different dimer configurations. In (a–c), non-hybrid (homogeneous) dimers are represented: (a) two gold NPs, (b) two silicon NPs and (c) two MRI NPs. And in (d–f), hybrid dimers combining all three previous materials are shown. The red dot between the NPs represents the CdSe/ZnS QD. Full article ">Figure 3
The scattering efficiency and multipolar decomposition for metallic and dielectric isolated NPs in air. The nanoparticles were illuminated by a plane wave propagating along the negative direction of the z-axis (parallel to the disk axis) and linearly polarized along the x-axis (perpendicular to the disk axis). (a) A gold NP of R = 50 nm and H = 150 nm, (b) a silicon NP of R = 120 nm and H = 80 nm and (c) a MRI NP of R = 150 nm and H = 200 nm. Black dotted line: the scattering efficiency obtained with COMSOL. Purple solid line: the scattering efficiency obtained as the sum of the dipolar electric and magnetic, and quadrupolar electric and magnetic, contributions. Blue and red solid lines: dipolar electric and magnetic contributions, respectively. Green and yellow solid lines: quadrupolar electric and magnetic contributions, respectively. Full article ">Figure 4
(a–c) Scattering efficiency for homogeneous dimers: (a) Au-Au, (b) MRI-MRI and (c) Si-Si dimers. The gray vertical lines correspond to the excitation and emission wavelengths. (d–f) Near-field maps (Z-X plane) at the excitation wavelength (570 nm) for the homogeneous dimers: (d) Au-Au, (e) MRI-MRI and (f) Si-Si. A hot-spot is observed in between the NPs, specified as the reddish/greenish area. The dashed white line represents the position of the substrate. Full article ">Figure 5
(a–c) Scattering efficiency for hybrid dimers: (a) MRI-Au, (b) Si-Au and (c) MRI-Si dimers. The gray vertical lines correspond to the excitation and emission wavelengths. (d–f) Near-field maps (Z-X plane) at the excitation wavelength (570 nm) for the hybrid dimers: (d) MRI-Au, (e) Si-Au and (f) MRI-Si. The dashed white line represents the position of the substrate. Full article ">

12 pages, 2903 KiB

Open AccessArticle

Design of Thermo-Responsive Pervaporation Membrane Based on Hyperbranched Polyglycerols and Elastin-like Protein Conjugates

by Juliet Kallon, John J. Bang, Ufana Riaz and Darlene K. Taylor

Nanomaterials 2024, 14(22), 1821; https://doi.org/10.3390/nano14221821 - 14 Nov 2024

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Abstract

This paper reports the development of a highly crosslinked hyper-branched polyglycerol (HPG) polymer bound to elastin-like proteins (ELPs) to create a membrane that undergoes a distinct closed-to-open permeation transition at 32 °C. The crosslinked HPG forms a robust, mesoporous structure (150–300 nm pores), [...] Read more.

This paper reports the development of a highly crosslinked hyper-branched polyglycerol (HPG) polymer bound to elastin-like proteins (ELPs) to create a membrane that undergoes a distinct closed-to-open permeation transition at 32 °C. The crosslinked HPG forms a robust, mesoporous structure (150–300 nm pores), suitable for selective filtration. The membranes were characterized by FTIR, UV–visible spectroscopy, SEM, and AFM, revealing their structural and morphological properties. Incorporating a synthetic polypeptide introduced thermo-responsive behavior, with the membrane transitioning from impermeable to permeable above the lower critical solution temperature (LCST) of 32 °C. Permeation studies using crystal violet (CV) demonstrated selective transport, where CV permeated only above 32 °C, while water permeated at all temperatures. This hybrid HPG-ELP membrane system, acting as a molecular switch, offers potential for applications in drug delivery, bioseparations, and smart filtration systems, where permeability can be controlled by temperature. Full article

(This article belongs to the Section Synthesis, Interfaces and Nanostructures)

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