Decoration of Carbon Nanotubes With Metal Nanoparticles: Recent Trends

Hydrogen storage efficiency of Fe doped carbon nanotubes: molecular simulation study

Given that adsorption is widely regarded as a favorable technique for hydrogen storage, it is appropriate to pursue the development of suitable adsorbent materials for industrial storage. This study aimed to assess the potential of Fe-doped carbon nanotubes (FeCNT) as a remarkable material for hydrogen storage. The structures of pure and Fe-doped CNTs were optimized based on quantum mechanical calculations using density functional theory (DFT) with the Perdew-Burke-Ernzerhof (PBE) method. To gain a comprehensive understanding of the adsorption behavior, Monte Carlo simulation was employed to investigate the adsorption of hydrogen molecules on FeCNT. The study specifically examined the impact of temperature, pressure, and hydrogen mole percentage on the adsorption capacity of FeCNT. The findings indicated that the uptake of hydrogen increased as the pressure increased, and when the pressure exceeded 5 MPa, FeCNT reached a state of near saturation. At room temperature and pressures of 1 and 5 MPa, the hydrogen capacities of FeCNT were determined to be 1.53 and 6.92 wt%, respectively. The radial distribution function diagrams confirmed the formation of a one-layer adsorption phase at pressures below 5 MPa. A comparison of the temperature dependence of hydrogen adsorption between FeCNT and pure CNT confirmed the effectiveness of Fe doping in hydrogen storage up to room temperature. FeCNT exhibited a greater reduction in initial hydrogen capacity at temperatures above room temperature. To evaluate the safety of the system, the use of N2 as a dilution agent was investigated by examining the hydrogen uptake of FeCNT from pure and H2/N2 mixtures at 300 K. The results showed that the addition of N2 to the environment had no significant effect on FeCNT hydrogen storage at pressures below 4 MPa. Furthermore, the study of H2 selectivity from the H2/N2 mixture indicated that FeCNT demonstrated a preference for adsorbing H2 over a wide range of bulk mole fractions at pressures of 4 and 5 MPa, suggesting that these pressures could be considered optimal. Under these conditions, Fe doping can offer an efficient and selective adsorption surface for hydrogen storage.

A Highly Sensitive Surface-Modified Porous Carbon Nanotube-Based Sensor for Ammonia Gas Detection

In this work, we compared the gas sensing behaviors of pristine and decorated multi-walled carbon nanotubes (MWCNTs) and examined the response behavior of bare and adorned MWCNTs in gas sensing. According to the data, the decorated response was 144%, which is higher than the bare CNT response of 117% in terms of the sensing response. The RF-sputtering method is used to decorate the carbon nanotubes by pure Indium (In) metal nanoparticles. Every measurement was performed in a temperature-controlled environment. Tests of the entire procedure were conducted at a 10 ppm concentration of ammonia gas. We have observed the quick reaction time (1-10 s) in pristine and (1-7 s) in decorated MWCNTs. The response was obtained 117% for the pristine and 144, 115, and 73% for the second (3 min decoration), third (6 min decoration), and fourth (9 min decoration) MWCNTs, respectively. The as-prepared pristine samples and all the decorated sensors had sensitivity values of 0.45, 0.50, 0.51, and 0.57 for time intervals of 0, 3, 6, and 9 min, respectively. It amounted to 45% for the pure and 50, 51, and 57% for the remaining as-prepared decorated sensors, respectively. Based on the measured sensor response graph, a recovery of between 80 and 85% was achieved. For a period of 10 days at a constant concentration, the stability was also assessed and we have analyzed the structural, electrical, and elemental composition of the prepared CNTs by FESEM, EDX, Raman spectroscopy, FTIR, and XRD.

Bacterial nano-factories as a tool for the biosynthesis of TiO2 nanoparticles: characterization and potential application in wastewater treatment

The development of reliable and eco-conscious processes for nanoparticle synthesis constitutes a significant element in nanotechnology. TiO2 nanoparticles (NPs) are becoming essential due to their potential uses in dentistry, surgery, agriculture, and pharmacy. This leads to the development of various procedures for producing TiO2 NPs using various physicochemical methods. Still, the drawbacks of these conventional methods are associated with the emission of toxic chemicals into the atmosphere and high energy demands in production, hence endangering the health and the environment. Problems issued are solved by green nanotechnology, which offers tools as nano-factories by utilizing biological sources to subside the improper effects of conventional methods and produces nanoparticles through synthesis methods that are clean, safe, energy-efficient, and cost-effective. Among the biogenic sources, microbial cells such as bacteria possess intrinsic pathways of converting metallic salt to nanoparticles due to their ability to produce reductase enzymes. Also, they can offer features to products such as high dispersity and produce sustainable nanoparticles at a large scale. Biosynthesized TiO2 NPs have high oxidizing potential and a wide range of applications, specifically as photosensitizers and antimicrobial agents. This review will address bacterial nano-factories that can be utilized for the biosynthesis of TiO2 NPs, the characterization of biosynthesized nanoparticles, and their potential application in wastewater treatment.

Nanoparticles: A Potential and Effective Method to Control Insect-Borne Diseases

Insects act as vectors to carry a wide range of bacteria and viruses that can cause multiple vector-borne diseases in humans. Diseases such as dengue fever, epidemic encephalitis B, and epidemic typhus, which pose serious risks to humans, can be transmitted by insects. Due to the absence of effective vaccines for most arbovirus, insect control was the main strategy for vector-borne diseases control. However, the rise of drug resistance in the vectors brings a great challenge to the prevention and control of vector-borne diseases. Therefore, finding an eco-friendly method for vector control is essential to combat vector-borne diseases. Nanomaterials with the ability to resist insects and deliver drugs offer new opportunities to increase agent efficacy compared with traditional agents, and the application of nanoagents has expanded the field of vector-borne disease control. Up to now, the reviews of nanomaterials mainly focus on biomedicines, and the control of insect-borne diseases has always been a neglected field. In this study, we analyzed 425 works of the literature about different nanoparticles applied on vectors in PubMed around keywords, such as"nanoparticles against insect," "NPs against insect," and "metal nanoparticles against insect." Through these articles, we focus on the application and development of nanoparticles (NPs) for vector control, discussing the lethal mechanism of NPs to vectors, which can explore the prospect of applying nanotechnology in the prevention and control of vectors.

Grafting Copper Atoms and Nanoparticles on Double-Walled Carbon Nanotubes: Application to Catalytic Synthesis of Propargylamine

The decoration of carbon nanotubes (CNTs) by metal nanoparticles (NPs) combines the advantages of a high specific surface material with catalytic properties of metal nanocrystals. Little work has been devoted to the decoration of CNTs with copper NPs, and no evidence of copper atomic decoration of CNTs has shown up until now. Herein, we demonstrate that the strong acidic oxidation of double-walled CNTs (dwCNTs) is very efficient for the decoration of the carbon surface by copper NPs and atoms. This treatment severely degraded the CNT walls and generated a large amount of disordered sp³ carbon. This amorphous carbon film bears many chemically active functions like carboxyl and hydroxyl ones. In such conditions, the CNT walls behave as very efficient ligands for the stabilization of copper obtained by the thermolysis of the mesityl precursor in organic solution under mild dihydrogen pressure. In addition to copper NPs, we evidenced the presence of a regular coverage with copper atoms over the dwCNTs. This nanocomposite catalyzes the quantitative synthesis of propargylamines via one A³-type coupling reaction. Five consecutive catalytic cycles with 100% yield could be performed with no loss of activity, and the combination of Cu supported on dwCNTs allows a facile recycling of the catalytic material.

Characterization of Carbon Nanomaterials Dispersions: Can Metal Decoration of MWCNTs Improve Their Physicochemical Properties?

A suitable dispersion of carbon materials (e.g., carbon nanotubes (CNTs)) in an appropriate dispersant media, is a prerequisite for many technological applications (e.g., additive purposes, functionalization, mechanical reinforced materials for electrolytes and electrodes for energy storage applications, etc.). Deep eutectic solvents (DES) have been considered as a promising "green" alternative, providing a versatile replacement to volatile organic solvents due to their unique physical-chemical properties, being recognized as low-volatility fluids with great dispersant ability. The present work aims to contribute to appraise the effect of the presence of MWCNTs and Ag-functionalized MWCNTs on the physicochemical properties (viscosity, density, conductivity, surface tension and refractive index) of glyceline (choline chloride and glycerol, 1:2), a Type III DES. To benefit from possible synergetic effects, AgMWCNTs were prepared through pulse reverse electrodeposition of Ag nanoparticles into MWCNTs. Pristine MWCNTs were used as reference material and water as reference dispersant media for comparison purposes. The effect of temperature (20 to 60 °C) and concentration on the physicochemical properties of the carbon dispersions (0.2-1.0 mg cm^-3) were assessed. In all assessed physicochemical properties, AgMWCNTs outperformed pristine MWCNTs dispersions. A paradoxical effect was found in the viscosity trend in glyceline media, in which a marked decrease in the viscosity was found for the MWCNTs and AgMWCNTs materials at lower temperatures. All physicochemical parameters were statistically analyzed using a two-way analysis of variance (ANOVA), at a 5% level of significance.

Microbe-Mediated Biosynthesis of Nanoparticles: Applications and Future Prospects

Nanotechnology is the science of nano-sized particles/structures (~100 nm) having a high surface-to-volume ratio that can modulate the physical, chemical and biological properties of the chemical compositions. In last few decades, nanoscience has attracted the attention of the scientific community worldwide due to its potential uses in the pharmacy, medical diagnostics and disease treatment, energy, electronics, agriculture, chemical and space industries. The properties of nanoparticles (NPs) are size and shape dependent. These characteristic features of nanoparticles can be explored for various other applications such as computer transistors, chemical sensors, electrometers, memory schemes, reusable catalysts, biosensing, antimicrobial activity, nanocomposites, medical imaging, tumor detection and drug delivery. Therefore, synthesizing nanoparticles of desired size, structure, monodispersity and morphology is crucial for the aforementioned applications. Recent advancements in nanotechnology aim at the synthesis of nanoparticles/materials using reliable, innoxious and novel ecofriendly techniques. In contrast to the traditional methods, the biosynthesis of nanoparticles of a desired nature and structure using the microbial machinery is not only quicker and safer but more environmentally friendly. Various microbes, including bacteria, actinobacteria, fungi, yeast, microalgae and viruses, have recently been explored for the synthesis of metal, metal oxide and other important NPs through intracellular and extracellular processes. Some bacteria and microalgae possess specific potential to fabricate distinctive nanomaterials such as exopolysaccharides, nanocellulose, nanoplates and nanowires. Moreover, their ability to synthesize nanoparticles can be enhanced using genetic engineering approaches. Thus, the use of microorganisms for synthesis of nanoparticles is unique and has a promising future. The present review provides explicit information on different strategies for the synthesis of nanoparticles using microbial cells; their applications in bioremediation, agriculture, medicine and diagnostics; and their future prospects.

Navigation of Silver/Carbon Nanoantennas in Organic Fluids Explored by a Two-Wave Mixing

Within this work are analyzed third-order nonlinear optical properties with a potential influence on the dynamic mechanics exhibited by metal/carbon nanofluids. The nanofluids were integrated by multiwall carbon nanotubes decorated with Ag nanoparticles suspended in ethanol or in acetone. Optical third-order nonlinearities were experimentally explored by vectorial two-wave mixing experiments with a Nd-YAG laser system emitting nanosecond pulses at a 532 nm wavelength. An optically induced birefringence in the metal/organic samples seems to be responsible for a significant modification in density and compressibility modulus in the nanosystems. The measured nonlinear refractive index was associated with a thermal process together with changes in density, compressibility modulus and speed of sound in the samples. Nanofluid diffusivity was studied to characterize the dynamic concentration gradients related to the precipitation of nanostructures in the liquid solutions. The evolution of the nanoparticle density suspended in the nanofluids was considered as a temporal-resolved probabilistic system. It is stated that the incorporation of Ag nanoparticles in carbon nanotubes produces strong mechanical changes in carbon-based nanofluids. According to numerical simulations and optical evaluations, immediate applications for developing dynamic nanoantennas optical logic gates and quantum-controlled metal/carbon systems can be contemplated.

Hydrophilicity and carbon chain length effects on the gas sensing properties of chemoresistive, self-assembled monolayer carbon nanotube sensors

Here we describe the development of chemoresistive sensors employing oxygen-plasma-treated, Au-decorated multiwall carbon nanotubes (MWCNTs) functionalized with self-assembled monolayers (SAMs) of thiols. For the first time, the effects of the length of the carbon chain and its hydrophilicity on the gas sensing properties of SAMs formed on carbon nanotubes are studied, and additionally, the gas sensing mechanisms are discussed. Four thiols differing in the length of the carbon chain and in the hydrophobic or hydrophilic nature of the head functional group are studied. Transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are used to analyze the resulting gas-sensitive hybrid films. Among the different nanomaterials tested, short-chain thiols having a hydrophilic head group, self-assembled onto Au-decorated carbon nanotubes were most responsive to nitrogen dioxide and ethanol vapors, even in the presence of ambient humidity. In particular, this nanomaterial was about eight times more sensitive to nitrogen dioxide than bare Au-decorated carbon nanotubes when operated at room temperature. This response enhancement is attributed to the interaction, via strong hydrogen bonding, of the polar molecules tested to the polar surface of hydrophilic thiols. The approach discussed here could be extended further by combining hydrophilic and hydrophobic thiol SAMs in Au-MWCNT sensor arrays as a helpful strategy for tuning sensor response and selectivity. This would make the detection of polar and nonpolar gas species employing low-power gas sensors easier, even under fluctuating ambient moisture conditions.

Fabrication of multi-walled carbon nanotube–metallic nanoparticle hybrid nanostructure based electrochemical platforms for sensitive and practical colchicine detection

A MWCNT–Au–Pt hybrid nanostructure was used in the fabrication of electrochemical colchicine sensors for the first time.

Gas Sensing with Iridium Oxide Nanoparticle Decorated Carbon Nanotubes

The properties of multi-wall carbon nanotubes decorated with iridium oxide nanoparticles (IrO_x-MWCNTs) are studied to detect harmful gases such as nitrogen dioxide and ammonia. IrO_x nanoparticles were synthetized using a two-step method, based on a hydrolysis and acid condensation growth mechanism. The metal oxide nanoparticles obtained were employed for decorating the sidewalls of carbon nanotubes. Iridium-oxide nanoparticle decorated carbon nanotube material showed higher and more stable responses towards NH₃ and NO₂ than bare carbon nanotubes under different experimental conditions, establishing the optimal operating temperatures and estimating the limits of detection and quantification. Furthermore, the nanomaterials employed were studied using different morphological and compositional characterization techniques and a gas sensing mechanism is proposed.