Synthesis of Reduced Graphene Oxide as a Support for Nano Copper and Palladium/Copper Catalysts for Selective NO Reduction by CO

High-performance flexible piezoelectric nanogenerator assisted by a three-phase PVDF/WS2/rGO nanocomposite

The emergence of piezoelectric nanogenerators (PENGs) presents a promising alternative to supply energy demands within the realms of portable and miniaturized devices. In this article, the role of 2D transition metal dichalcogenide tungsten sulfide (WS2) and conductive rGO sheets as filler materials inside the polyvinylidene fluoride (PVDF) matrix on piezoelectric performances has been investigated extensively. The strong electrostatic interaction between C-F and C-H monomer bonds of PVDF interacted with the large surface area of the WS2nanosheets, increasing the electroactive polar phases and resulting in enhanced ferroelectricity in the PVDF/WS2nanocomposite. Further, the inclusion of rGO sheets in the PVDF/WS2composite allows mobile charge carriers to move freely through the conductive network provided by the rGO basal planes, which improves the internal polarization of the PVDF/WS2/rGO nanocomposites and increases the electrical performance of the PENGs. The PVDF/WS2/0.3rGO nanocomposite-based PENG exhibits maximum piezoresponses with ∼8.1 times enhancements in the output power density than the bare PVDF-based PENG. The mechanism behind the enhanced piezoresponses in the PVDF/WS2/rGO nanocomposites has been discussed.

Construction of a novel ternary synergistic CuFe2O4-SnO2-rGO heterojunction for efficient removal of cyanide from contaminated water

Many industrial effluents release cyanide, a well-known hazardous and bio-recalcitrant pollutant, and thus, the treatment of cyanide wastewater is a major challenge. In the current study, a CuFe2O4-SnO2-rGO nanocomposite was synthesized to remove cyanide from an aqueous system. The structural and morphological characterizations of the nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive spectra (EDX) analysis. The results revealed that almost 97.7% cyanide removal occurred using the nanocomposite at an initial concentration of 100 mg L-1 within 1 h. The experimental data were fitted to various adsorption models, among which the Langmuir model fitted the data very well, confirming the monolayer adsorption process. The kinetic investigation revealed that the cyanide adsorption process followed a pseudo-second-order kinetic model, indicating a chemisorption process with a high cyanide adsorption capacity of 114 mg g-1. The result of the intraparticulate diffusion model fitting revealed a decreasing slope value (K) from stage 1 to stage 2, indicating that external mass transfer is the predominating step. Moreover, the CuFe2O4-SnO2-rGO nanocomposite shows excellent reusability.

NiFe Nanoparticle Nest Supported on Graphene as Electrocatalyst for Highly Efficient Oxygen Evolution Reaction

Designing cost-efffective electrocatalysts for the oxygen evolution reaction (OER) holds significant importance in the progression of clean energy generation and efficient energy storage technologies, such as water splitting and rechargeable metal-air batteries. In this work, an OER electrocatalyst is developed using Ni and Fe precursors in combination with different proportions of graphene oxide. The catalyst synthesis involved a rapid reduction process, facilitated by adding sodium borohydride, which successfully formed NiFe nanoparticle nests on graphene support (NiFe NNG). The incorporation of graphene support enhances the catalytic activity, electron transferability, and electrical conductivity of the NiFe-based catalyst. The NiFe NNG catalyst exhibits outstanding performance, characterized by a low overpotential of 292.3 mV and a Tafel slope of 48 mV dec-1, achieved at a current density of 10 mA cm- 2. Moreover, the catalyst exhibits remarkable stability over extended durations. The OER performance of NiFe NNG is on par with that of commercial IrO2 in alkaline media. Such superb OER catalytic performance can be attributed to the synergistic effect between the NiFe nanoparticle nests and graphene, which arises from their large surface area and outstanding intrinsic catalytic activity. The excellent electrochemical properties of NiFe NNG hold great promise for further applications in energy storage and conversion devices.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

Wastewater purification from Rhodamine B and Gemifeloxacine by graphene oxide/pectin/ferrite nanocomposite: A novel molecular dynamics simulation for experimental contaminants removing

In this study, the synthesized nanocomposite was evaluated novel graphene oxide/pectin/ferrite (GOPF) adsorbent to the adsorption of Rhodamine B (RhB) and Gemifloxacin (GEM) from wastewater. Theoretical studies were carried out using quantum simulation via the Forcite module in Material Studio 2017. The simulation results demonstrated RhB and GEM adsorption over other dyes and drugs. The synthesized nanocomposite was identified by BET, TGA, FT-IR, FE-SEM, XRD, VSM, and EDS. The nanocomposite's ability to effectively take RhB and GEM from an aqueous solution was checked by performing a series of experiments based on the effect of adsorbent dose, initial condensation, contact time, pH, and temperature. The nanocomposite kinetics follow a PSO. The Freundlich isotherm model was applied for maximum adsorption capacity of GEM (124.37 mg/g) and RhB (86.60 mg/g) on GOPF nanocomposite. According to the antibacterial activity test, the synthesized nanocomposite can kill bacteria 5 mm in diameter. Also, the anti-cancer test of nanocomposite was done with 75% viability in high concentrations of nanocomposite. Thus, GOPF application results are not only suitable for dyes but only satisfying for drugs. PRACTITIONER POINTS: GOPF nanocomposite was fabricated for adsorption dye and drug and characterized. The effect of different process parameters, pH, catalyst dosage, contact time, and temperature effect was surveyed. The MD simulation were investigated to adsorb various dyes and drugs. The equilibrium isotherm and adsorption kinetic follow from Freundlich and pseudo-second-order kinetics; GOPF nanocomposite was used for about six cycles. The antibacterial activity and anticancer test of GOPF nanocomposite were investigated by satisfying results.

Chitosan hydrogel anchored phthalocyanine supported metal nanoparticles: Bifunctional catalysts for pollutants reduction and hydrogen production

Metal nanoparticles possess high catalytic activity in various organic transformation reactions. A catalyst must be recovered and re-used effectively and economically to lower the overall reaction cost. The recovery of a catalyst remains a challenge due to their extreme small size. In this research work, catalytic metal nanoparticles were synthesized on Zn-phthalocyanine (ZnPc) and chitosan hydrogel (CH) composite which acts as catalyst support. The ZnPc-CH support facilitate the easy recovery of the loaded metal nanoparticles. Metal nanoparticles (M⁰) based on Cu⁰, Ag⁰, Ni⁰, Co⁰ and Fe⁰ were decorated inside and on ZnPc-CH hydrogel surface. The developed M⁰@ZnPc-CH were utilized for the enhanced selective reduction of toxins and hydrogen production by methanolysis and hydrolysis of NaBH₄. Effective catalytic reduction and hydrogen generation was successfully achieved with Co⁰@ZnPc-CH and ZnPc-CH. Under optimized conditions, Co⁰@ZnPc-CH showed complete reduction of 4-nitrophenol (4-NP) in 8.0 min with the fast 4-NP reduction kinetics (K = 0.611 min^-1). Among the developed catalysts, ZnPc-CH showed fast H₂ generation with high H₂ generation rate (HGR = 4100 mLg^-1min^-1) under optimized conditions. Metal leaching from Co⁰@ZnPc-CH was negligible during recycling of the catalyst, suggesting that it could be implemented to 4-NP treatment from real water samples. Similarly, ZnPc-CH could produce same quantity of H₂ throughout 4 continuous cycles of durability testing without any deactivation and leaching and ZnPc-CH showed high stability, indicating the effectiveness of the catalyst to be applied for H₂ production on large scale.

Dynamics of reduced graphene oxide: synthesis and structural models

Technological advancements are leading to an upsurge in demand for functional materials that satisfy several of humankind's needs. In addition to this, the current global drive is to develop materials with high efficacy in intended applications whilst practising green chemistry principles to ensure sustainability. Carbon-based materials, such as reduced graphene oxide (RGO), in particular, can possibly meet this criterion because they can be derived from waste biomass (a renewable material), possibly synthesised at low temperatures without the use of hazardous chemicals, and are biodegradable (owing to their organic nature), among other characteristics. Additionally, RGO as a carbon-based material is gaining momentum in several applications due to its lightweight, nontoxicity, excellent flexibility, tuneable band gap (from reduction), higher electrical conductivity (relative to graphene oxide, GO), low cost (owing to the natural abundance of carbon), and potentially facile and scalable synthesis protocols. Despite these attributes, the possible structures of RGO are still numerous with notable critical variations and the synthesis procedures have been dynamic. Herein, we summarize the highlights from the historical breakthroughs in understanding the structure of RGO (from the perspective of GO) and the recent state-of-the-art synthesis protocols, covering the period from 2020 to 2023. These are key aspects in the realisation of the full potential of RGO materials through the tailoring of physicochemical properties and reproducibility. The reviewed work highlights the merits and prospects of the physicochemical properties of RGO toward achieving sustainable, environmentally friendly, low-cost, and high-performing materials at a large scale for use in functional devices/processes to pave the way for commercialisation. This can drive the sustainability and commercial viability aspects of RGO as a material.

Ultra-Sensitive and Fast Humidity Sensors Based on Direct Laser-Scribed Graphene Oxide/Carbon Nanotubes Composites

In this paper, the relative humidity sensor properties of graphene oxide (GO) and graphene oxide/multiwalled nanotubes (GO/MWNTs) composites have been investigated. Composite sensors were fabricated by direct laser scribing and characterized using UV-vis-NIR, Raman, Fourier transform infrared, and X-ray photoemission spectroscopies, electron scanning microscopy coupled with energy-dispersive X-ray analysis, and impedance spectroscopy (IS). These methods confirm the composite homogeneity and laser reduction of GO/MWNT with dominant GO characteristics, while ISresults analysis reveals the circuit model for rGO-GO-rGO structure and the effect of MWNT on the sensor properties. Although direct laser scribing of GO-based humidity sensor shows an outstanding response (|ΔZ|/|Z| up to 638,800%), a lack of stability and repeatability has been observed. GO/MWNT-based humidity sensors are more conductive than GO sensors and relatively less sensitive (|ΔZ|/|Z| = 163,000%). However, they are more stable in harsh humid conditions, repeatable, and reproducible even after several years of shelf-life. In addition, they have fast response/recovery times of 10.7 s and 9.3 s and an ultra-fast response time of 61 ms when abrupt humidification/dehumidification is applied by respiration. All carbon-based sensors' overall properties confirm the advantage of introducing the GO/MWNT hybrid and laser direct writing to produce stable structures and sensors.

Noble Metal Nanoparticles Decorated Boron Nitride Nanotubes for Efficient and Selective Low-Temperature Catalytic Reduction of Nitric Oxide with Carbon Monoxide

Parallel to CO₂ emission, NO_x emission has become one of the menacing problems that seek a simple, durable, and high-efficiency deNO_x catalyst. Herein, we demonstrated simple syntheses of platinum group metal nanoparticle-decorated f-BNNT (PGM = Pd, Pt, and Rh, and f-BNNT stands for -OH-functionalized boron nitride nanotubes) as a catalyst for efficient and selective reduction of NO by CO at low-temperature conditions. PGM/f-BNNT with a low amount of noble metal nanoparticles (0.7-0.8 wt %) presents very efficient catalytic activity for NO reduction as well as CO oxidation during their removal process. The removal efficiencies of NO and CO with Pd/f-BNNT, Pt/f-BNNT, and Rh/f-BNNT catalysts were investigated under various temperatures, flow rates, and reaction times, respectively. For most cases, NO catalytic reduction with CO reaction was >99% at a temperature as low as ∼200 °C. The catalyst robustness and efficiency were also verified by presenting almost 100% conversion of NO using a Rh/f-BNNT catalyst, which was aged under humid air at 600 and 700 °C for 24 h, respectively. The synergic effect of the catalytic efficacy of the well-dispersed noble metal nanoparticles and the excellent surface properties of BNNT are reasons for the high selectivity and catalytic property at a low temperature. On the basis of this investigation, we demonstrated that the noble metal nanoparticle-decorated f-BNNT catalysts are possible to save expensive PGM catalysts, such as Pt, Pd, and Rd, as much as 100 times while presenting similar or better catalytic performance for simultaneous NO and CO removals.

Synthesis of Boron-Doped Carbon Nanomaterial

A new method for the synthesis of boron-doped carbon nanomaterial (B-carbon nanomaterial) has been developed. First, graphene was synthesized using the template method. Magnesium oxide was used as the template that was dissolved with hydrochloric acid after the graphene deposition on its surface. The specific surface area of the synthesized graphene was equal to 1300 m²/g. The suggested method includes the graphene synthesis via the template method, followed by the deposition of an additional graphene layer doped with boron in an autoclave at 650 °C, using a mixture of phenylboronic acid, acetone, and ethanol. After this carbonization procedure, the mass of the graphene sample increased by 70%. The properties of B-carbon nanomaterial were studied using X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and adsorption-desorption techniques. The deposition of an additional graphene layer doped with boron led to an increase of the graphene layer thickness from 2-4 to 3-8 monolayers, and a decrease of the specific surface area from 1300 to 800 m²/g. The boron concentration in B-carbon nanomaterial determined by different physical methods was about 4 wt.%.

NO reduction with CO over a highly dispersed Mn/TiO2catalyst at low temperature: a combined experimental and theoretical study

A highly dispersed Mn/TiO₂catalyst, which has high efficiency for NO conversion with CO and almost completed N₂selectivity at a low-temperature range (350-550 K), was investigated using experimental and DFT theoretical calculation. The characterization results illustrated that the catalyst assembled with nanoparticles and the Mn doping into the TiO₂surface lattice led to the formation of Mn-O-Ti configuration, which enhanced the dispersion of Mn on the body of TiO₂. The DFT study mapped out the complete catalytic cycle, including reactants adsorption, oxygen vacancy generation, N₂O intermediates formation, N₂formation in Eley-Rideal (ER), Langmuir-Hinshelwood, and termolecular Eley-Rideal mechanisms. With thermodynamic and kinetic analysis combined with experimental results, the ER reaction process was considered to be the fundamental mechanism over the highly dispersed Mn/TiO₂catalyst. The calculation results indicated that N₂O was a significant intermediate. However, the rapid N₂O reduction process led to high N₂selectivity. The rate-limiting step was the deoxygenation step of NO-MnO_v/TiO₂from N-O bond scission. The active site Mn-O_vpair embedded in Mn/TiO₂was responsible not only for the formation of N-Mn/TiO₂in the ER-1 step but also for the N₂O deoxygenation process to make the final product N₂in the ER-2 step. The synergetic effect between Mn 3d electron and the oxygen vacancy of TiO₂were responsible for the catalytic activity of Mn/TiO₂.