Facile Microwave Synthesis of Hierarchical Porous Copper Oxide and Its Catalytic Activity and Kinetics for Carbon Monoxide Oxidation

The synthesis of copper oxide (CuO)-based nanomaterials has received a tremendous deal of interest in recent years. Particularly, the design and development of novel CuO structures with improved physical and chemical properties have attracted immense attention, especially for catalysis applications. We report on a rational, rapid, and surfactant-free microwave synthesis (MWS) of hierarchical porous copper oxide (HP-CuO) with a three-dimensional (3D) sponge-like topology using an MWS reactor. The activity of the microwave (MW)-synthesized HP-CuO catalysts for carbon monoxide (CO) oxidation was studied and compared to CuO prepared by the conventional heating method (CHM). Results showed that HP-CuO catalysts prepared by MWS for 10 and 30 min surpassed the CuO catalyst prepared by CHM, exhibiting T 80 of 98 and 115 °C, respectively, as compared to 185 °C of CuO prepared by CHM (T80 is the temperature corresponding to 80% CO conversion). In addition, the MW-synthesized HP-CuO catalysts outperformed the CHM-synthesized CuO, achieving a 100% CO conversion at 150 °C compared to 240 °C in the case of CuO prepared by CHM. Interestingly, the HP-CuO catalyst expressed workable CO conversion kinetics with a reaction rate of c.a.35 μmol s-1 g-1 at 150 °C and apparent activation energy (E a) of 82 kJ mol-1. The HP-CuO catalyst showed excellent cycling and long-term stabilities for CO oxidation up to 4 cycles and 72 h on the stream, respectively. The enhanced catalytic activity and stability of the HP-CuO catalyst appear to result from the unique topological and structural features of HP-CuO, which were revealed by SEM, XRD, Raman, BET, TGA, XPS, and TPR techniques.

Fast-response MEMS xylene gas sensor based on CuO/WO3 hierarchical structure

CuO/WO₃ hierarchical hollow microspheres, assembled from irregular two dimensional (2D) nanosheets, were prepared by ultrasonic-wet chemical etching and pyrolysis in this study. The sensing performance of Micro-Electro-Mechanical System (MEMS) xylene gas sensor based on CuO/WO₃ hierarchical structure were evaluated. It was found that the CuO/WO₃ MEMS sensors showed an enhanced gas sensing performance compared with pristine WO₃ sensor. The CuO/WO₃-3 (the mass ratio of CuO to WO₃ is 3%) sensor exhibited faster response-recover speed and the highest response value to xylene. Moreover, the CuO/WO₃-3 sensor possessed higher selectivity and long-term stability. The good sensing properties can be attributed to the unique three dimensional (3D) hierarchical structure and p-n heterojunction of CuO-WO₃. Considering the above advantages, the CuO/WO₃-3 sensor has a great potential for the rapid detection and monitoring of xylene.

Rapid reduction of real-time industry effluent using novel CuO/MIL composite

In this study, a series of novel metal organic framework based composite materials was synthesized using a facile combustion synthesis method. The synthesized materials were characterized using standard analytical techniques for crystallite size, surface functional groups, surface area, porosity, optical properties, and particle size. The increase in the amount of CuO in the composite material resulted decrease in surface area and pore volume. The band-gap energy of the synthesized composites reduced with increase in the amount of CuO. Among the composite, 0.9 CuO:0.1 MIL displayed least emission intensity indicating lower electron-hole recombination and thereby superior charge separation of the material. The increase in the amount of CuO NPs in the composite resulted in increase in the average particle size and decrease in the zeta potential. As an application, the NaBH₄-mediated reduction of Methyl orange dye was studied using the synthesized materials. The increased amount of CuO in the composite resulted in the higher activity of the material. Highest activity was observed with the composite containing 9:1 ratio of CuO and MIL, and this material was further used to investigate the reduction of methylene blue, Rhodamine B, 4-nitrophenol, 2-nitrophenol, and 2, 4-dichlorophenol. The material exhibited excellent activity for all the selected organic pollutants. Finally, the composite containing 9:1 ratio of CuO and MIL was employed for the reduction of a real-time industry effluent and the observed results were encouraging. The reusability aspect of the synthesized material was investigated. Based on the LC-MS analysis, a possible reduction mechanism is proposed.

Magnetic nanomaterials with unique nanozymes-like characteristics for colorimetric sensors: A review

Colorimetric sensors for the rapid detection of numerous analytes have been widely applied in many fields such as biomedicine, food industry and environmental science due to their highly sensitive and selective response, easy operation and visual identification by naked eyes. In this review, the recent progress of the colorimetric sensors based on the magnetic nanomaterials with unique nanozymes-like catalytic activity (magnetic nanozyme) and their colorimetric sensing applications are presented. Emerging magnetic nanozyme-based colorimetric sensors, such as metal oxide/sulfides-based, metal-based, carbon-based, and aptamer-conjugated magnetic nanomaterials, offer many desirable features for target analytes detection. And due to the unique nanoscale physical-chemical properties, magnetic nanozymes have been used to mimic the catalytic activity of natural enzymes such as peroxidases, oxidases and catalases. This review also highlights the catalytic mechanisms of enzyme-like reactions, and promising colorimetric sensing system for the detection of chemical compounds like H₂O₂, pesticide, ascorbic acid, dopamine, tetracyclines, perfluorooctane sulfonate, phenolic compounds, heavy metal ion and sulfite have been deeply discussed. In addition, the remaining challenges and future directions in utilizing magnetic nanozyme for colorimetric sensors are addressed.

Effective and viable photocatalytic degradation of rhodamine B dye in aqueous media using CuO/PVA nanocomposites

Graphical representation of CuO/PVA nanocomposite synthesis to degrade rhodamine B dye in aqueous medium

Sonochemical synthesis and structural characterization of an organic-inorganic nanohybrid based on a copper-dithiocarbamate complex and PMo12O403- polyanion as a novel sonocatalyst

A new organic-inorganic nanohybrid compound, ([Cu{(HOCH₂CH₂)₂NCS₂}₂]₃[PMo₁₂O₄₀] (1)), has been prepared by sonochemical technique using copper(II) dithiocarbamate complex and a Keggin-type polyoxomolybdate in this research. FT-IR, XRD, FE-SEM, TEM, EDX, UV-Vis, TGA, BET, and single crystal XRD analyses were applied to describe the properties of the composition of the nanohybrid. Compound (1) is composed of [PMo₁₂O₄₀]^3- building blocks and [Cu{(HOCH₂CH₂)₂NCS₂}₂]¹⁺ cationic moieties, and electrostatic forces and substantial hydrogen-bonding interactions were applied to pack them; and consequently, a three dimensional supramolecular framework was made based on single-crystal X-ray diffraction patterns. FE-SEM and TEM images approved the morphology of the nanohybrid sample to be extremely penetrable. Very good sonocatalytic performance is shown by this supramolecular nanohybrid in the degradation of Rhodamine B (RhB), which is a cationic organic dye. The results showed complete degradation of cationic RhB (25 mg/L) within 70 min with the rate constant of 0.039min^-1 in the presence of nanohybrid (1) and H₂O₂ (4 mmol/L). Also, sonocatalytic activity of the nanohybrid (1) was higher than H₃PMo₁₂O₄₀, showing that the combining Cu(DEDTC)₂ complex with H₃PMo₁₂O₄₀ could be an excellent choice to improve its sonocatalytic activity. The used nanohybrid (1) can be recycled after easily removing from the reaction media by centrifuging, and there was no considerable loss of catalytic activity and retention of the structure.

Iron oxide Permeated Mesoporous rice-husk nanobiochar (IPMN) mediated removal of dissolved arsenic (As): Chemometric modelling and adsorption dynamics

Adsorption based technologies are most widely used to mitigate the global predominance of heavy-metal groundwater contaminants like Arsenic (As), owing to their high efficiency and economic operation. The current study involves the optimization of Iron oxide Permeated Mesoporous rice-husk nanobiochars (IPMN) for As removal, which were synthesized through a chemically amended pyrolytic approach. The IPMN variants were screened based on preliminary OVAT (one-variable-at-a-time) studies for As removal. Chemometric investigations employing a central composite design matrix of Response surface methodology was further used to understand the influence of the process parameters on the adsorption of As on the most efficient IPMN variant. A Multi-Layered-Perceptron based artificial neural network was further used to confirm the veracity of the experimental and predictive conditions, to derive the optimal condition for the best adsorption efficiency. In addition, the dynamics of As adsorption by the optimal IPMN variant was modelled using pseudo-first-order (Lagergren) and pseudo-second-order (Ho) rate kinetic equations followed by isotherm studies using non-linear regression of Langmuir, Freundlich and Sips adsorption isotherms. The IPMNs have an appreciably higher uptake capacity (>90%) for dissolved As, as compared to the native milled rice husk (∼20%), alongside a substantial recyclability, thereby establishing their potential as a highly efficient, economical and sustainable nanobiochar for As removal.

Synthesis, Characterization and Anti-Microbial Activity of Oxalate-Assisted CO3O4 Nanoparticles Derived from Homogeneous Co-Precipitation Method

Nano-sized cobalt oxide particles exhibit unique and fascinating physical, chemical and anti-microbial activity owing to their large surface to volume ratio. The study of metal oxide nanoparticles interaction with pathogenic microorganisms is great importance for various biomedical applications. The main purpose of this work is to study the anti-bacterial and anti-fungal behavior of cobalt oxide (CO3O4) nanoparticles against gram-positive and gram-negative bacterial strains and different fungi. The structure and morphology of CO3O4 nanoparticles were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and UV-Visible Spectroscopy, respectively. The CO3O4 nanoparticles showed a significant anti-bacterial activity against two gram-positive bacteria, Staphylococcusaureus (G[Formula: see text]), Streptococcus mutans (G[Formula: see text]), and two gram-negative bacteria, Klebsilla pneumonia (G[Formula: see text]), E. coli (G[Formula: see text]), and it shows a good anti-fungal activity against the two different fungal i.e., Aspergillus flavus (F) and Aspergillus niger (F), at different solvents. It was noted that synthesized CO3O4 nanoparticles exhibited the solvent-dependent anti-bacterial activity against all tested bacterial strains. CO3O4 NPs could be employed effectively for anti-microbial applications.

Functional nanomaterials with unique enzyme-like characteristics for sensing applications

We highlight the recent developments in functional nanomaterials with unique enzyme-like characteristics for sensing applications.

Greener Biogenic Approach for the Synthesis of Palladium Nanoparticles Using Papaya Peel: An Eco-Friendly Catalyst for C-C Coupling Reaction

The development of a green and sustainable synthetic methodology still remains a challenge across the globe. Encouraging the prevailing challenge, herein, we have synthesized Pd nanoparticles (Pd NPs) in a green and environmentally viable route, using the extract of waste papaya peel without the assistance of any reducing agents, high-temperature calcination, and reduction procedures. The biomolecules present in the waste papaya peel extract reduced Pd(II) to nanosize Pd(0) in a one-pot green and sustainable process. As a catalyst, the new Pd NPs offer a simple and efficient methodology in direct Suzuki-Miyaura and Sonogashira coupling with excellent yields under mild reaction conditions.

Ultrafast NH3 Sensing Properties of WO3@CoWO4 Heterojunction Nanofibres at Room Temperature

Highly selective detection, quick response times (<5 s), and superior response (|Rn – Ra|/Ra = 1.17) to NH3 gas, particularly at room temperature (RT), are still enormous challenges in gas sensor applications. In this paper, a rational design and facile synthesis for a NH3 sensor have been proposed. Massage ball-like WO3@CoWO4 (Co-W) nanofibres (NFs) were prepared by a facile one-step synthesis utilising an electrospinning approach, followed by appropriate calcination. A Co-W NF sensor with a Co-to-W atomic ratio of 3 : 10 (Co-W-3), which consisted of nano-sized WO3 protrusions (10–15 nm) on submicrometre-sized single crystal CoWO4 particles (100–150 nm) exhibited excellent gas-sensing properties at RT due to the single crystal CoWO4–CoWO4 homojunction structure and distinct massage ball-like WO3–CoWO4 heterojunction. The approach developed in this work will be important for the low-cost and large-scale production of a Co-W-3 ultrafast sensing material with highly promising applications in gas sensors.

Dissimilitude behaviour of Cu2O nano-octahedra and nano-cubes towards photo- and electrocatalytic activities

Nano-octahedra are photocatalytically active for the removal of organic contaminants of water, whereas nanocubes are electrocatalytically active towards oxygen reduction reactions.

1,3-Disulfoimidazolium chloronickellate immobilized HZSM-5 framework as visible-light-induced heterogeneous photocatalyst for advanced oxidation process

Hybrid photocatalysts of [Dsim]₂[NiCl₄]/HZSM-5 were prepared by wet impregnation and their application is demonstrated as feasible heterogeneous photocatalysts for oxidative degradation of methylene blue under sunlight.

Biomimetic synthesis of urchin-like CuO/ZnO nanocomposites with excellent photocatalytic activity

Highly photocatalytic urchin-like CuO/ZnO nanocomposites were synthesized using glutamine as a growth regulator by a hydrothermal process with subsequent calcination.

Recent advances in nanomaterials for water protection and monitoring

Nanomaterials (NMs) for adsorption, catalysis, separation, and disinfection are scrutinized. NMs-based sensor technologies and environmental transformations of NMs are highlighted.

Shape-controlled synthesis of Sn-doped CuO nanoparticles for catalytic degradation of Rhodamine B

The uniform Sn-doped CuO nanoparticles were synthesized by a simple solution method at a low temperature. The prepared samples were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy techniques (HRSEM, HRTEM, SAED, STEM and EDS elemental mapping), atomic force microscopy (AFM), UV/Vis spectroscopy, nitrogen physisorption (BET) and by evaluation of the catalytic activity on the degradation of Rhodamine B. The tin doping had a considerable influence on the morphology of CuO. The gradual narrowing of the particles morphology in the crystallographic [010] direction was observed with increasing the dopant concentration. The plate-like, rectangularsquare and rod-like CuO nanoparticles were obtained. The mechanism of a crystal growth of CuO associated with doping is proposed. The tin doping also affected the structural and optical properties of CuO. Increasing the amount of a dopant led to a red-shift of a band gap from 1.33 to 1.18eV. The incorporation of tin into the structure of copper oxide was confirmed by XRD and distribution of tin mapped by EDS analysis. The good catalytic properties of the as-prepared doped material were demonstrated by the enhanced catalytic removal of Rhodamine B in the presence of H2O2. The undoped CuO nanosheets reached only 24% efficiency in the removal of Rhodamine B within two hours. The best result exhibited CuO_050Sn sample containing 4at.% of tin and the degradation of Rhodamine B reached 99% within the same time. We have demonstrated a simple, scalable process for the preparation of catalytically very active Sn-doped CuO nanoparticles with varying properties.

Facile and Scale Up Synthesis of Red Phosphorus-Graphitic Carbon Nitride Heterostructures for Energy and Environment Applications

The development of heterostructured materials for efficient solar energy conversion and energy storage devices are essential for practical applications. In this study, a simple and relatively inexpensive method was used to improve the visible light-driven photocatalytic activity and electrochemical supercapacitor behavior of the graphitic carbon nitride (g-C₃N₄) by elemental red phosphorus (RPh). The as-prepared RPh-g-C₃N₄ was characterized in detail using a range of spectroscopic techniques to understand the structure, morphology, chemical interaction, and chemical state of the materials. The visible light-driven photocatalytic activity and supercapacitive electrode performance were assessed by the photodegradation of model colored, non-colored organic pollutants, and electrochemical half-cell measurements, respectively. The RPh-g-C₃N₄ heterostructure with 30 weight percent of RPh exhibited remarkably high photocatalytic activity for the degradation of pollutants compared to the bare constituent materials, which was further confirmed by the photoelectrochemical study under similar visible photoirradiation conditions. The RPh-g-C₃N₄ heterostructure supercapacitor electrode displayed a high capacitance of 465 F/g and excellent cyclic stability with capacitance retention of 90% after 1000 cycles at a current of 10 A/g. The superior performance was attributed mainly to the narrow band gap, high surface area, capacitive nature of RPh, and nitrogen-rich skeleton of g-C₃N₄.

Influence of CuO morphology on the enhanced catalytic degradation of methylene blue and methyl orange

The sheet-like CuO shows enhanced catalytic activity, compared to polycrystalline CuO for the catalytic degradation of methylene blue and methyl orange.