Fabrication of Bi2MoO6 nanoplates hybridized with g-C3N4 nanosheets as highly efficient visible light responsive heterojunction photocatalysts for Rhodamine B degradation

The Bi₂MoO₆/g-C₃N₄ heterojunction photocatalysts have been successfully fabricated using a simple liquid chemisorptions and thermal post-treatment. These nanostructured Bi₂MoO₆/g-C₃N₄ composites were extensively characterized by X-ray diffraction(XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR),UV–vis diffuse reflectance spectra (UV–vis DRS) and Photoluminescence (PL). The photocatalytic results show that 20 wt% Bi₂MoO₆/g-C₃N₄ sample exhibits efficient visible light activity and excellent photo-stability. The kinetic constant of RhB degradation over 20 wt% Bi₂MoO₆/g-C₃N₄ is about 5 and 2.5 times higher than that over pure Bi₂MoO₆ and g-C₃N₄ nanosheets, respectively. The enhanced photocatalytic performance is attributed to the construction of heterogeneous interface to promote photo-induced charge carrier pairs separation.     

Comparison of the photocatalytic degradation of trypan blue by undoped and silver-doped zinc oxide nanoparticles

Zinc oxide (ZnO) and silver doped zinc oxide (ZnO:Ag) nanoparticles were prepared using nitrates of zinc and silver as oxidizers and ethylene diaminetetraacetic acid (EDTA) as a fuel via low-temperature combustion synthesis (LCS) at 500 °C. X-ray diffraction (XRD) pattern indicates the presence of silver in the hexagonal wurtzite structure of ZnO. Fourier transform infrared (FTIR) spectrum indicates the presence of Ag–Zn–O stretching vibration at 510 cm⁻¹. Transmission electron microscopy (TEM) images shows that the average particle size of ZnO and ZnO:Ag nanoparticles were found to be 58 nm and 52 nm, respectively. X-ray photoelectron spectroscopy (XPS) data clearly indicates the presence of Ag in ZnO crystal lattice. The above characterization techniques indicate that the incorporation of silver affects the structural and optical properties of ZnO nanoparticles. ZnO:Ag nanoparticles exhibited 3% higher photocatalytic efficiency than pure ZnO nanoparticles. ZnO:Ag nanoparticles show better photocatalytic activity for the degradation of trypan blue (TrB) compared to undoped ZnO nanoparticles.     

The role of oxidizing agents in the structural and morphological properties of CeO2 nanoparticles

Cerium oxide (CeO₂) nanoparticles with good crystallinity and smooth surface are prepared by chemical precipitation method with different bases (NH₃, NaOH and KOH) using cerium nitrate as a source material. The effect of precipitating agents on the growth of cerium oxide nanoparticles are investigated by Photoluminescence (PL), X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FTIR), thermo gravimetric–differential thermal analysis (TG-DTA), Scanning electron microscope (SEM), Transmission electron microscope (TEM), and X-ray Photoelectron Spectroscopy (XPS). Cubic fluorite crystallites are detected by XRD pattern with preferred orientation along (1 1 1) direction. PL spectra revealed the presence of a strong and broad emission band at425 nm due to the blue shift in the visible region. The broad band below 700 cm⁻¹ is due to the envelope of the phonon band of metal oxide (Ce–O) network as revealed by the IR spectra. The TG-DTA curves revealed that the total weight loss of the samples is 19.67% when the samples are heated upto 800 °C. SEM images exhibits weakly agglomerated spheroid crystallites are obtained with the typical size in the range 10–50 nm. TEM images display that the particles are nearly spherical and square in shape with diameter 8–12 nm. XPS spectrum confirms the existence of Ce⁴⁺ oxidation states in CeO₂samples.     

Cobalt-doped cerium oxide nanoparticles: Enhanced photocatalytic activity under UV and visible light irradiation

CeO₂ nanoparticles (NPs) were synthesized by coprecipitation using cerium(III) nitrate hexahydrate as the precursor and ethanol as the solvent. Different concentration of cobalt-doped cerium oxide NPs (3mol % and 6 mol %) were prepared by adding various concentrations of cobalt chloride to cerium nitrate. The as-synthesized NPs were characterized through X-ray diffraction (XRD) measurements, ultraviolet (UV)–visible spectroscopy, Photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). XRD results reveal that the as-prepared CeO₂ NPs had a face-centered cubic structure with crystallite size in the range of 5–8 nm. TEM analyses showed that the CeO₂ NPs and Co-doped CeO₂ NPs had a homogenous size distribution (sizes were within 5–12 nm). Band-edge absorption of CeO₂ NPs redshifted upon increasing the Co concentration as compared to undoped CeO₂ NPs. PL spectra reveal a peak shift of CeO₂ emission upon cobalt doping, which were due to an increase in oxygen defects localized between the Ce4f and O2p energy levels (i.e., via formation of Ce³⁺ states). Photocatalytic degradation of methylene blue in aqueous solution under UV and visible (sunlight) irradiation in the presence of pure CeO₂ NPs and of Co-doped CeO₂ NPs was investigated. The efficiency of photocatalytic degradation of CeO₂ NPs increased with the Co concentration both under UV irradiation and under visible light. Co-doped CeO₂ NPs (6 mol%) showed degradation efficiencies of 98% and 89% at 420 min of exposure to UV irradiation and to visible light, respectively.     

Effects of silver substrates on the visible light photocatalytic activities of copper-doped titanium dioxide thin films

Novel copper-doped titanium dioxide (Cu-doped TiO₂) thin films on silver (Ag) substrates with different thicknesses were prepared by sol–gel and magnetron sputtering methods. The influences of the Ag substrate thickness on the morphology and performance of the films were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, UV–visible spectroscopy, and photocatalytic degradation testing with methylene blue aqueous solution under visible light irradiation. The results indicated that Ag substrates with an optimal thickness of 30 nm not only maintained the tiny nanocrystals but also greatly improved dispersion of the nanoparticles on the surface of the nanofilms. Furthermore, during the calcination process, part of the Ag atoms diffused from the substrates into the Cu–TiO₂ films and substituted for the Cu ions to form Ag–TiO₂. A proper Ag substrate thickness (30 nm) greatly improved the photocatalytic properties of TiO₂ with photocatalytic efficiency, reaching approximately 86% in 300 minutes under visible light irradiation. However, an excess of Ag substrate not only led to the Cu ion separating out in the form of CuO but also resulted in the agglomeration of TiO₂ particles on the surface, which were detrimental to photocatalytic activities.     

Nitrogen dioxide (NO2) sensing performance of p-polypyrrole/n-tungsten oxide hybrid nanocomposites at room temperature

Polypyrrole (PPy)–tungsten oxide (WO₃) hybrid nanocomposite have been successfully synthesized using different weight percentages of tungsten oxide (10–50%) dispersed in polypyrrole matrix by solid state synthesis method. The sensor based on PPy–WO₃ was fabricated on glass substrate using cost effective spin coating method for detection of NO₂ gas in the low concentration range of 5–100 ppm. The gas sensing performance of hybrid material was studied and compared with those of pure PPy and WO₃. It was found that PPy–WO₃ hybrid nanocomposite sensor can complement the drawbacks of pure PPy and WO₃. The structure, morphology and surface composition properties of PPy–WO₃ hybrid nanocomposites were employed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The presence of WO₃ in PPy matrix and their interaction was confirmed using XRD, FTIR techniques. The porous surface morphology was observed with addition of WO₃ in PPy matrix which is useful morphology for gas sensing applications. TEM image of PPy–WO₃ hybrid nanocomposites shows the average diameter of 80–90 nm. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of nanocomposites. It was observed that 50% WO₃ loaded PPy sensor operating at room temperature exhibit maximum response of 61% towards 100 ppm of NO₂ gas and able to detect low concentration of 5 ppm NO₂ gas with reasonable response of 8%. The hybrid sensor shows better sensitivity, selectivity, reproducibility and stability compared to pure PPy and WO₃. The proposed sensing mechanism of hybrid nanocomposite in presence of air and NO₂ atmosphere was discussed with the help of energy band diagram. Furthermore, the interaction of NO₂ gas with PPy–WO₃ hybrid nanocomposites sensor was studied by cole–cole plot using impedance spectroscopy.     

Facile synthesis and enhanced trimethylamine sensing performances of W-doped MoO3 nanobelts

The pure and W-doped MoO₃ nanobelts were prepared via a facile one-step hydrothermal method. The morphology and microstructure of the developed nanobelts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The characterization results showed that as-prepared samples are uniform nanobelts with a mean length of 20 µm and width range of 100–200 nm, and W element was distributed uniformly in MoO₃ nanobelts. The comparison between pure and doped samples was carried out to reveal the superior gas sensing performance of W-doped MoO₃ nanobelts. The results of sensing properties indicate that the sensors based on W-doped MoO₃ nanobelts exhibit high response, good selectivity, and long term stability characteristics towards trimethylamine (TMA) gas, which are promising for trimethylamine sensors used to monitor air-quality and environmental.     

Visible light photocatalytic activity of reduced graphene oxide synergistically enhanced by successive inclusion of γ-Fe2O3, TiO2, and Ag nanoparticles

Novel magnetic nanocomposites are synthesized by loading reduced graphene oxide (r-GO) with three brands of nanoparticles consisting of titanium dioxide (TiO₂), gamma-iron(III) oxide (γ-Fe₂O₃), and silver (Ag) with varying amounts. The resulting Ag/TiO₂/γ-Fe₂O₃@r-GO demonstrates synergistically enhanced visible light photocatalytic activity, on degradation of wastewater׳s toxic crystal violet (CV). Specifically, it exhibits higher photoactivity than those of neat graphene oxide (GO), TiO₂@GO, γ-Fe₂O₃@GO, and TiO₂/γ-Fe₂O₃@GO, possibly because of effective separation of photogenerated carriers via strongly coupled Ag/γ-Fe₂O₃@r-GO cocatalyst and the enrichment of organic molecules on the graphene nanosheets. A higher photocatalytic efficiency is observed when 11.5 wt% Ag nanoparticles are incorporated in TiO₂/γ-Fe₂O₃@GO. After 3 successive cycles, the latter nanocomposite maintains 97% removal efficiency with excellent stability and easy recovery. Considering its facile preparation and high photocatalytic activity, it is hoped that this photocatalyst will find its application in various fields such as air purification and wastewater treatment. The structure and properties of Ag/TiO₂/γ-Fe₂O₃@r-GO are characterized by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), ultraviolet–visible spectrometry (UV–vis) and Raman spectroscopy techniques.     

Fabrication of heterojunction SnO2/BiVO4 composites having enhanced visible light photocatalystic activity

SnO₂/BiVO₄ heterojunction composite photocatalysts with various mole ratios have been prepared via a simple hydrothermal method. The structure, composition and optical properties of the SnO₂/BiVO₄ composites were determined by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface analysis, X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). Photocatalytic activities of the composites were evaluated by studying the degradation of methylene blue (MB) solutions under simulated visible light irradiation (500 W halogen tungsten lamp). The 3:7 mol ratio SnO₂/BiVO₄ composite exhibited the highest photocatalytic performance, leading to 72% decompositon of MB within 120 min of irradiation.     

Rapid microwave-assisted synthesis of silver decorated-reduced graphene oxide nanoparticles with enhanced photocatalytic activity under visible light

A facile, fast, and scalable microwave irradiation (MWI) method for the synthesis of Ag nanoparticles (Ag NPs) dispersed on graphene sheets has been developed. The reduction of graphene oxide takes place in ethanol solution within 2 min of MWI without any additional reducing agent or complicated treatment. The morphology and microstructure of the as-prepared hybrid were characterized by Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) images. The result showed the Ag NPs with an average size of 5–10 nm decorated on the rGO sheets. X-ray powder diffraction (XRD) determined that the crystallographic structure of Ag is face-centered cubic and there was a strong interaction between Ag NPs and rGO sheets. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that GO had been reduced to rGO in our hybrid. Moreover, visible photocatalytic activity of the rGO–Ag nanocomposites was tested using Rhodamine B (RhB) as the model contaminant. This result indicates that rGO–Ag nanocomposites display distinctly enhanced photocatalytic activities. The investigation gave a promise to the development of original yet highly efficient graphene-based photocatalysts that utilize visible light as an energy source.     

Preparation and photocatalytic activity of Ag/bamboo-type TiO2 nanotube composite electrodes for methylene blue degradation

Photocatalysis phenomena in TiO₂ have been intensively investigated for its potential application in environmental remediation. The present work reports improved photocatalytic degradation of methylene blue dye in aqueous solution by using bamboo-type TiO₂ nanotubes deposited with Ag nanoparticles via electrochemical deposition. The photocatalytic processes are performed on Ag-modified TiO₂ bamboo-type nanotube arrays, Ag-modified smooth-walled nanotube arrays, and bare smooth-walled nanotube arrays. Both Ag-modified bamboo-type and smooth-walled nanotube arrays show improved photocatalytic degradation efficiencies (64.4% and 52.6%) compared to smooth-walled TiO₂ nanotubes of the same length (44.4%), due to the enhanced electron–hole seperation and more surface area provided by bamboo ridges. The photocatalytic activity and kinetic behavior of Ag-modified bamboo-type nanotube arrays are also optmized by tuning pulse deposition time of Ag nanoparticles. Bamboo-type nanotubes deposited with Ag nanoparticles via pulse deposition time of 0.5 s/1.5 s shows the highest methylene blue degradation efficiency of 78.5%, which represents 21.9% and 76.8% enhancement of efficiency compared to those of bare bamboo-type and smooth-walled nanotubes, respectively, indicating that a proper amount of Ag nanoparticles on TiO₂ can maximize the photocatalytic processes. In addition, overly long pulse deposition time will not further increase photocatalytic activity due to agglomeration of Ag paticles. For example, when the pulse deposition time is increased to 2 s/6 s, Ag-modified bamboo-type nanotube array exhibits a lower photocatalytic degradation efficiency of 62.9%.     

Influence of propyl alcohol addition during processing of molybdenum trioxide powders: Observation of novel dual-wavelength excitation photochromism

The novel dual-wavelength excitation photochromic molybdenum trioxide (MoO₃) powders are fabricated successfully via the hydrothermal method by the addition of propyl alcohol. The samples were fully characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis), and colorimetry. The characteristic spectrum of XRD demonstrates that the as-obtained products are highly pure. The results show that the flowerlike MoO₃ sample with the inducer of propyl alcohol has better photochromic properties, which was analyzed by colorimetry. It is shown that both of the samples exhibit a strong adsorption band between 250 and 400 nm in the UV range. Moreover, the UV–vis spectra shows that MoO₃ synthesized with added propyl alcohol absorbs light not only between 250 and 400 nm but also displays an additional band between 500 and 800 nm, demonstrating novel dual-wavelength excitation photochromic properties.     

Synthesis and characterization of cerium–silver co-doped zinc oxide as a novel sunlight-driven photocatalyst for effective degradation of Reactive Red 120 dye

Cerium–silver (Ce–Ag) co-doped ZnO was synthesized by precipitation–decomposition and tested for the degradation of Reactive Red 120 dye under natural sun light irradiation. Three weight percent Ce co-doped Ag–ZnO was found to be most efficient. Hence, this catalyst (3 wt% Ce–Ag–ZnO) has been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). XRD and XPS reveal the presence of metallic Ag and tetravalent Ce. Ag and Ce shift the absorption of ZnO to entire visible region. It was found that the Ce–Ag–ZnO exhibited higher degradation efficiency when compared to Ag-ZnO, Ce–ZnO, prepared ZnO, Commercial ZnO, TiO₂, and TiO₂-P25 at neutral pH (=7). Quantum yields of all processes were calculated and compared. Higher activity of Ce–Ag–ZnO in natural sunlight may be due to higher visible light absorption of Ce–Ag–ZnO when compared to native ZnO. The influences of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization of RR 120 have been analyzed. The mineralization of RR 120 dye was confirmed by chemical oxygen demand (COD) measurements. A dual mechanism has been proposed for efficient degradation of RR 120 dye by Ce–Ag–ZnO under solar light at neutral pH. This photocatalyst was found to be reusable up to four runs.     

Photocatalytic degradation of methyl orange and gas-sensing performance of nanosized ZnO

ZnO nanoparticles were synthesized by calcining composites of zinc nitrate and poly(vinyl pyrrolidone) (PVP, molecular weight 30 000) at a mass ratio of 1:2 at 500 °C for 2 h. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were used to characterize the as-synthesized ZnO nanoparticles. The particles ranged in size from 30 to 50 nm. Infrared spectra of PVP and the PVP+Zn(NO₃)₂·6H₂O composite revealed coordination between the carbonyl (C=O) of PVP and Zn²⁺ of zinc nitrate, which led to a uniform nanoparticle morphology. The gas-sensing properties and photocatalytic performance of the final product were systematically investigated. The results show that the ZnO nanoparticles exhibit both a high response for ethanol detection and excellent photocatalytic activity for degradation of methyl orange under UV irradiation for 30 min.     

A unique and facile preparation of lanthanum ferrite nanoparticles in emulsion nanoreactors: Morphology,structure, and efficient photocatalysis

Lanthanum ferrite nanoparticles (LaFeO₃ NPs) with light absorption properties in the visible region were successfully synthesized in CTAB (cetyltrimethyl ammonium bromide) emulsion nanoreactors at room temperature. The morphology, size, structure, elemental composition, and optical properties of these particles were characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), and ultraviolet–visible absorption (UV–Vis) spectroscopy. Through this method, highly crystalline and well-dispersed perovskite LaFeO₃ NPs with a phase-pure were successfully obtained. The band gap energy (E_g) of the LaFeO₃ NPs was calculated by UV-Vis spectroscopy at the wavelength of about 517 nm and is observed to have a value of 2.43 eV. The photocatalytic activities of LaFeO₃ NPs were evaluated by the degradation of toluidine blue O (TBO, used as a probe) dye under visible light irradiation, which exhibits a high photocatalytic TBO dye degradation activity as compared to the commercial P-25 titania powder. This phenomenon is due to smaller band gap energy and changing from bulk to nanostructure. The higher photocatalytic activity is also related to the photo absorption.     

Structural and optical properties of CdS/PEO nanocomposite solid films

In this paper solution mixing and casting of Cd(NO₃)₂·4H₂O and poly(ethylene oxide) (PEO) at different molar ratios (1:100–1:600) followed by hydrogen sulfide treatment were employed to fabricate solid films of cadmium sulfide (CdS)/polyethylene oxide (PEO) nanocomposites. The nanocomposites were found to exhibit uniform distribution of CdS nanoparticles in the polymer matrix without any additional capping agent. Systematic investigations on the role of PEO on the optical properties of CdS are presented. The optical properties of the composites examined by UV–vis absorption spectroscopy show that the band gap of CdS nanoparticles increases from 2.45 eV to 2.54 eV with decreasing concentration of CdS in PEO films. X-ray diffraction pattern shows the broadening in shape of the PEO peaks which is induced by the CdS particles in PEO matrix. The CdS particle sizes ranging from 10 to 20 nm are clearly seen in a transmission electron microscope (TEM). The X-ray photoelectron spectroscopic studies (XPS) also confirm the presence of CdS in PEO. Fourier transform infrared spectroscopy studies using attenuated total reflectance (FTIR-ATR) indicate the influence of Cd²⁺ ion on C–O–C stretching in PEO and confirm the presence of CdS nanoparticles within PEO. Photoluminescence spectroscopy (PL) shows the broad emission due to the presence of surface trapped carrier states.     

Visible-light-responsive γ-Fe2O3/PMMA/S-TiO2 core/shell nanocomposite: Preparation,characterization and photocatalytic activity

Organic-inorganic composite materials have demonstrated many potential applications in environmental field. This paper presented a facile preparation method for γ-Fe₂O₃/PMMA/S-TiO₂ nanocomposite with core-shell structure and its application in degradation of phenanthrene under visible light irradiation. Firstly, γ-Fe₂O₃/PMMA nanoparticles were synthesized by the modified-suspension-polymerization method. Then γ-Fe₂O₃/PMMA/S-TiO₂ core-shell nanocomposites were prepared by adding as-synthesized γ-Fe₂O₃/PMMA nanoparticles into the sol solution formed by sol-gel method using tetrabutyltitanate as Ti source and thiourea as sulfur source. The characterization result of the obtained products by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy indicated that the layer of sulfur doped titania was successfully coated onto the surface of γ-Fe₂O₃/PMMA nanoparticles. Thermogravimetry (TG) analysis presented that the layer of sulfur doped TiO₂ could efficiently reduce the decomposition of polymethylmethacrylate (PMMA) even at higher temperature up to 500 °C. UV–vis diffuse reflectance spectroscopy showed that γ-Fe₂O₃/PMMA/S-TiO₂ nanocomposite clearly exhibits the red-shift of the absorption edge compared with γ-Fe₂O₃/PMMA/TiO_2. The photocatalytic activity evaluation showed that the γ-Fe₂O₃/PMMA/S-TiO₂ nanocomposite exhibited the best photocatalytic activity for degradation of phenanthrene under the conditions of 0.8 mol% of sulfur doping, calcination temperature at 300 °C and the addition concentration of 1.0 g/L. Moreover, the nanocomposites have good recovery ability by the recovery experiment.     

Photocatalytic and antimicrobial activity of NiWO4 nanoparticles stabilized by the plant extract

In recent years, biosynthesis of nanoparticles using plant extract has attracted great attention owing to its cost effective, non-toxic, eco-friendly and as an alternative approach to physical and chemical methods. Nickel tungstate (NiWO₄) nanoparticles were synthesised via the aqueous leaf extract of Azadirachta indica plant. The prepared nanoparticles were characterized using UV–visible diffuse reflectance spectroscopy (UV–vis-DRS), fourier transform infra-red spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) techniques. SEM results showed that plant extract modified NiWO₄ (PNT) was composed of tiny sphere in shape. XRD results revealed that the average crystallite size of PNT was smaller (12.12 nm) when compared to the bare NiWO₄ (NT) prepared using precipitation method (31.11 nm). The photocatalytic activity of NiWO₄ nanoparticles were investigated using methylene blue (MB) as a model organic pollutant under visible light irradiation. PNT showed high efficiency for the degradation of MB compared to NT. The effect of operation parameters such as initial dye concentration, pH and catalyst concentration has been investigated in detail. PNT was subjected to antimicrobial studies and significant results were obtained.     

Studies on structural,morphological, magnetic and optical properties of chromium sesquioxide (Cr2O3) nanoparticles: Synthesized via facile solvothermal process by different solvents

Chromium sesquioxide (Cr₂O₃) nanoparticles have been successfully synthesized via the facile solvothermal process, by using CrO₃ in different solvents. The as-synthesized nanoparticle sizes are calculated and confirmed to be 25–45 nm, by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The functional groups of the samples were tested by the Fourier transform infrared (FTIR) spectroscopy. Fine and spherical-like morphologies and compositional elements of the products were observed by the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. A weak ferromagnetic (WFM) property was observed for sample by the vibrating sample magnetometer (VSM). The observed band gap values (E_g=4.33–3.54 eV) higher than that of bulk Cr₂O₃ (~3.4 eV) indicated that the particles had been successfully synthesized in the nano region, and measured by ultra-violet visible (UV–vis) absorption spectroscopy. The broad visible emission at ~399 nm, in the photoluminescence spectroscopy revealed the high purity and perfect crystallinity of the samples.     

Biosynthesis of zinc oxide nanoparticles from Azadirachta indica for antibacterial and photocatalytic applications

Green synthesis of nanoparticles is gaining importance and has been suggested as possible alternatives to chemical and physical methods. The present work reports low-cost, green synthesis of zinc oxide (ZnO) nanoparticles using 25% (w/v) of Azadirachta indica (Neem) leaf extract. The biosynthesized nanoparticles were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). The synthesized ZnO nanoparticles were pure, predominantly spherical in shape with size ranging from 9.6 to 25.5 nm. In the present work, the biosynthesized ZnO nanoparticles have been used for antibacterial and photocatalytic applications. The antibacterial activity of characterized samples was determined using different concentrations of biosynthesized ZnO nanoparticles (20 µg/mL, 40 µg/mL, 60 µg/mL, 80 µg/mL and 100 µg/mL) against Gram-positive and Gram-negative bacteria: Staphylococcus aureus, Streptococcus pyogenes and Escherichia coli using shake flask method. The obtained results revealed that the bacterial growth decreases with increase in concentration of biosynthesized ZnO nanoparticles. In Addition, Gram-positive bacteria seemed to be more sensitive to ZnO nanoparticles than Gram-negative bacteria. The biosynthesized ZnO nanoparticles showed photocatalytic activity under the UV light enhancing the degradation rate of methylene blue (MB), which is one of the main water-pollutant released by textile industries.