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[Display omitted] • Chemically and Green synthesized Fe 3 O 4 NPs obtained by a facile hydrothermal method. • Lattice Parameter observed via HR-TEM & XRD (3 1 1) peak matches well with standard one. • Comparative Antimicrobial studies of chemically & green synthesized Fe 3 O 4 NPs explored. • Antibacterial studies of Green synthesized NPs showed effectiveness against Xcc. • Antifungal studies shows potential of synthesized Fe 3 O 4 NPs even at 0.125 mg/ml conc. The present study explores the antimicrobial properties of Fe 3 O 4 nanoparticles synthesized by chemical and green routes using hydrothermal methods. In this respect, the neem tree (Azadirachta indica) bark extract was used as a green source to utilize the advantage of the phytochemicals present in it. The synthesized nanoparticles (NPs) were characterized by UV–visible spectroscopy, HR-TEM, DLS, XRD and FTIR. The average particle size of chemically synthesized and phytofabricated NPs was ∼ 23 nm and ∼ 6 nm, respectively. FTIR spectra confirmed the presence of different phytochemicals like phenols, amines, aromatic, amides and carboxylic groups in the phytofabricated Fe 3 O 4 NPs. Further, its antibacterial activity was evaluated using the agar well diffusion method against phytopathogens: Xanthomonas campestris pv. campestris Xcc –C7, Bacillus subtilis DTBS-5 and Pseudomonas fluorescens DTPF-3 (PSfl) under in vitro conditions. The antifungal property of NPs was studied by poison food agar assay against mycopathogens, i.e., Fusarium graminearum and Phytophthora spp. The phytofabricated Fe 3 O 4 NPs showed bactericidal action against Xcc and inhibited the fungal growth as well. The outcome of this study will be beneficial for its potential application in the management of bacterial and fungal plant pathogens during crop cultivation in agriculture. [ABSTRACT FROM AUTHOR]

CdS-PVP nanocomposites grown with various concentrations of Cd + /S − and PVP are studied using Raman and atomic force microscopy mapping on same selected areas. The study shows that CdS nanocrystals are embedded in either a thin-film or spheres of PVP, formation of which depends on relative ratio of Cd + /S − concentration (density of nanocrystals) to PVP. Collapse of PVP from planer matrix to the sphere morphology is correlated with high density of CdS nanocrystals and the attractive interaction between CdS nanocrystals and PVP polymer leading to a co-operative growth mechanism. The understanding developed can be used to control the growth of CdS-PVP nanocomposites with desired properties for optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Correlation between size, bonding of Si and O at the surface/interface of Si nanocrystals and frequency of Si phonons in Si-SiO 2 nanocomposites is established using Raman mapping and X-ray photoelectron spectroscopy. Corroboration of these results with absorption spectroscopy shows that lowering of direct transition of light electron conduction band to heavy hole valence band ∼2.8 and 2.95 eV is a result of the interplay between effect of electron confinement (increases band gap) and oxidation bonding environment at the surface/interface (decreases band gap) of a nanocrystal in Si-SiO 2 nanocomposites. These studies have generated deeper insight into the fundamental understanding of the nanocomposite, which can allow easy optical microscopy monitoring of Si-SiO 2 based device fabrication. [ABSTRACT FROM AUTHOR]

Raman and atomic force microscopy (AFM) mapping on the same selected area are used to get unique information about the morphology of Si nanocrystals (NCs) embedded in SiO 2 , which is difficult to obtain by any other conventional technique. The sensitivity of Raman spectroscopy to surface/interface and confinement effects in NCs is effectively used to correlate the Raman intensity profile in Raman mapping with the topography obtained from AFM to understand that Si NCs are clustered in i) smaller clusters (∼100 nm) organized closely in two dimensions (2D) and ii) big (∼2 μm) three dimensional (3D) isolated clusters, although the growth is carried out to be multilayer (Si/SiO 2 ). Raman mapping performed by varying the focal spot along the depth shows stacking of larger (>∼60 Å) to smaller sizes (<∼40 Å) Si NCs from bottom to top for some clusters. To understand the observed morphologies, further study of specially grown Si–SiO 2 nanocomposites is performed, which suggest formation of smaller Si NCs at the top due to annealing at 800 °C in Si rich SiO 2 and possible existence of thermal gradient in an insulating matrix of SiO 2. Larger Si NCs are formed in the laser induced plume (plasma) itself. [ABSTRACT FROM AUTHOR]

Semiconductor photocatalysts were utilized widely for degrading organic pollutants in water using the advanced, environment-friendly, low-cost, and highly efficient photocatalysis technique. There are various complex energy-consuming techniques used for the refinement of wastewater. However, the photocatalysis process is the cleanest technique used for degrading organic pollutants in wastewater into the water; carbon dioxide, other small molecules, and inorganic pollutants were reduced or oxidized into harmless substances. SrTiO 3 nanoparticles (NPs) synthesized by the chemical method are the topic of attention among researchers because of their physical, chemical & photocatalytic properties under sunlight for water purification applications. This paper dealt with the study of The photocatalytic properties of SrTiO 3 and its composites under sunlight irradiation. Here, we evaluated the photodegradation of methyl orange (MO) and methylene blue (MB) pollutants using SrTiO 3 as a photocatalyst for de-ionized (DI) water and hard water, respectively. Later on, the ex-situ decoration of Ag and Au nanoparticles (NPs) on SrTiO 3 NPs results in enhancing the photocatalytic activity of SrTiO 3. This article shows the abnormal behaviour of MO degradation compared to MB dye because there was no degradation of methyl orange for both bare SrTiO 3 and Ag, Au@SrTiO 3 nanocomposites. However, for bare-SrTiO 3 , the photocatalytic degradation of MB dye for de-ionized and hard water was accomplished in 210 min and 300 min, respectively. Here, SrTiO 3 with MB dye shows enhanced photocatalytic activity for de-ionized water than hard water, and thus we determined the degradation of SrTiO 3 nanocomposites with DI water only. While in the case of SrTiO 3 nanocomposites, degradation occurred in 210min for Ag and 180 min for Au in DI water which signifies that Au a better co-catalyst for photodegradation. Although, degradation of MO in both DI water and hard water does not show any photocatalytic activity even in 6 and 7 h, respectively, for bare SrTiO 3 and its nanocomposites. Therefore, it gives an idea about the different behaviour of dyes in photocatalytic degradation of DI and hard water using bare SrTiO 3 and noble metal doped SrTiO 3 as photocatalysts for water remediation applications. At a glimpse, this work focus on the photocatalytic removal of various water pollutants using the efficient noble metal (Au & Ag) doped SrTiO 3 as a photocatalyst and discusses the properties of those materials and also discuss the prospects for the utilization of those photocatalysts in complex form for the wastewater treatment. [Display omitted] • Photocatalytic degradation of MB & MO with SrTiO 3 in DI & hard water under sunlight. • Reported anomalous behaviour of MO dye with SrTiO 3 in DI & hard water. • Degradation of MB with Au & Ag as co-catalyst and SrTiO 3 as photocatalyst. • Reported degradation of MB with SrTiO 3 –Au & SrTiO 3 –Ag in 180 & 210 min. • First reported water pollutant removal with >99% efficiency using SrTiO 3 and Au, Ag. [ABSTRACT FROM AUTHOR]

• Unveiling the role of carbonate in Ni-based core/shell plasmonic photocatalyst. • Revealing amorphous NiCO 3 as an active side for H 2 reduction via DFT calculations. • Enhancing photocatalytic activity by the incorporation of NiO as a middle layer. • Optimizing the photocatalytic performance by post-vacuum annealing thermal treatment. Though carbonates are known for several decades, their role in sun-light driven photocatalysis is still hidden. Herein, carbonate boosted solar water splitting in nickel-based plasmonic hybrid nanostructures is disclosed for the first time via in-situ experiments and density-functional theory (DFT)-based calculations. Ni@NiO/NiCO 3 core@shell (shell consisting of crystalline NiO and amorphous NiCO 3) nanostructure with varying size and compositions are studied for hydrogen production. The visible light absorption at ∼470 nm excludes the possibility of NiO as an active photocatalyst, emphasizing plasmon driven H 2 evolution. Under white light irradiation, higher hydrogen yield of ∼80 µmol/g/h for vacuum annealed sample over pristine (∼50 µmol/g/h) complements the spectroscopic data and DFT results, uncovering amorphous NiCO 3 as an active site for H 2 absorption due to its unique electronic structure. This conclusion also supports the time-resolved photoluminescence results, indicating that the plasmonic electrons originating from Ni are transferred to NiCO 3 via NiO. The H 2 evolution rate can further be enhanced and tuned by the incorporation of NiO between Ni and NiCO 3. [ABSTRACT FROM AUTHOR]

Ensembles of silicon nanoparticles (Si-nps) embedded in SiO2 matrix were grown by alternate ablation of Si and SiO2 targets using KrF excimer laser based pulsed laser deposition (PLD). The sizes of Si-nps (mean size ranging from 1-5 nm) were controlled by varying the ablation time of silicon target. Transmission electron microscopy (TEM) along with selected area electron diffraction (SAED) and Raman spectroscopy were used to confirm the growth of silicon nanoparticles, its size variation with growth time and the crystalline quality of the grown nanoparticles. TEM analysis showed that mean size and size distribution of Si-nps increased with increase in the ablation time of Si target. Intense peaks ~521 cm-1 in Raman analysis showed reasonably good crystalline quality of grown Si-nps. We observed asymmetric broadening of phonon line shapes which also redshift with decreasing size of Si-nps. Photoluminescence (PL) from these samples, obtained at room temperature, was broad band and consisted of three bands in UV and visible range. The intensity of PL band in UV spectral range (peak ~3.2 eV) was strong compared to visible range bands (peaks ~2.95 eV and ~2.55 eV). We observed a small red-shift (~0.07 eV) of peak position of UV range PL with the decrease in the mean sizes of Si-nps, while there was no appreciable size dependent shift of PL peak positions for other bands in the visible range. The width of UV PL band was also found to increase with decrease of Si-nps mean sizes. Based on the above observations of size dependent redshift of UV range PL band together with the PL lifetimes and PL excitation spectroscopy, the origin of UV PL band is attributed to the direct band transition at the Г point of Si band structure. Visible range bands were ascribed as defect related transitions. The weak intensities of PL bands ~2.95 eV and ~2.55 eV suggested that Si nanoparticles grown by PLD were efficiently capped or passivated by SiO2 with low density of surface/interface related defects. [ABSTRACT FROM AUTHOR]

[Display omitted] • The advantages of BMOFs and their composites are summarized and discussed. • BMOFs and their composites exhibit high electro/photoelectrocatalytic properties. • We investigated the current problems and future solutions of BMOFs. • The challenges of BMOFs for electro/photoelectrocatalysts are summarized. • This is the first review dedicated to BMOFs for electro/photoelectrocatalysts. Owing to the growing demand in areas such as energy, environmental science, electro- and photoelectrocatalysis, different reactions such as HER (hydrogen evolution), OER (oxygen evolution), ORR (oxygen reduction), and CO 2 RR (CO 2 reduction) represent attractive strategies to overcome the challenges in sustainable energy conversion and usage. The competition for introducing catalysts with higher performance and cost-efficiency in comparison to the previous systems based on noble metals is one of the most interesting directions in this field. By merging the advantages of inorganic and organic materials, MOFs (metal–organic frameworks) have gained an ample attention as highly versatile electro- and photoelectrocatalytic platforms. This is governed by the intricate features of MOFs including extraordinary surface area, exceptional porosity, tailorable pore size, vast structural and chemical tunability, and pre- and post-synthesis structural modifiability. In contrast to monometallic compounds, bimetallic MOFs (BMOFs) and their composites offer many advantages, including improved electrical conductivity, extended active sites, high charge capacity, and adjustable electrochemical activity. Metal-organic frameworks can also be combined with other electrochemically active materials, resulting in advanced composites with large specific area, increased electrical conductivity, and superiour dispersion. Besides, some BMOFs show an enhanced electrocatalytic activity under light irradiation, thus permitting their application as photoelectrocatalysts. The present review summarizes the state-of-the-art on bimetallic MOFs and derived composites for the main current types of electro- and photoelectrocatalytic applications. The study also aims to highlight the challenges and opportunities in this area, with a focus on future perspectives of such multimetallic compounds and materials, with a particular emphasis in the field of energy and electrophotocatalysis. [ABSTRACT FROM AUTHOR]