Tungsten trioxide (WO₃) thin films are of great interest as counter electrodes in electrochromic (EC) devices such as ‘smart window’ for energy-efficient buildings. Uniform WO₃ nanoplates filmed as EC working electrodes were fabricated on seed-free fluorine-tin-oxide (FTO) coated glass via a facile and addictive agent-free hydrothermal process. The WO₃ nanoplates were characterised by scanning electron microscopy and the X-ray photoelectron spectroscopy. The morphological analysis of the film showed that the WO₃ nanoplates lying on the FTO glass uniformly. Fourier transform infrared spectroscopy was applied to study the vibrational information of the sample. Furthermore, uniform WO₃ nanoplates exhibit well performance of EC properties. Owing to the highly two-dimensional nanostructure, a fast switching speed of 12 and 3 s for colouration and bleaching are achieved for WO₃ film. These properties of the WO₃ nanoplates film endow its promising practical applications in smart windows.

Synthesising gold nanoprobes in the near infrared (NIR) region is of particular interest in developing nanosensors due to the minimal light attenuation from biomolecules. Here, the controlled synthesis and tunability of gold nanostars’ two distinct localised surface plasmon resonances (LSPRs) at around 700 and 1100 nm is reported. By using UV–Vis–NIR absorption measurements and finite-difference time-domain calculations, the induction of the LSPR and the multipolar nature of the resonances have been investigated experimentally and theoretically. Simulation results demonstrate that large electric fields are confined at the tips of the branches, where the LSPR can be induced specifically by controlling the polarisation of the incident electric field. The surface-enhanced Raman scattering (SERS) capability of these dual plasmonic gold nanostars (DPGNS) has also been demonstrated using a Raman reporter, diethylthiatricarbocyanine iodide and high SERS enhancement factor (EF) of 2 × 10⁷ is obtained with 785 nm excitation. With ease of synthesis, LSPR at NIR and high SERS EF, DPGNS demonstrated the capability to be an effective SERS substrate and the potential to elicit the highest SERS EF ever reported for gold nanoparticles, with further longer wavelength excitations at and beyond 1064 nm.

This study reports the unprecedented, novel and eco-friendly method for the synthesis of three-dimensional (3D) copper nanostructure having flower like morphology using leaf extract of Ficus benghalensis. The catalytic activity of copper nanoflowers (CuNFs) was investigated against methylene blue (MB) used as a modal dye pollutant. Scanning electron micrograph evidently designated 3D appearance of nanoflowers within a size range from 250 nm to 2.5 μm. Energy-dispersive X-ray spectra showed the presence of copper elements in the nanoflowers. Fourier-transform infrared spectra clearly demonstrated the presence of biomolecules which is responsible for the synthesis of CuNFs. The catalytic activity of the synthesised CuNFs was monitored by ultraviolet–visible spectroscopy. The MB was degraded by 72% in 85 min on addition of CuNFs and the rate constant (k) was found to be 0.77 × 10⁻³ s⁻¹. This method adapted for synthesis of CuNFs offers a valuable contribution in the area of nanomaterial synthesis and in water research by suggesting a sustainable and an alternative route for removal of toxic solvents and waste materials.

Potential of luminescent bacteria in production of metal nanoparticles (NPs) has not been well evaluated up until now. These bacteria contain lux operon which is included of reductase enzymes, by increasing bacterial cell density, the expression of aldehyde synthetic enzymes elevate and enhance the yields of NPs synthesis. Therefore, extracellular synthesis of gold NPs (AuNPs) using natural occurring luminescent bacteria, VLA, VLB, VLC and genetically engineered luminescent bacteria, Pseudomonas putida KT2440 and Pseudomonas fluorescence OS8 have been successfully conducted. NPs were characterised and their antibacterial activity evaluated using microtitre plates at different concentrations against some hospital pathogenic bacteria. Biosynthetic AuNPs produced had maximum absorption at the ranges of 500–550 nanometre wavelengths. Transmission electron microscopy images showed particle sizes between 10 and 50 nanometres and confirmed the success of purification process. The NPs were spherical and the FTIR analysis showed the existence of biomolecules on surface of purified NPs that could be most probably related to reductase enzymes that are stabilised on NPs surfaces. Further investigation on antibacterial properties of these novel NPs which coated by reductase enzymes showed that any increase or decrease in antibacterial activity is dependent on NPs concentration.

Mesoporous nanocrystalline magnesium aluminate (MgAl₂O₄) particles with different surface area (70–230 m² g⁻¹) were synthesised via the homogeneous co-precipitation method using different surfactants (cationic, anionic and non-ionic). The obtained powders were used as the support to prepare 10.5 nickel (Ni)/MgAl₂O₄ catalysts, and the resulting samples were tested in the steam pre-reforming of natural gas. The obtained samples were characterised by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller (BET), X-ray diffraction, thermogravimetric/differential thermal analysis, transmission electron microscopy and temperature programmed desorption (TPD) techniques. Experimental results showed that the shape, surface area and porosity of MgAl₂O₄ particles were strongly dependent on the type of surfactants used. In addition, the Ni catalyst supported on the MgAl₂O₄ with the highest surface area exhibited the smallest size of Ni particles (14.1 nm). This catalyst has over 97% of ethane and propane conversions in steam pre-reforming of natural gas under atmospheric pressure, 550°C, low steam to carbon molar ratio (S/C = 1.5) and high gas hourly space velocity (GHSV = 100,000 ml g⁻¹ _catalysth⁻¹).

Square-like nano-CeO₂ mingled with Ce(OH)₃ was successfully synthesised via a hydrothermal route using CeCl₃·7H₂O as cerium source, N₂H₄·H₂O as mineraliser, and ethylenediamine as complexant. The as-synthesised nanoparticles were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, high-resolution transmission electron microscopy, Raman scattering, photoluminescence spectra (PL), and magnetisation measurements. It was found that nano-CeO₂ has a fluorite cubic structure, and there are defects and vacancies in the sample. PL spectrum showed excellent near-UV emission. M–H curve exhibited excellent room-temperature ferromagnetism with saturation magnetisation of 0.0300 emu/g, coercivity of 73.706 Oe, and residual magnetisation of 2.37 × 10⁻³ emu/g, which can be mainly associated with the surface Ce⁴⁺/Ce³⁺ pairs and oxygen vacancies in the nano-CeO₂.

Large-scale production of high-quality graphene nanosheets has been considered to be an interesting and significant challenge. A new approach is reported regarding the fabrication of high-quality graphene nanosheets via chemical reduction with the combination of reducing reagents from graphene oxide (GO). High-conducting reduced GO (RGO) was provided with the combination of hydrazine hydrate and hydroiodic acid. RGO was characterised by X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman, thermo gravimetric analysis, atomic force microscopy and four-probe conductivity tester. Characterisation results indicated that oxygenated functional groups were removed from GO, and high graphitisation has occurred in GO reduction process. The electrical conductivity of RGO was considerably improved and the C/O ratio of RGO was higher than that prepared by single reducing reagent. Combination of hydrate hydrazine and hydroiodic acid have showed high reduction efficiency and good synergistic effect in GO reduction process. The findings in this work can promote research on prepared graphene-based nanosheets composites by a quick and effective processing technique.

Mono-dispersed ceria (CeO₂) hollow nanospheres about 400 nm have been prepared via a facile one-step hydrothermal method, wherein cerium nitrate hexahydrate (Ce(NO₃)₃·6H₂O) was used as cerium sources with the assistance of polyvinylpyrrolidone (PVP) in the ethylene glycol aqueous solution. X-ray diffraction, X-ray photoelectron spectra, scanning electron microscope, transmission electron microscope, nitrogen adsorption–desorption and Fourier transform infrared results indicate that PVP can improve the dispersion and control the morphology and sizes of CeO₂ hollow nanospheres as a surfactant, and the internal diameter of CeO₂ hollow nanosphere gradually increases with reaction time. Based on the time-dependent experiment, the formation mechanism was proposed and discussed. These CeO₂ hollow nanospheres show an excellent adsorption rate of heavy metal ions for Cr(VI) and the adsorption rate is about 70%. The CeO₂ hollow nanospheres also had exhibited superior performance in the degradation of methyl orange dye.

Applications of nanotechnology and nano-science have ever-expanding breakthroughs in medicine, agriculture and industries in recent years; therefore, synthesis of metals nanoparticle (NP) has special significance. Synthesis of NPs by chemical methods are long, costly and hazardous for environment so biosynthesis has been developing interest for researchers. In this regard, the extracellular biosynthesis of gold nanotriangles (AuNTs) performed by use of the soil Streptomycetes. Streptomycetes isolated from rice fields of Guilan Province, Iran, showed biosynthetic activity for producing AuNTs via in vitro experiments. Among all 15 Streptomyces spp. isolates, isolate No. 5 showed high biosynthesis activity. To determine the bacterium taxonomical identity at genus level, its colonies characterised morphologically by use of scanning electron microscope. The polymerase chain reaction (PCR) molecular analysis of active isolate represented its identity partially. In this regard, 16S rRNA gene of the isolate was amplified using universal bacterial primers FD1 and RP2. The PCR products were purified and sequenced. Sequence analysis of 16S rDNA was then conducted using National Center for Biotechnology Information Basic Local Alignment Search Tool method. The AuNTs obtained were characterised by ultraviolet–visible spectroscopy, atomic force microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction spectroscopy analyses. The authors results indicated that Streptomyces microflavus isolate 5 bio-synthesises extracellular AuNTs in the range of 10–100 nm. Synthesised SNPs size ranged from 10 to 100 nm. In comparison with chemical methods for synthesis of metal NPs, the biosynthesis of AuNTs by Streptomyces source is a fast, simple and eco-friendly method. The isolate is a good candidate for further investigations to optimise its production efficacy for further industrial goals in biosynthesis of AuNTs.