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Metal hydroxides are extensively studied by researchers on account of the potential of these materials to be used in electrodes of energy storage devices. Remarkable electrochemical properties of nanostructured binary/ternary/quaternary metal hydroxides and their nanocomposites with carbonaceous materials prompted the investigation of these material groups for supercapacitor electrode applications. Zinc–aluminium binary hydroxide (ZAH) nanosheets and their nanocomposite with activated carbon (ZAH-AC) were synthesized by means of a hydrothermal method. X-Ray diffraction, selected area electron diffraction, Fourier transform infrared spectroscopy, and high resolution transmission electron microscopy were employed to study the basic characteristics of the synthesized samples. The electrochemical properties were studied using cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy using a three-electrode system. At 1 A g−1 current density, ZAH and ZAH-AC nanosheets achieved specific capacitances of ∼159 F g−1 and ∼573 F g−1, respectively. A two-electrode system was utilized to confirm the workability of ZAH-AC as an electrode material. This system exhibited a high capacitance retention of 152% after 2000 charge–discharge cycles. The addition of AC to ZAH led to the enhancement of the specific capacitance without any crystal structural alterations in ZAH. The synergistic effect of the charge storage mechanisms of AC and ZAH resulted in a highly stable electrode material with pseudocapacitive behaviour. [ABSTRACT FROM AUTHOR]

The discovery of nanoparticles with varied size, shape and composition has stretched the limits of nanotechnology in almost any field. One of the important areas of interest is the use of nanoparticles in heterogeneous catalysis, whereby it offers an advantage by providing large surface area. Our present work focussed on the development of a graphene-based nanocatalyst (Pd@NGO) as an efficient tool to study various organic transformations. The prepared mesoporous catalyst was characterised by X-ray diffraction (PXRD), thermogravimetric analysis (TGA), field emission-scanning electron microscopy (FE-SEM), Brunauer–Emmett–Teller (BET), high resolution transmission electron microscopy (HR-TEM) and Fourier transformer infrared spectroscopy (FT-IR), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray photoelectron spectroscopy (XPS). TEM images showed the light grey sheets of N-GO on which Pd(0) nanoparticles were immobilised. BET analysis confirmed the mesoporous texture of the designed nanocatalyst by giving the surface area of 12.933 m2 g−1 with a pore volume and average pore diameter of 0.020685 cm3 g−1 and 6.39 nm, respectively. Also, FTIR data affirmed the presence of a characteristic C–N peak near 1271 cm−1 showing successful doping of nitrogen over graphene oxide. The XPS data revealed the presence of various elements like carbon (C 1s), nitrogen (N 1s), oxygen (O 1s) and Pd 3d. The prepared nanocatalyst was explored in Suzuki coupling reaction under green conditions, reduction of nitro compounds and the photodegradation of methyl orange with a degradation efficiency of 98.77%. The photodegradation of dyes is viewed as a potential method for the treatment of industrial wastewater due to its low cost, ecologically acceptable procedure, and lack of secondary contamination. Through direct photodegradation or a degradation process involving sensitization, this approach exhibits the light-enhanced creation of charge carriers and reactive radicals that non-selectively break down a variety of organic dyes into water, CO2, and other organic molecules. Moreover, Pd@NGO shows excellent stability and can be used multiple times, and hence possesses efficient reusability. [ABSTRACT FROM AUTHOR]

Metal halide-perovskite-quantum dots (MH-PQDs) have gained wide attention due to their tunable optoelectronic properties and better stability against the ambient environment compared to organometal halide-based PQDs. The stability of the perovskite QDs is of utmost importance, considering their application in light emitting diodes and photodetectors. Herein, we have systematically analyzed the stability of perovskite QDs and have fabricated a photodetector device by using the most stable Mn2+:CsPb(Br1−xClx)3 QDs. The manuscript discusses the synthesis of CsPbBr3 QDs and manganese (Mn) doped Mn2+:CsPb(Br1−xClx)3 QDs using the ligand-assisted re-precipitation (LARP) technique and have studied the correlation between various dopant concentrations and stability. Different concentrations of Mn2+ doping (0.7, 1, 1.5, and 3 mmol of MnCl2·4H2O) in CsPb(Br1−xClx)3 QDs were investigated to study the stability by aging and the optimum concentration of Mn2+ that could be doped into CsPb(Br1−xClx)3 QDs which offered better stability concerning its photoluminescence was found. The optical properties of the synthesized QDs were characterized using UV-Vis absorbance, photoluminescence (PL), and time resolved photoluminescence spectroscopy (TRPL) techniques. The formation of CsPbBr3 QDs with a size of 25.80 ± 3.69 nm and Mn2+:CsPb(Br1−xClx)3 QDs with a size of 22.65 ± 3.28 nm was confirmed by using the high resolution transmission electron microscopy (HR-TEM) technique. TRPL analysis revealed the d–d emission of the Mn2+:CsPb(Br1−xClx)3 QDs at 600 nm due to Mn2+ doping. Furthermore, the self-powered photodetector device was fabricated by using stable 0.7 mmol Mn2+-doped CsPb(Br1−xClx)3 QDs and achieved a quick response, such as a rise time (ton) of 438 ± 8 ms and fall time (toff) of 592 ± 11 ms under one sun illumination. This work could be useful in the field of optoelectronics, especially in the study of doped semiconductor QDs. [ABSTRACT FROM AUTHOR]

Liquid cell electron microscopy (LCEM) has long suffered from irreproducibility and its inability to confer high-quality images over a wide field of view. LCEM demands the encapsulation of the in-liquid sample between two ultrathin membranes (windows). In the vacuum environment of the electron microscope, the windows bulge, drastically reducing the achievable resolution and the usable viewing region. Herein, we introduce a shape-engineered nanofluidic cell architecture and an air-free drop-casting sample loading technique, which combined, provide robust bulgeless imaging conditions. We demonstrate the capabilities of our stationary approach through the study of in-liquid model samples and quantitative measurements of the liquid layer thickness. The presented LCEM method confers high throughput, lattice resolution across the complete viewing window, and sufficient contrast for the observation of unstained liposomes, paving the way to high-resolution movies of biospecimens in their near native environment. [ABSTRACT FROM AUTHOR]

Lignin is expected to replace traditional fossil energy and convert it into a carbon material with excellent performance because of its advantages of being green and renewable, and its abundant reserves that are cheap and easy to obtain. The substitution of lignin for petroleum-based materials can not only effectively realize the high-value utilization of biomass, but reduce environmental pollution and energy loss. This work reported a simple and relatively low-temperature method to produce lignin-based graphene-like carbon materials. In this study, a lignin-based graphene-like film with micron thickness was successfully prepared by carbonization at a relatively low temperature (800 °C) using alkali lignin (AL) as a solid carbon source and large-area metal Ni sheets as catalyst. Through a series of characterization studies of the obtained products at different temperatures, the structural changes of AL and the growth process of the crystal nucleus are further explained. Moreover, the lattice fringes in few-layer graphene were observed by high resolution transmission electron microscopy, which showed that graphitic carbon structures are formed under the catalysis of metal Ni sheets. To sum up, the process was simple and low in energy consumption, and successfully converted biomass resource AL into high value-added carbon material products, alleviating the current problems of energy consumption and climate pollution. [ABSTRACT FROM AUTHOR]

In spite of advanced research on functional colloidal inorganic nanoparticles and their reactivity, room temperature reactive interactions between two different colloids have remained challenging so far. Laser ablation of titanium monoxide and silicon monoxide in ethanol and water allows the generation of TiO-derived and SiO-derived colloidal nanoparticles which were characterized for their stability, size distribution and zeta potentials with dynamic light scattering and after evaporation of solvent examined for their morphology, chemical and phase composition by scanning electron microscopy, Raman spectroscopy, high resolution transmission electron microscopy and electron diffraction and small angle X-ray scattering. Aqueous and ethanolic TiO-derived colloids consist of anatase and monoclinic TiO, while ethanolic SiO-derived colloids are composed of crystalline and amorphous Si, nanocrystalline Si and SiO2 and aqueous SiO-derived colloids contain, in addition to these phases, a high pressure form of cristobalite. Simple room temperature mixing of ethanolic TiO- and SiO-derived colloids allows the formation of TiSi2, which is a case of so far unreported room temperature reactive interactions between two colloidal species. All colloids absorb solar light and act as photocatalysts for methylene blue degradation. These findings present a challenge for further search for feasible room-temperature reactions between distinct colloidal particles and open the potential for green synthesis of other desirable and hardly achievable phases. [ABSTRACT FROM AUTHOR]

NaCrO2 particles for high-rate sodium ion batteries were prepared on a multigram scale in segmented flow from chromium nitrate and sodium nitrate using a segregated flow water-in-oil emulsion drying process. Microfluidic processing is an environmentally friendly and rapid synthetic method, which can produce large-scale industrial implementation for the production of materials with superior properties. The reaction time for NaCrO2 particles was reduced by almost one order of magnitude compared to a normal flask synthesis and by several orders of magntitude compared to a conventional solid-state reaction. In addition, it allows for an easy upscaling and was generalized for the synthesis of other layered oxides NaMO2 (M = Cr, Fe, Co, Al). The automated water-in-oil emulsion approach circumvents the diffusion limits of solid-state reactions by allowing a rapid intermixing of the components at a molecular level in submicrometer-sized micelles. A combination of Raman and nuclear magnetic resonance spectroscopy (1H, 23Na), thermal analysis, X-ray diffraction and high resolution transmission electron microscopy provided insight into the formation mechanism of NaCrO2 particles. The new synthesis method allows cathode materials of different types to be produced in a large scale, constant quality and in short reaction times in an automated manner. [ABSTRACT FROM AUTHOR]

The use of croconic acid disodium salt (CADS) as an organic gelator with Cd(II) salt to obtain an efficient soft-scaffold supramolecular self-healable metallogel (Cd-CADS) in N,N-dimethyl formamide (DMF) media was investigated following an ultrasonication technique. The experimentally scrutinized rheological values of the fabricated metallogel not only revealed the visco-elastic property and mechanical stiffness, but also exposed the self-healable behaviour of the gel material. Two-dimensional (2D) nanosheets of hexagonal boron nitride (h-BN) were incorporated within the gel network to obtain a 2D nanosheet dispersed metallogel of Cd(II) croconate (h-BN@Cd-CADS). The microstructural investigations of the original gel network and hexagonal boron nitride (h-BN) 2D nanosheet dispersed gel-network were performed through field emission scanning electron microscopy (FESEM) and established the interconnecting rod-like fibrous type morphological patterns and inter-connected hexagonal type rod-shaped architecture pattern, respectively. High resolution transmission electron microscopy (HRTEM) was used to visualize the morphological distinction of the Cd-CADS metallogel with the h-BN 2D nanosheets. The infrared spectral (FT-IR) outputs helped to identify the formation pathway to construct the semi-solid self-healing flexible metallogel and h-BN 2D nanosheet dispersed metallogel nanocomposite, respectively. Fascinating electronic-charge transportation was revealed in the as-fabricated Cd-CADS and h-BN@Cd-CADS metallogel-based devices. Furthermore, h-BN 2D-nanosheet-directed modulation of the non-linear rectifying feature of the supramolecular Cd-CADS-metallogel was observed, with the h-BN@Cd-CADS metallogel showing a greater rectifying property, implying that it has a higher conductivity compared to the Cd-CADS metallogel. [ABSTRACT FROM AUTHOR]

In this study, we report on the preparation of a copper oxide/reduced graphene oxide/titanium dioxide (CuO/rGO/TiO2) photocatalyst and its application in a coupling reaction for carbon–nitrogen bond formation under visible light irradiation. The CuO/rGO/TiO2 nanocomposite was synthesized from graphene oxide, Cu and Ti precursors and was fully characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), cyclic voltammetry (CV), UV-vis absorption, and photoluminescence (PL) spectroscopy. The photocatalytic effectiveness of the CuO/rGO/TiO2 nanocomposite was explored in a pseudo 4-component reaction of salicylaldehyde, malononitrile and secondary amines for the preparation of benzopyranopyrimidines in high yields (75–95%) under visible light irradiation (60–120 min) in ethanol as the solvent at room temperature. Furthermore, the photocatalytic activity of the CuO/rGO/TiO2 nanocomposite was studied in a domino reaction for the coupling of salicylaldehyde and malononitrile in the presence of other aldehydes and secondary amines under the same reaction conditions to afford the corresponding benzopyranopyrimidine derivatives in 77–93% yields after 120–180 min. The reusability investigation of the CuO/rGO/TiO2 photocatalyst showed that it could be recovered and recycled for 5 runs without a significant decrease in its catalytic activity. [ABSTRACT FROM AUTHOR]

In the current investigation, HA nanorods and nanoplates with a high surface area have been synthesized using the chemical precipitation method via alcogel formation employing L -arginine as a crystal growth modifier. The prepared HA particles have been characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FESEM), High resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray analysis (EDXA) and nitrogen adsorption–desorption analysis. A representative morphology-dependent catalysis of the synthesized HA particles has been attempted using the Henry reaction under solventless conditions. The HA nanorods have been found to catalyze the Henry reaction with 100% conversion and 84.1% yield while the nanoplates were found to be catalytically inactive. A plausible mechanism supported by DFT studies has been proposed for the observed morphology-dependent catalysis of Henry reaction signifying the importance of surface Ca2+ ions in lowering the LUMO levels of the substrate besides assembling the reactants to proximity. [ABSTRACT FROM AUTHOR]

The deteriorating quality of water owing to the existence of toxic chemicals in ecological water sources due to industrial effluents has become a cause for concern these days. An electrocatalytic device was fabricated for the detection of the haematotoxic pollutant quinol (QL) using barium titanate nanoparticles (BaTiO3 NPs). A sustainable co-precipitation method was employed to synthesize the BaTiO3 NPs. Then, their physical characteristics were confirmed using techniques such as X-ray diffraction to elucidate their crystalline nature, scanning electron microscopy and high resolution transmission electron microscopy to study their surface morphology, and energy dispersive X-ray spectroscopy to analyze their elemental composition. The prepared BaTiO3 NPs were applied over a disposable screen-printed electrode and used for the determination of QL with a wide dynamic response range (0.001–340 μM), low detection limit (0.009 μM) and excellent sensitivity (1.19 μA μM−1 cm−2). The superior electrical conductivity of the BaTiO3 NPs/SPCE is associated with a low s-value and high number of non-bridging oxygen ions present in the nanoparticle structure. The proposed sensor displays excellent selectivity, reproducibility and storage stability as a QL sensor. Additionally, the superior sensing performance of the BaTiO3 NPs was effectively applied in water samples, with acceptable recovery values towards hazardous environmental pollutants. [ABSTRACT FROM AUTHOR]

This work presents the results of a multi-technique (HRTEM – high resolution transmission electron microscopy, EDX – energy-dispersive X-ray spectroscopy, XRD – X-ray diffraction and H2-TPR – temperature programmed reduction by H2) study on the hierarchical organization of Yb-doped ceria nanocrystals (Ce1−xYbxO2−x/2) into tube-like macro-particles. Hierarchically organized ceria-based mixed oxides (macroparticles) were prepared by a wet chemical method. It was observed that the predetermined shape of the investigated macroparticles was kept up to x = ∼0.2. Above this value, additional forms (like large, un-shapely aggregates of the nanoparticles) were created. A very important feature of these materials is the very high shape stability, even at high temperatures. The overall shape of the macroparticles remained unchanged even at up to 900 °C. Moreover, the effect of the hierarchical arrangement of nanocrystallites into the tube-like macroparticles on the activity for propane oxidation and soot combustion reactions has been investigated. The CeO2 nanopowder (prepared by the microemulsion technique) was used as an example of an unorganized structure. It was concluded that the presence of a 3D structure composed of CeO2 nanocrystals significantly improves the catalytic activity of the tube-like material in comparison to the ceria nanopowder. The investigated oxides are good candidates for catalysts of soot oxidation. For the tube-like ceria, the temperature of half oxidation (T50% = 468 °C) was 62 °C lower than that for the nanopowder (T50% = 538 °C) and 103 °C lower than that for non-catalysed oxidation (T50% = 592 °C). Moreover, introduction of Yb3+ ions into the ceria matrix led to further improvement of the propane oxidation performance. For the tube-like Ce0.9Yb0.1O1.95, the temperature of half oxidation (T50% = 455 °C) was 40 °C lower than that for undoped tube-like CeO2 (T50% = 495 °C) and 95 °C lower than that for the ceria nanopowder (T50% = 550 °C). [ABSTRACT FROM AUTHOR]

A novel zeolitic imidazolate framework-8 (ZIF-8) alginate composite hydrogel material (PVA/SA@ZIF-8) is an alginate composite bead which was fabricated by grafting ZIF-8 on the surface of the sodium alginate hydrogel beads using an in situ growth method. The synthetic material was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The PVA/SA@ZIF-8 bead was used to effectively adsorb Cu(II) from aqueous solutions. The initial concentration of copper ions, adsorbent dose, initial pH of copper ions solution, temperature, and contact time for the synthesis of the material were optimized. The adsorption isotherms and kinetics fitted to the Langmuir isotherm model (R2 = 0.9992) and the pseudo-second-order kinetic model (R2 = 0.9967) respectively. According to the Langmuir isotherm adsorption model, the maximum theoretical adsorption capacity of the adsorbent for Cu(II) was 166.94 mg g−1. In addition, the recycling application of the adsorbent was possible as it was easily collected and reused after five adsorption-regeneration cycles. The results indicated the PVA/SA@ZIF-8 hydrogel has unlimited potential in the treatment of heavy metal wastewater. Moreover, the combination of sodium alginate hydrogel and metal–organic frameworks would broaden the potential application of hydrogel materials in other fields. [ABSTRACT FROM AUTHOR]