Characterization of newly synthesized ZrFe2O5 nanomaterial and investigations of its tremendous photocatalytic properties under visible light irradiation

High functional ZrFe2O5 nanoparticles were synthesized using coprecipitation technique. The chemical composition of nanomaterials was studied by energy-dispersive X-ray (EDX). To observe the morphology, field emission scanning electron microscopy (FE-SEM) was used. X-ray diffraction (XRD) technique was utilized to appraise the structure of the synthesized material. The photocatalytic behavior of ZrFe2O 5 nano-particles was investigated by measuring the degradation rate of toluidine blue O (TBO) dye in aqueous solution in the presence of ZrFe 2O5 nano-particles under visible light irradiation. A steady decrease in absorption peak under visible light irradiation was observed by increasing exposure time. The degradation efficiency was observed as 92% after 140 min of exposure to visible light. Besides, ZrFe2O 5 nanophotocatalyst could be recovered and recycled easily. The rate of TBO and total organic carbon (TOC) removal under visible light irradiation decreased by only 5% and 10%, respectively, after seven cycles of use, demonstrating the high photostability of the synthesized nano-photocatalyst material

Catalytic Reductive Degradation of Methyl Orange Using Air Resilient Copper Nanostructures

The study describes the application of oxidation resistant copper nanostructures as an efficient heterogeneous catalyst for the treatment of organic dye containing waste waters. Copper nanostructures were synthesized in an aqueous environment using modified surfactant assisted chemical reduction route. The synthesized nanostructures have been characterized by UV-Vis, Fourier transform infrared spectroscopy FTIR spectroscopy, Atomic force microscopy (AFM), Scanning Electron Microscopy (SEM), and X-ray diffractometry (XRD). These surfactant capped Cu nanostructures have been used as a heterogeneous catalyst for the comparative reductive degradation of methyl orange (MO) in the presence of sodium borohydride (NaBH4) used as a potential reductant. Copper nanoparticles (Cu NPs) were found to be more efficient compared to copper nanorods (Cu NRds) with the degradation reaction obeying pseudofirst order reaction kinetics. Shape dependent catalytic efficiency was further evaluated from activation energy (EA) of reductive degradation reaction. The more efficient Cu NPs were further employed for reductive degradation of real waste water samples containing dyes collected from the drain of different local textile industries situated in Hyderabad region, Pakistan

Solvent-free fabrication of broadband WS2 photodetectors on paper

Paper-based devices have attracted extensive attention due to the growing demand for disposable flexible electronics. Herein, we integrate semiconducting devices on cellulose paper substrate through a simple abrasion technique that yields high-performance photodetectors. A solvent-free WS2 film deposited on paper favors an effective electron-hole separation and hampers recombination. The as-prepared paper-based WS2 photodetectors exhibit a sensitive photoresponse over a wide spectral range spanning from ultraviolet (365 nm) to near-infrared (940 nm). Their responsivity value reaches up to ~270 mA W−1 at 35 V under a power density of 35 mW cm−2. A high performance photodetector was achieved by controlling the environmental exposure as the ambient oxygen molecules were found to decrease the photoresponse and stability of the WS2 photodetector. Furthermore, we have built a spectrometer using such a paper-based WS2 device as the photodetecting component to illustrate its potential application. The present work could promote the development of cost-effective disposable photodetection devices

Low-cost and biodegradable thermoelectric devices based on van der Waals semiconductors on paper substrates

We present a method to fabricate handcrafted thermoelectric devices on standard office paper substrates. The devices are based on thin films of WS2, Te, and BP (P-type semiconductors) and TiS3 and TiS2 (N-type semiconductors), deposited by simply rubbing powder of these materials against paper. The thermoelectric properties of these semiconducting films revealed maximum Seebeck coefficients of (+1.32 ± 0.27) mV/K and (-0.82 ± 0.15) mV/K for WS2 and TiS3, respectively. Additionally, Peltier elements were fabricated by interconnecting the P-type and N-type films with graphite electrodes. A thermopower value up to 6.11 mV/K was obtained when the Peltier element is constructed with three junctions. The findings of this work show proof-of-concept devices to illustrate the potential application of semiconducting van der Waals materials in future thermoelectric power generation as well as temperature sensing for low-cost disposable electronic device

Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size

The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm. Increase of the exchange bias field (HEB) and the coercivity (HC) (12 times and 27 times, respectively) was observed in the nanostructured films compared to the non-patterned film. The marked dependence of HEB and HC with antidot hole diameters pinpoints an in-plane to out-of-plane changeover of the magnetic anisotropy at a nanohole diameter of ∼75 nm. Micromagnetic simulation shows the existence of antiferromagnetic layers that generate an exceptional magnetic configuration around the holes, named as antivortex-state. This configuration induces extra high-energy superdomain walls for edge-to-edge distance >27 nm and high-energy stripe magnetic domains below 27 nm, which could play an important role in the change of the magnetic easy axis towards the perpendicular directionEl interés por las nanoestructuras magnéticas que exhiben anisotropía magnética perpendicular y efecto de sesgo de intercambio (EB) ha aumentado en los últimos años debido a sus aplicaciones en una nueva generación de dispositivos espintrónicos que combinan varias funcionalidades. Presentamos un proceso de nanofabricación utilizado para inducir una componente significativa fuera del plano del eje magnético fácil y del EB. En este estudio, se depositaron multicapas de CoO/Co de 30 nm de espesor sobre plantillas de alúmina nanoestructurada con un amplio rango de diámetros de poro, 34 nm ≤ Dp ≤ 96 nm, manteniendo el parámetro de red hexagonal en 107 nm. Se observó un aumento del campo de polarización de intercambio (HEB) y de la coercitividad (HC) (12 veces y 27 veces, respectivamente) en las películas nanoestructuradas en comparación con la película sin patrón. La marcada dependencia de HEB y HC con los diámetros de los agujeros antidotados señala un cambio de la anisotropía magnética de dentro a fuera del plano a un diámetro de nanoagujero de ∼75 nm. La simulación micromagnética muestra la existencia de capas antiferromagnéticas que generan una configuración magnética excepcional alrededor de los agujeros, denominada estado de antivórtice. Esta configuración induce paredes de superdominio extra de alta energía para la distancia de borde a borde >27 nm y dominios magnéticos de franja de alta energía por debajo de 27 nm, que podrían desempeñar un papel importante en el cambio del eje magnético fácil hacia la dirección perpendicula

Regulating C2H2/CO2 adsorption selectivity by electronic-state manipulation of iron in metal-organic frameworks

Article reports a metal electronic-state manipulation strategy to construct a pair of isostructural and interconvertible Fe-MOFs featuring open Fe centers with different electron densities for efficient C₂H₂/CO₂ separation. The authors show that the presence of Fe[II] centers with a medium-spin-state trail plays a crucial role in the enhanced C₂H₂ selective adsorption

Electrochemical and photochemical routes to semiconducting transition metal-tetracyanoquinodimethane coordination polymers

TCNQ·− radical anions (TCNQ = 7,7,8,8,-tetracyanoquinodimethane) form a wide range of semiconducting coordination polymers when coordinated to transition metals. Some such as CuTCNQ and AgTCNQ exhibit molecular switching and memory storage properties; others have intriguing magnetic properties and for example may behave as molecular magnets at low temperature. In this review, the electro- and photo-chemical synthesis and characterization of this important class of material is reviewed. In particular, the electrochemistry and the redox properties of TCNQ derivatives of coordination polymers based on Cu, Ag, Mn, Fe, Co, Ni, Zn and Cd transition metals are surveyed, with an emphasis on the mechanistic aspects of their electrochemical formation via nucleation–growth processes. Given that TCNQ is an extremely good electron acceptor, readily forming TCNQ•− and TCNQ2-, electrochemical reduction of TCNQ in the presence of a transition metal ion provides an ideal method for synthesis of metal-TCNQ materials by electrocrystallization from organic solvents and ionic liquids or solid-solid transformation using TCNQ modified electrodes from aqueous media containing transition metal electrolytes. The significance of the reversible formal potential (E0f) in these studies is discussed. The coupling of electrocrystallisation on electrode surfaces and microscopic characterization of the electrodeposited materials reveals a wide range of morphologies and phases which strongly influence their properties and applications. Since TCNQ also can be photo-reduced in the presence of suitable electron donors, analogous photochemical approaches to the synthesis of TCNQ-transition metal derivatives are available. The advantages of electrochemical and photochemical methods of synthesis relative to chemical synthesis are outlined

Construction of an Ultrasensitive and Highly Selective Nitrite Sensor Using Piroxicam-Derived Copper Oxide Nanostructures

In this work, piroxicam-based copper oxide nanostructures (Px-CuO NSs) were synthesized via hydrothermal precipitation in the presence of ammonia. The prepared Px-CuO NSs were subjected to scanning electron microscopy (SEM) and X-ray diffraction (XRD) to obtain morphology and crystallinity, respectively. The SEM study reveals that these Px-CuO NSs are in the form of porous rose-like nanopetals with dotted particles on their surface, while the XRD study confirms their crystalline nature. The Px-CuO NS-based sensors were fabricated by drop-casting them onto the surface of a glassy carbon electrode (GCE) and they were tested for nitrite detection using voltammetry and amperometry. The results show these Px-CuO NSs to be highly stable on the GCE surface with linear amperometric (current vs. time) responses to wide range of nitrite concentrations from 100 to 1800 nM, with limits of detection (LOD) and quantification (LOQ) being 12 nM and 40 nM, respectively. Importantly, the fabricated sensor showed negligible effects for a 10-fold higher concentration of common interfering agents and exhibited excellent selectivity. It was applied successfully for nitrite detection in water samples such as river water, mineral water, and tap water