Soft Chemical Route Research Articles

Exploring novel nanostructural architecture of doubly doped ceria (Ce0.85Sr0.075Sm0.075O2-δ) and barium cerate (BaCeO3) as electrolytes for low-temperature solid oxide fuel cells

This study presents the development of a composite electrolyte for use in low-temperature (300–500 °C) Solid oxide Fuel Cells, focusing on a novel nanostructural design. The electrolyte comprises co-doped ceria (Ce0.85Sr0.075Sm0.075O2-δ, DCO) and barium cerate (BaCeO3, BCO), integrated into a unique nanostructural architecture. Initially, the constituent phases of the composite DCO and BCO are synthesized using a soft-chemical route separately, followed by their integration through liquid mixing technique in various compositions (90:10, 80:20, 70:30, 60:40, 50:50) of DCO:BCO in weight ratio. The composite structure is confirmed by X-ray diffraction, and refined the structural data by Rietveld refinement indicating a structural agreement with cubic and fluorite phases of DCO and BCO, respectively. Scanning Electron microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) reveal a uniform distribution of two phases with fine size distribution below 50 nm. Transmission Electron microscopy (TEM) images illustrate the core-shell-like integration of the two phases. High-resolution TEM images indicate that the core consists of the DCO phase, while the shell is composed of the BCO phase. The microstructure of sintered pellets exhibits gas-tight densification, with grains dominated by the DCO phase and BCO phase dispersed along grain boundaries. The ionic conductivity of composite systems is extracted from Electrochemical impedance spectroscopy (EIS) studies, showing that DCO-BCO-40 exhibits the highest conductivity 1.132 × 10−3 Scm−1 @400 °C, which is higher than pristine DCO (0.34 × 10−4 Scm−1 @400 °C). Single cells fabricated using DCO-BCO-40 electrolytes deliver a power output of 280 mW cm−2 whereas pristine DCO showed 279 mW @500 °C. This study exhibits the potential of the core-shell-like nanostructural architecture of electrolytes in advancing Low-temperature solid oxide Fuel cell (LT-SOFC) technology and facilitating the transition toward sustainable energy systems.

Facile synthesis of MIL-100(Fe)-supported zinc oxide quantum dots (ZnO/MIL-100(Fe)) for enhanced Malachite green removal

Abstract In the present study, a synthesis route for ZnO/MIL-100(Fe) composites is proposed through a one-pot synthesis at room temperature with 25% ZnO QDs, where ZnO QDs were prepared in a soft chemical route by aging process. The X-Ray diffraction (XRD) and Fourier transform infrared (FTIR) results indicated that there is a suitability between MIL-100(Fe) and ZnO/MIL-100(Fe). Scanning electron microscope (SEM) image for the composite undergoing a change due to the presence of ZnO QDs. The materials were then utilized as adsorbents and photocatalysts for the removal of Malachite Green (MG) from aqueous solutions. As a result, the adsorption and photocatalytic process of ZnO/MIL-100(Fe) and MIL-100(Fe) fitted well with the pseudo-second-order kinetic model. More specifically, ZnO/MIL-100(Fe) showed better photocatalytic activity than MIL-100(Fe) towards the degradation of these dyes under irradiation with 92% removal. This indicates that the increased photocatalytic performance of ZnO/MIL-100(Fe) is a benefit of the synergistic effect between the semiconductor ZnO QDs and MIL-100(Fe).

Photostable selenium-assisted ZnS nanocomposite with efficient visible light photocatalytic activity

Selenium-assisted ZnS nanocomposite has been successfully prepared through a simple soft chemical route and their photocatalytic activity was also investigated for degradation of methylene and rhodamine B dye under ultraviolet and sunlight irradiation. Various surface analysis techniques such as XRD, SEM, TEM, UV-visible, XPS, and photoluminescence were used to analyze the formation of Se/ZnS nanocomposites. XRD studies confirmed the formation of the selenium phase along with ZnS and zinc methacrylate. SEM images showed that ZnS and Se nanoparticles self-aggregated to form three-dimensional spherical nano-assemblies of an average size of about 527 nm. The presence of a different type of defect in Se/ZnS was analyzed from PL spectra. The photocatalytic study revealed the complete degradation of methylene blue in 75 min with a rate constant of 0.073 min−1 under UV light irradiation. In contrast, rhodamine B (RhB) degraded in 90 min with a corresponding rate constant of 0.038 min−1 under the same time duration. Further, this nanocomposite was also efficient under natural sunlight, and almost 85% degradation was achieved after 180 min. Thus, the synergistic effect of strong absorption under UV and visible light source of Se/ZnS nanocomposite minimizes the photogenerated electron-hole pair recombination., which makes them excellent photocatalysts towards the degradation of dyes. Also, this nanocomposite reduced the photo-corrosion under light irradiation and improved photocatalytic stability. In addition, scavenger studies and electron spin resonance in combination with spin trapping technique were used to analyze the contribution of reactive species involved in photocatalysis process.

Probing the Mo-Redox in Alluaudite Battery Materials

Alluaudites are essentially naturally occurring mixed metal (Mn and Fe) phosphate-based minerals [1] consisting of an open framework structure to support fast alkali migration. The general formula for alluaudite can be expressed by A(1)A(2)M(1)M(2)2(XO4)3 where A and M sites are alkali ion and transition metals respectively and X can be S, P, As, Mo, W, V and so on [2]. The presence of polyanionic moieties (XO4) assures structural stability and high-voltage operation arising from the inductive effect [3]. Till date, a variety of phosphate and sulfate-based alluaudites have been reported as cathodes for Li-ion and Na-ion batteries [4,5].In 2017, the first molybdate-based alluaudite material, Na2.67Mn1.67(MoO4)3, was reported as a 3.45 V Mn-based cathode [6]. Inspired by this work, we have explored other 3d (Co, Ni) based molybdate alluaudite homologues as potential compounds with desirable electrochemical and electrocatalytic activities. Solution combustion synthesis was employed to prepare phase pure Na36Co1.32(MoO4)3 by restricting the annealing duration to one minute as compared to the reported solid-state route warranting prolonged (100 h) annealing. It was found to act as a high-voltage cathode (4 V vs Na/Na+ and 4.1 V vs Li/Li+) involving Co3+/Co2+ redox center [7] while cycling between 3.0 V to 4.3 V. The above-mentioned alluaudite consists of Mo species, which can be redox-active at lower voltages. When cycled in a low-voltage window (0.01 V to 3.0 V), this material was found to act as an anode for both Li-ion and Na-ion batteries. High capacity (ca 400-500 mAh/g) was obtained with a central potential ~0.6 V involving conversion and (de)insertion reaction mechanism. The Ni-analogue, Na4Ni0.8(MoO4)2 alluaudite, was studied as an anode material in both Li-ion and Na-ion batteries involving conversion and (de)intercalation redox mechanisms like the Co- analogue. The underlying redox mechanism will be described for both cases involving post-mortem diffraction, electron microscopy, and spectroscopic tools as well as with the help of the density functional theory (DFT) approach. Finally, alluaudite Na4Cu(MoO4)3 was prepared by soft chemistry route, which was found to work as an anode material in the voltage window of 0.01 V to 3.0 V. The phase transformation and underlying redox mechanism will be elucidated.

Dielectric analysis of surface modified nano-graphite: effects of frequency and thickness

The nano-graphite (NG) and acid modified nano-graphite (ANG) have been synthesized from graphite powder via mixture of strong acid (sulphuric acid and nitric acid) respectively by a soft chemistry route involving microwave, ultrasonic method and characterized by high-resolution electron microscopy (HR-TEM), scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), clearly demonstrated the successful synthesis of acid modified NG. SEM images confirmed the surface morphology of NG, and ANG and HR-TEM study shows the nanoparticles size of NG and ANG. FTIR data confirmed the presence of acid functional groups on the surface of synthesized NG powder. XRD data of NG and ANG shows that 2θ is at 26.43° and 0.336 nm is an interlayer distance (d). NG and ANG pellets have been prepared for their dielectric analysis with frequency for different thickness. The dielectric loss tangent (tanδ) spectra show relaxation peak with frequency and peak shifts due to presence of polar groups in the ANG. The capacitance values of NG and ANG decrease with frequency and increase with thicknesses due to the capacitive nature of nanoparticles. The dielectric permittivity decreases with frequency and increases with thickness due to the charge orientation and dipole moment change of functional groups of synthesized NG, and ANG. The electrical conductivity of NG and ANG nanoparticles increases with frequency and thickness of NG and ANG pellets due to the conductive nature. Electrical conductivity and dielectric permittivity of NG and ANG are found to highly rely on thickness, according to the dielectric evaluation.

Aluminium and fluorine doped tungsten oxide hybrid nanoparticles via simplified soft chemical route for the photocatalytic degradation of methylene blue dye

Aluminium and fluorine doped tungsten oxide hybrid nanoparticles via simplified soft chemical route for the photocatalytic degradation of methylene blue dye

The size dependence and defect induced room temperature ferromagnetism of ZnO and Zn 1-x-y AlxZyO (Z=Mg/Ni) nanocomposites

In the current research, Al-Mg-ZnO and Al-Ni-ZnO nanocomposites were synthesized by using simple soft chemical route. Prepared nanocomposites of Al-Mg-ZnO and Al-Ni-ZnO with capsule shape distributed magnetite nanostructured were carried out under the calcinated at 120 C for 12 h in furnace. The structural morphology and characterization analysis of as prepared nanocomposites was analyzed by XRD, UV–vis. FTIR, PL, TEM, VSM studies. XRD analysis confirmed the highly pure crystallized cubic phases. The XRD peaks show that the crystalline sizes are of the order of 22 nm, 19 nm, and 11nm. Magnetic property of the prepared nanocomposites was discussed in room temperature using VSM measurement. In spite of a number of researchers reporting the effect of codoping ZnO nanoparticles (NPs) with two different metals was modify the properties of the entire system such as enrich in room-temperature ferromagnetism. In this research we tried to by experimentally observed the magnetic properties of a series of soft chemical synthesized Zn1-x-yAlxZyO (Z=Mg/Ni) nanocomposites. Interestingly, it was found that in comparison to un-doped ZnO NPs and co-doped with two different metals. The ferromagnetic signal changes in a co-doped system in which one of the Mg/Ni ions increases the concentration of defects mechanism when Mg/Ni ions exhibited only one oxidation state. The potential role of charge transfer ferromagnetism is involving Mg2+ and Ni2+ ions substituted into ZnO lattice, The origin of magnetism in the nanocomposites is due to exchange interaction between local spin polarized electrons and the conduction electrons. The potential role of charge transfer ferromagnetism involving mixed valence ions and effects defect mechanism was used to explain the room temperature ferromagnetism.

Photocatalytic Characteristics of Cobalt Doped ZnO and Cobalt/Manganese Co-Doped ZnO Nanocrystalline Materials Synthesized by Soft Chemical Route: Effective Elimination of Orange G Dye under UV Light

The cobalt (Co) doped ZnO (Zn1-xCoxO1-δ) and cobalt (Co)/manganese (Mn) co-doped ZnO (Zn1-x-yMnxCoyO1-δ) nanocrystalline materials were prepared using soft chemical synthesis route. Their fundamental and photo-physical properties were studied by XRD, FTIR, EDAX, SEM, TEM, BET and UV techniques. The photocatalytic studies of the samples were carried out using Orange G (OG) dye as a model contaminant where 25 mol% Co/Mn co-doped ZnO (CM-25) showed a higher degradation percentage (80%) than that of all Co doped ZnO samples. The factors influencing photocatalytic degradation of dye such as, amount of catalyst, dye concentration and pH were also studied.

Acid-Assisted Soft Chemical Route for Preparing High-Quality Superconducting 2M-WS2

Acid-Assisted Soft Chemical Route for Preparing High-Quality Superconducting 2M-WS₂

A soft-chemistry route to prepare halide perovskite nanocrystals with tunable emission and high optical performance

AbstractCesium lead halide perovskites constitute a benchmark family of inorganic perovskites for high performance optoelectronic devices. Hot injection is by far the most extended procedure to fabricate CsPbX3 (X: Cl, Br, and/or I) perovskite nanocrystals (PNCs) of high quality. However, the tedious N2-vacuum cycles and fast heating/cooling steps hinder the large-scale production of these materials. This work presents a fast one-step methodology to fabricate small CsPb(ClxBr1-x)3 nanocrystals with good control of the particle size and shape by using a Soft Chemistry strategy (ligand-mediated controlled growth) and microwave heating. We demonstrate that the procedure can be extended to different mixed halide perovskites, thus providing a fine tuning of the chemical composition and consequently, tunable photoluminescence (PL) emission from 522 nm for pure CsPbBr3 to 477 nm for CsPb(Cl0.4Br0.6)3, high photoluminescence quantum yield (PLQY) up to ~86% (for CsPbBr3) and narrow PL full width at half maximum ~18–26 nm. In addition, the protocol was designed in such a way that the chemistry involved in the crystal nucleation and growth of perovskites is as close as possible to that of the hot injection process, which is mechanistically well-understood, to facilitate their adoption by the perovskite research community. Graphical Abstract

Novel rare earth metal and aluminium codoped ZnO photocatalysts for degradation of rhodamine b dye

In this study, samarium and aluminium codoped zinc oxide nanostructures were produced via a soft chemical route, and their structural, morphological, optical, and photocatalytic capabilities were investigated. X-ray diffraction (XRD) patterns and photoluminescence (PL) studies show that both undoped and Sm & Al codoped ZnO nanostructures have a hexagonal wurtzite crystal structure. The shape of the sample's hexagonal nanostructures, as seen in FESEM pictures, changes as the amount of Sm3+ doping increases. Sm3+ and Al2+ ions have been incorporated into ZnO, as seen by the EDX spectra. ZnO nanostructures were thoroughly studied to learn how Al2+ and Sm3+ doping affected their structure, shape, absorption, emission, and photocatalytic activity. The capacity to absorb visible light is enhanced by the incorporation of Sm3+ ions, which causes a red shift in the optical energy band gap from 2.5 to 3.2 eV. Based on the results of in-depth photocatalytic tests, it has been shown that Sm & Al codoped ZnO nanostructures exhibit the highest photodegradation efficiency for RhB dye for Sm0.04MAl0.04MZn0.92MO, i.e. 84%, when exposed to visible light. ZnO, when doped with a rare earth metal ion (Sm3+), displays enhanced photocatalytic efficiency and might have real-world uses. In this research, nanoscale photocatalysts, as manufactured, degrade RhB dye effectively as a photocatalyst

Studies on Catalytic and in Vitro Cytotoxicity Effects of ZnO Nanorods Containing Ag and Their Structural, Morphological, and Antimicrobial Properties

Zinc oxide (ZnO) and Ag-doped ZnO nanoparticles were synthesized using a soft chemical route, and their properties were characterized using various techniques, including X-ray diffraction (XRD), high-resolution scanning electron microscope (HRSEM), energy dispersive X-ray diffraction spectroscopy (EDS), and high-resolution transmission electron microscope (HRTEM). The ZnO (Ag[Formula: see text]Zn[Formula: see text]O (where [Formula: see text], 0.02 and 0.03) exhibited a hexagonal Wurtzite structure, and Ag doping resulted in the formation of nanorods with decreased grain size. The synthesized materials were found to have antimicrobial properties against human pathogenic bacteria and fungi. MTT assays showed that Ag-doped ZnO had higher cytotoxicity against human embryonic kidney cancer cell lines (HEK 293) compared to pure ZnO. The samples also demonstrated active activity towards the catalyst for the selective oxidation of alcohols. Finally, a statistical model was developed for antibacterial studies using ANOVA, which was consistent with the experimental findings. These results demonstrate the potential of Ag-doped ZnO nanoparticles for use in biomedical and catalytic applications.

The influence of Eu3+ doping on the optical and structural properties of the Ge2Y2O7 crystalline phase through a soft chemical process

The present work reports on the synthesis, structural and optical properties of Ge2Y2-xEuxO7 composition powders, with x ranging from 0.0 to 0.16 (from 0.0 to 4.0 mol% Eu3+). We synthesized stable and transparent sols, homogeneous gels, and powders treated at 1100 °C by a soft chemical route, and the effect of Eu3+ concentrations was evaluated. X-ray diffraction (XRD), infrared vibrational spectroscopy (FTIR), Raman spectroscopy, diffuse reflectance spectroscopy (DRS), emission and excitation photoluminescence spectroscopy (PL, PLE), decay curves of emission intensity as a function of time and quantum yield were obtained. An annealing temperature of 1100 °C was enough to obtain a single Ge2Y2O7 crystalline phase and the decrease of Χ2 value (from 2.32 to 1.74) with the increase of Eu3+ doping in the matrix, observed with the Rietveld refinement of the XRD patterns of the samples, is due to the crystallization process. Diffuse reflectance spectra and optical bandgap of 4.7 eV for Ge2Y0.88Eu0.12O7 (3.0 mol% Eu3+) – determined by Kubelka- Munk model – showed the good optical quality of the samples, which were considered non-conducting. All doped samples possessed visible photoluminescence emission from Eu3+ ions under excitation at 394 nm, with higher emissions occurring in the red region from 5D0 → 7F2 transition, with R/O relation equal to 2.6 and purity of red color higher than 85 % for the sample with x = 0.012. Analyzing photoluminescence emission spectra, the lifetime values and Judd-Ofelt parameters, we determined that Eu3+ occupied two different sites of the Ge2Y2O7 host matrix, replacing Y3+ ions, with the quenching concentration occurring between x = 0.12 and x = 0.16. The average decay lifetime of 5D0 level from Eu3+ was around 1.66 ms, with average quantum efficiency around of 48 % and an internal quantum yield equal to 7.17 %. Moreover, we evaluated their emission luminescence properties upon 394 nm excitation to explore for the first time the possibility of using this material in thermal sensing applications.

In-situ crystallization of lanthanide titanate stannate (Ln2TiSnO7) pyrochlore in glass: A glass-ceramic system for potential nuclear waste sequestration

Ln2TiSnO7 (Ln = Nd-Er) pyrochlore glass-ceramics are produced by calcining the pelletized oxide mixture and sodium aluminoborosilicate glass precursor at 1200 °C for 4 h. The ceramic Ln-Ti-Sn oxide mixture is prepared by a soft chemistry route to enhance reactant reactivity and product homogeneity. X-ray diffraction, Raman spectroscopy, and electron microscopy techniques are used to confirm the formation of the pyrochlore structure in glass. The cell parameters of the pyrochlores by Le Bail fitting are consistent with the calculated data. The variation of the lanthanide on pyrochlore A-site has insignificant effect on the Raman F2g mode ∼ 310 cm−1, but has an apparent influence on A1g mode ∼ 504–512 cm−1, which gradually shifts to low frequencies with increasing Ln3+ionic radii. The average sizes of the pyrochlore crystals are ∼ 0.31–0.62 μm, which are uniformly distributed in glass phase. These Ln2TiSnO7 pyrochlore glass-ceramics with mixed elements on B-site, possessing high radiation tolerance feature due to the presence of Sn, could be used as nuclear waste forms.

Synthesis of yttrium titanate stannate (Y2Ti2−xSnxO7, x = 0–2) pyrochlore glass–ceramics as potential nuclear waste form

AbstractY2Ti2−xSnxO7 (x = 0–2) pyrochlore sodium aluminoborosilicate glass–ceramics (GCs) are produced by calcining the pelletized Y–Ti–Sn oxide mixture and glass precursor at 1200 or 1300°C for 4 h. The metal oxide mixture is prepared by a soft chemistry route. X‐ray diffraction, Raman spectroscopy, and electron microscopy are employed to investigate the formation of pyrochlore GCs and local crystal structures. Near phase pure Ti‐rich pyrochlores are produced with minor phase SnO2 observed for Sn‐rich materials. The cell parameters of the pyrochlore structures refined by Le Bail fitting are in good agreement with the published data and increase linearly with the gradual increment of Sn substitution. With progressively increasing Sn proportion on pyrochlore B‐site, Raman characteristic bands of the pyrochlore structure become sharper and well defined. The Raman A1g peak position and its full width at half‐maximum are linearly progressed with increasing x (Sn). The presence of the melting glass facilitates the pyrochlore formation, with ceramic grain sizes ranging from submicron to microns. Transmission electron microscopy and selected area electron diffraction observations indicate the sample possesses a relatively high crystallographic perfection at the atomic level. This new series of pyrochlore GCs and the method disclosed herein may pave the way for further materials development as potential nuclear waste forms.

A resource-efficient and portable nanotechnology-enabled disinfection system: Performance studies and a novel strategy to recycle spent material

The paper describes developing a point-of-use disinfection system consisting of a film-forming nanocomposite packed in a nylon sachet. The composite film consists of silver nanoparticles embedded in a matrix containing chitosan, reduced graphene oxide, and tannic acid. The long-term ability of the portable sachet bag to release silver ions and disinfect surface and groundwater is demonstrated. The sachet bag's disinfection potential is demonstrated by taking Escherichia coli MTCC 443 as the model microorganism. The system produced a complete and consistent 3 log10 reduction of E. coli over multiple cycles of use. The paper also describes a green recycling approach to utilise spent composite film and prevent AgNPs from entering the waste stream. The spent nanocomposite film is transformed into a concrete micro-crack sealant through a soft chemical route. The sealant's ability to plug micro-cracks in concrete is demonstrated, and the mechanism of sealant interaction with concrete is proposed. The sealant can fill cracks and solidify in an alkaline environment. The concrete cube specimens repaired with sealant showed enhanced compressive strength compared to the residual concrete cube specimens. The possible leaching of residual silver from the sealant in concrete is investigated via toxicity characteristic leaching procedure analysis. The study demonstrates that silver leaching is negligible (< 0.05 mg/L) and well below the permissible limit of 5 mg/L.

Synthesis of hierarchical mesoporous cerium titanate brannerite and uranyl adsorption properties at pH 3.8.

Cerium titanates possessing brannerite structure are produced by employing soft and hard templates via sol-gel processing. Powders synthesized with various hard template sizes and template to brannerite weight ratios are composed of nanoscale 'building blocks' with size ∼20-30 nm and characterized on macro-, nano- and atomic scales. These polycrystalline oxide powders exhibit specific surface area up to ∼100 m2 g-1, pore volume ∼0.4 cm3 g-1, and uranyl adsorption capacity ∼0.221 mmol (53 mg) U per gram powder. Remarkably, the materials possess significant proportion of mesopores with 5-50 nm pores representing 84-98% of total pore volume, which facilitate fast accessibility of the adsorbate to the internal surfaces of the adsorbent with adsorbed uranyl reaching over 70% of the full capacity within 15 min of contact. These mesoporous cerium titanate brannerites synthesized by the soft chemistry route are highly homogenous, stable at least in 2 mol L-1 acidic or basic solution, and may attract attention for other applications like catalysis at high temperature.

(H3dien)[Ni(NO3)(C2O4)2].2H2O: Synthesis, crystal structure, catalytic activity and magnetic study

• The hybrid material (H 3 dien)[Ni(NO 3 )(C 2 O 4 ) 2 ].2H 2 O was synthesized using a soft chemistry route. • The crystal structure has been determined by X-ray single crystal diffraction. • Thermal behavior of title compound has been studied by TGA/DTA analysis. • The new compound turned to be an effective catalyst for the reduction reaction of the three nitrophenol isomers. • The negative Curie-Weiss temperature reveals antiferromagnetic coupling between the spin holders. The complex (H 3 dien)[Ni(NO 3 )(C 2 O 4 ) 2 ].2H 2 O, with (dien) is the diethylenetriamine (NH 2 CH 2 CH 2 ) 2 NH, and was synthesized in solution. It was characterized using single-crystal X-ray diffraction, Infrared (FT-IR) and UV-Visible spectroscopies, and TG-DTA thermal analysis. FT-IR confirmed the characteristic bands of diethylenetriamine, nitrate and oxalate groups. (H 3 dien)[Ni(NO 3 )(C 2 O 4 ) 2 ].2H 2 O crystallizes into the monoclinic system (P2 1 /c). Nickel has a square-based pyramidal NiO5 coordination. O-H...O and N-H...O H-bonds connect ionic entities and water molecules into bc -plane-parallel slabs. The UV-Visible spectrum shows absorption bands compatible with a six-coordinated high-spin octahedral Ni(II). Magnetization and a.c. susceptibility measurements were measured. The catalytic efficiency of the title compound in the reduction by NaBH4 of three nitrophenol isomers to their corresponding aminophenols was tested.

Ferromagnetic Ni1-xVxO1-y Nano-Clusters for NO Detection at Room Temperature: A Case of Magnetic Field-Induced Chemiresistive Sensing.

Surface modulation of functional nanostructures is an efficient way of improving gas sensing properties in chemiresistive materials. However, synthesis methods employed so far in achieving desired performances are cumbersome and energy intensive. Moreover, nano-engineering-induced magnetic properties of these materials which are expected to enhance sensing responses have not been utilized until now in improving their interaction with target gases. In particular for gasses with paramagnetic nature such as NO or NO2, the inherent magnetic property of the chemiresistor might assist in enabling superior sensing performance. In this work, vanadium-doped NiO nano-clusters with ferromagnetic behavior at room temperature have been synthesized by a simple and effective combination of soft chemical routes and employed in efficient and selective detection of paramagnetic NO gas. While NiO is typically anti-ferromagnetic, the nanoscale engineering of NiO- and V-doped NiO samples have been found to tune the inherent anti-ferromagnetic behavior into room-temperature ferromagnetism. Surface modification in terms of formation of nano-clusters led to an increased Brunauer-Emmett-Teller surface area of ∼120 m2/g. The sample Ni0.636V0.364O has been observed to exhibit a selective and high response of ∼98% to 1 ppm NO at room temperature with fast response (14 s) and recovery (95 s). The improved sensing response of this sample compared to other doped NiO variants could be explained in terms of lower remnant magnetic moment of the sample accompanied with higher excess negative charge at the surface. The sensing response of this sample was increased by 30% in the presence of an external magnetic field of 280 gauss, highlighting the importance of magnetic ordering in chemiresistive gas sensing between the magnetic sensor material and target analyte. This material stands as a potential gas sensor with excellent NO detection properties.

Electronic, magnetic, optical properties, and morphological characteristics of nanocrystalline based on zinc–cobalt molybdate prepared by soft chemistry route

We report on a simple technique for the preparation of nanocrystalline metal molybdate Zn1-xCoxMoO4 (0 ≤ x ≤ 1) using the polymeric route. The formation mechanism, homogeneity, and structure of the obtained powders were investigated with thermal analysis (TGA–DTA), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The morphology was examined by scanning electron microscopy (SEM), field emission scanning electron microscopy (SEM–FEG) and Brunauer–Emmett–Teller analysis (BET). The particle size was determined by transmission electron microscopy (TEM). UV–Visible spectroscopy and CIE L*a*b* colorimetric parameters were used for color characterization and measurement. According to the XRD analysis of the obtained compounds, for cobalt content greater than or equal to 45 %, the phase formed after grinding is isomorphic to α-CoMoO4. A triclinicphaseof zinc molybdate α-ZnMoO4 polycrystals compound is observed for the cobalt content less than or equal to 30 %. A triclinicstructure of α-ZnMoO4 and monoclinic symmetry of CoMoO4 coexist for cobalt contents between 30 % and 45 %. The solid solution Zn0.7Co0.3MoO4(ZnCoMo-0.3–600), which was obtained in an acidic environment, was formed of grains of quasi-spherical shape with nanometric sizes between 30 and 100 nm. The specific surface area (BET) of the nanocrystalline powders decrease as a function of the substitution of Co2+ in the ZnMoO4, the highest value recorded for the ZnCoMo-0.3–600 powder was about 56.7 m2g−1. As a result, we can claim clearly from the analysis of the diffuse reflection spectra that the thermochromism occurs from the shift of the O2–→Mo6+charge transfer band towards high energies. According to the optical band-gap energy (Eg = 2.153 eV), the monoclinic ZnCoMo-1–700 (CoMoO4) was classified as a semiconductor nanomaterial. The theoretical magnetic moment of this sample is approximately μtheorical = 5.00049 μB.