Room-temperature Co-precipitation Method Research Articles

Facile fabrication of mesoporous Ag-doped γ-MnO2 nanowires with rich oxygen defects for boosting performance of aqueous Zn-ion batteries

In recent years, the aqueous zinc-ion batteries (AZIBs) have attracted a remarkable attention due to their low cost, abundance, low toxicity and high safety. MnO2 is considered a potential electrode for AZIBs owing to its high theoretical capacity and abundance. However, MnO2 suffers a challenging issue of poor cyclability. Herein, mesoporous Ag-doped γ-MnO2 nanowires were fabricated for the first time by a facile room temperature co-precipitation method under the assistance of Ag+ and investigated electrochemically as cathode for AZIBs. The as-obtained sample electrode delivers a remarkable discharge specific capacity of 978 mAh g-1 at the 65th cycle at a current rate of 0.1 C to be steady at 804 mAh g-1 after 150 cycles and exhibits an excellent rate capability at high C-rate due to the surface-controlled capacitive process of the electrochemical reaction, which is attributed to the unique structure of Ag-doped γ-MnO2 nanowires with rich oxygen defects and crystal water for more active sites and stable structure. This work offers aspiration for the future cathode material engineering as AZIBs.

BiPO4:Ln3+ (Ln = Eu, Tb, Eu/Tb) nanorods: Room-temperature synthesis, reaction mechanism, and color-tunable emission

Ln3+ (LnEu, Tb, Eu/Tb) doping hexagonal BiPO4 nanorods were synthesized by a room-temperature co-precipitation method using ethylene glycol as solvent. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), thermal gravimetric (TG), and photoluminescence spectroscopy (PL) were utilized to investigate the structure, morphology, surface chemistry, and fluorescence performance of the obtained phosphors, respectively. The results showed that hexagonal phase of BiPO4 formed at room temperature, which consisted almost entirely of nanorods with an average diameter of 70 nm and an average length of 292 nm. The chemical reactions mechanism was well elucidated. Under short-wavelength UV light excitation, the as-obtained BiPO4:Eu3+ and BiPO4:Tb3+ samples exhibited strong orange-red and green emissions, respectively. Moreover, the photoluminescence color could be tuned from red, orange, yellow, and green-yellow, to green by simply adjusting the relative doping concentrations of Tb3+ and Eu3+ ions. The room-temperature synthesis reported in the present study could be extended to prepare other rare-earth doped inorganic luminescent materials.

Investigation of Cation and Cation Vacancy Distributions in the Zinc Substituted Maghemite, Prepared by One Pot Room Temperature Co-precipitation Method

Investigation of Cation and Cation Vacancy Distributions in the Zinc Substituted Maghemite, Prepared by One Pot Room Temperature Co-precipitation Method

Catalytic synthesis, in-vitro anti-inflammatory activity, and molecular docking studies of novel hydrazone derivatives bearing N and S-heterocycles

An easy ZnO-TiS2 synthesis is described by a room temperature co-precipitation method. EDX, SEM, TEM methods were the main characteristics of the prepared nanocatalyst. For easy, efficient and green hydrazone, derivatives (5a-c) synthesis under the reflux temperature conditions, several factors such as the effect of molar ratios, catalyst loading, reaction time and the effect of solvent were investigated. The influence of catalyst loading on reactivity was studied, which resulted in an optimum catalyst load of 12 mol percent, giving the best return with a minimum of time compared with other catalysts. In this report, a fast and cost -effective synthesis of nanocatalysts and its diverse uses for hydrazone derivatives synthesis is reported. The analytical and spectral data of the synthesized hydrazone compounds have been characterized. The in vitro anti - inflammatory activities have been examined with the HRBC method for all the synthesized compounds. The anti - inflammatory activity was high in all compounds; compound 5a, in particular, produced a better effect, i.e. an IC50 value 165.7 similar to regular diclofenac. All the synthesized hydrazone derivatives were also studied through docking analysis for their interactions with COX-I enzymes. The binding affinities of each compound with the enzyme were good for the maximum value of −10 kcal/mol for 5c against COX-I.

Functional applications and luminescence properties of emission tunable phosphors CaMoO4@SiO2:Ln3+ (Ln=Eu, Tb, Dy)

In this present work, a room temperature coprecipitation method for the synthesis of CaMoO4@SiO2:Ln (Eu3+, Tb3+, Dy3+) phosphors was reported. These particles were characterized using X-ray diffraction (XRD), Energy dispersive spectrometer (EDS), Fourier Transform IR spectroscopy (FTIR), scanning electron microscope (SEM), UV-visible spectrophotometer and photoluminescence (PL) respectively. The results indicated that emission intensity of SiO2 modified samples increased by about 2 times, compared with no-silica modified samples. Multicolor phosphors were also designed by changing the lattice activators (Eu3+, Tb3+, Dy3+). To further explore its applications, the transparent photoluminescent film was developed through the incorporation of polyvinyl alcohol (PVA), and selective and sensitive detection performance on dichromate was demonstrated in detail. In addition, red emission LED devices was assembled with as-prepared phosphors. The present results provide not only the high-performance phosphors modified by silica, but also a deep explanation of the structure-property relationship of the as-prepared sample. Based on these findings, it can be foreseen that these microparticles will be applied in versatile filed.

Pseudocapacitive Lithium Storage of Cauliflower-Like CoFe2 O4 for Low-Temperature Battery Operation.

Binary transition-metal oxides (BTMOs) with hierarchical micro-nano-structures have attracted great interest as potential anode materials for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical cauliflower-like CoFe2 O4 (cl-CoFe2 O4 ) via a facile room-temperature co-precipitation method followed by post-synthetic annealing. The obtained cauliflower structure is constructed by the assembly of microrods, which themselves are composed of small nanoparticles. Such hierarchical micro-nano-structure can promote fast ion transport and stable electrode-electrolyte interfaces. As a result, the cl-CoFe2 O4 can deliver a high specific capacity (1019.9 mAh g-1 at 0.1 A g-1 ), excellent rate capability (626.0 mAh g-1 at 5 A g-1 ), and good cyclability (675.4 mAh g-1 at 4 A g-1 for over 400 cycles) as an anode material for LIBs. Even at low temperatures of 0 °C and -25 °C, the cl-CoFe2 O4 anode can deliver high capacities of 907.5 and 664.5 mAh g-1 at 100 mA g-1 , respectively, indicating its wide operating temperature. More importantly, the full-cell assembled with a commercial LiFePO4 cathode exhibits a high rate performance (214.2 mAh g-1 at 5000 mA g-1 ) and an impressive cycling performance (612.7 mAh g-1 over 140 cycles at 300 mA g-1 ) in the voltage range of 0.5-3.6 V. Kinetic analysis reveals that the electrochemical performance of cl-CoFe2 O4 is dominated by pseudocapacitive behavior, leading to fast Li+ insertion/extraction and good cycling life.

TiO2/ZnCo2O4 porous nanorods: Synthesis and temperature-dependent dual selectivity for sensing HCHO and TEA

Selective detection of different gases on a sensor based on metal oxide semiconductor (MOS) is greatly desired but still remains a challenge. Herein, we demonstrated a strategy to realize highly sensitive and selective detection of formaldehyde (HCHO) and triethylamine (TEA) by using TiO2-decorated ZnCo2O4 porous nanorods (PNRs) as sensing material. The TiO2/ZnCo2O4 PNRs were prepared via a facile dual-oxalate sacrificial template method, in which ZnC2O4/CoC2O4 solid nanorods were synthesized in advance through a simple room temperature co-precipitation method and then applied as sacrificial templates for TiO2/ZnCo2O4 PNRs by immersing them in C10H14O5Ti ethanol solution before calcination. The prepared TiO2/ZnCo2O4 PNRs feature an assembly of randomly stacked nanoparticles with the size about 20 nm. In comparison with pure ZnCo2O4 PNRs, the TiO2/ZnCo2O4 PNRs showed an improved gas sensitivity. More importantly, the sensor based on 4TZCO (TiO2/ZnCo2O4 PNRs with optimized TiO2 content of 4 wt%) could realize selective detection of HCHO and TEA at ppm level by controlling the working temperature at 130 °C and 220 °C, respectively. The ZnCo2O4-TiO2 p-n heterostructure-related gas sensing mechanism was discussed.

The NHx Group Induced Formation of 3D α‐Co(OH)2 Curly Nanosheet Aggregates as Efficient Oxygen Evolution Electrocatalysts

Recently, the curly structure attracts researchers' attention due to the strain effect, electronic effect, and improved surface area, which exhibits enhanced electrocatalytic activity. However, the synthesis of metastable curved structures is very difficult. Herein, a simple room temperature coprecipitation method is proposed to synthesize 3D cobalt (Co) hydroxide (α-Co(OH)2 ) electrocatalysts that consist of curly 2D nanosheets. The formation process of curly nanosheets is elaborated systematically and the results demonstrate that the NHx group has great effect on the formation of curly structure. Combining the advantage of 2D curly nanosheet and 3D aggregate structure, the as-prepared α-Co(OH)2 curly nanosheet aggregates show the best water oxidation activity with an overpotential of 269 mV at j = 10 mA cm-2 in 1.0 m KOH. The electrocatalytic process studies demonstrate that the formation of CoIV O species is the rate-determining step. Theoretical calculations further confirm the beneficial effect of the bent structure on the conductivity, the adsorption of OH- and the formation of OOH* species.

Extremely straightforward room temperature co-precipitation method to synthesize cubic KYF4:Yb/Er up-conversion nanoparticles in deionized water-ethanol solution

Through extremely facile RT (room temperature) co-precipitation method in mixed deionized water and ethanol solution, cubic KYF4:10%Yb/5%Er up-conversion nanoparticles with excellent emission intensity and desirable fluorescence lifetime after annealing under 974 nm pulsed laser excitation have been successfully synthesized. The X-ray powder diffraction pattern has been refined by profile fit in order to obtain accurate lattice parameters. The mean crystallite size and microstrain have been calculated by Williamson-Hall method. Joint effect of crystallite size and microstrain on photoluminescence properties have been studied based on the obtained samples. Green-to-red ratios of the emission spectra and slopes of the emission intensity versus excitation laser power have been investigated. The fluorescence lifetimes of the present samples have also been reported. The extraordinarily facile synthesis route, in environment-friendly solvents, provides a novel proposal to remove some of the obstacles that hinder the up-conversion nanoparticles development.

Dilatometer studies of praseodymium doped ceria: Effect of synthesis methods on sintering behaviour

Praseodymium-doped ceria (Ce0.9Pr0.1O2, PDC), as an electrolyte material for IT-SOFCs, is investigated with respect to the effect of synthesis method and a detailed analysis was carried out to understand the effect on crystallite size, morphology, specific surface area and sintering behaviour. The various synthesis routes such as microwave assisted co-precipitation method, room temperature co-precipitation method and EDTA-citrate complexing method was adopted for the synthesis of praseodymium doped ceria-based nano-materials. XRD pattern confirms the fluorite-type crystal structure of ceria and Raman spectroscopy analysis confirms the structure with the presence of oxygen vacancies. PDC synthesised by microwave assisted co-precipitation method using isopropyl alcohol as solvent exhibited better sintering activity, reduced the sintering temperature and promoted the densification rate when compared to other synthesis methods with uni-model shrinkage behaviour with shrinkage maxima at 765 °C. Based on two sintering models (CHR/Dorn method), the initial stage sintering mechanism was investigated in the present study and confirmed that the grain boundary diffusion (m = 2) as the dominant mechanism and the activation energy was found to be 116 kJ/mol (CHR model) and 176 kJ/mol (Dorn Method) for initial stages of sintering for PDC material synthesised by microwave assisted co-precipitation method using isopropyl alcohol as solvent.

All-inorganic lead halide perovskite nanohexagons for high performance air-stable lithium batteries.

All-inorganic Cs4PbBr6 perovskite nanohexagons, pre-synthesized by a room temperature co-precipitation method, have been electrochemically investigated in a conventional aqueous electrolyte for potential application as an anode material in Li-ion batteries. The nanohexagons were uniformly deposited on ITO precoated glass substrate and subsequently annealed at ambient air to form a mechanically stable perovskite layer. These perovskite layers showed excellent performance during continuous Li-ion intercalation/deintercalation scans in an aqueous electrolyte, exhibiting a diffusion coefficient of 7.34 × 10-8 cm2 s-1, a specific discharge capacity of 377 mA h g-1, a capacity retention of 75% and coulombic efficiency that deteriorated to 98% after 100 scans. A water-triggered transformation of the Cs4PbBr6 to the CsPb2Br5 was initially observed followed by a reversible Li intercalation/deintercalation in the CsPb2Br5 structure for 40 consecutive scans. Following this period, an irreversible conversion reaction of CsPb2Br5 to CsBr and PbBr2 took place. The excellent electrochemical performance observed is promising towards the potential application of all-inorganic perovskite nanocrystals for air-stable, lithium storage applications.

Facile room-temperature coprecipitation of uniform barium chlorapatite nanoassemblies as a host photoluminescent material

As an emerging host phosphor material, barium chlorapatite (Ba5(PO4)3Cl), is attracting growing attention. However, rare earth-doped Ba5(PO4)3Cl phosphors have mainly been obtained via high temperature-based, energy-consuming techniques. In this contribution, we developed a straightforward, facile room-temperature coprecipitation method in the presence of a specific amount of ethylenediaminetetraacetic acid disodium salt that provided Ba5(PO4)3Cl nanoparticles self-assembled to construct uniform Ba5(PO4)3Cl nanoassemblies (diameter: 80–120nm) as well as rare earth Tb3+-doped Ba5(PO4)3Cl:xTb3+ nanophosphors. The nanoassemblies were transparent within the ultraviolet and visible spectral range. The Ba5(PO4)3Cl:xTb3+ nanophosphors exhibited four emission peaks under 228-nm excitation, and the optimal doping amount of Tb3+ was 4.0%. In contrast to traditional energy-consuming, high-temperature techniques, the facile room-temperature coprecipitation method developed here represents an attractive alternative route to obtain uniform Ba5(PO4)3Cl nanoassemblies and Ba5(PO4)3Cl:xTb3+ nanophosphors that are candidate luminescent hosts.

A Green Route to Hexagonal and Monoclinic BiPO4:Ln3+ (Ln = Sm, Eu, Tb, Dy) Nanocrystallites for Tailoring Luminescent Performance.

Selective synthesis of specific phased nanomaterials via a green route is a promising yet challeng- ing task. In the present work, the hexagonal and monoclinic phases of BiPO4:Ln3+ (Ln = Sm, Eu, Tb, Dy) were prepared via room temperature co-precipitation method. For adjusting the phase of the products, the prepared mediums selected were the most common solvents, i.e., water and ethanol. It was very important that the prepared mediums could be easily recycled and reused by evapo- rating the filtrate. The formation mechanisms of hexagonal in water and monoclinic in ethanol were investigated. Interestingly, the growth behaviors of these phases were quite distinct and thus gave rise to distinct morphology and particle size. The hexagonal phase possesses a rod-like morphol- ogy with diameters of 50-160 nm and lengths of 65-400 nm while the monoclinic phase consists of almost entirely irregular nanoparticles. Also, it was found that the bending and stretching vibrations of O-H and PO4 tetrahedra were quite different for the products prepared in water and ethanol. Moreover, it was found that the luminescence properties, including emission intensity, lifetime, quan- tum efficiency, and color, could be readily tailored through controlling the phase structures and microstructures. The results showed that the monoclinic phase exhibited superior luminescent per- formance to the hexagonal phase. The methodologies reported in this work were fundamentally important, which could be easily extended to large-scale synthesis of other phased nanomaterials for potential applications as electroluminescent devices, optical integrated circuits, or biomarkers.

Influenced of Hydrothermal- and High temperature-Treatment on Luminescence Properties of BiPO4: Tb3+ Nanocrystals

Nanocrystals of BiPO4 and BiPO4: Tb were prepared by a room-temperature co-precipitation method, and then followed by post hydrothermaland high temperature-treatment. X-ray diffraction (XRD) analyses indicated that all the prepared samples are crystalline as a pure low-temperature monoclinic phase of BiPO4. The spectra of BiPO4: Tb powders showed the characteristics of Tb emission at 544 nm corresponding to the transition of 5D4→7F5 under irradiation of 370 nm light. Finally, the processing parameters were further optimized to acquire the BiPO4: Tb + to possess proper crystallinity, surface hydration layers and ethanol species, and thereby to get optimal luminescence performance for the BiPO4: Tb powders.

Carbon-coated mesoporous LiTi2(PO4)3 nanocrystals with superior performance for lithium-ion batteries

Carbon-coated LiTi2(PO4)3 (LTP/C) nano- and/or microcrystals have been subjected to extensive research due to their potential application in aqueous rechargeable lithium-ion batteries (ARLBs) with enhanced electrochemical performance. In this paper, mesoporous LTP/C nanocrystals have been prepared by annealing the precursor obtained through a simple room-temperature co-precipitation method. The mesoporous LTP/C nanocrystals have been evaluated in the role of anode materials for lithium-ion batteries (LIBs) with organic and water electrolyte, respectively. After 1000 cycles at 5 and 20C, the specific discharge capacity of the LTP/C electrode with organic electrolyte retains 116.9 and 80.4mAhg−1, with capacity retention of 94.4% and 80.4%, respectively. After 1000 cycles at 1.37C, the specific discharge capacity of the LTP/C‖LiMn2O4 pouch cells with 1molL−1 Li2SO4 electrolyte retains 20.1mAhg−1, presenting a discharge voltage plateau around 1.21V and a capacity retention of 71.5%. The enhanced electrochemical performance of the mesoporous LTP/C nanocrystals makes them a promising candidate functioning as anode materials for LIBs and hybrid supercapacitors.

Structural and spectroscopic diagnosis of ZnO/SnO2 nanocomposite influenced by Eu3+

Europium doped ZnO/SnO2 nanocomposite phosphors were synthesized via room temperature co-precipitation method. In this work structural changes, optical properties and the associated photoluminescence response were investigated for different compositions of ZnO and SnO2 activated with Eu3+ ions. The prepared samples were systematically characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy for obtaining the structural information about the prepared materials. Diffuse reflectance (DR) UV-Vis spectrometer and photoluminescence (PL) spectroscopy technique were employed for studying the optical properties of prepared materials. XRD results confirmed the presence of both phases, hexagonal ZnO as well as tetragonal SnO2 simultaneously and further using Debye Scherrer's and Hall-Williamson relations, crystallite size were estimated and it was found to be in the range of 8–14 nm. The FTIR studies revealed the presence of different stretching and bending modes of Zn–O and Sn–O with an additional stretching and bending vibration of absorbed water (O–H) molecules. FESEM images suggested that the particle size lied in the range of 50 to 70 nm, which were almost spherical in shapes. A long range multi colour emission from blue to red region was observed for the 320 nm excitation wavelength. The observed emission involved sharp emission due to 5D0→7F1 transition that corresponded to the magnetic dipole transition. The study showed that the Eu3+ doped nanocomposite was more suitable material than singly Eu3+ doped ZnO and Eu3+ doped SnO2 with enhanced opto-electronic and luminescence properties and potential applications in display devices.

Luminescence investigation of R3+-doped alkaline earth tungstates prepared by a soft chemistry method

Highly luminescent rare earth (R3+) doped alkaline-earth tungstates MWO4:R3+ (M2+: Ca, Sr and Ba, R3+: Eu, Tb, Gd) were prepared with a room temperature coprecipitation method. The phosphors were characterized by X-ray powder diffraction (XPD), thermal analysis (TG), infrared absorption spectroscopy (FTIR) and UV excited photoluminescence. The as-prepared MWO4:R3+ particles belong to the tetragonal scheelite phase, and are well crystallized and are of the average size of 16–48nm. The excitation and emission spectra of the materials were recorded at 300 and 77K temperatures. The luminescent materials exhibit intense red (Eu3+) and green (Tb3+) colors under UV excitation. The excitation spectra of the Eu3+ doped materials show broad bands arising from the ligand-to-metal charge transfer transitions (O2−→WVI and O2−→Eu3+) as well as narrow bands from 4f–4f intraconfigurational transitions of Eu3+. 4f–4f emission data of the Eu3+ and Tb3+ in the MWO4 host matrices as well as the values of emission quantum efficiencies of the 5D0 level and the 4f–4f experimental intensity parameters of Eu3+ ion are presented and discussed.

Lattice defect quenching effects on luminescence properties of Eu3+-doped YVO4 nanoparticles

A room-temperature co-precipitation method was explored to synthesize Eu3+-doped YVO4 precursors as constructed by an aggregation of several primary particles. After calcination treatment, the primary particles underwent an oriented attachment process and grew into the regular square-like nanoparticles (NPs). These square-like NPs exhibited an improvement in quantum yield of luminescence emission, as indicated by greatly enhanced excitation intensity and lifetime. Further studies on these square-like NPs by electron paramagnetic resonance demonstrated a defect structure as characterized by lower valence state vanadium ions and oxygen vacancies that were produced during the growth process in nitrogen atmosphere. The formation of these defect structures was significantly influenced by the calcination atmospheres, which enables us to uncover the relationships between defect structures and luminescence properties of YVO4:Eu3+ nanocrystals.

A novel approach for the synthesis of nanocrystalline zinc oxide powders by room temperature co-precipitation method

A single step co-precipitation route has been employed for the first time in the preparation of ZnO nanoparticles using ammonium hydroxide and zinc nitrate tetrahydrate. The X-ray diffraction analysis revealed that the synthesized powder has the hexagonal (wurtzite) structure. The as-prepared ZnO powder was well crystalline, without any calcination. This is a promising result compared to those mentioned in the literature, in which crystallization of ZnO nanoparticles was detected at > 300 °C. The average crystallite size of the as-prepared ZnO nanopowder is 20–40 nm. The nanocrystalline ZnO could be sintered to ~ 95% of the theoretical density at 1300 °C in 4 h.

Facile synthesis of visible light excited La 1-xGd xF 3: Eu 3+ micro-meter sphere using polyvinylpyrrolidone as a template

Lanthanide fluorides exhibited unique luminescent properties in terms of their low phonon energy can restrict the luminescence quenching and extend luminescent lifetimes. Here, a room-temperature co-precipitation method was used to synthesize europium(III) activated La 1- x Gd x F 3 solid phosphors. X-ray diffraction (XRD) data confirmed the crystalline phases of synthesized sample belongs to orthorhombic system. All the as-derived materials exhibited red luminescence ( 5D 0→ 7F 1) under the excitation at longer wavelengths (394 and 466 nm). The powder with the most intense emission was achieved in terms of 10 mol.% doping concentration (Eu content, La/Gd=1/9) and sample sintered at 700 °C. Scanning electron microscopy (SEM) investigated the morphology and crystalline of the samples, showing that many regular and large balls (5-10 μmol/L) were dispersed within the micro-meter scale composites. We proved that the above crystal growth structures were controllable and predicable based on the surface functionalization by polyvinylpyrrolidone ligand.