Microwave-assisted Hydrothermal Approach Research Articles

Biomass-Derived Co/MPC Nanocomposites for Effective Sensing of Hydrogen Peroxide via Electrocatalysis Reduction

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly dispersive Co/MPC material. Characterization results indicated that Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on a carbon-based skeleton via a microwave-assisted hydrothermal synthesis approach, providing high-activity space. Thus, the prepared material was limited to glassy carbon; on the electrode surface, a cobalt-based sensing platform (Co/MPC/GCE) was built. On the basis of this constructed sensing platform, a linear equation was fitted by the concentration change of current signal I and H2O2. The linear range was 0.55–100.05 mM; the detection limit was 1.38 μM (S/N = 3); and the sensitivity was 103.45 μA cm−2 mM−1. In addition, the effect this sensor had on H2O2 detection of actual water samples was conducted by using a standard addition recovery method; results disclosed that the recovery rate and RSD of H2O2 in tap water samples were 94.0–97.6% and 4.1–6.5%, respectively.

Enhanced butanone chemoresistive sensor utilizing cobalt oxide nanoparticles

Detection of volatile organic compounds (VOCs), particularly 2-butanone, has become crucial due to their widespread use and associated risks to human health. In this study, we present a novel synthesis method for spinel Co3O4 nanoparticles (NPs) employing a microwave-assisted hydrothermal approach followed by calcination and investigate their efficiency in VOC sensing applications. The Co3O4 NPs exhibit remarkable sensitivity and selectivity towards butanone at relatively low operating temperatures. VOC-sensing experiments reveal an optimal operating temperature of 250 °C, showcasing an advantage over existing sensors. Notably, the sensor exhibits high selectivity for butanone, with signal values 1.6–4.5 times higher than those for other VOCs, including acetaldehyde, ethanol, isopropanol, methanol, acetone, m-xylene, toluene, and benzene. Additionally, the Co3O4 NPs-based sensor demonstrates high sensitivity, detecting concentrations as low as 5 ppm of butanone, with fast response/recovery times of 41/86 s for 200 ppm of butanone and robust long-term stability. These findings underscore the potential of Co3O4 NPs as promising candidates for low-temperature butanone detection, which is essential for environmental and human health monitoring purposes.

Microwave-Assisted Hydrothermal Synthesis of Na3V2(PO4)2F3 Nanocuboid@Reduced Graphene Oxide as an Ultrahigh-Rate and Superlong-Lifespan Cathode for Fast-Charging Sodium-Ion Batteries.

Na3V2(PO4)2F3 (NVPF) has been regarded as a favorable cathode for sodium-ion batteries (SIBs) due to its high voltage and stable structure. However, the limited electronic conductivity restricts its rate performance. NVPF@reduced graphene oxide (rGO) was synthesized by a facile microwave-assisted hydrothermal approach with subsequent calcination to shorten the hydrothermal time. NVPF nanocuboids with sizes of 50-150 nm distributed on rGO can be obtained, delivering excellent electrochemical performance such as a longevity life (a high capacity retention of 85.6% after 7000 cycles at 10 C) and distinguished rate capability (116 mAh g-1 at 50 C with a short discharging/charging time of 1.2 min). The full battery with a Cu2Se anode represents a capacity of 116 mAh g-1 at 0.2 A g-1. The introduction of rGO can augment the electronic conductivity and advance the Na+ diffusion speed, boosting the cycling and rate capability. Besides, the small lattice change (3.3%) and high structural reversibility during the phase transition process between Na3V2(PO4)2F3 and NaV2(PO4)2F3 testified by in situ X-ray diffraction are also advantageous for Na storage behavior. This work furnishes a simple method to synthesize polyanionic cathodes with ultrahigh rate and ultralong lifespan for fast-charging SIBs.

LiFe[formula omitted]O[formula omitted]-based gas sensor: A machine learning approach for selective VOCs detection

This work presents the development of novel LiFe5O8 micro-flowers through a single-step microwave-assisted hydrothermal approach. LiFe5O8 micro-flowers were used as a sensing element for the detection of highly cross-sensitive volatile organic compounds (VOC). Various characterization methods were also used to validate the material characteristics of the sensor. The measured response/recovery curve revealed that these unique micro flowers can detect even at 5 ppm concentrations of acetone, ethanol, and methanol with response values of 1.17, 1.37, and 1.23 at 100 °C respectively. The sensor’s selectivity issue was addressed by employing simpler Machine Learning (ML) algorithms (decision tree, random forest, K-nearest neighbor, and support vector machine) using the measured response values ranging from 5 ppm to 200 ppm. Further, the classification of the mixture and pure gases was performed using a random mixture of the three VOCs to enhance the selectivity. The article compares various extracted features to determine the best feature set for the deployed ML algorithms. Optimization algorithms such as grid and randomized search were employed to identify the most suitable parameters for achieving the best models. The testing results report an average classification accuracy of 98% and an R2-score of 0.98 for the three gases from the best model.

Mechanistic Insight into the Defect-Engineered White Light Emission from the Single-Phase Orthovanadate Phosphor Synthesized by a Facile Rapid Microwave-Assisted Synthesis.

The synthesis of single-phase barium orthovanadate phosphors by a one-pot microwave-assisted hydrothermal approach has been reported, wherein the homogeneous thermal zone generated at the molecular level by microwave radiation gives rise to tunable distortion in the tetrahedral VO4-3 and oxygen vacancies, eventually enabling intrinsic white light emission with CIE of 0.31,0.38, high photoluminescence internal quantum efficiency of 35%, and external quantum efficiency of 28% whereas phosphor synthesized by the hydrothermal route exhibits only bluish-green emission (PLQE: 0.5%). The Rietveld refinement confirms the formation of a single trigonal phase having dissimilar V-O bond lengths and bond angles, implying the formation of a distorted phosphor under optimized conditions, and corroborates with Raman and Fourier transform infrared analyses. The X-ray photoelectron spectroscopy and electron paramagnetic resonance analysis reveal that the origin of white light emission is due to short- and long-range defects, in particular the oxygen vacancies, which eventually form an intermediate energy level in the forbidden region between the valence and conduction bands. Lifetime spectra show triexponential fitting, corresponding to two charge transfer blue and green emission bands (3T2, 3T1 to 1A1) and one oxygen vacancy-related red emission at RT. Furthermore, these phosphors are thermally stable, as no change in the structure or emission characteristics are observed. A prototype fabricated using a 365 nm chip exhibits white-light-emission CIE of 0.353,0.392, correlated color temperature of 4867 K, color rendering index of 85, and high luminous efficacy of 102 lm/W at 140 mA operating current, portentous for practical applications.

Decorated ZnO nanorods with Bi2S3 nanosheets for enhanced photocatalytic removal of antibiotics and analgesics: Degradation mechanism and pathway

Novel nanorods (NRs) of Bi2S3-ZnO (BZ) heterojunction have been prepared using a microwave-assisted hydrothermal approach. The photocatalytic behavior of BZ heterojunction NRs has been investigated under simulated solar irradiation against the mineralization of meloxicam (MX) analgesics, sulfamethoxazole (SMX), trimethoprim (TMP) antibiotics, as well as crystal violet (CV) and malachite green (MG) dyes. XRD, FTIR, SEM, EDX, TEM, UV–Vis, BET, Zeta potential, and Pl techniques are used to characterize the prepared samples. The TEM results showed that the ZnO NRs are wrapped with Bi2S3 NSHs. For SMX and MX, the degradation rate of BZPCis 2.46 and 1.6 fold greater than that for pristine ZnO NRs, respectively. Furthermore, the BZ NRs heterojunction demonstrated 100% degradation efficiency for SMX, SM, TMP, and CV after 120 min, and after 60 min for MG. The enhanced photodegradation activity of BZ NRs photocatalyst (PC) is assigned to its high absorption ability for visible light, increased surface area, adsorption capability, as well as inhibition of the hole-electron recombination process according to the PL study. Furthermore, the quenching experiment exposed that hydroxyl radicals (·OH) exhibit a significant role in the photodegradation process.Moreover, after 5 cycles, the photocatalytic degradation efficiency of the BZ PC remained constant, confirming its high stability and reusability. The special charge transfer pathway over the BZ PC has been investigated, which will assistin the design of systems with superior photocatalytic properties. The degraded productsand pathwaysis also proposed.Conclusively, BZis considered stable, efficient, and non-selective PC for green solar-driven photocatalytic degradation.

Green preparation of ginger-derived carbon dots accelerates wound healing

Inflammation is thought to impact the wound healing pathology and is highly related to many chronic wounds which do not heal. Natural derived herbs with anti-inflammation effects have gained attention with their availability and affordability for clinical treatment. In this study, the ginger (Zingiber officinale) -derived carbon dots (GCDs) were prepared by a green, fast, low-cost microwave-assisted hydrothermal approach at 180 °C by using ginger aqueous as the only precursor without any organic reagent or surface passivation agents. The GCDs showed a small size distribution with the mean particle size of 2.3 nm, enable emit intense blue photoluminescence and exhibited good biocompatibility. The GCDs was successfully applied in a bio-imaging in vitro. Accelerating wound healing by high anti-inflammatory activity was verified both in vivo and in vitro. Moreover, the GCDs effectively blocked the toll-like receptor 4 (TLR4)-mediated nuclear factor-kappa B (NFκB) pathway to significantly dephosphorylate IκBα and inhibited the nuclear translocation of p65 protein, which reduced the expression of proinflammatory factors. On the mRNA levels, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and Nitric oxide (NO) were decreased, and the inhibition rate were 51.6%, 81.7%, 86.0%, and 58.7%, respectively, all of which indicated excellent anti-inflammatory effect of the GCDs. Therefore, fluorescent GCDs have a promising application as an imaging tool and functional wound dressing for wound clinical management. The study also brings a new idea for the discovery of effective special substances that is not limited to bioactive small-molecule compounds.

In vitro and in vivo toxicological evaluation of carbon quantum dots originating from Spinacia oleracea

Food-derived carbon quantum dots (CQDs) can relatively easily be synthesized and chemically manipulated for a broad spectrum of biomedical applications. However, their toxicity may hinder their actual use. Here, Spinacia oleracea-derived CQDs i.e., CQD-1 and CQD-2, were synthesized by means of different shredding methods and followed by a microwave-assisted hydrothermal approach. Subsequently, these CQDs were analyzed in vitro and in an in vivo mice model to test their biocompatibility and potential use as bioimaging agents and for activation of osteogenic differentiation.When comparing CQD-1 and CQD-2, it was found that CQD-1 exhibited 7.6 times higher photoluminescent (PL) emission intensity around 411 nm compared to CQD-2. Besides, it was found that the size distribution of CQD-1 was 2.05 ± 0.08 nm, compared with 2.14 ± 0.04 nm for CQD-2. Upon exposure to human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro, CQD-1 was endocytosed into the cytoplasm and significantly increased the differentiation of hBMSCs up to 10 μg mL−1 after 7 and 14 days. Apparently, the presence of relatively low doses of CQD-1 showed virtually no toxic or histological effects in the major organs in vivo. In contrast, high doses of CQD-1 (1 mg mL-1) caused cell death in vitro ranging from 35% on day 1 to 80% on day 3 post-exposure, and activated the apoptotic machinery and increased lymphocyte aggregates in the liver tissue. In conclusion, S. oleracea-derived CQDs have the potential for biomedical applications in bioimaging and activation of stem cells osteogenic differentiation. Therefore, it is postulated that CQD-1 from S. oleracea remains potential prospective material at appropriate doses and specifications.

Rapid microwave fabrication of red-carbon quantum dots as fluorescent on-off-on probes for the sequential determination of Fe(III) ion and ascorbic acid in authentic samples.

In this study, fluorescent red-carbon quantum dots (R-CQDs) with an ultrahigh fluorescence quantum yield of 45% were rapidly and easily synthesized by thermal pyrolysis of 2,5-diaminotoluene sulfate and 4-hydroxyethylpiperazineethanesulfonic acid using a one-step microwave-assisted hydrothermal approach. R-CQDs possessed the excitation-independent fluorescence property with the optimal emission peak at 607 nm under the excitation wavelength of 585 nm. R-CQDs exhibited excellent fluorescence stability under extremely harsh conditions in a pH range of 2-11, high ionic strength (1.8 M of NaCl), and long UV light irradiation time (160 min). The fluorescence quantum yield of these R-CQDs was as high as 45%, implying their preferable application in chemosensors and biological analysis. Because Fe3+ ion bound with R-CQDs and statically quenched the fluorescence of R-CQDs, the fluorescence intensity of R-CQDs was recovered after the addition of ascorbic acid (AA) via its redox reaction with Fe3+ ion. R-CQDs were developed as highly sensitive fluorescent on-off-on probes for sequentially sensing Fe3+ ions and AA. Under the optimal experimental conditions, the linear range for Fe3+ ion detection was 1-70 μM with a detection limit of 0.28 μM, and the linear range for AA detection was 1-50 μM with a detection limit of 0.42 μM. The successful detection of Fe3+ ions in authentic water samples and the successful sensing of AA in human body fluids and vitamin C tablets further proved the practical application prospects of this efficient strategy in the environmental protection and disease diagnosis fields.

Hierarchically-ordered nanorods of Ga2O3 derived from microwave-assisted hydrothermal approach: Investigation of calcination-induced structural evolution and optical behavior

Hierarchically-ordered nanorods of gallium oxide (Ga 2 O 3 ) were synthesized via a simple microwave-assisted hydrothermal method, and their structural, morphological, and optical properies were investigated in detail. The as-synthesized powders crystallized in orthorhombic gallium oxyhydroxide α-GaOOH phase as confirmed by X-ray diffraction (XRD). Through calcining at 406℃ and 597 ℃, the α-GaOOH powders were transformed into rhombohedral α-Ga 2 O 3 and monoclinic β-Ga 2 O 3 phases, respectively. The scanning electron microscopy (SEM) micrographs showed that the synthesized powders consisted of hierarchically-ordered nanorods linked by side-by-side arrangement. This morphology was attributed to a combinatorial effect of using microwaves and the chosen solution pH. The average length and width of each bunch of rods were ~7 μm and 0.8 μm respectively, while the average width of each rod was 200 nm. The optical bandgap energies, bond vibrational characteristics, photoluminescence (PL) properties and surface defects of the synthesized structures were examined using UV-Visible diffuse reflectance spectroscopy, Raman spectroscopy, PL spectroscopy and X-ray photoelectron spectroscopy (XPS) respectively. The data obtained indicated changes in the structural phases, particle morphologies and surface defects because of variations in the calcination temperature. The β-Ga 2 O 3 rods showed intense room-temperature blue emission attributed to the presence of oxygen vacancy (V O ) defects making this β-Ga 2 O 3 with unique particle morphology a potential candidate in gas sensing or optoelectronic device applications.

Microwave-assisted hydrothermal preparation of magnetic hydrochar for the removal of organophosphorus insecticides from aqueous solutions

Hydrochar-loaded iron nanoparticles (HC-FeNPs) were effectively synthesized through a microwave-assisted hydrothermal approach, characterized and examined for removing three noxious organophosphorus insecticides, namely Ethoprophos (ETH), Terbufos (TER), and Diazinon (DIA), from aqueous solutions. The effect of different factors, including adsorbent dosage (40–90 mg), initial concentration of insecticides (0.25–3 mg/L), incubation time (20–240 min), and pH (4–10) on the adsorption efficiency, was analyzed using batch adsorption experiments. According to kinetic data, the removal adequately fits the pseudo-second-order and intraparticle diffusion kinetic models. The analysis of adsorption data of ETH, TER, and DIA by Freundlich, Langmuir, Dubinin–Radushkevich, and Temkin isotherms revealed that experimental data were best fitted by the Langmuir isotherm with maximum adsorption capacity (qmax) of 3.19, 3.07, and 3.19 mg/g, respectively. Additionally, thermodynamic studies demonstrated the adsorption process was chemisorption, spontaneous, and endothermic. Under the optimized conditions, HC-FeNPs were successfully employed to eliminate insecticides from environmental water samples. Regeneration and reusability tests showed that HC-FeNPs composite had outstanding recoverability and significant recycling potential. The proposed composite is an effective, economical, and ecological adsorbent with high adsorption affinity toward the organophosphorus insecticides, making the adsorption process a viable and efficient process for treating water containing such contaminants.

Phase-manipulated hierarchically core-shell Na3(VO1-xPO4)2F1+2x (0≤x≤1)@Na3V2(PO4)3 and its synergistic effect with conformally wrapped reduced graphene oxide framework towards high-performance cathode for sodium-ion batteries

Sodium-ion batteries (SIBs) are regarded as promising candidates for large-scale stationary energy storage systems because of the high abundance of Na resources. Na superionic conductor polyanionic cathode (NASICON), such as Na3(VO1-xPO4)2F1+2x (0 ≤ x ≤ 1, NVPF1+2x) and Na3V2(PO4)3 (NVP), shows intriguing electrochemical performances due to their robust open structure and superior cycle stability. Inspired by phase manipulation and conductive reduced graphene oxide (rGO) incorporation, a hierarchical NVPF1+2x@NVP core-shell structure is elaborately synthesized and conformally wrapped by rGO via a facial microwave-assisted hydrothermal approach. F-free surface of NVPF1+2x@NVP particle possesses intimate contact with rGO framework without strong mutual repulsive force while conductive rGO endows NVPF1+2x@NVP with high electronic conductivity to ensure fast electron transport. Combining the synergistic effect between delicate design of core-shell structure and conductive rGO framework, the NVPF1+2x@NVP/rGO-600 °C electrode achieves a high discharge capacity of 105.9 mAh g−1 at 0.5 C with an impressive capacity retention of 99.1% after 200 cycles, delivering an excellent rate capability of 90.6 mAh g−1 at 10 C. Moreover, the NVPF1+2x@NVP/rGO-600 °C electrode possesses an alleviated polarization, small impedance and fast electron/Na + diffusion properties due to this synergistic effect. The full cell using NVPF1+2x@NVP/rGO-600 °C cathode and hard carbon (HC) anode shows an initial discharge capacity of 80.0 mAh g−1 at 0.2 C and rate capability of 45.2 mAh g−1 at 10 C, which could light an LED lamp and manifest its prospective application. Our findings provide new insights into a broadly applicable material design combining morphological phase manipulation with conductive rGO framework incorporation, which synergistically boosts the electrochemical performance of NASICON cathode towards advanced SIBs with a higher energy density, faster charging rate and more practical applications.

Ultra-Fine Ruthenium Oxide Quantum Dots/Reduced Graphene Oxide Composite as Electrodes for High-Performance Supercapacitors.

This study synthesized ultra-fine nanometer-scaled ruthenium oxide (RuO2) quantum dots (QDs) on reduced graphene oxide (rGO) surface by a facile and rapid microwave-assisted hydrothermal approach. Benefiting from the synergistic effect of RuO2 and rGO, RuO2/rGO nanocomposite electrodes showed ultra-high capacitive performance. The impact of different RuO2 loadings in RuO2/rGO nanocomposite on their electrochemical performance was investigated by various characterizations. The composite RG-2 with 38 wt.% RuO2 loadings exhibited a specific capacitance of 1120 F g−1 at 1 A g−1. In addition, it has an excellent capacity retention rate of 84 % from 1A g−1 to 10 A g−1, and excellent cycling stability of 89% retention after 10,000 cycles, indicating fast ion-involved redox reactions on the nanocomposite surfaces. These results illustrate that RuO2/rGO composites prepared by this facile process can be an ideal candidate electrode for high-performance supercapacitors.

VO2·0.26H2O nanobelts@reduced graphene oxides as cathode materials for high-performance aqueous zinc ion batteries.

A simple microwave-assisted hydrothermal approach is adopted to synthesize VO2·0.26H2O nanobelts@reduced graphene oxide (VO2·0.26H2O@rGO), which is regarded as a promising cathode material for ZIBs. Compared to VO2·0.26H2O, VO2·0.26H2O@rGO has a large specific surface area and low charge transfer resistance, improving its electrochemical properties. The large lattice spacing, high capacitive Zn2+ storage behavior, fast Zn2+ transfer rate and stable structure are also responsible for the performance.

Morphology, size, and defect engineering in CeOHCO3 hierarchical structures for ultra-wide band microwave absorption

CeOHCO3 hierarchical structures with tunable size and defects were synthesized via a simple and rapid microwave-assisted hydrothermal approach for ultra-wide band microwave absorption for the first time.

Manipulating the Phase Compositions of Na3(VO1-xPO4)2F1+2x (0 ≤ x ≤ 1) and Their Synergistic Effects with Reduced Graphene Oxide toward High-Rate Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have aroused intense research and academic interest due to the natural abundance and cost-effectiveness of sodium resources. Presently, cathode materials based on the Na3(VO1-xPO4)2F1+2x (0 ≤ x ≤ 1, NVPF1+2x) polyanionic framework show intriguing electrochemical performances toward practical and advanced SIBs due to its high operating voltage (>3.9 V) and high energy density (>500 Wh kg-1). Different from conventional approaches focusing on delicate morphology design, metal ion substitution, and the conductive matrix's incorporation to overcome the low intrinsic electrical conductivity, here we adopt a one-step microwave-assisted hydrothermal approach to optimize the electrochemical performances of NVPF1+2x via manipulating its phase compositions with different vanadium sources and distinguishing the tetragonal (I4/mmm) symmetry of the Na3(VOPO4)2F phase from the orthorhombic symmetry (Amam) of the Na3V2(PO4)2F3 phase. The introduction of the conductive reduced graphene oxide (rGO) framework and its impacts on the phase compositions were systematically investigated. The rGO framework with different calcination temperature can alter the phase composition and the electrical conductivity of NVPF1+2x cathodes significantly, thus having a great impact on their electrochemical performances. Galvanostatic charge/discharge, cyclic voltammetry, electrochemical impedance spectroscopy, and the galvanostatic intermittent titration technique are adopted to compare their electrode polarization and kinetics difference and show that NVPF@rGO-600 °C possesses a high rate, small polarization, and fast kinetics electrochemical properties. This work provides new insights into manipulating phase compositions of the NVPF1+2x cathode by modulating the synthesis conditions and revealing their synergistic effect with a rGO conductive framework toward a superior rate capability and more realistic practical applications for SIBs.

Fabrication of strontium and simvastatin loaded hydroxyapatite microspheres by one-step approach

The development of multi-functional strontium (Sr) and simvastatin (SIM) loaded biomaterials to promote angiogenesis and osteogenesis is a promising therapeutic strategy. In order to overcome the complex synthesis process, low drug loading and burst release of drug-loaded biomaterials, in this study, we developed a microwave-assisted hydrothermal one-step approach to prepare Sr- and SIM-loaded hydroxyapatite microspheres for achieving long-term sustained-release of Sr and SIM. The developed one-step preparation method can maintain the chemical structure of simvastatin, and the drug loading rate of simvastatin can reach more than 30 wt%. The prepared double-loaded hydroxyapatite microspheres could sustainable release Sr and SIM for more than 35 days. The prepared hydroxyapatite microspheres containing Sr and SIM have a good application prospect in promoting bone formation. This simple and feasible one-step method can also provide reference for the preparation of other drug-loading microspheres.

Evaluation of the effects of Au addition into ZnFe2O4 nanostructures on acetone detection capabilities

Spinel type zinc ferrite (ZnFe2O4) nanostructured based sensors are conducive to the detection of volatile organic compounds. However, their poor sensing capabilities hinder practical application. Herein, we produced pure ZnFe2O4 and Au modified ZnFe2O4 nanostructures to evaluate the effects of ZnFe2O4 surface modification towards acetone detection. The pure and Au modified ZnFe2O4 nanostructures were facilely prepared using a microwave-assisted hydrothermal approach. Successful incorporation of Au into ZnFe2O4 NPs and the subsequent influence on ZnFe2O4 nanostructure was evaluated by X-ray diffraction, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy. Comparative gas sensing analysis between the pure and Au modified ZnFe2O4 based sensors demonstrated that the modified sensor exhibited high response and selectivity towards acetone (C3H6O) at an operating temperature of 120 °C compared to the pure sensor owing to a high concentration of defects and sensitization effects.

An enhancement on supercapacitor properties of porous CoO nanowire arrays by microwave-assisted regulation of the precursor

A microwave-assisted hydrothermal approach with a follow up thermal treatment was employed to prepare 1D porous CoO nanowires, which is constructed by numerous high crystallinity nanoparticles. A significant change in crystal structure of the precursor were observed, as position shift and absence of some diffraction peaks, which was induced by the microwave-assistance during hydrothermal process. Moreover, the precursor’s purity was also effectively improved. As a result, the as-synthesized CoO annealed from the microwave-assisted precursor exhibited a morphology and phase structure significantly different from that of without microwave involvement. Benefiting from the ‘microwave effect’, the microwave-assisted as-fabricated porous CoO nanowires showed an enhanced specific capacitance (728.8 versus 503.7 F g−1 at 1 A g−1 ), strengthened rate performance (70.0% versus 53.2% maintenance at 15 A g−1), reduced charge transfer resistance (1.06 Ω versus 2.39 Ω), enlarged window voltage (0.85 versus 0.7 V) and enhanced cycle performance (82.3% versus 76.5% retention after 5000 cycles at 15 A g−1), compared with that of sample without microwave assistance. In addition, the corresponding electrochemical properties are also higher than those reported CoO sample prepared by solvothermal method. In conclusion, this work provides a practical way for enhancing electrochemical properties of supercapacitor materials through adjusting the precursor by microwave assistance into hydrothermal process.

Visible light-activated room temperature NH3 sensor base on CuPc-loaded ZnO nanorods

A one-step microwave-assisted hydrothermal synthetic approach was used to synthesize CuPc-loaded ZnO nanorods. Several characterization techniques were applied to analyze the compositional, structural and morphological information of the products, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV − vis spectrophotometer (UV-vis) and X-ray photoelectron spectroscopy (XPS). Both pure ZnO and CuPc-loaded ZnO were characterized in terms of their gas sensing performances towards various gases under light illumination. The results indicated that CuPc/ZnO sensor delivers excellent sensitivity and selectivity towards ammonia, accompanied with rapid response/recovery rate, remarkable humidity resistance and a low detection limit down to 0.8 ppm at room temperature under red light illumination. This work will open-up new vistas in the development of room temperature gas sensors based on wide-band gap semiconductors with visible-light irradiation.