One-pot Hydrothermal Route Research Articles

Rapid detection of low concentration CO using Pt-loaded ZnO nanosheets

Unloaded and Pt-loaded ZnO nanosheets with 120–170 nm sizes were successfully synthesized by a facile one-pot hydrothermal route followed by a calcination treatment. The as-synthesized samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It can be clearly observed that Pt nanoparticles with the diameter of 3–5 nm were uniformly loaded on the surface of ZnO nanosheets. A contrastive study based on CO gas sensing performance of bare ZnO and Pt/ZnO was carried out. According to the measurement results, the loading of Pt remarkably upgraded the sensing capability toward CO. The 0.50 at.% Pt/ZnO based gas sensor exhibited an obvious response value of 3.57 toward 50 ppm CO and fast response/recovery time (6/19 s). Besides, the detection limit was as low as 0.10 ppm and the optimal operating temperature was decreased from 210 °C to 180 °C. The enhanced CO sensing performance by Pt nanoparticles could be attributed to the combination of chemical sensitization and electronic sensitization. The 0.50 at.% Pt/ZnO is an efficient sensor material for rapidly detecting low-concentration CO.

A dual-template method for the synthesis of bimetallic CuNi/SSZ-13 zeolite catalysts for NH3-SCR reaction

A series of bimetallic CuNi/SSZ-13 catalysts with various Cu/Ni ratios were successfully synthesized via a one-pot hydrothermal route by using nickel-diethylenetriamine (Ni-DETA) and copper-tetraethylenepentamine (Cu-TEPA) as co-templates. Significantly, thanks to the introduction of Ni species which could inhibit the formation of copper oxides, bimetallic CuNi/SSZ-13 catalysts show enhanced performance for selective catalytic reduction of NOx with NH3 compared with Cu/SSZ-13 counterpart.

One-step fabrication of highly dispersed Ag nanoparticles decorated N-doped reduced graphene oxide heterogeneous nanostructure for the catalytic reduction of 4-nitrophenol

Inspired by the high catalytic activity of Ag nanopartilces (NPs) as well as N-doped reduced graphene oxide (N-rGO), the heterogeneous nanostructure comprised of Ag NPs and N-rGO is expected to be an excellent catalyst. Herein, heterogeneous nanostructures of N-rGO decorated with well-dispersed Ag NPs were synthesized via a simple one-pot hydrothermal route. The doping of nitrogen atoms, formation of Ag NPs and reduction of graphene oxide were completed simutaneously. The average diameter of the spherical Ag NPs with a narrow size distribution is determined to be 15 nm. The as-synthesized catalyst exhibited outstanding high catalytic activity with a full transformation of 4-nitrophenol to 4-aminophenol within 45 s and good stability up to ten cycles. The catalytic reduction reaction has a pseudo-first-order rate constant of 7.7 × 10−2 s-1, which is significantly higher than the other reported graphene based heterogeneous nanostructures thus far at room temperature. Moreover, the resultant nanocomposites displayed superior surface enhanced Raman scattering effect.

Fabrication, characterization and response surface method optimization for quantum efficiency of fluorescent nitrogen-doped carbon dots obtained from carboxymethylcellulose of oil palms empty fruit bunch

Abstract Bio based nitrogen doped carbon dots (N-CDs) were obtained from empty fruit bunch carboxymethylcellulose and ethylenediamine (EDA) through one-pot hydrothermal carbonization route. The optimum as-formed N-CDs were thoroughly characterized via Transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR), X-ray photoelectron spectra (XPS), UV–vis spectra (UV–Vis) and Fluorescence spectra (PL). Response surface methodology was statistically used to assess three independent variables that have major influence on the fluorescence quantum yield (QY), including temperature (230–270 °C), time (2–6 h) and EDA mass (10%–23.3%). Based on analysis of variance (ANOVA) results, synthesis temperature was found to be the most influential factor on the QY, followed by time and EDA mass. Higher temperature, long synthesis time and high amount of EDA were satisfactorily enough for efficient carbonization conversion rate and obtaining highest QY of N-CDs. The obtained quadratic model (R2 = 0.9991) shows a good correlation between the experimental data and predicted values. The optimum synthetic parameters are of 270 °C temperature, 6 h reaction time and 23.3% of EDA mass. The optimized as-made N-CDs exhibited blue photoluminescence with both excitation dependent/independent phenomena and high nitrogen content. The maximum emission intensity was 426 nm at a maximum excitation wavelength of 320 nm, with a QY of up to 22.9%. XPS and FTIR data confirmed the existence of polar containing groups, such as carbonyl, carboxyl, hydroxyl and amino groups over the surface of N-CDs whereas nitrogen species in the form of (pyridinic and graphitic − N) were introduced in the aromatic carbon domains, which imparts the hydrophilic and photostability of N-CDs. Taking into account the low-cost and sustainable production of N-CDs, this method considered a feasible route for converting low quality waste into value-added nanomaterials and utilizing for different functionalization processes and analytical applications.

Ultrathin SnO2 nanosheets anchored on graphene with improved electrochemical kinetics for reversible lithium and sodium storage

SnO2 is regarded to be promising for both Li-ion and Na-ion batteries. Thus, it is imperative to fabricate SnO2-based anode with improved lithiation reaction kinetics using simple but effective method. Herein, we develop a one-pot hydrothermal route to fabricate two-dimensional SnO2 nanosheets and the graphene supported SnO2 nanosheet composite with decreased SnO2 nanosheet of about 5–10 nm. The ultrathin nanosheet structure anchored on graphene supporting can effectively accelerate the conversion/alloying reaction. Electrochemical researches demonstrate that the reaction kinetics of the lithiation/delithiation reaction can be significantly enhanced by the graphene supported SnO2 nanosheets. As a result, a capacity of 817.2 mAh g−1 after 100 cycles in the potential window of 0.01 to 3 V are achieved at 500 mA g−1. The full cell performance and the sodium storage performance are both demonstrated to be good. These promising results suggest that such strategy to fabricate two-dimensional SnO2-based anode is of great interest for next-generation Li-ion and Na-ion batteries.

Cobalt-molybdenum disulfide supported on nitrogen-doped graphene towards an efficient hydrogen evolution reaction

Abstract Herein, the cobalt-molybdenum bimetallic sulfide catalysts supported on nitrogen-doped graphene (CoMoS2/NGO) were facilely synthesized by a one-pot hydrothermal route. These composites exhibit various special nanostructures, rich in abundant edge site exposure and defects, which play an important role in providing active sites for catalyzing hydrogen evolution reaction (HER). When hydrogen peroxide (H2O2) was used as an additive in hydrothermal process, the as-fabricated composite exhibited more efficiency towards HER, showing as low onset overpotential (ηon) as −54 mV in 0.5 M H2SO4. Typical H2O2-assisted composite realized a remarkable cathodic current density of 30 mA cm−2 at an overpotential η = −137 mV and it possessed a small Tafel slope of 34.13 mV dec−1. Moreover, it exhibited an excellent cycling stability and superior electronic exchange rate. The results prove that CoMoS2/NGO catalysts have great potential for electrochemical HER.

Selenium and nitrogen co-doped carbon quantum dots as a fluorescent probe for perfluorooctanoic acid

Highly fluorescent carbon quantum dotsco-doped withselenium and nitrogen (SeN-CQDs) were fabricated via a one-pot hydrothermal route using selenomethionine as the sole precursor. The SeN-CQDs aggregates have sizes between 30 and 45nm and displayblue fluorescence with a quantum yield of 8% at excitation/emission wavelengthsof 350/445nm. The fluorescence is pH dependent and decreases under acidic conditions. The doping of the CQDs with selenium and nitrogen was proven by X-ray photoelectron spectroscopy (XPS). Fluorescence is selectively quenched by perfluorooctanoic acid (PFOA), and this is accompanied by a decreased fluorescence lifetime. Quenching is not due to aggregation in view of the unaltered sizes of nanoparticles as revealed by TEM and DLS analyses. UV-vis absorption titration suggested the formation of an excited state complex between SeN-CQDs and PFOA, and quenching originates from the internal electron transfer in the excited state complex. The method was used to detect PFOA quantitatively in the linear range of 10-70μM with a 1.8μM detection limit. The nanoprobe has a high selectivity for PFOA over potentially interfering molecules. The practicability of the method was ascertained by accurate detection of PFOA in real samples by the standard addition method. The method may be further improved by tuning the interaction between PFOA and SeN-CQDs through optimizing the doping and the surface composition of the SeN-CQDs. Graphical abstract Schematic presentation of a fluorometric method for perfluorooctanoic acid detection by using a selenium and nitrogen co-doped carbon quantum dots as the fluorescent probe.

Low-cost TiO2-graphitic carbon core/shell nanocomposite for depriving electron, hole recombination

TiO2 nanoparticles have emerged as prominent heterogeneous photocatalysts for hydrogen (H2) production. But pristine TiO2 suffers from photogenerated charge-carrier recombination and limited absorption towards visible light. Present work is about preparation of economically viable TiO2-graphitic carbon core/shell nanocomposite for hydrogen production via one-pot hydrothermal route. The prepared core/shell catalyst is successful in depriving recombination of photogenerated charge carriers and extending the visible light absorption of TiO2. These improvements resulted in higher H2 production values upto 27.1 mmol g−1 h−1 under optimized conditions.

Synergetic effect of Fe2O3 and BiVO4 as photocatalyst nanocomposites for improved photo-Fenton catalytic activity

Photo-Fenton reactions and the related functional nanomaterials have been widely studied for applications in wastewater treatment industry. Herein, visible-light-responsive Fe2O3 nanoparticle-decorated BiVO4 nanoplates were designed and successfully prepared through a one-pot hydrothermal route. The as-prepared Fe2O3/BiVO4 nanocomposites exhibit excellent photo-Fenton catalytic activity toward the discoloration of methylene blue (MB) and Rhodamine B (RhB) dye molecules in the presence of H2O2. The experimental results indicate that nearly 100% of MB (100 mL, 10 mg L−1) and RhB (100 mL, 5 mg L−1) dye molecules are degraded in the presence of 1 g L−1 Fe2O3/BiVO4-1 (FB-1) photo-Fenton catalyst and 0.5 mL of H2O2 within 20 min. The Fe2O3/BiVO4 Fenton photocatalyst also demonstrates high reusability under visible light irradiation with λ ≥ 420 nm. The photoinduced electrons on the conduction band of BiVO4 nanoplates can move toward the surface of Fe2O3/BiVO4 to accelerate the reduction of Fe3+; then, the as-formed Fe2+ ions on the surface of the catalyst greatly enhance the decomposition of H2O2 to form reactive ·OH species for the use in photodegradation of MB and RhB dye molecules. The synergetic effect of Fe2O3 and BiVO4 reported in this work might provide more opportunity to fabricate other novel semiconductor-based Fenton nanocomposites for contamination treatments in wastewater.

Electrochemical behavior of SrFe12O19/CoFe2O4 composite nanoparticles synthesized via one-pot hydrothermal method

SrFe12O19/CoFe2O4 composite nanoparticles were successfully synthesized by a one-pot hydrothermal route and the structural and morphological properties were studied in details. The XRD pattern results confirmed SrFe12O19/CoFe2O4 composite formation at Co/Sr ratio of 0.5 with some residual second phases of SrCO3 and Fe2O3. FTIR spectra showed the strong absorption bands in the range of 440–650 cm−1, which are related to FeO bonds. FESEM images illustrated that the Co-ferrite nanoparticles would nucleate on the surface of plate-liked Sr-ferrite particles by increasing of Co/Sr ratio. At the ratio of 0.5, whole surface of Sr-ferrite particles was covered by Co-ferrite nanoparticles. HRTEM images confirmed the SrFe12O19/CoFe2O4 nanocomposite formation with the average particle size of 8 nm at the Co/Sr ratio of 0.5. Cyclic voltammetry suggesting the pseudocapacitance behavior of the samples where the specific capacitance in the potential window of −1.4 -0 V and scan rate of 50 mV s−1 increased from 133 F g−1 in pure Sr-ferrite to 634 F g−1 at the Co/Sr = 0.5. Subsequently, specific capacitance decreased to 275 F g−1 at Co/Sr = 1. These results were also confirmed by galvanostatic charge-discharge (GCD) curves and the effect of variation of the scan rates were evaluated. 79% of the initial capacitance maintains for the sample with Co/Sr ratio of 0.5 after 5000 continuous cyclic voltammetry at the scan rate of 50 mV s−1 which confirms the superior performance of the prepared electrode as a supercapacitor material.

Loading of metallic silver onto ZnO for enhancement of electron population and photocatalytic activity

ZnO is a well-known metal oxide for photocatalysis purpose. In a real setting, nonetheless, its photocatalytic activity is still rather poor, and thus, needs to be improved. In this research, ZnO is loaded with metallic Ag with varied Ag loading amount through a one-pot hydrothermal route for the improvement of photocatalytic activity. Various characterization techniques, including synchrotron XANES, XPS, XRD, Raman, ICP-OES, DRS, Raman, light-induced IR, SEM, and HR-TEM, are employed for elucidating the physicochemical features of the prepared samples. XPS and XANES confirm that the oxidation state of the loaded Ag is 0, while HR-TEM confirms the presence of Ag in the form of nanoclusters with a size of about 3 nm on the ZnO surface. An enhanced population of photoexcited electrons is observed following the Ag loading. Upon the Ag loading, the photocatalytic activity of ZnO for the mineralization of several recalcitrant organic compounds is also enhanced. Volcano-like enhancement patterns of the electron population and photocatalytic activity are present. The electron population is linearly correlated with photocatalytic activity, confirming the electron population, and thus the presence of metallic Ag, for controlling the photocatalytic activity of Ag-loaded ZnO.

One-pot synthesis of a novel hierarchical Co(II)-doped TiO2 nanostructure: Toward highly active and durable catalyst of peroxymonosulfate activation for degradation of antibiotics and other organic pollutants

A novel hierarchical Co(II)-doped TiO2 (hCTO) nanostructure with abundant and easily accessible active sites was fabricated through a simple one-pot hydrothermal route and innovatively studied as the potential alternative to conventional cobalt-based catalysts for peroxymonosulfate (PMS) activation. Detailed characterization indicated that hCTO was well organized by two-dimensional porous crystalline nanosheets, exhibiting a corolla-like morphology with large surface area (131.2 m2 g−1) and highly open structure. More interestingly, the Co(II) ions were found to be preferentially doped into TiO2 surface lattice, which led to a high density of surface active sites. Due to the combination of multiple unique characteristics, hCTO displayed an excellent catalytic efficiency in PMS solution, enabling almost complete removal of ofloxacin in a short time period, with a rate constant (1.22 min−1) significantly higher than that (0.099 min−1) of Co3O4. Through identification of active radicals and intermediate products in the degradation process, the catalytic mechanism and the potential degradation pathway were proposed. Moreover, hCTO was demonstrated to be highly efficient in activating PMS for degradation of other recalcitrant organic pollutants including norfloxacin, rhodamine B, and methyl orange. Besides, the hCTO exhibited excellent catalytic reusability, without obvious activity loss after reuse several times. This work provides a promising approach on the rational design of cost-effective, highly active, and durable PMS activators for environmental remediation.

Metal-Support Synergetic Effect for Elevating PtPd Electrocatalytic Performance

The direct methanol fuel cell calls for designing various highly active catalysts containing less platinum, still keeping with reasonable stability. In this work, through controlling reaction system under acidic media (pH = 1), ∼3 nm PtPd nanoparticles are dispersed onto the TiO2 support (3PtPd/TiO2) via a facile one-pot hydrothermal route. In comparison with that of homemade Pt/TiO2 and commercial Pt black catalysts, as-synthesized 3PtPd/TiO2 shows a better performance for directly electrochemical catalysis of methanol and simultaneously exhibits high ability against poison from carbon oxide species. Clearly, the optimized usage of anatase TiO2 not only enhances catalytic activity due to the metal-support interactions but also improves long durability, which could be attributed to the OH existing at the surfaces of TiO2 and Pd.

Facile Production of Mesoporous WO3-rGO Hybrids for High-Performance Supercapacitor Electrodes: An Experimental and Computational Study

This work explored a promising supercapacitor electrode material (WO3-rGO hybrids) synthesized via a simplistic one-pot hydrothermal synthesis route. Various analytical studies (X-ray diffraction s...

Creation of Hollow Calcite Single Crystals with CQDs: Synthesis, Characterization, and Fast and Efficient Decontamination of Cd(II)

In this work, carbon quantum dots were first prepared through one-pot hydrothermal route of the propyl aldehyde and sodium hydroxide via an aldol condensation reaction, and a novel solid-phase extraction adsorbent of hollow calcite single crystals was prepared via the precipitation of metal nitrates by the CO2 diffusion method in the presence of CQDs and further applied for excessive Cd(II) ions removal from water. The spectra and morphologies of the etched calcite were investigated by X-ray diffraction, Fourier transform infrared spectrometry, Scanning electron microscope, and Transmission electron microscopy. The results show that the CQDs etching technique successfully furnish a strategy for manufacturing interface defects onto the calcite crystal. Bath studies were done to evaluate the effects of the major parameters onto Cd(II) adsorption by the etched calcite, such as pH, contact time, and initial Cd(II) concentration. The Cd(II) adsorption onto the new adsorbent could reach a maximum adsorption amount of 66.68 mg/g at 120 min due to the abundant exterior adsorption sites on the adsorbent. The adsorption kinetics and adsorption isotherms of Cd(II) on the etched calcite were also investigated. The experimental datum showed that the adsorption kinetics and isotherms of Cd(II) on the etched calcite were well-fitted by the pseudo-second-order kinetic model and the Freundlich isotherm model respectively. The adsorption mechanisms could be primarily explained as the formation of Cd(OH)2 and CaxCd1−xCO3 solid solution on the adsorbent surface with the help of X-ray photoelectron spectroscopy.

Iron-doping as an effective strategy to enhance supercapacitive properties of nickel molybdate

Iron-doped hydrated nickel molybdate (FexNi1-xMoO4.0.75H2O, x = 0–0.10) nanorods were successfully synthesized via a simple one-pot hydrothermal route. Our investigations showed that hydrated nickel molybdate (HNMO) possesses identical crystal structure to CoMoO4.0.75H2O with a triclinic crystal structure and P1¯ space group. Electron microscopy studies showed that the HNMO powders consist of single crystalline nanorods with [12¯2] growth direction. The effectiveness of iron-doping into the crystalline lattice of the HNMO was demonstrated by powder x-ray diffraction (PXRD), UV–visible spectroscopy and electrochemical impedance spectroscopy (EIS). Upon iron-doping, the band gap energy values reduced from 4.03 eV for the un-doped powder to 3.48 eV for 10 at.% iron-doped HNMO. Electrochemical performance of the nanorods was characterized by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and EIS. The electrochemical properties along the optical data demonstrate that there is a direct relation between the electrochemical performance and the level of iron-doping due to improvement of electrical conductivity. A specific capacitance of 718 F/g related to the HNMO was improved by 47%–1057 F/g upon 10 at.% iron-doping.

MoS2/nitrogen doped graphene hydrogels p-n heterojunction: Efficient charge transfer property for highly sensitive and selective photoelectrochemical analysis of chloramphenicol

Constructing junctions between semiconductors is an effective way to promote charge separation and thus to improve the photoelectrochemical (PEC) performances, and specifically, p-n heterojunction is considered as a very promising structure. Herein, we designed and fabricated MoS2/nitrogen doped graphene hydrogels (MoS2/NGH) p-n heterojunction by a facile one-pot hydrothermal route. The as-fabricaterd MoS2/NGH heterostructures demonstrated the excellent PEC activity, exhibiting enhanced photocurrent intensity by the fast transfer and separation rate of photogenerated electron-hole owing to the construction of p-n heterojunction. Based on the high PEC performances of the MoS2/NGH heterostructure, a novel sensitive PEC sensor was developed for the determination of chloramphenicol (CAP) with the assistance of aptamer. In the presence of target molecules, the as-fabricated PEC sensor could recognize the CAP quickly and then consume the holes in the interface of heterostructures, inhibiting the recombination of photogenerated electron-hole pairs, resulting the enhanced photocurrent. Specially, with the concentration of CAP increased, the photocurrent enhanced gradually. Excellent linearity was obtained in the concentration range from 32.3 ng/L to 96.9 μg/L, and the limit of detection was 3.23 ng/L. Moreover, the as-fabricated PEC sensor exhibited rapid response, high stability, low-cost and high selectivity, which could be successfully applied to the analysis of CAP in honeycomb samples.

Blue TiO2 nanosheets as a high-performance electrode material for supercapacitors

We are reporting the use of blue titanium oxide (b-TiO2) nanostructures as advanced electrode material for high performance supercapacitor for the first time. A one-pot hydrothermal route was employed for the oxidation of layered titanium diboride (TiB2) into b-TiO2 nanosheets. The b-TiO2 nanosheets are prepared via hydrothermal oxidation of TiB2. Physico-chemical characterizations such as X-ray diffraction, UV–visible, photoluminescence spectroscopy, electron spin resonance spectroscopy, laser Raman spectrum, X-ray photoelectron spectroscopy, and morphological studies revealed the formation of sheet-like b-TiO2 nanostructures. The energy storage properties of the b-TiO2 electrode were examined using aqueous and organic electrolytes. The cyclic voltammetry and charge-discharge analysis of b-TiO2 electrode using 1 M Na2SO4 revealed their pseudocapacitive nature with a high specific capacitance (∼19 mF cm−2). The b-TiO2 based symmetric supercapacitor (SSC) device using organic liquid (1 M TEABF4) works over a wide operating potential window (3 V) and delivered a high specific capacitance (6.67 F g−1 or 3.58 mF cm−2), possess high energy density and power density with excellent cyclic stability over 10,000 cycles. Collectively, these studies demonstrated the usefulness of b-TiO2 as a novel electrode material for high performance supercapacitor.

Template-free synthesis of nanoarrays SnO2 hollow microcubes with high gas-sensing performance to ether

Hierarchical nanoarrays SnO2 hollow microcubes were successfully synthesized by a simple one-pot template-free hydrothermal route without any substrates. The as-prepared products demonstrated novel hollow SnO2 microcubes with side length of 2–3 μm. Noticeably, the SnO2 cubic surfaces exhibited a hierarchical architecture of well-aligned nanorod arrays. The gas-sensing properties indicated that the nanoarrays SnO2 hollow microcubes possessed superior sensitivity towards ether at the heating voltage of 4.5 V. The formation and sensing mechanism of the nanoarrays SnO2 hollow microcubes were proposed in this paper.

Highly improved visible-light-driven photocatalytic removal of Cr(VI) over yttrium doped H-Titanate nanosheets and its synergy with organic pollutant oxidation

Rare earth metal (yttrium-Y) doped H-Titanate nanosheets (Y-HTNSs) were synthesized via a facile (one-pot) hydrothermal route. The samples exhibit a lamellar structure with the surface area ranging from 336 to 371 m2/g and smaller thickness. The process of the structural transformation of the P25 nanoparticles from three dimensions (3D) to two dimensions (2D) of the H-Titanate nanosheets was controlled by changing the weight percent of the yttrium source. The proportion of Ti3+ in the Y-HTNS samples gradually increased with the concentration of doped yttrium. The Y doping of H-Titanate nanosheets leads a shift in the absorption edge toward higher wavelengths, improving the utilization of the energy in the visible region of the solar spectrum. The photocatalytic performance of Y-HTNSs for the solution with RhB and Cr (VI) was enhanced initially with the concentration of Y up to 1.0 at.%, showed optimal performance at 1.0 at.% and then decreased for concentrations higher than 1.0 at.%. It was demonstrated that the appropriate amount of Y (≤1.0 at.%) effectively improves the separation efficiency of the photoelectron-hole pairs. However, for heavy doping (Y > 1.0 at.%), yttrium ions serve as electrons/hole pair recombination centers, resulting in a reduction in the efficiency of charge separation. In addition, the co-existence of RhB significantly promoted the photocatalytic degradation of Cr(VI), suggesting a synergy between the degradation of RhB and Cr(VI). Combining the surface photocurrent and electrochemical impedance spectral investigations, the mechanism of enhanced photocatalytic performance of Y-HTNS samples was proposed and explained.