Irregular Nanoparticles Research Articles

Impact of ethanol shock on the structural change and emulsifying capacity of bovine lactoferrin

The current study was focused on the structural change and emulsifying property of bovine lactoferrin (bLF) shocked by diverse ethanol levels (0%, 15%, 30%, 45%, 60%, and 75%, v/v). The fraction of β-sheet conformation was around 38.0% and dominated the bLF secondary structural component with the ethanol level from 0% to 75% (v/v). Both Try and Trp residues were involved in the interaction between bLF and ethanol. Hydrophobic effects and hydrogen bonds played crucial roles in the associations between bLF and ethanol molecules. Morphological observation revealed that the individual microstructures of bLF shocked by different levels of ethanol were irregular nanoparticles, worm-like structures, and short bars. The result of emulsifying capacity suggested that the bLF emulsion was stable at the ethanol level of 45% (v/v). Interfacial tensions were significantly decreased from 17.28 ± 0.27 to 1.78 ± 0.05 mN/m for single aqueous ethanol solutions, and from 13.58 ± 0.41 to 0.39 ± 0.01 mN/m for the bLF-E solutions with the ethanol level from 0% to 75% (v/v). Particle size distribution results and confocal laser scanning microscopy images evidenced that ethanol molecules were adsorbed at the oil-water interface, and bLF molecules escaped from the interface with the ethanol levels from 0% to 60% (v/v). As the level of ethanol was increased from 0% to 60% (v/v), the bLF surface load was significantly decreased from 98.44 ± 0.81 to 0.06 ± 0.06 mg/m 2 . The findings facilitated an understanding of the impacts of the structural variation of bLF and the concentration alteration of ethanol as a co-emulsifier on the emulsifying capacity of bLF. • Ethanol altered the tertiary conformation of bLF and led to its local denaturation. • BLF exhibited a prominent emulsifying capacity at the ethanol level of 45% (v/v). • Ethanol and bLF synergistically reduced the interfacial tension at the oil-water interface. • The structural change of bLF was intrinsically driven to enhance its emulsifying activity. • As a co-emulsifier ethanol modulated the emulsifying capacity of bLF.

Fabrication of NiCo2Se4@ NiWO4 nanocomposites for high performance supercapacitor applications

The rational designing and fabrication of transition metal selenium-based nanomaterials showed great attraction to improve the reliable and proficient energy storage device. NiCo2Se4@ NiWO4 nanocomposites prepared using a two-step hydrothermal process for high-performance supercapacitor's applications. The XRD, SEM, FT-IR, Raman, UV–Vis and PL emission spectroscopy were used to investigate the structural, morphological, elemental composition and optical properties of the as-prepared samples. Moreover CV and GCD used to study the electrochemical properties. The result indicates that crystallite size increasing while the bandgap energy reduces to 2.07 e V as the NiWO4 content increases. SEM revealed that prepared samples have irregular shape non uniform nanoparticles. Among all composites we obtained a high value of capacitance of 828.731 F/g for the 6 % composite of NiCo2Se4@NiWO4 at the scan rate of 50 mV/s within the potential range of 0.0–0.7 V. Thus 6 % composites show best electrochemical property. The prepared nanomaterials have the potential to be a promising electrode material for further study and practical applications in the energy storage industry.

Influence of Reagents on the Synthesis Process and Shape of Silver Nanoparticles.

The aim of this study was to prepare the silver nanoparticles (AgNPs) via chemical reduction and analyze the impact of used reduction agents: sodium borohydride (NaBH4), trisodium citrate (TSC), polyvinylpyrrolidone (PVP), and hydrogen peroxide (H2O2) on the reduction rate of Ag+ ions to Ag0, and on nanoparticles shape. It was proven that combinations of reduction agents dramatically influence the synthesis rate of AgNPs and the color of solutions, which depends on the shape and size of nanoparticles. NaBH4, TSC, and PVP showed good reduction power. In particular, TSC proved to be a key factor influencing the shape of AgNPs. The shape of nanoparticles influences the color of colloidal solutions. Yellow solutions, where UV-vis absorbance maxima (ABSmax) are in the wavelength interval 380–420 nm, contain spherical particles with a mean size of 25 nm, whereas the blue shift of ABSmax to wavelengths higher than 750 nm indicate the presence of triangular nanoparticles (size interval 18–150 nm). A mixture of spherical, triangular, irregular, and hexagonal nanoparticles give different color, e.g., green. The formation and stability of AgNPs was tracked by UV-vis spectroscopy, size and shape by TEM techniques, and particle size distribution was studied by particle size analyzer.

Crystal Growth of Osmium(IV) Dioxide in Chlorine-Bearing Hydrothermal Fluids

A mineral’s morphology is usually related to its growth process and environment. This study reported crystal growth of OsO2 through hydrolysis experiments of K2OsCl6 at 150–550 °C and 100 MPa to investigate the growth mechanism of OsO2 and the transport and enrichment of Os in chlorine-bearing hydrothermal fluids. Time-series experimental results showed that the OsO2 crystals grow from 40–150 nm irregular nanoparticles to 150–450 nm nanospheres with time. As the temperature and initial solution concentrations increase, OsO2 can form more uniform and larger OsO2 nanosphere crystals, suggesting a positive effect of temperature and initial solution concentration on the crystal growth of OsO2. The results indicate that the nucleation and aggregate growth driven by the hydrolysis of Os–chloride complex controls the early growth of OsO2 crystals for a short duration; however, after the hydrolysis reaches equilibrium, the growth process of OsO2 nanosphere crystals is dominated mostly by the Ostwald ripening, where the diffusion of Os ions along the fluid–nanocrystal boundary facilitates the coarsening. Given that the transport and cycle of Os from the lithosphere to the hydrosphere is controlled mainly by the stability of the Os–chloride complex, OsO2 nanosphere crystals could occur in seafloor hydrothermal vent systems.

Controlling the crystalline orientation and textual morphologies of the VO2 film and the effect on insulator–metal transition properties

Monoclinic VO2 films were prepared over quartz substrates through thermal oxidation of sputtered vanadium films under continuous O2 flow in a vacuum. It was found that an additional vacuum pre-heating before the thermal oxidation could have a great effect on film crystalline orientation and textual morphologies. The film exhibits a preferable growth along [011] direction and consists of uniform small inter-connected nanoparticles, while the untreated film shows (200) orientation and is composed of large irregular nanoparticles that connect via disorder boundaries. The (011) orientated film shows slightly higher full solar and IR light modulations. The electric resistance results also show that the metal–insulator transition (MIT) of the (011) orientated film presents a larger amplitude, higher sharpness, and narrower hysteresis as compared to the (200) orientated film. The difference in textual structures of the orientated films is the main physical reason that affects the MIT of m-VO2 films.

One-pot controlled microwave synthesis of Broadband-light absorbing irregular gold nanoparticles for solar cell application

Improvement of light-harvesting efficiency using the localized surface plasmon resonance (LSPR) from the metals nanoparticles (MNPs) is a promising approach to boost the efficiency of the solar energy conversion systems. To attain the narrowband SPR, synthesis of the monodisperse MNPs with particular shapes and sizes is cumbersome and has great importance for (surface-enhanced Raman spectroscopy) SERS application. Contrary, broadband SPR is prominent for solar cell applications to absorb maximum sunlight from the solar spectrum. Incorporating polydisperse MNPs of mixed shapes and sizes is a unique approach to realizing the broadband SPR for solar cell application. However, the synthesis of polydisperse MNPs with good reproducibility is challenging. To address this issue, we report facile one-pot microwave synthesis of mixed shapes and sizes of Au nanoparticles (Au-Mx), possessing broadband SPR with decent reproducibility. Microwave-assisted uniform heating provides the control over the reaction parameter to produce identical SPR. Further, the light-harvesting ability of the Au-Mx is demonstrated by incorporating ∼ 1% of Au-Mx in photoanode while fabricating the dye-sensitized solar cells (DSSCs). The photoconversion efficiency (PCE) of the Au-Mx loaded DSSCs improved by ∼ 30% compared to the reference devices, indicating the effective utilization of broadband SPR for efficient charge generation in plasmonic devices.

The synthesis of long-term stable amorphous calcium carbonate in water-free ethylene glycol system without any phase stabilizer

Amorphous calcium carbonate (ACC) plays an important role in the biomineralization process and has a wide application in biological medicine area. In the present work, stable ACC was successfully prepared in water-free ethylene glycol system, by mixing the ethylene glycol solution of CaCl2 and K2CO3 without phase stabilizer. The CaCO3 obtained at different aging times (from 1 min to 3 months) and reaction temperatures (from 0 °C to 60 °C) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electronic diffraction (SAED). XRD results indicate that ACC is the only phase in all samples and SAED results verify the existence of ACC. SEM and TEM images display that the irregular nano-particles were aggregated into irregular porous micro-particles, the pores become smaller with the aging time increase and the reaction temperature elevating, and some relative regular particles (near ellipsoidal or spherical) were formed when system is aged for a long time (3 months) at a low temperature (20 °C) or for a short time (30 min) at a high temperature (60 °C). As-synthesized ACC can be persistent in vacuum or organic solvent for a long time (1 month) at room temperature.

Preparation and properties of SnSb/C/DLC nanofibers with different precursors based on AP-PECVD

In order to explore the morphology and improved electrochemical performance of diamond-like carbon (DLC) deposited on SnSb/C nanofiber derived from different precursors by the atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technology. SnCl4•5H2O/SbCl3 (I), Sn(CH3COO)2/Sb(CH3COO)3 (II) were used as SnSb precursors, respectively, the SnSb/C nanofiber membranes were prepared by electrospinning and carbonization, and then DLC was deposited on different SnSb/C nanofibers to obtain SnSb/C/DLC nanofibers. It is shown that the densified and irregular cubic-like DLC nanoparticles were deposited on SnSb/C (I) nanofibers. While on the SnSb/C(II) nanofibers, DLC nanoparticles exhibited as sparse and spherical. Meanwhile, both SnSb/C/DLC nanofibers have good structural stability, especially higher sp3/sp2 ratios DLC was shown in the SnSb/C/DLC (I) nanofiber than that of SnSb/C/DLC (II) one. By comparison, SnSb/C/DLC(I) nanofibers have excellent electrochemical performance, the capacity retention is 69.33% after 100 cycles, and the capacity retention rate from 20 to 100 cycles is 109.24%. This reveals that DLC materials with higher C–C content and uniform distribution have a positive effect on the aspect of inhibiting SnSb alloys volume expansion.

Influence of preparation methods of supports on the deNOx performance and alkali-metal resistance over TiO2/CeO2 catalysts in NH3-SCR reaction

Two kinds of CeO2 supports were synthesized by precipitation method and hydrothermal method, respectively, and then TiO2 species were loaded on their surface to prepare two TiO2/CeO2 catalysts (abbreviated as Ti/Ce-PM and Ti/Ce-HM). Experimental results show that Ti/Ce-PM and Ti/Ce-HM catalysts exhibit irregular nanoparticle morphology and specific tubular morphology, respectively, while the deNOx performance and anti-K poisoning ability of Ti/Ce-HM catalyst are worse than those of Ti/Ce-PM catalyst, which suggests that the random loading of TiO2 species on the tubular CeO2 support doesn’t enhance the deNOx performance and alkali-metal resistance. However, physicochemical property characterizations display that the excellent deNOx performance of Ti/Ce-PM catalyst can be attributed to better dispersion of TiO2 species, more excellent redox performance and surface acidity (especially B acid), larger Ce3+ content and Oα ratio, stronger electron interaction between Ce and Ti through the redox cycle of Ce3+ + Ti4+ ↔ Ce4+ + Ti3+, as well as easier desorption and decomposition of the adsorbed NOx species. Furthermore, stronger anti-K poisoning ability of Ti/Ce-PM catalyst results from that the negative impact of K2O species on the redox performance, surface acidity, Ce3+ content, and Oα ratio of Ti/Ce-PM catalyst is smaller than that on Ti/Ce-HM catalyst.

In silico modeling of the antagonistic effect of mercuric chloride and silver nanoparticles on the mortality rate of zebrafish (Danio rerio) based on response surface methodology.

In this study, in silico modeling was designed to examine the antagonistic effect of mercuric chloride (HgCl2) and silver nanoparticles (AgNPs) on the mortality rate of zebrafish (Danio rerio) based on response surface methodology (RSM). Adult zebrafish (Danio rerio) with an average weight of 0.75 ± 0.16g were used in this study. An interaction between HgCl2 and AgNPs was evaluated using DLS, TEM, and EDX mapping. In addition, RSM was applied to determine and predict the mortality rate of zebrafish induced by HgCl2 in the presence of non-lethal concentrations of AgNPs and to optimize dependent and independent variables. Following exposure to HgCl2, in vitro observations showed an increase in the hydrodynamic size of AgNPs and the formation of irregular nanoparticles. EDX mapping analysis also demonstrated the deposition of Hg ions on the surface of AgNPs, indicating the interaction between HgCl2 and AgNPs (i.e., the amalgamation of Hg and AgNPs). Moreover, in silico and in vivo findings illustrated that the mortality rate of zebrafish increased significantly in a concentration-dependent manner; however, the mortality rate reduced greatly in the presence of AgNPs during 96-h exposure. Statistically significant correlation and regression were also observed for the mortality rate between the actual and predicted values based on the ANOVA results, showing that the proposed model fits well. The most critical conditions of mortality rate were occurred by HgCl2 concentration of 0.23mg L-1 and AgNP concentration of 0.04mg L-1 that yielding maximum fish mortality rate of 96.541%. Additionally, the obtained value for model desirability was equal to 1.000 (i.e., the highest possible value). In conclusion, this statistical model could accurately describe the relationship between independent and dependent variables, and consequently boost substantially the experimental design of ecotoxicological studies by reducing the number of model organisms, toxic and chemical substances, time, and budget.

Synthesis of V Doped Ca Bismuthate Nanoflakes for Photocatalytic Removal of Crystal Violet Dye

Background: Crystal Violet Dye (CV) can cause severe eye irritation and cancer due to its adsorption, ingestion, and inhalation effect. Therefore, CV in wastewater systems poses as a severe risk to human health and the environment. It is essential to remove CV before CV is discharged in the environment. Methods: Vanadium doped calcium bismuthate nanoflakes with the vanadium mass ratio of 1 wt%, 3 wt.%, 5 wt.%, and 10 wt.% have been synthesized by a simple hydrothermal route using sodium vanadate as a vanadium raw material. The obtained vanadium doped calcium bismuthate products were analyzed by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and solid diffuse reflection spectrum. Results: XRD patterns show that the vanadium in the doped nanoflakes exists as triclinic Bi3.5V1.2O8.25 and monoclinic Ca0.17V2O5 phases. SEM observations show that the morphology of the products is closely related to the vanadium mass ratio. The morphology changes from the nanoflakes to irregular nanoparticles is observed by increasing the vanadium mass ratio. The bandgap of the nanoflakes decreases to 1.46 eV and 1.01 eV when the doped vanadium mass ratio reaches 5 wt.% and 10 wt.%, respectively. The photocatalytic performance for the CV removal can be greatly enhanced using 5 wt.% and 10 wt.% vanadium doped calcium bismuthate nanoflakes, respectively. By increasing the irradiation time, vanadium mass ratio, and dosage of the nanoflakes, the photocatalytic activity for the CV removal can be improved. Conclusion: 10 wt.% vanadium doped calcium bismuthate nanoflakes have the best photocatalytic performance for CV removal. Vanadium-doped calcium bismuthate nanoflakes exhibit great application potential for the removal of organic pollutants.

Sustainable Claisen-Schmidt chalcone synthesis catalysed by plasma-recovered MgO nanosheets from seawater

Chalcones enable the biosynthesis of flavonoids which protect plants from infections and parasites and have emerged as valuable medicines against diverse human diseases. The common way to synthesize chalcones through the homogeneous catalytic Claisen-Schmidt condensation reaction is compromised from difficult catalyst recovery, waste generation, side reactions, and low yield. As a solution, solid base catalysts are developed as a green catalytic process. It is still a major challenge to synthesize highly active heterogeneous catalysts with a quick, simple, sustainable, and economical approach in the chalcone synthesis. To address these issues, a simple and sustainable synthesis of chalcones has been accomplished here by the solvent-free Claisen-Schmidt condensation reaction using magnesium oxide (MgO) nanosheets as the catalyst. The heterogeneous two-dimensional (2D) MgO catalyst was synthesized using salt recovered from inexhaustible seawater, using an atmospheric pressure plasma (APP)-assisted method making the whole method sustainable and potentially economically feasible. The catalytic activity of the 2D nanosheets was compared with irregular MgO nanoparticles. Irregular MgO showed 25% of benzaldehyde and 10% of acetophenone conversion, while 2D MgO showed >99% of conversion of both reactants with a product selectivity of 100%, while no products were formed in the absence of a catalyst. The effect of substituent groups on the benzaldehyde moiety on the catalytic activity was also analysed. The prepared 2D MgO catalyst showed reusability up to three cycles without any significant loss in the catalytic activity.

Carbon foam-supported CoN nanoparticles and carbon nanotubes hybrids as bifunctional reduction electrocatalyst

CoN nanoparticles and carbon nanotubes hybrid supported on carbon foam (INPs-CoN/CNTs-CF) electrocatalyst was synthesized by one-step pyrolysis of irregular nanoparticles ZIF-67 (ZIF-67-INPs) with melamine foam. The INPs-CoN/CNTs-CF electrocatalyst exhibited remarkable activity for ORR with a high half-wave potential of 0.862 V vs. RHE, and a good HER electrocatalytic activity with overpotential of 180 mV at 10 mA cm−2 and a Tafel slope of 102.5 mV dec−1. This electrocatalyst can be a promising bifunctional alternative for both ORR and HER. This work provides a new insight for the design of new-type multi-functional electrocatalysts for practical applications.

Synthesis of Vanadium Doped Lanthanum Bismuthate Nanorods for Enhanced Photocatalytic Activity.

Vanadium doped lanthanum bismuthate nanorods with vanadium ratio of 1%, 3%, 5% and 10 wt.% were fabricated through the hydrothermal method using sodium orthovanadate as vanadium source. Vanadium doped lanthanum bismuthate nanorod products were analyzed by scanning electron microscopy, X-ray diffraction pattern and diffuse reflection spectrum. X-ray diffraction patterns show that vanadium in the vanadium doped lanthanum bismuthate nanorods exists as triclinic Bi23V₄O44.5 and monoclinic LaVO₄ phases. Scanning electron microscopy observations show that the size and micro-morphology of the vanadium doped products are closely relative to the vanadium mass ratio. The length of the vanadium doped nanorods decreases and the morphology changes from nanorods to irregular nanoparticles with increasing the vanadium mass ratio. Solid UV-vis diffuse reflectance measurement shows that the bandgap value of the doped lanthanum bismuthate nanorods is narrowed from 2.37 eV to 2.25 eV after the vanadium doping ratio is increased from 1% to 10%. The doped lanthanum bismuthate nanorods illustrate enhanced photocatalytic performance for methylene orange (MO) removal with the irradiation of sunlight. The catalytic performance for MO removal depends on the irradiation time, vanadium content and dosage of the nanorods. The doped lanthanum bismuthate nanorods with the vanadium mass ratio of 10% possess the best MO catalytic degradation performance.

Simple Fabrication of Visible Light-Responsive Bi-BiOBr/BiPO4 Heterostructure with Enhanced Photocatalytic Activity

A Bi-BiOBr/BiPO4 heterojunction structure was successfully synthesized via a two-step solvothermal method with ethylene glycol as a reducer. Little BiPO4 irregular polyhedrons and little metal Bi spherical nanoparticles were uniformly dispersed on the surface of BiOBr nanosheets with intimate contact and formed a heterojunction structure between BiPO4 and BiOBr. It was found that Bi-BiOBr/BiPO4 had a significant improvement in photocatalytic performance for RhB degradation compared to bare BiOBr and BiPO4. The photocatalytic degradation rate constant of 0.2-Bi/BiOBr/BiPO4 was 1.44 h-1, which was 3.8 times and 14.2 times more than that of bare BiOBr and BiPO4, respectively. This is attributed to the formation of a ternary heterojunction, which benefits the separation of photogenerated electron-hole pairs. Furthermore, with the introduction of metal Bi, the SPR effect of metal Bi can effectively improve the absorption ability of Bi-BiOBr/BiPO4 photocatalyst, resulting in enhanced photoactivity. In this work, the mechanism of photocatalytic degradation was studied by using the photochemical technique and the capture experiment of active species, and it was revealed that h+ and ⋅O2- played a major role in the photocatalytic process.

Sonochemical Synthesis of Vaterite-Type Calcium Carbonate Using Steamed Ammonia Liquid Waste without Additives.

Herein, metastable spheroidal vaterite calcium carbonate (CaCO3) was prepared using a simple ultrasound technique. The fabricated material comprises an irregular nanoparticle aggregate when steamed ammonia liquid waste, that is, (CaCl2) and (NH4)2CO3, is used as the raw material at atmospheric temperature, without any surfactants. The effects of ultrasound amplitude, probe immersion depth, and solution volume on particle properties were investigated. The obtained samples were identified and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and the Brunauer–Emmett–Teller technique. Our experiments show that the probe immersion depth and the reaction volume are the key parameters that impact the diameter size and size distribution of the fabricated spheroidal vaterite CaCO3 particles. The ultrasound amplitude considerably affected the particle size and the specific surface area. A possible formation mechanism for pure vaterite is proposed herein, which suggests that simple vaterite CaCO3 is formed owing to the special properties of steamed ammonia liquid waste and the synergistic effects of the ultrasonic system. This study may provide a new method for vaterite CaCO3 synthesis.

Biogenic Silver Nanoparticles from Iris tuberosa as Potential Preservative in Cosmetic Products.

Biogenic-silver nanoparticles emerge as new nanosilver platforms that allow us to obtain silver nanoparticles via “green chemistry”. In our study, biogenic-silver nanoparticles were obtained from Iris tuberosa leaf extract. Nanoparticles were characterized by a UV-vis spectroscopy, dynamical light scattering technique. The transmission electron microscope revealed spheric and irregular nanoparticles with 5 to 50 nm in diameter. Antimicrobial properties were evaluated against typical microbial contaminants found in cosmetic products, showing high antimicrobial properties. Furthermore, natural moisturizing cream was formulated with biogenic-silver nanoparticles to evaluate the preservative efficiency through a challenge test, indicating its promising use as preservative in cosmetics.

Electrochemical detection of carbendazim with mulberry fruit-like gold nanocrystal/multiple graphene aerogel and DNA cycle amplification.

An aptasensor for electrochemical detection of carbendazim is reported with mulberry fruit-like gold nanocrystal (MF-Au)/multiple graphene aerogel (MGA) and DNA cycle amplification. HAuCl4 was reduced by ascorbic acid in a CTAC solution containing KBr and KI and formed trioctahedron gold nanocrystal. The gold nanocrystal underwent structural evolution under enantioselective direction of l-cysteine. The resulting MF-Au shows a mulberry fruit-like nanostructure composed of gold nanocrystals of about 200 nm as the core and many irregular gold nanoparticles of about 30 nm as the shell. The exposure of high-index facets improves the catalytic activity of MF-Au. MF-Au/MGA was used for the construction of an aptasensor for electrochemical detection of carbendazim. The aptamer hybridizes with assistant strand DNA to form duplex DNA. Carbendazim binds with the formed duplex DNA to release assistant strand DNA, triggering one three-cascade DNA cycle. The utilization of a DNA cycle allows one carbendazim molecule to bring many methylene blue–labeled DNA fragments to the electrode surface. This promotes significant signal amplification due to the redox reaction of methylene blue. The detection signal is further enhanced by the catalysis of MF-Au and MGA towards the redox of methylene blue. A differential pulse voltammetric signal, best measured at − 0.32 V vs. Ag/AgCl, increases linearly with the carbendazim concentration ranging from 1.0 × 10−16 to 1.0 × 10−11 M with a detection limit of 4.4 × 10−17 M. The method provides ultrahigh sensitivity and selectivity and was successfully applied to the electrochemical detection of carbendazim in cucumber.Graphical abstract This study reports on an ultrasensitive aptasensor for electrochemical detection of carbendazim in cucumber based on mulberry fruit–like gold nanocrystal–multiple graphene aerogel and DNA cycle double amplification.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-021-04886-y.

Bimetallic MOFs-derived coral-like Ag-Mo2C/C interwoven nanorods for amperometric detection of hydrogen peroxide.

Coral-like Ag-Mo2C/C-I and blocky Ag-Mo2C/C-II composites were obtained from one-step in situ calcination of [Ag(HL)3(Mo8O26)]n·nH2O [L: N-(pyridin-3-ylmethyl) pyridine-2-amine] under N2/H2 and N2 atmospheres, respectively. The coral-like morphology of Ag-Mo2C/C-I is composed of interwoven nanorods embedded with small particles, and the nano-aggregate of Ag-Mo2C/C-II is formed by cross-linkage of irregular nanoparticles. The above composites are decorated on glassy carbon electrode (GCE) drop by drop to generate two enzyme-free electrochemical sensors (Ag-Mo2C/C/GCE) for amperometric detection of H2O2. In particular, the coral-like Ag-Mo2C/C-I/GCE sensor possesses rapid response (1.2 s), high sensitivity (466.2 μA·mM-1·cm-2), and low detection limit (25 nM) towards trace H2O2 and has wide linear range (0.08 μM~4.67 mM) and good stability. All these sensing performances are superior to Ag-Mo2C/C-II/GCE, indicating that the calcining atmosphere has an important influence on microstructure and electrochemical properties. Theexcellent electrochemical H2O2 sensing performance of Ag-Mo2C/C-I/GCE sensor is mainly attributed to the synergism of unique microstructure, platinum-like electron structure of Mo2C, strong interaction between Mo and Ag, as well as the increased active sites and conductivity caused by co-doped Ag and carbon. Furthermore, this sensor has been successfully applied tothe detection of H2O2 in human serum sample, contact lens solution, and commercial disinfector, demonstrating the potential in related fields of environment and biology. Graphical abstract.

Significant magnetic, dielectric and magnetodielectric properties of CuO nanoparticles prepared by exploding wire technique

The CuO nanoparticles, prepared by exploding wire technique (EWT) followed by annealing in oxygen atmosphere at 900 °C, have been studied for phase purity and structure formation by employing X ray diffraction (XRD) method. Rietveld refinement and Debye-Scherrer analyses ensured the formation of monoclinic single phase of CuO nanoparticles with an average crystallite size of ~ 21 nm. Irregular shape nanoparticles in the size range of 5–30 nm were observed by Transmission Electron Microscopy. The temperature dependent (5–300 K) magnetization measurements have been performed to ascertain the magnetic properties of the prepared nanoparticles, which indicated the antiferromagnetic behavior around 230 K. The temperature dependent (10–300 K) dielectric measurements in 0 T and 1.3 T external magnetic fields demonstrated the frequency dependent dispersive behavior of CuO nanoparticles in the temperature range 100–200 K. The dielectric relaxation mechanism of CuO nanoparticles was further analyzed and found to follow the Arrhenius like behavior. Finally, we could observe that the Variable range hopping (VRH) is more precise in present case of CuO nanoparticles. Notably, the magnetodielectric response (MDR) of the order of 2.5 is also observed at 12 kHz frequency at the temperature around 150 K in the optimal magnetic field of 1.3 T. This proves to be an uncommon interesting property of prepared CuO nanoparticles and may lead to new technological applications.