Copper oxide nanosheets as an effective nanozyme with haloperoxidase-like activity for the colorimetric detection of H2O2 and glucose.

Copper oxide nanosheets (CuO NSs) have been successfully obtained by exploiting an effective one-step approach of sugar-blowing method followed by calcination. The nanosheets were characterized by several techniques like X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Impressively, CuO NSs display haloperoxidase (HPO) like catalytic activity which catalyses the oxidation of chloride ions by H2O2 giving rise to reactive chlorine species (RCS). A sensitive and selective colorimetric sensor was then demonstrated via the oxidation of chromogenic substrate 3,3',5,5'- tetramethylbenzidine (TMB) by the novel nanoenzyme CuO NSs through the generation of RCS for H2O2 and glucose detection with limit of detection of 109 nM and 21 nM in the linear ranges of 4.6 µM to 769 µM and 0.22 µM to 19.57 µM respectively. Additionally, the methodology is validated for the analysis of glucose in real samples.

Enhanced photocatalytic degradation of Rhodamine B using gold nanoparticles decorated on BaTiO3 with surface plasmon resonance enhancement.

This study focused on synthesizing and applying gold nanoparticle (Au NP) decorated barium titanate (BaTiO3) nanoparticles for photocatalytic purposes. BaTiO3 NPs were synthesized using a facile hydrothermal method. Various techniques were employed to characterize the structure and morphological characteristics of the prepared materials. The photocatalytic degradation of Rhodamine B over the Au NPs-modified BaTiO3 photocatalysts was studied. Trapping experiments were conducted using different scavengers to elucidate the degradation mechanism and the involvement of photogenerated species. The incorporation of an appropriate amount of Au NPs into the composites resulted in a significant improvement in photocatalytic activity, attributed to the combined effect of Schottky junction at the interface and the surface plasmon resonance of Au NPs.

Gum Arabic-mediated synthesis of silver nanoparticles for their applications as colorimetric and SERS-based detection of hydrogen peroxide.

We report on the one-step green method to synthesize Gum Arabic stabilized silver nanoparticles (GA-Ag NPs). The synthesized particles are monodispersed and in the size range of 15-20 nm. The synthesized Ag NPs are used as a colorimetric sensor for the detection of H2O2 and glucose with a detection limit of 11.7 nM and 0.13 µM, respectively. The sensor has also been used for the detection of H2O2 in water samples and glucose in human blood serum samples. The GA-Ag NPs decorated on filter paper have also shown excellent SERS activity for the detection of H2O2 with a detection limit of 0.56 µM.

Solution-processed CZTS thin films and its simulation study for solar cell applications with ZnTe as the buffer layer.

Using zinc tellurium (ZnTe) as the buffer layer in the Cu2ZnSnS4 (CZTS)-based solar cells showed an improvement in overall efficiency. ZnTe is investigated as an alternative to replace the conventional toxic Cd-contained buffer layers. It may also reduce the overall cost of these cells as both layers (ZnTe and CZTS) have eco-friendly and earth-abundant constituents. The sol-gel spin coating method is used for the deposition of CZTS thin films on the corning glass substrates. The X-ray diffraction studies showed the peaks corresponding to (112), (200), (220), and (312) planes which confirmed the formation of the essential kesterite phase. The optical band gap of the deposited films was found at around 1.45 eV by the UV-visible-NIR spectrophotometer. The optimum thickness of the absorber layer (CZTS) and buffer layer (ZnTe) was investigated based on the performance of the ZnO:Al/ZnO/ZnTe/CZTS/Mo cell structure by using the AMPS-1D simulation tool. In contrast, the tool was molded by the experimentally investigated data for the constituent materials of the cell structure. The solar cells' efficiency was increased by 23.47% at 2500 nm and 50 nm thickness of the CZTS and ZnTe layers, respectively. In addition, it was analyzed and found that the current density value showed an improvement with operating temperature as it is one of the requirements in the high solar radiation areas where the temperature even rises more than 50 °C in the summer.

Effect of dissolved salt on the anomalies of water at negative pressure.

Adding salt to water at ambient pressure affects its thermodynamic properties. At low salt concentration, anomalies such as the density maximum are shifted to lower temperature, while at large enough salt concentration, they cannot be observed any more. Here, we investigate the effect of salt on an anomaly recently observed in pure water at negative pressure: the existence of a sound velocity minimum along isochores. We compare experiments and simulations for an aqueous solution of sodium chloride with molality around 1.2 mol kg-1, reaching pressures beyond -100 MPa. We also discuss the origin of the minima in the sound velocity and emphasize the importance of the relative position of the temperatures of sound velocity and density anomalies.

Brillouin spectroscopy of fluid inclusions proposed as a paleothermometer for subsurface rocks.

As widespread, continuous instrumental Earth surface air temperature records are available only for the last hundred fifty years, indirect reconstructions of past temperatures are obtained by analyzing "proxies". Fluid inclusions (FIs) present in virtually all rock minerals including exogenous rocks are routinely used to constrain formation temperature of crystals. The method relies on the presence of a vapour bubble in the FI. However, measurements are sometimes biased by surface tension effects. They are even impossible when the bubble is absent (monophasic FI) for kinetic or thermodynamic reasons. These limitations are common for surface or subsurface rocks. Here we use FIs in hydrothermal or geodic quartz crystals to demonstrate the potential of Brillouin spectroscopy in determining the formation temperature of monophasic FIs without the need for a bubble. Hence, this novel method offers a promising way to overcome the above limitations.

Electrical conductivity and glass formation in nitrile-functionalized pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids: chain length and odd-even effects of the alkyl spacer between the pyrrolidinium ring and the nitrile group.

The electrical conductivity of a series of pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids, functionalized with a nitrile (cyano) group at the end of an alkyl chain attached to the cation, was studied in the temperature range between 173 K and 393 K. The glass formation of the ionic liquids is influenced by the length of the alkyl spacer separating the nitrile function from the pyrrolidinium ring. The electrical conductivity and the viscosity do not show a monotonic dependence on the alkyl spacer length, but rather an odd-even effect. An explanation for this behavior is given, including the potential energy landscape picture for the glass transition.

Nematic-nematic phase transition in the liquid crystal dimer CBC9CB and its mixtures with 5CB: a high-resolution adiabatic scanning calorimetric study.

The phase transition behavior of the liquid crystal dimer α,ω-bis(4,4'-cyanobiphenyl)nonane (CBC9CB), which has been reported to exhibit a nematic-nematic phase transition, has been investigated by means of high-resolution adiabatic scanning calorimetry. This nematic-nematic phase transition is weakly first-order with a latent heat of 0.24±0.01 kJ kg(-1). Mixtures up to 40 wt % with 4-pentyl-4'-cyanobiphenyl (5CB) liquid crystals have also been investigated, which also show this nematic to nematic phase transition. The transition stays weakly first-order with a decreasing latent heat with increasing concentration of 5CB. For mixtures with more than 40 wt % uniaxial nematic-unknown nematic phase transition was not observed.

Large heat capacity anomaly near the consolute point of the binary mixture nitromethane and 3-pentanol.

The large critical anomaly in the isobaric heat capacity C(p,x)(T) of the binary mixture nitromethane + 3-pentanol is measured using high-resolution adiabatic scanning calorimetry. The unique features of this technique provided an alternative approach to the study of the critical behavior of C(p,x)(T), providing further C(p,x)(T) related quantities from which valuable information could be extracted. Our data are in full agreement with the predictions of the Modern Theory of Critical Phenomena; specifically, 3D-Ising model values for the critical exponent α and the universal amplitude ratio values of the leading critical amplitudes, as well as for the first correction-to-scaling ones, provide the optimum fits to represent the experimental data. Evidence for the need of higher-order terms, i.e., first correction-to-scaling term, is given. The large value of the coefficient E for the linear temperature dependence of the background obtained is ascribed to a possible contribution of the regular linear background term, of a higher-order asymmetry term, and of the second correction-to-scaling term. Internal consistency of C(p,x)(T) and its related quantities is successfully checked.

Order of phase transitions and tricriticality in mixtures of octyloxycyanobiphenyl and nonyloxycyanobiphenyl liquid crystals: a high-resolution study by adiabatic scanning calorimetry.

A detailed study has been performed for mixtures of octyloxycyanobiphenyl (8OCB) and nonyloxycyanobiphenyl (9OCB) liquid crystals and nine of their mixtures by means of high-resolution adiabatic scanning calorimetry. The isotropic to nematic transitions are weakly first order with latent heat values in the range usually encountered for this transition in other liquid crystals. With the exception of pure 8OCB, for which only an upper limit of 1.8 J kg(-1) for the latent heat could be established, finite latent heats have been obtained for the nematic to smectic-A transition of all the mixtures and of pure 9OCB. The concentration dependence of their latent heats could be well fitted with a crossover function consistent with a mean-field free-energy expression that has a nonzero cubic term induced by the Halperin-Lubensky-Ma (HLM) coupling between the smectic-A order parameter and the orientational director fluctuations. Clearly first-order transitions with measurable latent heats are found for mole fractions of 9OCB in the mixtures where the effective critical exponent for the specific-heat capacity has substantially lower values than the tricritical one (0.5). This is qualitatively different from what has been observed so far in other liquid-crystal systems and yields strong experimental evidence from a calorimetric experiment for the HLM coupling between the smectic-A order parameter and the director orientation fluctuations.