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Raman thermometry in water, ethanol and ethanol/nitrogen-mixtures from ambient to critical conditions
摘要： We present investigations into remote liquid temperature sensing with Raman spectroscopy using different evaluation methods for the OH stretching vibration band. Water, ethanol and ethanol saturated with nitrogen, all as liquids or liquid-like supercritical fluids, are pumped through a heated microcapillary system at elevated pressures. Raman spectra are recorded from the liquid inside the microcapillary and are evaluated with respect to the temperature sensitivity of the OH stretching vibration. The four approaches applied are (i) to evaluate the center position of the Raman OH-band, (ii) the integrated absolute difference spectrum, (iii) the intensity ratio of two regions of the OH-band, and (iv) the intensity ratio of two fitted Gaussian peaks. The temperature range investigated covers from ambient temperature to the component’s respective boiling temperature or critical temperature at sub- and supercritical pressures. Precision and robustness of the employed methods are characterized. It is shown that two out of the four methods feature temperature deviations smaller than 5 K at all pressures, and that one method can also be applied to liquid mixtures of ethanol and nitrogen. Applicability to other liquids and mixtures is discussed.
关键词： temperature sensing,supercritical fluids,OH stretching vibration,water,Raman spectroscopy,nitrogen,microcapillary,ethanol
更新于2025-09-04 15:30:14
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Automated syringe-pump-based flow-batch analysis for spectrophotometric determination of trace hexavalent chromium in water samples
摘要： In this work, we established an automated spectrophotometric method for determining hexavalent chromium in water samples using an integrated syringe pump-based environmental water analyzer (iSEA) based on the classic 1,5-diphenylcarbazide chemistry. The device was computer-controlled with programs written by LabVIEW. The effects of reagent concentration, sample salinity and foreign ion interferences were investigated. Standard solutions (GBW(E)081584-1) were used to test the accuracy of the method. When equipped with a 5 cm Z-shaped flow cell, the detection limit was 0.024 μM with sample throughput of >30 h-1. In order to meet the requirements for trace Cr(VI) determination, the system was modified with a 2.5 m liquid waveguide capillary cell (internal diameter of 0.55 mm). The sample consumption was less than 2.1 mL. The detection limit was 0.54 nM with sample throughput of 20 h-1 and good linearity with R2=0.9985 (n=110, obtained over 14 days). The two methods were successfully applied to determine Cr(VI) level in different water samples including tap water, river water, industrial wastewater and 37 brands of bottled water with spiked recovery in the range of 89.5%-117%.
关键词： hexavalent chromium,bottled water,Flow-batch analysis,syringe pump,liquid waveguide capillary cell
更新于2025-09-04 15:30:14
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Dual-Phase Molybdenum Nitride Nanorambutans for Solar Steam Generation under One Sun Illumination
摘要： Water evaporation and steam production have been recognized to be considerably crucial due to the vast applications, ranging from waste water treatment, water purification, to alternative green energy solutions by water splitting, catalysis, and in-door heating. Albeit the big variety of photothermal conversion materials (PCMs) developed for this purpose, certain drawbacks, e.g. high cost, complicated synthesis, weak/narrow absorbance, bulkiness, and low evaporation rate, have hindered the application potential. Herein, we report the dual-phase molybdenum nitride nanorambutans, synthesized by a facile method, for solar steam generation. Not only the inherent properties, including strong full-spectrum absorbance, high-efficiency photothermal conversion, and super-hydrophilicity, benefit their water evaporation performance, the interconnected open mesopores of the nanorambutans further boost their capability of light harvesting and water/vapor transportation. Solar energy conversion efficiency of ～97% under one sun together with excellent cycling stability has been demonstrated. In the desalination systems, integrating with the high salt rejection rate, the nanorambutans film can produce a water evaporation rate as high as ～1.70 kg m?2 h?1 with an efficiency of ～98%. Besides its compact size, the record-breaking water evaporation performance of these nanorambutans has exceeded the previous best inorganic PCM. This work introduces molybdenum nitride as a new PCM for efficient solar steam generation and all applications that can benefit from highly localized heating from nano to macro scale.
关键词： desalination,water evaporation,photothermal conversion,molybdenum nitride,solar energy
更新于2025-09-04 15:30:14
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A porous Ni-O/Ni/Si photoanode for stable and efficient photoelectrochemical water splitting
摘要： Excellent photoelectrochemical activity was demonstrated for an easily prepared porous Ni-O/Ni/Si photoanode with an onset potential of 0.93 VRHE, a photocurrent of 39.7 mA cm?2 at 1.23 VRHE, an energy conversion efficiency of 3.2% and a stability above 100 h.
关键词： stability,water splitting,porous Ni-O/Ni/Si photoanode,energy conversion efficiency,photoelectrochemical
更新于2025-09-04 15:30:14
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<i>In situ</i> topotactic fabrication of direct Z-scheme 2D/2D ZnO/Zn <sub/>x</sub> Cd <sub/>1?x</sub> S single crystal nanosheet heterojunction for efficient photocatalytic water splitting
摘要： Direct Z-scheme heterojunction can effectively enhance the photocatalytic activity due to its low carrier recombination rate and high redox ability. In this study, a 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet heterojunction is synthesized in situ by topotactic sulfurization/oxidization pyrolysis of Zn/Cd/Al layer double hydroxides (LDHs). Its unique structure provides not only numerous intimate interfaces but also a direct Z-scheme junction. The in situ topotactic fabrication of ZnO by the oxidation process causes some Zn ions to dissolve out from the Zn0.67Cd0.33S solid solution nanosheets with increase in annealing temperature and time. The longer the time for oxidation, the more ZnO is obtained. The formation of ZnO yields 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet heterojunction, which increases the visible light absorption and boosts the separation of photogenerated carriers. The ZnO/ZnxCd1?xS-4 single crystal nanosheet heterojunction presents the highest photocatalytic activity under visible light irradiation (38.93 mmol h?1 g?1), which is nearly 16.93 times higher than that of Zn0.67Cd0.33S-300, and an external quantum efficiency of 40.97% at λ = 420 nm. The proposed synthetic route for the construction of 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet provides a direct Z-scheme structure with highly efficient photocatalytic hydrogen evolution activity.
关键词： 2D/2D ZnO/ZnxCd1?xS,photocatalytic water splitting,Zn/Cd/Al layer double hydroxides,Direct Z-scheme heterojunction,topotactic sulfurization/oxidization pyrolysis
更新于2025-09-04 15:30:14
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Nanorods Array of SnO2 Quantum Dots Interspersed Multiphase TiO2 Heterojunctions with Highly Photocatalytic Water Splitting and Self-Rechargeable Battery-Like Applications
摘要： Facing an ever-growing demand for sustainable and renewable power sources, it has detonated the development of novel materials for photocatalytic water splitting, but how to enhance the photocatalytic efficiency remains a core problem. Herein, we reported a conceptual effective and experimental confirmed strategy in SnO2 quantum dots (QD) interspersed multiphase (Rutile, Anatase) TiO2 nanorods arrays (SnO2/RA@TiO2 NRs) to immensely enhance the carrier separation for highly efficient water splitting by merging simultaneously the QD, multiphase, and heterojunction approaches. Under this synergistic effect, a doping ratio of 25% SnO2 QD interspersed into multiphase TiO2 NRs exhibited a superior optical adsorption and excellent photocurrent density (2.45 mA/cm2 at 1.0 V), giving rise to a largely enhanced incident light to current efficiency (IPCE) in the UV region (45~50 %). More importantly, this material-based device can act as power supply with a voltage of ~2.8 V after illumination, which can automatically self-recharging by reacting with oxygen vacancy and water molecule to realize reusing. The current study provide a new paradigm about heightening the carrier separation extent of QD interspersed multiphase heterojunctions, fabricate a new solar energy converting material/device, and achieve a highly photocatalytic water splitting/self-charging battery-like application.
关键词： Photocatalytic,Water splitting,Titanium Dioxide,Heterojunction
更新于2025-09-04 15:30:14
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Improved ATR-FTIR detection of hydrocarbons in water with semi-crystalline polyolefin coatings on ATR elements
摘要： In situ measurement of hydrocarbons in water is critical for assuring the safety and quality of drinking water and in environmental remediation activities such as the cleanup of oil spills. Thus, effective detection methods of hydrocarbons in aqueous environments are important and several methods have been used for this type of sensing, including spectroscopic techniques, fiber optic sensors, and chromatography. However, under aqueous conditions, small amounts of hydrocarbons are difficult to detect due to their low concentration in water and robust sensing of these types of compounds in an aqueous environment remains a challenging analytical task. Hydrophobic polymer coatings have been widely used to concentrate hydrocarbons for attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) detection at the surface of an ATR crystal by preventing water molecules from penetrating into the polymer coating while absorbing hydrocarbons. However, in typical coating designs only thin films (<5 μm) can be applied onto the ATR sensor due to the decrease in detection limit and sensitivity to hydrocarbons with increasing film thickness. This paper demonstrates that a semi-crystalline linear low-density polyethylene (LLDPE) polymer coating with thicker thickness (40 μm) can be applied effectively for in situ ATR-FTIR detection of hydrocarbons in aqueous solution. The ATR signal is enhanced by the polymer coating which swells in response to the hydrocarbons and prevents water accumulation at the IR detection interface. Coating the ATR element with a LLDPE film (crystallinity = 12%) reduced the detection time for various hydrocarbons, including toluene, benzene and chloroform. The detection limits and kinetics of the ATR-FTIR detection were not significantly altered when the thickness of the LLDPE coating was increased to improve its mechanical properties which represents a significant improvement from coatings published in the literature. The LLDPE coating described in this research has the potential to be applied as a sensor coating for rapid detection of hydrocarbon-based substances or non-polar biomolecules in aqueous environments.
关键词： LLDPE,water,hydrocarbons,ATR-FTIR,sensor
更新于2025-09-04 15:30:14
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Synthesis of core–shell ZIF-67@Co-MOF-74 catalyst with controllable shell thickness and enhanced photocatalytic activity for visible light-driven water oxidation
摘要： In this paper, a core–shell ZIF-67@Co-MOF-74 catalyst was synthesized by coating 2,5-dihydroxyterephthalic acid (DHTP) molecules on the surface of ZIF-67 crystals via the ligand exchange method. Notably, the ZIF-67@Co-MOF-74 catalyst with shell thicknesses of 10 nm, 25 nm and 50 nm can be further obtained by adjusting the mass ratio of ZIF-67 and DHTP. Compared to individual ZIF-67 or Co-MOF-74 catalyst, the as-prepared core–shell MOF catalyst exhibited enhanced photocatalytic activities for light-driven water oxidation reaction. Furthermore, the content of oxygen evolution by water splitting increased gradually with the increase in shell thickness. The formation of crystal defects and the uncoordinated hydroxyl and carboxyl groups on the surface of core–shell MOFs facilitated the exposure of the metal catalytic center and the adsorption of water molecules through hydrogen bonding interactions to react with the catalytic active center effectively. In addition, the photogenerated holes and electrons could be excellently separated and rapidly transferred at the interface of ZIF-67 (core) and Co-MOF-74 (shell), resulting in effective increase in the interfacial charge transfer rate. Furthermore, this simple and novel method is also applicable to three other carboxylic acid ligands, which implies that it may be a general method that can be extended to other ligands for fabricating different core–shell ZIF-67@MOF crystals.
关键词： ZIF-67@Co-MOF-74,ligand exchange method,water oxidation,core–shell,photocatalytic activity
更新于2025-09-04 15:30:14
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Ta <sub/>3</sub> N <sub/>5</sub> /Co(OH) <sub/>x</sub> composites as photocatalysts for photoelectrochemical water splitting
摘要： Ta3N5 nanotubes (NTs) were obtained from nitridation of Ta2O5 NTs, which were grown directly on Ta foil through a 2-step anodization procedure. With Co(OH)x decoration, a photocurrent density as high as 2.3 mA cm?2 (1.23 V vs. NHE) was reached under AM1.5G simulated solar light; however, the electrode suffered from photocorrosion. More stable photoelectrochemical (PEC) performance was achieved by first loading Co(OH)x, followed by loading cobalt phosphate (Co–Pi) as double co-catalysts. The Co(OH)x/Co–Pi double co-catalysts may act as a hole storage layer that slows down the photocorrosion caused by the accumulated holes on the surface of the electrode. A “waggling” appearance close to the “mouth” of Ta2O5 NTs was observed, and may indicate structural instability of the “mouth” region, which breaks into segments after nitridation and forms a top layer of broken Ta3N5 NTs. A unique mesoporous structure of the walls of the Ta3N5 NTs, which is reported here the first time, is also a result of the nitridation process. We believe that the mesoporous structure makes it difficult for the nanotubes to be fully covered by the co-catalyst layer, hence rationalizing the remaining degradation by photocorrosion.
关键词： photoelectrochemical water splitting,photocorrosion,Co–Pi,Co(OH)x,mesoporous structure,Ta3N5 nanotubes
更新于2025-09-04 15:30:14
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Biomimetic Hierarchical TiO <sub/>2</sub> @CuO Nanowire Arrays-Coated Copper Meshes with Superwetting and Self-Cleaning Properties for Efficient Oil/Water Separation
摘要： Creating a practical and energy-efficient method with high efficiency to separate oil–water mixtures and emulsions is essential for sustainable aquatic ecosystem and waste oil recycling. Herein, we reported a completely inorganic hierarchical TiO2@CuO nanowire array-coated copper mesh membrane fabricated using chemical oxidation and hydrothermal recrystallization. The biomimetic hierarchical nano-/micro-structure can form a lotus-leaf-like interface with fine surface roughness and hydration ability, thus endows the membrane superhydrophilic and underwater superoleophobic nature. Thus, the as-synthesized TiO2@CuO nanowire array-coated copper mesh membrane demonstrated promising water flux of 87.6 kL·h-1·m-2 and ultrahigh separation efficiency with oil residue of only 12.4 mg·L-1 in the permeate. Moreover, the uniformly immobilized TiO2 nanoparticles exhibit UV-irradiated photocatalytic ability, which can be effectively regenerate the contaminated membrane after exposure to UV irradiations for 60 min. Therefore, this high efficiency, reusable, and easy-scalable membrane fabrication strategy may possess practical potential for next-generation oil/water separation application.
关键词： Biomimetic morphology,self-cleaning,nano-/micro- hierarchical structure,oil/water separation
更新于2025-09-04 15:30:14