Interrupted growth and photoelectrochemistry of Cu2O and Cu particles on TiO2

Virucidal activity of Cu-doped TiO2 nanoparticles under visible light illumination: Effect of Cu oxidation state

Copper (Cu) is an effective antimicrobial material; however, its activity is inhibited by oxidation. Titanium dioxide (TiO2) photocatalysis prevents Cu oxidation and improves its antimicrobial activity and stability. In this study, the virucidal efficacy of Cu-doped TiO2 nanoparticles (Cu-TiO2) with three different oxidation states of the Cu dopant (i.e., zero-valent Cu (Cu0), cuprous (CuI), and cupric (CuII) oxides) was evaluated for the phiX174 bacteriophage under visible light illumination (Vis/Cu-TiO2). CuI-TiO2 exhibited superior virucidal activity (5 log inactivation in 30 min) and reusability (only 11 % loss of activity in the fifth cycle) compared to Cu0-TiO2 and CuII-TiO2. Photoluminescence spectroscopy and photocurrent measurements showed that CuI-TiO2 exhibited the highest charge separation efficiency and photocurrent density (approximately 0.24 μA/cm2) among the three materials, resulting in the most active redox reactions of Cu. Viral inactivation tests under different additives and viral particle integrity analyses (i.e., protein oxidation and DNA damage analyses) revealed that different virucidal species played key roles in the three Vis/Cu-TiO2 systems; Cu(III) was responsible for the viral inactivation by Vis/CuI-TiO2. The Vis/CuI-TiO2 system exhibited substantial virucidal performance for different viral species and in different water matrices, demonstrating its potential practical applications. The findings of this study offer valuable insights into the design of effective and sustainable antiviral photocatalysts for disinfection.

Recent Advances in TiO2-based Photoanodes for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting has attracted a great attention in the past several decades which holds great promise to address global energy and environmental issues by converting solar energy into hydrogen. However, its low solar-to-hydrogen (STH) conversion efficiency remains a bottleneck for practical application. Developing efficient photoelectrocatalysts with high stability and high STH conversion efficiency is one of the key challenges. As a typical n-type semiconductor, titanium dioxide (TiO 2 ) exhibits high PEC water splitting performance, especially high chemical and photo stability. But, TiO 2 has also disadvantages such as wide band gap and fast electron-hole recombination rate, which seriously hinder its PEC performance. This review focuses on recent development in TiO 2 -based photoanodes as well as some key fundamentals. The corresponding mechanisms and key factors for high STH, and controllable synthesis and modification strategies are highlighted in this review. We conclude finally with an outlook providing a critical perspective on future trends on TiO 2 -based photoanodes for PEC water splitting.

Advances of Drugs Electroanalysis Based on Direct Electrochemical Redox on Electrodes: A Review

The strong development of mankind is inseparable from the proper use of drugs, and the electroanalytical research of drugs occupies an important position in the field of analytical chemistry. This review mainly elaborates the research progress of drugs electroanalysis based on direct electrochemical redox on various electrodes for the recent decade from 2011 to 2021. At first, we summarize some frequently used electrochemical data processing and electrochemical mechanism research derivation methods in the literature. Then, according to the drug therapeutic and application/usage purposes, the research progress of drugs electrochemical analysis is classified and discussed, where we focus on drugs electrochemical reaction mechanism. At the same time, the comparisons of electrochemical sensing performance of the drugs on various electrodes from recent studies are listed, so that readers can more intuitively compare and understand the electroanalytical sensing performance of each modified electrode for each of the drug. Finally, this review discusses the shortcomings and prospects of the drugs electroanalysis based on direct electrochemical redox research.

Two-Dimensional Restructuring of Cu2O Can Improve the Performance of Nanosized n-TiO2/p-Cu2O Photoelectrodes under UV-Visible Light

p-Cu₂O/n-TiO₂ photoanodes were produced by electrodeposition of octahedral p-type Cu₂O nanoparticles over n-type TiO₂ nanotubes. The photoresponse of the composite p-n photoanodes was evaluated in photoelectrochemical cells operating at "zero-bias" conditions under either visible or UV-vis irradiation. In both operating conditions, the produced electrodes invariably followed the p-n-based photoanode operations but exhibited lower photoelectrochemical performance as compared to the bare n-TiO₂ photoanode under UV-vis light. The reported experimental analysis evidenced that such decreased photoactivity is mainly induced by the scarce efficiency of the nanosized p-n interfaces upon irradiation. To overcome such limitation, a restructuring of the originally electrodeposited p-Cu₂O was promoted, following a photoelectrochemical post-treatment strategy. p-Cu₂O, restructured in a 2D leaf-like morphology, allowed reaching an improved photoelectrochemical performance for the p-n-based photoanode under UV-vis light. As compared to the bare n-TiO₂ behavior, such improvement consisted of photoanodic currents up to three times larger. An analysis of the mechanisms driving the transition from compact (∼100 nm) octahedral p-Cu₂O to wider (∼1 μm) 2D leaf-like structures was performed, which highlighted the pivotal role played by the irradiated n-TiO₂ NTs.

Facile Synthesis of Copper(I) Oxide Nanochains and the Photo-Thermal Conversion Performance of Its Nanofluids

In this thesis, Cu2O nanochains were synthesized by thermal decomposition with copper formate-octylamine as the precursor, oleic acid and oleylamine as the catalyst stabilizer agent and paraffin as the solvent. The phase structure and micromorphology of Cu2O nanochains were characterized by X-ray diffraction and transmission electron microscopy. The effect of reaction time and concentration of the precursor on the Cu2O nanochains were discussed, and the formation mechanism of the Cu2O nanochains was analyzed. The results show that Cu2O nanochains were self-assembled by Cu2O nanocrystals; with the extension of the reaction time, Cu2O nanochains gradually become granular; increasing the concentration of the precursor will increase the entanglement degree of the nanochains. Oleic acid contributes to the formation of Cu2O, and oleylamine plays a directional role in the formation of nanochains. On the basis of those phenomenon, a comparison of the Cu2O nanochain-water nanofluids with that of a water-based liquid showed that after irradiating for 3000 s, the temperature of nanofluids reached 91.1 °C while the water was only 75.7 °C. This demonstrates the better performance of the Cu2O nanochain-water nanofluid in the ability of light absorption, thermal conductivity and photothermal conversion.

Photocatalytic and photoelectrocatalytic performance of sonochemically synthesized Cu2O@TiO2 heterojunction nanocomposites

Cu₂O@TiO₂ heterojunction nanocomposites were prepared via ultrasonic method towards the removal of the environmental pollutant of MO by the visible light photocatalytic approach. The structure of prepared Cu₂O@TiO₂ heterojunction nanocomposites was analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, photoluminescence spectroscopy, UV-Visible absorption spectroscopy, diffused reflectance spectroscopy. The photocatalytic degradation ability was tested using methyl orange as a model pollutant. From the observed pseudo-first order reaction, it was clear that Cu₂O@TiO₂ nanocomposites showed enhanced photocatalytic activity (rate = 0.223 s^-1). The formation of demethylated methyl orange as an intermediate was identified from HPLC analysis at a retention time of 3.47 min. When doped with Cu₂O, the TiO₂ preserved the integrity of its structural, revealing the morphology there is no significant changes have been made, favoring photoelectrochemical appliances. In presence of illumination, the photocurrent of Cu₂O@TiO₂ was 4.5 folds greater than that of TiO₂, involving that incorporating with Cu₂O extensively enhanced mobility of electron via reducing the recombination rate of electron-hole pairs.

Photoelectrochemical oxidation of ibuprofen via Cu2O-doped TiO2 nanotube arrays

A p-n junction based Cu2O-doped TiO2 nanotube arrays (Cu2O-TNAs) were synthesized and used as a working anode in a photoelectrochemical (PEC) system. The results revealed that the Cu2O-TNAs were dominated by the anatase phase and responded significantly to visible light. XPS analyses indicated that with an amount of 24.79% Cu doping into the structure, the band gap of Cu2O-TNAs was greatly reduced. SEM images revealed that the supported TiO2 nanotubes had diameters of approximately 80nm and lengths of about 2.63μm. Upon doping with Cu2O, the TiO2 nanotubes maintained their structural integrity, exhibiting no significant morphological change, favoring PEC applications. Under illumination, the photocurrent from Cu2O/TNAs was 2.4 times larger than that from TNAs, implying that doping with Cu2O significantly improved electron mobility by reducing the rate of recombination of electron-hole pairs. The EIS and Bode plot revealed that the estimated electron lifetimes, τel, of TNAs and Cu2O/TNAs were 6.91 and 26.26ms, respectively. The efficiencies of degradation of Ibuprofen by photoelectrochemical, photocatalytic (PC), electrochemical (EC) and photolytic (P) methods were measured.

Helical TiO2 Nanotube Arrays Modified by Cu-Cu2O with Ultrahigh Sensitivity for the Nonenzymatic Electro-oxidation of Glucose

A novel Cu-Cu2O/TiO2/Ti electrode for the nonenzymatic electro-oxidation of glucose has been fabricated by secondary anodic oxidation combined with the electrodeposition method. It represents a new type of copper oxide-TiO2 complex nanostructure that demonstrates a new application. At the potential range from -1.0 to -1.6 V, Cu2+ was electrochemically reduced to Cu2O, accompanied by the simultaneous formation of Cu covering the top surface of the TiO2 nanotubes. The highest response current was obtained at the optimized fabrication conditions with a deposition charge of 1.5 C, a pH of 12, 4 mM CuSO4, and a deposition potential of -1.4 V. The results indicate that Cu2O helps to keep a broad linear range, and the incorporation of Cu nanoparticles improves the response current and sensitivity. The linearity between the response current and the glucose concentration was obtained in the range from 0.1 to 2.5 mM with a sensitivity of 4895 μA cm(-2) mM(-1). Such high sensitivity was attributed to the synergistic effect of the small Cu-Cu2O grain size and the large surface area of the helical TiO2 nanotube arrays as well as the fast electron transfer. Electrochemical impedance spectroscopy has been successfully applied to explain the differences among different electrode interfaces and the change rule of nonenzymatic electro-oxidation properties.

Enhanced photoelectrochemical and photocatalytic activity by Cu2O/SrTiO3 p–n heterojunction via a facile deposition–precipitation technique

In our study, a new visible-light-driven photocatalyst Cu₂O/SrTiO₃ (C/S) heterojunction was firstly prepared by a simple, facile and effective deposition–precipitation technique.

Mesoporous delafossite CuCrO₂ and spinel CuCr₂O₄: synthesis and catalysis

Delafossite CuCrO2 and spinel CuCr2O4 with mesoporous structures have been successfully synthesized using nanocasting methods based on a KIT-6 template. The functional activity of the mesoporous materials was evaluated in applications as heterogeneous catalysts. The activity for photocatalytic hydrogen production of the delafossite structures with different morphologies was characterized and the oxidation state changes associated with photocorrosion of Cu(+) investigated using electron energy loss spectroscopy (EELS). Mg(2+) doping was found to facilitate the casting of ordered structures for CuCrO2 and improves the photocorrosion resistance of delafossite structures. The mesoporous spinel CuCr2O4 nanostructures were found to be active for low temperature CO oxidation.