A Visible Light-Driven α-MnO2/UiO-66-NH2 S-Scheme Photocatalyst toward Ameliorated Oxy-TCH Degradation and H2 Evolution.

Photocatalytic hydrogen production and pollutant degradation using a heterogeneous photocatalyst remains an alternative route for mitigating the impending pollution and energy crisis. Hence, the development of cost-effective and environmentally friendly semiconducting materials with high solar light captivation nature is imperative. To overcome this challenge, α-MnO2 nanorod (NR)-modified MOF UiO-66-NH2 (UNH) was prepared via a facile solvothermal method, which is efficient toward H2 evolution and oxy-tetracycline hydrochloride (O-TCH) degradation. The field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HR-TEM) results of the α-MnO2@UNH (MnU) hybrid reveals its nanorod embedded in MOF matrix, and the X-ray photoelectron spectroscopy (XPS) result confirms the interaction of UNH moiety with α-MnO2 NRs. Additionally, the outstanding separation of photogenerated excitons and the charge-transfer efficacy are further validated by photoluminescence (PL), time-resolved photoluminescence (TRPL), electrochemical impedance spectroscopy (EIS), and transient photocurrent analysis, which are the key causes for photoactivity augmentation in the MnU composites. The MnU-2 composite shows a superior O-TCH degradation efficiency of 93.23% and an excellent H2 production rate of about 410.6 µmol h-1 upon light irradiation. This study provides significant evidence in favor of the suggested mediator-free S-scheme-adapted charge migration path, and it effectively explains the enhanced exciton separation leading to extraordinary catalytic efficiency of the proposed composite.

Compositionally engineered Cd-Mo-Se alloyed QDs toward photocatalytic H2O2 production and Cr(VI) reduction with a detailed mechanism and influencing parameters.

With the exceptional advantages of safety, greenness, and low cost, photocatalytic H2O2 generation has kindled a wonderful spark, although being severely hampered by the terrible photoinduced exciton recombination, migration, and surface decomposition. Here, employing reflux method, the Cd-Mo-Se quantum dots of varying molar ratios of Cd and Mo were synthesized using thioglycolic acid as the capping ligand to regulate their growth. This type of metal alloying promotes rapid charge migration, improves light harvesting, and reduces the rate of charge recombination. The improved optoelectronic properties and boosted activity of Cd-rich ternary CMSe-1 QDs led to the observed exceptional photocatalytic H2O2 yield of 1403.5 µmol g-1 h-1 (solar to chemical conversion efficiency, 0.27%) under visible light, outperforming the other ternary and Se-based QD photocatalysts. Additionally, CMSe-1 shows 93.6% (2 h) hazardous Cr(VI) photoreduction. The enhanced catalytic performance of CMSe-1 corresponds to effective charge carrier separation and transfer efficiency, well supported by PL, TRPL, and electrochemical measurements. Photocatalytic H2O2 production was also studied under varying experimental conditions and the scavenger test suggests a superoxide radical intermediate 2-step single electron reduction pathway. The catalyst-assisted Cr(VI) reduction is substantiated by the zero-order kinetics as well as the determination of the pHPZC value. The catalyst can be employed for a maximum of four times while retaining its activity, according to the photostability and reusability test outcomes. This research presents interesting approaches for producing ternary QDs and modified systems for efficient photocatalytic H2O2 production and Cr(VI) reduction.

Nanoarchitecture of a Ti3C2@TiO2 Hybrid for Photocatalytic Antibiotic Degradation and Hydrogen Evolution: Stability, Kinetics, and Mechanistic Insights.

Designing of a visible-light-driven semiconductor-based heterojunction with suitable band alignment and well-defined interfacial contact is considered to be an effective strategy for the transformation of solar-to-chemical energy and environmental remediation. In this context, MXenes have received tremendous attention in the research community due to their merits of abundant derivatives, elemental composition, excellent metallic conductivity, and surface termination groups. Meanwhile, a facile synthetic strategy for MXene-derived TiO2 nanocomposites with stable framework and higher photocatalytic activity under visible-light irradiation still remains a challenge for researchers. Herein, we report a novel synthetic strategy of preparing a two-dimensional Ti3C2@TiO2 nanohybrid by a facile reflux method under acidic conditions. In this oxidation reaction, protonation of the hydroxyl terminal group of MXene creates Ti more electrophilic and susceptible to an oxidative nucleophilic addition reaction with the presence of both water and oxygen. The physicochemical properties of the nanohybrid Ti3C2@TiO2 were verified by varieties of characterization techniques. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis specifically elucidated the intimate interfacial interaction between Ti3C2 and TiO2. The optimized Ti3C2@TiO2-48 h photocatalyst exhibited the highest tetracycline hydrochloride (TCH, 90% in 90 min) degradation efficiency in comparison to pristine TiO2 with a rate constant (k) of 0.02463 min-1. The major contribution of •O2- and •OH radicals throughout photocatalytic TCH degradation was confirmed by the trapping experiment. Moreover, the photocatalyst showed the highest hydrogen generation rate of 140.8 µmol h-1 along with an apparent conversion efficiency of 2.2%. The excellent photocatalytic activity of Ti3C2@TiO2 originated from the superior electrical conductivity of cocatalyst Ti3C2, which facilitated spatial photogenerated e-/h+ separation and transfer at the Ti3C2 MXene@TiO2 interface. Overall, this research work will describe a promising protocol of designing MXene-derived photocatalysts toward efficient environmental remediation and wastewater treatment applications.

Architecture and Kinetic Studies of Photocatalytic H2O2 Generation and H2 Evolution through Regulation of Spatial Charge Transfer via Z-Scheme Path over a (001) Facet Engineered TiO2@MXene/B-g-C3N4 Ternary Hybrid.

Spatial charge separation and migration are the critical shortcomings dominating the core energy conversion corridors of photocatalytic systems. Here, a biomimetic multi-interfacial architecture providing strong coupled interaction and rapid charge transmission for photostable and competent photocatalytic H2O2 production and H2 evolution is proposed. The triple-hybrid all-solid-state Z-scheme system was formed with the (001) facet exposed TiO2 nanosheets derived from MXene layers and B-g-C3N4 nanosheets (M/(001)TiO2@BCN) through an electrostatic self-assembly strategy with intimate electronic interaction due to Ti orbital modulation and proper stacking among the hybrids. The metallic and highly conductive MXene layers act as solid state electron mediators in the Z-scheme heterojunction that promote electron-hole separation and migration efficiency. Specifically, the MTBCN-12.5 composite provides optimum yield of H2O2 up to 1480.1 µmol h-1 g-1 and a H2 evolution rate of 408.4 µmol h-1 (with ACE 6.7%), which are 4 and 20 fold greater than the pristine BCN, respectively. The enhanced photocatalytic performance is systematically identified by the increased surface area, higher cathodic and anodic current densities of -1.01 and 2.27 mA cm-2, delayed charge recombination as supported by PL and EIS measurement, and excellent photostability. The Z-scheme charge transfer mechanism is validated by time-resolved photoluminescence (TRPL) analysis, cyclic voltametric analysis, and the radical trapping experiment as detected by PL analysis. This research marks a substantial advancement and establishes the foundation for future design ideas in accelerating charge transfer.

All-Aerosol-Jet-Printed Carbon Nanotube Transistor with Cross-Linked Polymer Dielectrics.

The printability of reliable gate dielectrics and their influence on the stability of the device are some of the primary concerns regarding the practical application of printed transistors. Major ongoing research is focusing on the structural properties of dielectric materials and deposition parameters to reduce interface charge traps and hysteresis caused by the dielectric-semiconductor interface and dielectric bulk. This research focuses on improving the dielectric properties of a printed polymer material, cross-linked polyvinyl phenol (crPVP), by optimizing the cross-linking parameters as well as the aerosol jet printability. These improvements were then applied to the fabrication of completely printed carbon nanotube (CNT)-based thin-film transistors (TFT) to reduce the gate threshold voltage (Vth) and hysteresis in Vth during device operation. Finally, a fully aerosol-jet-printed CNT device was demonstrated using a 2:1 weight ratio of PVP with the cross-linker poly(melamine-co-formaldehyde) methylated (PMF) in crPVP as the dielectric material. This device shows significantly less hysteresis and can be operated at a gate threshold voltage as low as -4.8 V with an on/off ratio of more than 104.

Synthesis of Printable Polyvinyl Alcohol for Aerosol Jet and Inkjet Printing Technology.

Polyvinyl Alcohol (PVA) is a promising polymer due to its high solubility with water, availability in low molecular weight, having short polymer chain, and cost-effectiveness in processing. Printed technology is gaining popularity to utilize processible solution materials at low/room temperature. This work demonstrates the synthesis of PVA solution for 2.5% w/w, 4.5% w/w, 6.5% w/w, 8.5% w/w and 10.5% w/w aqueous solution was formulated. Then the properties of the ink, such as viscosity, contact angle, surface tension, and printability by inkjet and aerosol jet printing, were investigated. The wettability of the ink was investigated on flexible (Kapton) and non-flexible (Silicon) substrates. Both were identified as suitable substrates for all concentrations of PVA. Additionally, we have shown aerosol jet printing (AJP) and inkjet printing (IJP) can produce multi-layer PVA structures. Finally, we have demonstrated the use of PVA as sacrificial material for micro-electro-mechanical-system (MEMS) device fabrication. The dielectric constant of printed PVA is 168 at 100 kHz, which shows an excellent candidate material for printed or traditional transistor fabrication.

High Permeability Photosintered Strontium Ferrite Flexible Thin Films.

The paper is focused on the development and optimization of strontium ferrite nanomaterial and photosintered flexible thin films. These magnetic thin films are characterized with direct current (DC) and high frequency measurements. For photosintered strontium ferrite samples, we achieved relative complex permeability of about 29.5-j1.8 and relative complex permittivity of about 12.9-j0.3 at a frequency of 5.9 GHz.

Inkjet-Printed Molybdenum Disulfide and Nitrogen-Doped Graphene Active Layer High On/Off Ratio Transistors.

Fully inkjet-printed device fabrication is a crucial goal to enable large-area printed electronics. The limited number of two-dimensional (2D) material inks, the bottom-gated structures, and the low current on/off ratio of thin-film transistors (TFTs) has impeded the practical applications of the printed 2D material TFTs. In the search for TFTs with high current ratios, we introduce a stable and efficient method of nitrogen-doped graphene (NDG) ink preparation for inkjet printing by liquid-phase exfoliation. The NDG thin film is print-stacked with molybdenum disulfide (MoS2) by multiple printing passes to construct a MoS2-NDG stack. We demonstrate top-gated fully inkjet-printed MoS2-NDG transistors with silver drain, source, and gate electrodes, and a barium titanate (BaTiO3) dielectric. A 100% inkjet-printed MoS2-NDG vertical 2D active heterostructure layer transistor with a current on/off ratio of 1200 is exhibited. The results may lead towards the development of all-printed 2D material-based transistor switches.