All that Glitters Is Not Gold: A Probe into Photocatalytic Nitrate Reduction Mechanism over Noble Metal Doped and Undoped TiO₂

Photocatalytic reduction of aqueous nitrate has been thoroughly studied over noble metals doped and pristine TiO₂ synthesized by a customized single step microwave assisted hydrothermal method. The synthesized catalysts are systematically characterized using XRD, Raman spectroscopy, FE-SEM, HR-TEM, XPS, diffuse reflectance spectroscopy, and PL measurements. The characterization reveals the successful synthesis of highly crystalline doped and undoped nano-TiO₂. The photocatalytic rate of aqueous nitrate reduction over undoped TiO₂ is found to be higher than that of noble metal doped TiO₂. Mechanistic studies of the photocatalytic reduction are carried out with the help of different hole (oxalic acid, and methanol) and electron (sodium persulfate) scavengers, which reveal that the photogenerated electrons are the primary agents toward efficient nitrate photoreduction. Detailed studies have revealed that the noble metal doping in TiO₂ helps in efficient photogeneration of H₂ compared to the undoped analogue, however, the <i>in situ</i> produced H₂ is found to be inefficient in reducing NO₃^–. The conduction band position from first principle calculations with respect to the nitrate and hydrogen reduction potentials derived from cyclic voltammetry provide insights to the electron transfer process in determining the reaction pathway

All that Glitters Is Not Gold: A Probe into Photocatalytic Nitrate Reduction Mechanism over Noble Metal Doped and Undoped TiO₂

Photocatalytic reduction of aqueous nitrate has been thoroughly studied over noble metals doped and pristine TiO₂ synthesized by a customized single step microwave assisted hydrothermal method. The synthesized catalysts are systematically characterized using XRD, Raman spectroscopy, FE-SEM, HR-TEM, XPS, diffuse reflectance spectroscopy, and PL measurements. The characterization reveals the successful synthesis of highly crystalline doped and undoped nano-TiO₂. The photocatalytic rate of aqueous nitrate reduction over undoped TiO₂ is found to be higher than that of noble metal doped TiO₂. Mechanistic studies of the photocatalytic reduction are carried out with the help of different hole (oxalic acid, and methanol) and electron (sodium persulfate) scavengers, which reveal that the photogenerated electrons are the primary agents toward efficient nitrate photoreduction. Detailed studies have revealed that the noble metal doping in TiO₂ helps in efficient photogeneration of H₂ compared to the undoped analogue, however, the <i>in situ</i> produced H₂ is found to be inefficient in reducing NO₃^–. The conduction band position from first principle calculations with respect to the nitrate and hydrogen reduction potentials derived from cyclic voltammetry provide insights to the electron transfer process in determining the reaction pathway

Hole Transfer Dynamics from a CdSe/CdS Quantum Rod to a Tethered Ferrocene Derivative

Hole transfer between a CdSe/CdS core/shell semiconductor nanorod and a surface-ligated alkyl ferrocene is investigated by a combination of ab initio quantum chemistry calculations and electrochemical and time-resolved photoluminescence measurements. The calculated driving force for hole transfer corresponds well with electrochemical measurements of nanorods partially ligated by 6-ferrocenylhexanethiolate. The calculations and the experiments suggest that single step hole transfer from the valence band to ferrocene is in the Marcus inverted region. Additionally, time-resolved photoluminescence data suggest that two-step hole transfer to ferrocene mediated by a deep trap state is unlikely. However, the calculations also suggest that shallow surface states of the CdS shell could play a significant role in mediating hole transfer as long as their energies are close enough to the nanorod highest occupied molecular orbital energy. Regardless of the detailed mechanism of hole transfer, our results suggest that holes may be extracted more efficiently from well-passivated nanocrystals by reducing the energetic driving force for hole transfer, thus minimizing energetic losses

Efficient Preparation of the Esters of Biomass-Derived Isohexides by Base-Catalyzed Transesterification under Solvent-Free Conditions

The monoesters and diesters of glucose-derived isosorbide (IS) have potential applications as sustainable dispersants, surfactants, emulsifiers, monomer units for polymers, and plasticizers. This work reports a solvent-free, high-yielding, and scalable pathway for producing the monoesters and diesters of IS by a transesterification reaction using K2CO3 as an efficient, inexpensive, and recyclable base catalyst. In the case of monoesters, the selectivity toward the exo-monoester of IS was found higher than that toward the endo-monoester. The methodology was successfully extended to synthesize the monoesters and diesters of isomannide and isoidide. The gram-scale preparation of alkyl, vinyl, and aryl esters of isohexides was optimized on the reaction temperature, duration, equivalence of the ester reagent, and catalyst loading. Under optimized conditions (50 mol % K2CO3, 180 °C, 6 h), various aryl and alkyl esters of the isohexides were isolated in satisfactory yields. The unsymmetrical diesters of the isohexides were conveniently synthesized by stepwise transesterification

Possible Room-Temperature Ferromagnetism in Self-Assembled Ensembles of Paramagnetic and Diamagnetic Molecular Semiconductors

Owing to long spin-relaxation time and chemically customizable physical properties, molecule-based semiconductor materials like metal-phthalocyanines offer promising alternatives to conventional dilute magnetic semiconductors/oxides (DMSs/DMOs) to achieve room-temperature (RT) ferromagnetism. However, air-stable molecule-based materials exhibiting both semiconductivity and magnetic-order at RT have so far remained elusive. We present here the concept of supramolecular arrangement to accomplish possibly RT ferromagnetism. Specifically, we observe a clear hysteresis-loop (<i>H</i>_c ≈ 120 Oe) at 300 K in the magnetization versus field (M–H) plot of the self-assembled ensembles of diamagnetic Zn-phthalocyanine having peripheral F atoms (ZnFPc; <i>S</i> = 0) and paramagnetic Fe-phthalocyanine having peripehral H atoms (FePc; <i>S</i> = 1). Tauc plot of the self-assembled FePc···ZnFPc ensembles showed an optical band gap of ∼1.05 eV and temperature-dependent current–voltage (I–V) studies suggest semiconducting characteristics in the material. Using DFT+U quantum-chemical calculations, we reveal the origin of such unusual ferromagnetic exchange-interaction in the supramolecular FePc···ZnFPc system