Hot Electron-Mediated Photocatalytic Degradation of Ciprofloxacin Using Au-Decorated SrTiO₃- and Ti₃C₂ MXene-Based Interfacial Heterostructure Nanoarchitectonics

Being the most abundant and cleanest form of energy, sunlight is utilized in producing electricity, charging batteries, and more such applications. Though the earth gets a good amount of sunlight on its surface each day, only a small fraction of it gets utilized. It is still a concern for scientists to use the broad spectrum to achieve maximum performance in photocatalysis. In this work, we have developed a series of perovskite oxide (SrTiO3)- and MXene (Ti3C2)-based interfacial heterostructures and decorated them with gold nanoparticles to enable plasmon-mediated electron transfer. These interfacial ternary heterostructures have been successfully utilized for photocatalytic environmental remediation of a colorless pharmaceutical pollutant under natural sunlight irradiation. The remarkable photocatalytic performance of these heterostructures can be attributed to broad-spectrum light harvesting, good charge separation, and quick charge transport. The stability and recyclability of these photocatalysts have also been demonstrated. This work validates that a combination of multi-component interfacial heterostructures can be successfully deployed for plasmon-mediated photocatalysis even under natural sunlight irradiation

Ammonia-Doped Polyaniline–Graphitic Carbon Nitride Nanocomposite as a Heterogeneous Green Catalyst for Synthesis of Indole-Substituted 4<i>H</i>‑Chromenes

A nanocomposite of polyaniline with graphitic carbon nitride (GCN) nanosheets has been synthesized by a facile oxidative polymerization of an aniline monomer and GCN to demonstrate its potential to catalyze the synthesis of various indole-substituted 4H-chromenes. The synthesized nanocomposite was thoroughly characterized using different spectroscopic techniques to confirm the morphology and composition. Subsequently, the fabricated nanocomposite was used as a heterogeneous catalyst to synthesize several bioactive indole-substituted 4H-chromenes in an aqueous medium. Organic transformation under benign and environmentally sustainable conditions is of paramount importance in the view of growing environmental pollution. Water is the universal Green solvent and has been a preferred choice of nature to perform various reactions. The catalyst developed in this work showed very good recyclability and adaptability for the synthesis of various medicinally significant indole-substituted 4H-chromenes. This multicomponent reaction imparts very high atom economy (94%) and low environmental factor (0.13)

Photocatalytic Reduction and Recognition of Cr(VI): New Zn(II)-Based Metal–Organic Framework as Catalytic Surface

This report deals with the fabrication and utilization of a novel 2D zinc-based metal–organic framework (MOF) {[Zn­(PA2–)­(4,4′-bpy)]­(H2O)}n (where PA = pamoic acid and 4,4′-bpy = 4,4′-bipyridine). The Zn-MOF has been synthesized via a solvothermal method and emanates green fluorescence. As Cr­(VI) is a fatal and carcinogenic ion, it is extremely important to discern and remove it from nature. The bright green fluorescence of Zn-MOF can be quenched upon interaction with a Cr2O72– ion, which implies the MOF’s applicability as a Cr­(VI) detector through turn-off fluorescence signaling. On the contrary, among various strategies to remove Cr­(VI), the photocatalytic reduction of Cr­(VI) to Cr­(III) is acknowledged as the most effective one. Delightfully, apart from being a Cr­(VI) sensor, this same Zn-MOF can be further recruited as a photocatalyst to convert Cr­(VI) to Cr­(III). The catalytic reduction is triggered by natural sunlight, acidic pH, and a hole scavenger. In addition, good stability and reusability of the Zn-MOF satisfies the quest for a potential photocatalyst for conversion of Cr­(VI) to Cr­(III). The limit of detection for fluorometric recognition of Cr­(VI) was found to be 4.12 μM, and almost a complete reduction of toxic Cr­(VI) ion was achieved

Potassium-Functionalized Graphitic Carbon Nitride Supported on Reduced Graphene Oxide as a Sustainable Catalyst for Knoevenagel Condensation

A nanocomposite of potassium-functionalized graphitic carbon nitride (KGCN) and reduced graphene oxide (RGO) was fabricated by a facile hydrothermal method and used as a heterogeneous catalyst for Knoevenagel condensation and sustainable synthesis of aryl substituted chromenes. The prepared KGCN–RGO nanocomposite catalyst has been characterized by using various techniques, such as powder X-ray diffraction technique (PXRD), Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscope, thermogravimetric analysis, and BET surface area analysis. After detailed characterization, the nanocomposite was used as a heterogeneous catalyst to synthesize various aryl substituted chromenes in ethanol. The developed KGCN–RGO nanocatalyst also rendered good recyclability for the explored catalytic reactions. In addition, a high value of atom economy and a low value of E-factor are also key highlights of this green and sustainable catalytic protocol

Surface Nanoarchitectonics of Boron Nitride Nanosheets for Highly Efficient and Sustainable <i>ipso</i>-Hydroxylation of Arylboronic Acids

One of the important industrial processes commonly employed in the pharmaceutical, explosive, and plastic manufacturing industries is ipso-hydroxylation of arylboronic acids. In this work, a straightforward, metal-free methodology for the synthesis of phenols from arylboronic acids has been demonstrated using hydroxyl functionalized boron nitride (BN–OH) nanosheets. The functionalized hydroxyl groups on the BN nanosheets act as the active sites for the hydroxylation reaction to take place. The detailed optimization of reaction parameters was done in order to attain high catalytic efficiency, and the reactions were conducted in water, which eliminates the use of toxic solvents. The as-synthesized catalysts exhibited excellent recyclability and reusability in addition to high product yields and good turnover numbers. The green metrics parameters were also evaluated for the model reaction to examine the sustainable nature of the developed protocol. The use of BN–OH catalysts for the ipso-hydroxylation reactions under base-free and metal-free conditions using environmentally benign solvents is utmost desired for industrial processes and can pave a way toward sustainable organic catalysis

Zn-MOF as a Single Catalyst with Dual Lewis Acidic and Basic Reaction Sites for CO₂ Fixation

Continuous increase in carbon dioxide (CO2) emissions are causing imbalances in the environment, which impact biodiversity and human health. The conversion of CO2 to cyclic carbonates by means of metal–organic frameworks (MOFs) as a heterogeneous catalyst is a prominent strategy for rectifying this imbalance. Herein, we have developed nitrogen-rich Zn (II) based metal–organic framework, [Zn­(CPMT)­(bipy)]n (CPMT = 1-(4-carboxyphenyl)-5-mercapto-1H-tetrazole; bipy = 4,4′-bipyridine), synthesized via a mixed ligand strategy. This Zn-MOF showed high chemical stability in both acidic and basic conditions, and in organic solvents for a long time. On account of the concurrent presence of acid–base active sites and strong chemical stability under abrasive conditions, this Zn-MOF was employed as an effective catalyst for the coupling of CO2 and epoxides, under atmospheric pressure, mild temperature, and neat conditions. This Zn-MOF shows remarkable activity by producing high yields of epichlorohydrin carbonate (98%) and styrene carbonate (82%) at atmospheric CO2 pressure, 70 °C temperature, and 24 h reaction time, with turnover numbers (TON) of 217 and 181, respectively. The Zn-MOF could be reused for up to seven cycles with structural and framework integrity. Overall, this work demonstrates the synthesis of a novel and highly efficient MOF for CO2 conversion

Sub-Picomolar Recognition of Cr³⁺ through Bioinspired Organic–Inorganic Ensemble Utilization

The work describes an integrated optical platform for recognition of Cr³⁺ at the picomolar level (0.66 pM). The condensation of a fluorene unit with l-leucine led to the development of a highly fluorescent molecular probe <b>L</b> which detects Cu²⁺ following a turn-off signaling mechanism. Further, the <b>L-Cu</b>^<b>2+</b> ensemble has been successfully utilized as a light-up signaling tool for selective turn-on sensing of Cr³⁺, for the first time, at the picomolar level through quencher displacement. This sensing process eventually detects selectively one paramagnetic cation through turn-on signaling by the displacement of another paramagnetic cation. We have successfully shown that the common sensitivity issues associated with displacement approaches can be overcome by suitable ligand design. The present integrated system, <b>L-Cu</b>^<b>2+</b>, has been found to be sensitive enough to detect Cr³⁺ at the picomolar level even in real samples, including water from different sources such as tap water, river water, and drinking water

Boosting Photocatalytic Nitrogen Fixation via Nanoarchitectonics Using Oxygen Vacancy Regulation in W‑Doped Bi₂MoO₆ Nanosheets

Ammonia and nitrates are key raw materials for various chemical and pharmaceutical industries. The conventional methods like Haber–Bosch and Ostwald methods used in the synthesis of ammonia and nitrates, respectively, result in harmful emission of gases. In recent years, the photocatalytic fixation of N2 into NH3 and nitrates has become a hot topic since it is a green and cost-effective approach. However, the simultaneous production of ammonia and nitrates has not been studied much. In this regard, we have synthesized W-doped Bi2MoO6 nanosheets in various molar ratios and demonstrated their potential as efficient photocatalysts for the simultaneous production of NH3 and NO3– ions under visible light irradiation. It was found that one of the catalysts (BMWO0.4) having an optimal molar ratio of doped tungsten showed the best photocatalytic NH3 production (56 μmol h–1) without using any sacrificial agents along with the simultaneous production of NO3– ions at a rate of 7 μmol h–1. The enhanced photocatalytic activity of the synthesized photocatalysts could be ascribed to oxygen vacancy defects caused by Mo substitution by a more electronegative W atom. Furthermore, density functional theory calculations verified the alteration in the band gap after doping of W atoms and also showed a strong chemisorption of N2 over the photocatalyst surface leading to its activation and thereby enhancing the photocatalytic activity. Thus, the present work provides insights into the effect of structural distortions on tailoring the efficiency of materials used in photocatalytic N2 fixation

Sub-Picomolar Recognition of Cr³⁺ through Bioinspired Organic–Inorganic Ensemble Utilization

The work describes an integrated optical platform for recognition of Cr3+ at the picomolar level (0.66 pM). The condensation of a fluorene unit with l-leucine led to the development of a highly fluorescent molecular probe L which detects Cu2+ following a turn-off signaling mechanism. Further, the L-Cu2+ ensemble has been successfully utilized as a light-up signaling tool for selective turn-on sensing of Cr3+, for the first time, at the picomolar level through quencher displacement. This sensing process eventually detects selectively one paramagnetic cation through turn-on signaling by the displacement of another paramagnetic cation. We have successfully shown that the common sensitivity issues associated with displacement approaches can be overcome by suitable ligand design. The present integrated system, L-Cu2+, has been found to be sensitive enough to detect Cr3+ at the picomolar level even in real samples, including water from different sources such as tap water, river water, and drinking water

Control of the Orientational Order and Nonlinear Optical Response of the “Push-Pull” Chromophore RuPZn via Specific Incorporation into Densely Packed Monolayer Ensembles of an Amphiphilic Four-Helix Bundle Peptide: Characterization of the Peptide−Chromophore Complexes

“Push-pull” chromophores based on extended π-electron systems have been designed to exhibit exceptionally large molecular hyperpolarizabilities. We have engineered an amphiphilic four-helix bundle peptide to vectorially incorporate such hyperpolarizable chromophores having a metalloporphyrin moiety, with high specificity into the interior core of the bundle. The amphiphilic exterior of the bundle facilitates the formation of densely packed monolayer ensembles of the vectorially oriented peptide−chromophore complexes at the liquid−gas interface. Chemical specificity designed into the ends of the bundle facilitates the subsequent covalent attachment of these monolayer ensembles onto the surface of an inorganic substrate. In this article, we describe the structural characterization of these monolayer ensembles at each stage of their fabrication for one such peptide−chromophore complex designated as AP0-RuPZn. In the accompanying article, we describe the characterization of their macroscopic nonlinear optical properties