Development of p-n Heterostructures Using Phosphorene and SnO2: Its Efficacy toward the Adsorption Study of CO2 and Rose Bengal Dye.

Adsorption-mediated methods for environmental pollution control are suitable as they are cost-effective and easy to use. Porous materials can play an important role in adsorption studies. Herein, we synthesized a p-n heterostructure of phosphorene and metal oxide using a simple hydrothermal approach. The synthesized material is porous in nature, with a surface area of 127.44 m2/g and pore volume of about 1.73 nm with appreciable thermal stability. As the material is microporous, we used it for the adsorption of CO2 gas and dye. For CO2 adsorption, we determined the CO2 gas uptake according to the mass balance principle of the ideal gas equation, and it was found to be about 21.478 mol/kg. We have also studied different isotherm models to check the adsorption phenomena. Moreover, for dye adsorption, we have chosen the xanthene-derived rose bengal (RB) dye, which shows a removal percentage of about 92.02%. In the case of dye adsorption, the material shows good reusability and significant adsorption up to five cycles.

Correction: Realization of multi-configurable logic gate behaviour on fluorescence switching signalling of naphthalene diimide congeners.

[This corrects the article DOI: 10.1039/D1RA06728A.].

Stimuli-Responsive Naphthalene Diimide as Invisible Ink: A Rewritable Fluorescent Platform for Anti-Counterfeiting.

Herein, we report an approach to combat counterfeiting and storage of valuable information based on the solid-state fluorescence switching behavior of isoniazid functionalized naphthalene diimide (ISO_NDI) in response to an external stimuli (i. e., HCl vapor). The unique feature of ISO_NDI is further utilized to develop an invisible ink (ISO_NDI-PVA) with commercial polymer polyvinyl alcohol (PVA). A solid-state fluorescence recovery was observed while loading with HCl vapors. This exclusive property of the material could be applied directly as a security ink for confidential data storage purpose. Based on above strategy, we successfully realized the rewritable application by using ISO_NDI-PVA ink and confirm its practical efficacy on various substrates by creating different patterns. The solid-state fluorescence switching behavior of ISO_NDI-PVA ink exhibited reversible on/off signal for multiple cycles under the influence of HCl/NH3 vapors. Mechanistic investigation supports a clear participation of intermolecular charge transfer (ICT) phenomenon in the solid-state fluorescence switching property. The ease of fabricating the ink with invisible to visible characteristics in response to HCl vapors provides new opportunities for exploring the application of ISO_NDI-PVA as invisible ink for targeted security applications.

Treatment of crude oil contaminated wastewater via an electrochemical reaction.

A cost-effective and catalyst-free approach for the treatment of oil field formation water has been extensively explored in this work. ZnO NPs were synthesized via an electrochemical reaction using hydrogen peroxide as the electrolyte. The XRD and TEM analysis depicted the high purity and wurtzite hexagonal structure of ZnO NPs with an average size of 35 ± 5 nm. TGA data showed the thermal stability of the synthesized material up to 750 °C. The efficiency of the removal of hydrocarbons from formation water by the combination of electrochemical reaction and synthesized ZnO NPs was monitored by GC-MS and FTIR. GC-MS analysis revealed that out of 214 compounds (present in the untreated sample), a total of 131 compounds were adsorbed by ZnO NPs. Further, the absence of any compound in the chromatogram of the treated sample attests that the rest of the compounds were completely or partially degraded by electrochemical degradation reaction. Moreover, this technique overcomes some of the important drawbacks of the existing techniques in the area of electrochemical research, such as the generation of toxic byproducts, unwanted side reactions, and involvement of hazardous chemicals.

High-performance water-borne fluorescent acrylic-based adhesive: synthesis and application.

Water-borne adhesives have immense importance in cellulose-based materials, where their durability, handling, and strength remain to be a major concern. The present work demonstrates the development of three water-borne adhesives, namely, poly(1-vinyl-2-pyrrolidone-co-acrylic acid), poly(acrylonitrile-co-acrylic acid), and poly(1-vinyl-2-pyrrolidone-co-acrylonitrile-co-acrylic acid) applicable for cellulose-based materials. These acrylic-acid based adhesives were characterized by Fourier-transform infra-red spectroscopy, thermogravimetric analysis, X-ray diffraction, gel permeation chromatography, and universal testing machine. The synthesized polymer adhesives can be stored in the powder form for a longer period, thus utilizing less space. In order to use as adhesives, suitable formulations can be prepared in water. The adhesives show thermal stability up to 300 °C. Our studies show that poly(1-vinyl-2-pyrrolidone-co-acrylonitrile-co-acrylic acid) showed higher lap shear strength (ASTM D-906) than commercially available adhesives. In addition, these adhesives, being fluorescent in nature, can be detected under UV light and thus are applicable for the detection of fractured joints of any specimen. This property also helps in anti-counterfeiting applications, thus adding further to their utility.

Enhancement of air-stability, π-stacking ability, and charge transport properties of fluoroalkyl side chain engineered n-type naphthalene tetracarboxylic diimide compounds.

In this study, the impact of fluoroalkyl side chain substitution on the air-stability, π-stacking ability, and charge transport properties of the versatile acceptor moiety naphthalene tetracarboxylic diimide (NDI) has been explored. A density functional theory (DFT) study has been carried out for a series of 24 compounds having different side chains (alkyl, fluoroalkyl) through the imide nitrogen position of NDI moiety. The fluoroalkyl side chain engineered NDI compounds have much deeper highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) than those of their alkyl substituted compounds due to the electron withdrawing nature of fluoroalkyl groups. The higher electron affinity (EA > 2.8 eV) and low-lying LUMO levels (<-4.00 eV) for fluoroalkyl substituted NDIs reveal that they may exhibit better air-stability with superior n-type character. The computed optical absorption spectra (∼386 nm) for all the investigated NDIs using time-dependent DFT (TD-DFT) lie in the ultra-violet (UV) region of the solar spectrum. In addition, the low value of the LOLIPOP (Localized Orbital Locator Integrated Pi Over Plane) index for fluoroalkyl side chain comprising NDI compounds indicates better π-π stacking ability. This is also in good agreement for the predicted π-π stacking interaction obtained from a molecular electrostatic potential energy surface (ESP) study. The π-π stacking is thought to be of cofacial interaction for the fluoroalkyl substituted compounds and herringbone interaction for the alkyl substituted compounds. The calculated results shed light on why side chain engineering with fluoroalkyl groups can effectively lead to better air-stability, π-stacking ability and improved charge transport properties.

New types of organic semiconductors based on diketopyrrolopyrroles and 2,1,3-benzochalcogenadiazoles: a computational study.

A comprehensive computational study is performed on model compounds based on 2,1,3-benzochalcogenadiazoles and diketopyrrolopyrroles of A-π-A'-π-A architecture (A and A' represent 2,1,3-benzochalcogenadiazoles and diketopyrrolopyrroles, respectively, and π is the bridging unit between them including thiophene, furan, and selenophene) for their utility as organic semiconductors. The compounds were found to possess planar geometry, which is a desired property for organic semiconductors. The electronic properties, including adiabatic and vertical electron affinity (EA), adiabatic and vertical ionization potential (IP), reorganization energy (λ), hole injection barrier and electron injection barrier, transfer integral, and charge mobility, were calculated. The electron affinity is higher in the case of thiophene/selenophene as the linker for a given terminal benzochalcogenadiazole than the corresponding compounds with furan as a linker, while the ionization potential is lowest for compounds having selenophene as the linker with a given terminal benzochalcogenadiazole moiety than the compounds having furan or thiophene as a linker. The hole injection barrier in these compounds is lower than the electron injection barrier, which facilitates the hole injection from the metal electrode, while hole reorganization energy is found to be larger than the electron reorganization energy. The compounds possess hole mobilities in the range of 2.50-4.91 cm2/Vs and electron mobilities in a similar range of 4.58-9.68 cm2/Vs. This study reveals that compounds based on a combination of diketopyrrolopyrrole and 2,1,3-benzochalcogenadiazole units would exhibit hole transporting properties and act as potential ambipolar materials.

Silk fibroin as a platform for dual sensing of vitamin B12 using photoluminescence and electrical techniques.

The amalgamation of natural origin materials and technologies for label-free and real time detection is pertinent in analytical field. In this study, Bombyx mori silk fibroin protein (BMSF) has been utilized for the dual sensing of vitamin B12 via fluorescence and electrical impedance techniques. The processing of BMSF is done to generate an aqueous solution of BMSF along with the development of micro patterned thin films via soft lithography technique. The BMSF aqueous solution exhibit auto fluorescence property and thereby utilized for label free detection of vitamin B12 with an estimated limit of detection (LOD) of about 0.003 × 10-6 g/uL. This is followed by impedimetric detection of vitamin B12 using the micro patterned BMSF thin films. A LOD of 17.8 ppm and 0.25 ppm are achieved in aqueous solution and human blood serum, respectively. Taken together, this work demonstrates a potential label free dual sensing mode for sensitive detection of micronutrient vitamin B12.

Macromolecular Systems with MSA-Capped CdTe and CdTe/ZnS Core/Shell Quantum Dots as Superselective and Ultrasensitive Optical Sensors for Picric Acid Explosive.

This work reports the development of highly fluorescent materials for the selective and efficient detection of picric acid explosive in the nanomolar range by fluorescence quenching phenomenon. Poly(vinyl alcohol) grafted polyaniline (PPA) and its nanocomposites with 2-mercaptosuccinic acid (MSA)-capped CdTe quantum dots (PPA-Q) and with MSA-capped CdTe/ZnS core/shell quantum dots (PPA-CSQ) are synthesized in a single step free radical polymerization reaction. The thermal stability and photo stability of the polymer increases in the order of PPA < PPA-Q < PPA-CSQ. The polymers show remarkably high selectivity and efficient sensitivity toward picric acid, and the quenching efficiency for PPA-CSQ reaches up to 99%. The detection limits of PPA, PPA-Q, and PPA-CSQ for picric acid are found to be 23, 1.6, and 0.65 nM, respectively, which are remarkably low. The mechanism operating in the quenching phenomenon is proposed to be a combination of a strong inner filter effect and ground state electrostatic interaction between the polymers and picric acid. A portable and cost-effective electronic device for the visual detection of picric acid by the sensory system is successfully fabricated. The device is further employed for quantitative detection of picric acid in real water samples.