Rajnish Kaur

Recent advances in the photovoltaic applications of coordination polymers and metal organic frameworks

Coordination polymers and metal organic frameworks (CPs/MOFs) have attracted a great deal of attention in a variety of scientific fields due to their unique and intriguing structural properties. Photovoltaic applications of these porous polymers belong to a relatively new area of research. The current status of research on this subject amply highlights the usefulness of CPs/MOFs in improving the properties of next-generation photovoltaic devices (e.g., dye-sensitized solar cells). This review article was written to cover the recent advancements that have been achieved in this rapidly expanding area of research. It also compares and contrasts the energy conversion efficiencies in photovoltaic applications using different MOFs and other systems.

Nanocomposite of europium organic framework and quantum dots for highly sensitive chemosensing of trinitrotoluene

Luminescent metal-organic frameworks (MOFs) are considered as next-generation sensor materials for small molecules and explosives. In the present work, a nanocomposite of luminescent europium organic framework (EuOF) and CdSe quantum dots (QDs) has been first time investigated for photoluminescence (PL) based highly sensitive detection of trinitrotoluene (TNT). The nanocomposite EuOF/QD has been synthesized by initiating the growth of EuOF in the presence of QDs. The successful synthesis of the product has been verified with the help of electron microscopy, X-ray diffraction analysis, and surface area measurements. Compared to EuOF alone, the EuOF/QD nanocomposite offers reproducible and stable measurements. The linear range of PL quenching based detection of TNT with EuOF/QD nanocomposite is 5-1000 ppb with the detection limit of 3 ppb. The detection of TNT with EuOF/QD is selective with respect to some other investigated aromatic compounds, such as phenol, o-cresol, toluene, benzene, nitrobenzene and nitrophenol.

Efficient photocatalytic and photovoltaic applications with nanocomposites between CdTe QDs and an NTU-9 MOF

A new photoactive hybrid nanostructure formed through an integration of quantum dots (QDs) and metal organic frameworks (MOFs) has been explored and assessed for its photocatalytic and photovoltaic performance. To this end, the QD–MOF nanocomposite was synthesized by mixing CdTe QDs during the formation of a titanium-based MOF ‘NTU-9,’ with titanium isopropoxide as a metal source and 2,5-dihydroxyterephthalic acid (H4DOBDC) as an organic ligand. The successful formation of this nanocomposite is verified using various microscopic and spectroscopic techniques. Because the CdTe/NTU-9 composite exhibited a considerably broadened light absorption profile, it has achieved a rapid (30 min) and visible light-driven photocatalytic degradation (>95%) of rhodamine 6G. Further, when this composite is tested as a photoanode material in a QD-sensitized solar cell (QD-DSSC), its power conversion efficiency improved by approximately 1.5% relative to the raw QD form. Accordingly, CdTe/NTU-9 is demonstrated as a potential candidate for future applications in photocatalysis and DSSCs. The key features of the proposed nanocomposite include improved light absorption, sub-micron scale processing, chemical and thermal stability, easier regeneration, and better photocatalytic/photovoltaic characteristics.

Synthesis, Characterization and Application of Silica‐Gold Nano‐Composites

Present work deals with the synthesis of silica‐gold shell nanocomposite and their characterization using UV‐Visible spectroscopy, SEM and XRD. Gold nanoparticles were prepared using hydrazine hydrate as reducing agent. Synthesis of Silica‐gold nano‐composites (silica@AuNPs), was achieved using Tetra Ethyl Ortho Silicate (TEOS) as silane reagent. Surface Plasmon Resonance (SPR) of synthesized AuNPs and silica@AuNPs was observed at 525 nm which corresponds to the approximate size of ±12 nm. The SPR intensity of Si@AuNPs was however reduced, which confirmed the formation of silica shell around AuNPs. SEM of nanoparticles showed spherical shape and are stable for about 4 weeks. XRD of AuNPs showed fcc lattice structure. Further, silica@AuNPs have been explored for their application in nitrobenzene detection, using UV‐Visible spectroscopy. As the varied concentration of nitrobenzene was added, the SPR of silica@AuNPs showed decrease in the intensity, confirming the adsorption of nitrobenzene on NP surface. Th...

Improved performance of carbon nanotubes—manganese doped cadmium sulfide quantum dot nanocomposite based solar cell

The nanocomposites of carbon nanotubes with quantum dots (MWCNT-QDS) display the capability of light induced charge dissociation and transport, which make them suitable for photovoltaic applications. The present work reports the coupling of multiwalled CNT (MWCNT) with L-cysteine (2-amino 3-mercaptopropionic acid) capped manganese doped cadmium sulfide QDs (CdS:Mn). The confirmation of the MWCNT-CdS:Mn nanocomposite formation is done with various instrumental techniques. Current–voltage studies of the MWCNT-CdS:Mn thin film indicate their semiconducting behavior. Further, cyclic voltammetry and frequency response analyses of the above MWCNT-CdS:Mn thin film have highlighted their potential application as a photoanode material in dye sanitized solar cells. It has been demonstrated that the use of MWCNT-CdS:Mn nanocomposite as a photoanode material offer better photocurrent characteristics as compared to QDS alone.

Synthesis and spectroscopic studies of functionalized graphene quantum dots with diverse fluorescence characteristics

In this research, we report a facile method for synthesizing a series of carboxyl functionalized graphene quantum dots (GQDs) using graphite flakes (300 meshes) as raw material. These highly luminescent GQDs emitted blue, light blue, green, yellow, and red light (400–700 nm intensity peaks) under ultraviolet irradiation conditions, while exhibiting quantum yields in the range of 50–70%. The products were comprehensively characterized using ultraviolet-visible, photoluminescence, infrared, Raman, and dynamic light scattering spectroscopies. The GQDs were found to remain highly stable against photobleaching when stored over a prolonged period of more than three months. The proposed method for the synthesis of high quality, multicolor GQDs can be utilized to extend the application of these nanoparticles to molecular biotechnology and bioengineering; for example, the immobilization of cancer markers on their surface. As such, carboxylic acid groups present on the surface of these GQDs help create complexes for in vivo sensing applications.

Nanomaterials for sensing of formaldehyde in air: Principles, applications, and performance evaluation

Despite the improvement in sensing technologies, detection of small and highly reactive molecules like formaldehyde remains a highly challenging area of research. Applications of nanomaterials/nanostructures and their composites have increased as effective sensing platforms (e.g., reaction time, sensitivity, and selectivity) for the detection of aqueous or gaseous formaldehyde based on diverse sensing principles. In this review, the basic aspects of important nanomaterial-based sensing systems (e.g., electrochemical, electrical, biological, and mass variation sensors) were evaluated in relation to performance, cost, and practicality of sensing gas phase formaldehyde. Accordingly, existing knowledge gaps in such applications were assessed in various respects along with suitable recommendations for building a new roadmap for the expansion of chemical sensing technology of gas phase formaldehyde.

An overview of different strategies to introduce conductivity in metal–organic frameworks and miscellaneous applications thereof

Metal–organic frameworks (MOFs) are known to possess many interesting material properties such as high specific surface area, tailorable porosity, adsorption/absorption capabilities, post-synthetic modifications, and chemical/thermal stabilities. Because of these unique features, they have been explored for the development of sensors for a variety of analytes. A large proportion of pre-existing MOF-based sensors are well suited for optical transductions due to a lack of electrical conduction in their pristine forms. Hence, the development of MOF-based electrochemical/electrical sensors requires specialized strategies through which MOFs are modified or hybridized with enhanced conductive moieties (e.g., via doping or post synthetic modification). In this review article, we provide a comprehensive review of various synthetic and integrating strategies to improve electrical conductivity and long-range charge transport properties in MOFs. To this end, we have compiled details of different techniques that have been used to develop electrically/electrochemically active platforms for MOF-based sensing of various targets.

Potential use of polymers and their complexes as media for storage and delivery of fragrances

ABSTRACT The use of fragrances is often essential to create an elegant, welcoming, or exhilarating environment. Through encapsulation, the release and delivery of fragrances are customized in many consumer products. For such purposes, cost‐effective techniques have been developed and employed with the use of various polymers and porous organic materials to efficiently impart fragrances to foods and various other consumer products. After entrapment or uptake/storage of fragrant molecules within a polymeric complex, the properties can be investigated by automated thermal desorption (ATD) analysis. For efficient delivery, fragrances are adsorbed (or entrapped) in some media (e.g., fabric or paper). The release of such entrapped fragrances usually is achieved by spraying. Fragrances can be also loaded in a media by purging aroma gases or by adding fragrance essence directly into a liquid medium. Porous materials, such as zeolites, have been traditionally used for air purification as well as in cosmetics and similar applications. Similarly, other polymeric porous complexes have also been used in fragrance delivery as a templating agent for aromatherapy textiles. Such polymeric materials offer an advantage in terms of development of new hybrid blends via homogenous mixing of two or more matrices. Such blends may possess different desirable physical properties as encapsulants. This review article is aimed at presenting an overview of polymers and their complexes as the main media of fragrance encapsulation. This study also discusses the expansion and future application of porous materials as host matrices for fragrances.