Deepak Kukkar

Metal–organic frameworks (MOFs): potential and challenges for capture and abatement of ammonia

Metal–organic frameworks (MOFs) have potential as air quality treatment media for various gaseous pollutants (e.g., ammonia) through diverse mechanisms (capture and catalytic degradation). A broad range of MOFs have been developed with numerous advantageous properties (e.g., high surface area, high degree of porosity, intrinsically tunable chemical structure, flexible architecture, and multifunctional properties) to meet strict air quality metrics. Nevertheless, the practical use of these novel materials has also been restricted due to certain drawbacks including high fabrication costs, poor selectivity, low capacity, and difficulties in recycling/regeneration. This review was organized to highlight the recent advancements in MOF technology for the mitigation of ammonia. The article aims to expand the use of MOFs in air quality treatments by identifying the research gaps in associated fields.

Potential Utility of Metal–Organic Framework-Based Platform for Sensing Pesticides

The progress in modern agricultural practices could not have been realized without the large-scale contribution of assorted pesticides (e.g., organophosphates and nonorganophosphates). Precise tracking of these chemicals has become very important for safeguarding the environment and food resources owing to their very high toxicity. Hence, the development of sensitive and convenient sensors for the on-site detection of pesticides is imperative to overcome practical limitations encountered in conventional methodologies, which require skilled manpower at the expense of high cost and low portability. In this regard, the role of novel, advanced functional materials such as metal-organic frameworks (MOFs) has drawn great interest as an alternative for conventional sensory systems because of their numerous advantages over other nanomaterials. This review was organized to address the recent advances in applications of MOFs for sensing various pesticides because of their tailorable optical and electrical characteristics. It also provides in-depth comparison of the performance of MOFs with other nanomaterial sensing platforms. Further, we discuss the present challenges (e.g., potential bias due to instability under certain conditions, variations in the diffusion rate of the pesticide, chemical interferences, and the precise measurement of luminesce quenching) in developing robust and sensitive sensors by using tailored porosity, functionalities, and better framework stability.

Highly Efficient Yttrium Based Metal Organic Framework for Removal of Pollutant Dyes

Highly porous crystalline luminescent metal Organic Frameworks (MOFs) were synthesized by conjugating Yttrium nitrate and Benzene Tri Carboxylate (BTC) in the presence of surfactant Cetyl Tri methyl Ammonium Bromide. A characteristic blue emission peak around 400 nm of Y upon excitation with UV light and peaks through Infra-Red spectroscopy revealed the formation of co-ordinate bond between Y and BTC, thereby confirming the formation of MOF nanoparticles (NPs). The nanoparticles were studied for potential removal of pollutants by encapsulation of the dye methylene blue (MB). Optical analysis affirmed the encapsulation of dye particles within the porous MOF NPs as dye absorption decreased around 600nm. This study offers great promise of using MOF NPs as platform for sensing of analytes in solution and removal of pollutant materials.

Enhanced catalytic reduction of 4-nitrophenol and congo red dye By silver nanoparticles prepared from Azadirachta indica leaf extract under direct sunlight exposure

ABSTRACT The manuscript reports an efficient approach for the synthesis of biogenic silver (Ag) nanoparticles from Azadirachta indica leaf extract-mediated reduction of silver nitrate under solar radiation at mild temperature conditions for nanoparticles (NPs) preparation. Spectroscopic and electron microscopic characterization studies revealed the formation of stable and monodisperse Ag NPs with sharp absorption band at 438 nm and average diameter of 10–15 nm. Catalytic potential of the NPs was descriptively investigated for the reduction of 4-nitrophenol to 4-aminophenol in alkaline medium. Apparent rate constant () values were determined to be 0.014, 0.0238, 0.0338, 0.063, and 0.0794 at 5, 10, 15, 20, 40, and 50 µL Ag NPs volume, respectively, thereby depicting linear relationship between the variables under study. Catalytic reduction of Congo red dye was achieved within 2 h, thus validating the efficacy of Ag NPs as a photocatalyst. The NPs also exhibited linear increment in antibacterial activity on cultured Escherichia coli plates with increasing volumes. These catalytic capabilities firmly advocate the applications of Ag NPs in purification of polluted water by the removal of toxic and contaminant materials and harmful/pathogenic bacteria.

Synthesis of Iron Based Biocompatible Metal Organic Frameworks for Microencapsulation of Docetaxel

Tunable properties of porous metal organic frameworks (MOFs) make them a potential candidate for sustained release of functionally active biomolecules. Current study describes in situ encapsulation of anti-cancer drug, docetaxel in iron based MOFs for drug delivery applications. MOFs were synthesized using emulsification approach by mixing FeCl3.4H2Oand benzene tricarboxylate (BTC) in 1:1 molar ratio in the presence of cetyl trimethyl ammonium bromide (CTAB). Optical characterization of the NMOFs was done using UV-visible and FTIR spectroscopy. The peak obtained at 265 nm in the UV-visible spectrum indicated the formation of iron-based NMOF. The peaks obtained at 3416, 1623 and 3343cm-1 corresponding to C=O, C=C and C=O groups in FTIR spectroscopy further supported our observations. Microencapsulation of docetaxel was achieved by mixing the drug with the iron salt during the synthesis of MOF. Drug encapsulation was affirmed by Transmission Electron Microscopy. Current study is an attempt in exploring the microencapsulation properties of MOFs.

Plasticizers Induced Formation of Microcapsules From Freeze Dried Polystyrene Microreactors

The article describes solvent induced preparation of polystyrene microcapsules from freeze-dried microreactors. An aqueous suspension of microreactors was exposed to a plasticizing solvent for a defined time period. Plasticizer molecules surround the polymer chains and repel the water molecules. It results in the movement of the monomers toward each other. The process leads to formation of microcapsules with a core-shell structure. For proof of concept, four plasticizing solvents, namely 1,4-dioxane, toluene, dichloromethane, and chloroform, were studied for annealing of the hollow particles. It was concluded that chloroform was the best plasticizer in terms of transforming microreactors into microcapsules. GRAPHICAL ABSTRACT

Encapsulation and Release of Doxorubicin from Plasticizer-Transformed Poly(ε-Caprolactone) Microcapsules

ABSTRACT The manuscript reports plasticizer-mediated conversion of poly(ε-caprolactone) hollow particles into microcapsules followed by encapsulation and sustained release of doxorubicin from the microcapsules through a progressive approach. Plasticizer molecules account for increased mobility of polymer chains. Chloroform was observed to be the best plasticizer for potential transformation of the hollow particles into microcapsules, compared to 1,4-dioxane, and toluene. In the next step, an anticancer drug doxorubicin was encapsulated in the hollow particles in presence of chloroform. In vitro release of drug from the microcapsules in phosphate buffer saline (pH 7.4) demonstrated sustained release pattern over 15 days. GRAPHICAL ABSTRACT

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.

Low Temperature Synthesis of Elongated Triangular Bipyramidal ZnO Nanostructures for Photocatalytic Activity

The manuscript reports wet chemical assisted low temperature synthesis of CTAB stabilized elongated triangular bipyramidal shape nanostructures of ZnO for photocatalytic degradation of methyle blue (MB) and congo red (CR) dyes. Physiochemical characterization has been carried out by X-ray diffraction, scanning electron microscope, transmission electron microscope and UV-visible spectroscope. Pure wurtzite structure of ZnO with crystallite size ~56 nm has been confirmed from X-ray study. Well dispersed particles with elongated triangular bipyramidal morphology have been observed through SEM. Fine resolved particles with varied aspect ratios ~80 X 200 ± 10 nm have been depicted by TEM images. UV-visible absorption analysis confirms the energy band gap of 3.43 eV for synthesized ZnO particles. Molecular composition and functional groups of CTAB were confirmed by FTIR spectroscopy. The potential applicability of the particles for photocatalytic degradation of MB and CR as standard analytical dyes was studied. Time bound study under UV irradiated source depicted more than 95% degradation of both dyes in separate experiments.

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.