Rajender S Varma

Rajender S Varma
United States Environmental Protection Agency | US EPA · Center for Environmental Solutions and Emergency Response

PhD

About

1,032
Publications
260,761
Reads
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47,422
Citations
Introduction
(H-Index 122, Highly Cited Researchers 2016,18, 19, 20, 21) Strong supporter of green and sustainable strategies as applied to chemical discipline; ~860 Papers, 58,400 citations.
Additional affiliations
August 2014 - present
Palacký University Olomouc
Position
  • Visiting scientist
Description
  • Visiting scientist at the Regional Center of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute
June 1999 - September 2020
United States Environmental Protection Agency
Position
  • Senior Researcher
Description
  • 48 years of multi-disciplinary research experience in development of Environmentally Benign Synthetic Methods, Greener Synthesis of Nanomaterials and Nanocomposites and their Applications in Catalysis and Sustainable Remediation of Hazardous Pollutants.
June 1999 - October 2019
United States Environmental Protection Agency
Position
  • Senior Researcher
Education
May 1973 - June 1976
University of Delhi
Field of study
  • Organic (Natural Products) Chemistry

Publications

Publications (1,032)
Article
Today, magnetic resonance imaging (MRI) is one of the most widely applied noninvasive clinical imaging modalities with excellent applicability in bio- and nanomedicine, particularly in specific detecting and high-quality three-dimensional imaging of tumors/cancers. In this context, the design of efficient nanoscale contrast agents (NCAs) for MRI wi...
Article
Heteropolyacids (HPAs) have been extensively investigated in view of their favorable attributes namely discrete ionic structure, high proton mobility, strong acidity, hydrothermal stability and reversible multi-electron redox behavior which renders them especially valuable in thermal and photocatalysis systems. Consequently, HPAs have found numerou...
Article
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We have seen four decades of human struggle to cure or eradicate HIV infection since the first clinical detection of HIV infection. Various developed drugs such as nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors, integrase inhibitors, microbicides, and others have kn...
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Metal-organic frameworks (MOFs) endowed with unique structural features, namely permanent porosity, high surface area, tunable pore size, and potential applications in diverse domains, have garnered immense attention in recent decades. The availability of large numbers of organic linkers, metal nodes, and multiple synthetic tactics has broadened th...
Article
The present work demonstrates a systematic study of pore size and specific surface area (SSA) of biomass-derived carbon and the choice of electrolyte concentrations affecting charge-storage mechanism (surface controlled and diffusion controlled) and electrochemical behaviour. Porous nanocarbons derived from Caesalpinia Sappan pods were synthesized...
Article
Catalysts have played a significant role in chemical industries and received significant attention as a result. Unfortunately, many common catalytic systems are comprised of a small number of elemental species or use similar synthetic strategies, which potentially limit innovation in areas such as the discovery of new transformations. Metal-organic...
Article
In view of their ease of synthesis, stability, functionalization, and low toxicity, biological processes are the excellent choice for the biosynthesis of nanoparticles (NPs). There is potential for NPs in alleviating plant diseases where these nano-sized materials are an ecological alternative to traditional chemical pesticides. Herein, silver nano...
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The accumulation of organic contaminants including dyes in aquatic systems is of significant environmental concern, necessitating the development of affordable and sustainable materials for the treatment/elimination of these hazardous pollutants. Here, a green synthesis strategy has been used to develop a self-assembled gum kondagogu-sodium alginat...
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Energy crisis is a matter of serious global concern as the depleting energy sources exert a deleterious effect on the economy. Additionally, the existing sources of energy are brimming with deleterious side effects on human health and the environment. Hence, a global effort is being made for the utilization of green chemistry for sustainable energy...
Article
Chitosan is a natural polymer with acceptable biocompatibility, biodegradability, and mechanical stability; hence, it has been widely appraised for drug and gene delivery applications. However, there has been no comprehensive assessment to tailor-make chitosan cross-linkers of various types and functionalities as well as complex chitosan-based semi...
Article
Tannic acid (TA), a natural polyphenol, is a hydrolysable amphiphilic tannin derivative of gallic acid with several galloyl groups in its structure. Tannic acid interacts with various organic, inorganic, hydrophilic, and hydrophobic materials such as proteins and polysaccharides via hydrogen bonding, electrostatic, coordinative bonding, and hydroph...
Preprint
A nanomagnetic hydrophilic heterogeneous copper catalyst, termed γ-Fe 2 O 3 @PEG@PAMAM G 0 -Cu, has been successfully prepared and characterized using FT–IR, XRD, FE-SEM, TEM, EDX, mapping, TGA/DTG, VSM and ICP analyses. The catalyst displayed excellent activity for the palladium-free Sonogashira cross coupling reaction of various aryl iodides and...
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Nanosponges with three-dimensional (3D) porous structures, narrow size distribution, and high entrapment efficiency are widely engineered for cancer therapy and drug delivery purposes. They protect the molecular agents from degradation and help to improve the solubility of lipophilic therapeutic agents/drugs with targeted delivery options in additi...
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Furfural is a platform molecule that can be catalytically converted using a cascade series of reactions into levulinic esters, essential compounds used as fuel additives. Bifunctional catalysts containing Lewis and Brønsted acid sites such as zeolites are commonly used for these conversions. However, microporous zeolites often present diffusional r...
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Nanoparticles synthesis under green conditions has been performed using natural resources to diminish the use of toxic chemicals. For instance, microbial synthesis has allowed to produce nanoparticles that are biocompatible, stable, and safe. Microorganisms allow crystal growth and prevent aggregation. Microorganisms act as reducing and capping age...
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Emergent application of antimicrobial strategies as symptomatic treatment in coronavirus disease (COVID-19) and linkage of severe acute respiratory syndrome coronavirus2 with microbial infections, has created colossal demand for antimicrobials. For the first time, this communication explore the physicochemical, antifungal, antibacterial, and photoc...
Article
Overexpression of proteins/antigens and other gene-related sequences in the bodies could lead to significant mutations and refractory diseases. Detection and identification of assorted trace concentrations of such proteins/antigens and/or gene-related sequences remain challenging, affecting different pathogens and making viruses stronger. Correspon...
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1H-Indole-3-carbaldehyde and related members of the indole family are ideal precursors for the synthesis of active molecules. 1H-Indole-3-carbaldehyde and its derivatives are essential and efficient chemical precursors for generating biologically active structures. Multicomponent reactions (MCRs) offer access to complex molecules. This review highl...
Article
The glass clover snail, Monacha cartusiana (M. cartusiana) is one of the most seriously impacting economic animal pests spreading across Egypt which inflicts severe damages to the agriculture. A green route is developed by deploying an abundant Rosemary plant leaves aqueous extract to synthesize ZnO and F-doped ZnO nanoparticles (NPs) that display...
Article
Multicomponent synthesis of novel coumarin-based fused pyrazolo[3,4-b]pyridine-3-carboxylate derivatives was developed using acidic ionic liquid, 1-acyl-3-methylimidazolium tetrachloroferrate ([AcMIm]FeCl4), under mild and environmentally benign reaction conditions. [AcMIm]FeCl4 served as a catalyst as well as the reaction medium and was reused for...
Article
It is crucial to fabricate cost-effective and efficient strategies for monitoring and eliminating hazardous metals in the water supplies. Among the many techniques, adsorption is one of the most powerful and facile ways for eliminating pollutants from effluents. It is also crucial to engineering high-performance low-cost adsorbents. In this regard,...
Article
Over the past decades, a number of 1,4‐naphthoquinones have been isolated from natural resources and several of naphthoquinone derivatives with diverse structural motif have been synthesized; they possess a multitude of biochemical properties and modulate numerous pharmacological roles that offer new targets for addressing the challenges pertaining...
Article
Among explored nanomaterials, nanosponge-based systems have exhibited inhibitory effects for the biological neutralization of, and antiviral delivery against, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). More studies could pave the path for clarification of their biological neutralization mechanisms as well as the assessment of the...
Article
Metallic nanocatalysts have been widely synthesized and deployed for assorted applications, including water splitting, degradation of pollutants, CO2 reduction, self-cleaning surfaces, hydrogen evolution, etc. Biosynthesis of such nanocatalysts encompasses crucial benefits of simplicity, up-scalability, inexpensiveness, and eco-friendliness, and ha...
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Synthesis of bi-functional covalent organic polymers in two distinctive morphologies has been accomplished by simply switching the solvent from DMF to DMSO when 1,3,5-tribenzenecarboxyldehyde and 2,5-diaminobenzene sulfonic acid were reacted via Schiff base condensation reaction to afford covalent organic polymers (COPs) encompassing flower (F-COP...
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Beta (β)-thalassemia is a group of human inherited abnormalities caused by various molecular defects, which involves a decrease or cessation in the balanced synthesis of the β-globin chains in hemoglobin structure. Traditional treatment for β-thalassemia major is allogeneic bone marrow transplantation (BMT) from a completely matched donor. The limi...
Article
The requirement of green and sustainable materials to prepare heterogeneous catalysts has intensified for practical reasons over the past few decades. Carbohydrates are possibly the most plentiful and renewable organic materials in nature with inimitable physiochemical properties, plausible low-cost and large-scale production, and sustainability fe...
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Heavy metal removal using genetically engineered organisms (GEOs) offer more cost and energy-efficient, safer, greener, and environmentally-friendly opportunities as opposed to conventional strategies requiring hazardous or toxic chemicals, complex processes, and high pressure/temperature. Additionally, GEOs exhibited superior potentials for biosyn...
Article
In the biomedical field, stimuli-responsive systems comprising smart nanoplatforms based on metal–organic frameworks (MOFs) have garnered immense attention in view of their high surface area, biocompatibility, facile synthesis, tunable structural features, adjustable pore size, and highly versatile composition. Interestingly, stimuli-responsive MOF...
Article
MXenes and their related nanocomposites with superior physicochemical properties such as high surface area, ease of synthesis and functionalization, high drug loading capacity, collective therapy potentials, pH-triggered drug release behavior,...
Article
Liposomes mainly comprise an aqueous core surrounded by a lipid bilayer, akin to cellular membranes. The encapsulation, loading, and release properties of therapeutic agents in both, the core and lipid bilayer can be prominently affected by the preparative processes for liposome which include hydration of lipid thin films, detergent removal, solven...
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Supercapacitors (SCs) are highly promising electrochemical energy conversion and storage devices. SCs display an outstanding power performance, excellent reversibility, long-term stability, simple operation, and high feasibility for integration into electronic devices, including consumer electronics, memory backup systems, and industrial power and...
Article
Scientists have always been inspired by nature to design complex nanostructures and architectures with special features and functions. Latest among these is the construction of bioinspired MXenes and MXene-based structures with unique features such as high flexibility, strong electrical conductivity, high stability/biocompatibility, lower toxicity,...
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Carbon nanotubes (CNTs) with attractive physicochemical characteristics such as high surface area, mechanical strength, functionality, and electrical/thermal conductivity have been widely studied in different fields of science. However, the preparation of these nanostructures on a large scale is either expensive or sometimes ecologically unfriendly...
Article
Significant upsurge in animal by-products such as skin, bones, wool, hides, feathers, and fats has become a global challenge and, if not properly disposed of, can spread contamination and viral diseases. Animal by-products are rich in proteins, which can be used as nutritional, pharmacologically functional ingredients, and biomedical materials. The...
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Exosomes, ranging in size from 30 to 150 nm as identified initially via electron microscopy in 1946, are one of the extracellular vesicles (EVs) produced by many cells and have been the subject of many studies; initially, they were considered as cell wastes with the belief that cells produced exosomes to maintain homeostasis. Nowadays, it has been...
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Bioengineered nanoparticles display unique characteristics at the cellular, atomic, and molecular levels with their geometric shapes dictating suitable actions and use. In the present study, bioengineered and bio-compatible silver nanoparticles (AgNPs) were obtained from Thalictrum foliolosum leaf extract which served as a capping and reducing agen...
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The use of a cheap and effective adsorption approach based on biomass-activated carbon (AC) to remediate heavy metal contamination is clearly desirable for developing countries that are economically disadvantaged yet have abundant biomass. Therefore, this review provides an update of recent works utilizing biomass waste-AC to adsorb commonly-encoun...
Article
Design and development of new materials and their hybrids are key to addressing current energy issues. Thanks to their tunable textural and physiochemical properties, metal–organic frameworks (MOFs) show great potential toward gas sorption, catalysis, sensing, and electrochemical energy applications. Nevertheless, practical applications of MOFs hav...
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Nanosponges have shown promising capabilities for efficient removal of organic/inorganic pollutants from water based on absorption/adsorption and disinfection processes. The application of nanosponges (especially cyclodextrin-based nanosponges) can be considered a cost-effective strategy with minimal energy and time requirements in comparison to ot...
Article
The release of pharmaceuticals into the environment induces adverse effects on the metabolism of humans and other living species, calling for advanced remediation methods. Conventional removal methods are often non-selective and cause secondary contamination. These issues may be partly solved by the use of recently-developped adsorbents such as mol...
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MXene quantum dots (QDs), with their unique structural, optical, magnetic, and electronic characteristics, are promising contenders for various pharmaceutical and biomedical appliances including biological sensing/imaging, cancer diagnosis/therapy, regenerative medicine, tissue engineering, delivery of drugs/genes, and analytical biochemistry. Alth...
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Plants encompass numerous phytochemicals like flavonoids, alkaloids, tannins, saponins, and other metabolites that have a major impact on the generation of nanomaterials with chief implications in current therapeutic methods for a variety of diseases including cancers; herbal extracts serve as potential means for the generation of nanomaterial via...
Article
Background 2-Hydroxy-1,4-Naphthoquinone (HNQ; Lawsone) is one of the most useful and the simplest naturally occurring naphthoquinones and have stimulated resurgence of interest in the past decades due to their wide range of pharmacological activities. Introduction and method This activity has led to unusually large emphasis being placed on the des...
Article
The efficiency of pollutant rejection (PR, %) and water purification of the zeolite membranes is highly dependent on their topology, i.e., porosity and chemical composition. Nevertheless, mechanisms controlling such a physicochemical phenomenon have been limitedly discussed. Herein, we provide insights into the physics and dynamics of water purific...
Article
With the world developing exponentially every day, the collateral damage to air is incessant. There are many methods to purify the air but using carbon nanotubes (CNTs) as adsorbents remains one of the most efficient and reliable methods, due to their high maximum adsorption capacity which renders them extremely useful for removing pollutants from...
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Liver performs number of critical physiological functions in human system. Intoxication of liver leads to accumulation of free radicals that eventually cause damage, fibrosis, cirrhosis and cancer. Carbon tetrachloride (CCl 4 ) belongs to hepatotoxin is converted to a highly reactive free radical by cytochrome P450 enzymes that causes liver damage....
Article
The release of pharmaceuticals and their metabolites into the environment has garnered much attention amidst societies and the scientific community because they induce detrimental effects on metabolic bioprocesses in humans and other living beings. Effective and efficient removal of these noxious chemical species before they enter the food chain is...
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A novel polysaccharide structure (PS-T80) was collected from Ophiocordyceps sobolifera biomass and characterized via a combination of chemical and spectral analyses. Employing high-performance gel permeation chromatography (HPGPC), the average molecular weight is proven to be 7.4 × 104 Da. Furthermore, a sugar composition analysis of the obtained p...
Article
Advanced nanotechnology is an enormously growing area due to its massive scope of applications for diverse domains of applied science and engineering. Numerous types of synthetic procedures are utilized for the creation of nanoparticles (NPs) due to their myriad application scenarios. However, known conventional physical and chemical strategies hav...
Article
Electrochemical conversion of CO2 to fuels and chemicals as a sustainable solution for waste transformation has garnered tremendous interest to combat the fervent issue of the prevailing high atmospheric CO2 concentration while contributing to the generation of sustainable energy. Monometallic palladium (Pd) has been shown promising in electrochemi...
Article
Biosensors are gaining interest in biomedical and environmental sciences. In particular, graphene-based biosensors are promising due to the unique properties of graphene. Here we review the synthesis, characterization, and applications of graphene in enzymatic sensors, immunosensors, DNA sensors, and wearable sensors. Graphene displays advantages s...
Article
Metal-organic frameworks (MOFs) biocompatible systems can host enzymes/bacteria/viruses. Herein we synthesized a series of fatty acid amide hydrolase (FAAH)-decorated UiO-66-NH2 based on Citrus tangerine leaf extract for drug delivery and biosensor applications. Five chemically manipulated FAAH-like benzamides were localized on the UiO-66-NH2 surfa...
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Polymeric nanocomposites have been outstanding functional materials and have garnered immense attention as sustainable materials to address multi-disciplinary problems. MXenes have emerged as a newer class of 2D materials that produce metallic conductivity upon interaction with hydrophilic species, and their delamination affords monolayer nanoplate...
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Cancer is one of the most critical human challenges which endangers many people's lives every year with enormous direct and indirect costs worldwide. Unfortunately, despite many advanced treatments used in cancer clinics today, the treatments are deficiently encumbered with many side effects often encountered by clinicians while deploying general m...
Article
Magnetic resonance imaging (MRI) is an effectual imaging technique for medical diagnosis, its non-invasive nature being a noteworthy attribute, in which magnetic contrast agents are employed to improve sensitivity and accuracy. Graphene exhibits excellent mechanical and physicochemical properties, and notable biocompatibility. In the quest for supe...
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Graphene-based materials have shown immense pertinence for sensing/ imaging, gene/drug delivery, cancer therapy/diagnosis, and tissue engineering/ regenerative medicine. Indeed, the large surface area, ease of functionalization, high drug loading capacity, and reactive oxygen species induction potentials have rendered graphene-(G-) and graphene oxi...
Article
Ionic liquids (ILs), are the organic salts and have been referred to as greener solvent, oftentimes also termed as designer solvents. They are separated into classes namely room temperature ILs (RTILs), task-specific ILs (TSILs), polyionic liquids (PLILs), and supported ILs, among others. ILs are used as solvents because of their low vapour pressur...
Chapter
The progression of conducting polymers has been prolific in recent years due to the extraordinary progress achieved by these materials. The types of preparative methods for conducting polymers and their nanocomposites as well as factors such as temperature, pH, the concentration of monomers, and oxidants can affect the polymers’ shape and physical-...
Chapter
Conducting polymers have been the focus of increased research in numerous fields due to their physicochemical, mechanical, and biological properties. This is especially true for their electrical conductivity because of the ease with which electrons pass along and between the polymer backbones. Dopants play a significant role in improving physicoche...
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The utilization of renewable and abundant agricultural waste such as Pomegranate (Punica granatum L.) peel extract has been developed wherein a simple extraction of dried peel in water offered a natural sensor; ensuing yellowish solution comprising phenolic compounds reacted explicitly to detect Fe⁺³ and I⁻ solutions by naked-eye. The UV–Vis absorp...
Preprint
Today, according to the progression and prevalence of cancer, efforts to discover new compounds to suppress the tumor and associated with less toxicity. Metal oxide nanoparticles have wide applications in biology and biomedicine due to their unique physical and chemical properties. They have great potential in the treatment of cancer, tumor targeti...
Article
The present study describes the enhanced photodegradation of organic pollutant dyes, congo red (CR) and rhodamine B (RhB) dyes under visible light irradiation. AgIO4 nanorods decorated on Bi2S3 nanoflakes in various proportions were synthesized via sono-chemical route wherein the deposition of varying amounts of AgIO4 on Bi2S3 plays a pivotal role...
Article
The application of quantum dots (QDs) for detecting and treating various types of coronaviruses is very promising, as their low toxicity and high surface performance make them superior among other nanomaterials; in conjugation with fluorescent probes they are promising semiconductor nanomaterials for the detection of various cellular procedures and...
Article
The present study highlighted the evaluation of visible light-driven catalytic efficiency of ZnFe2O4 decorated CeO2 nanocomposite (CeO2/ZnFe2O4 NCs) fabricated by chemical co-precipitation method for degradation of methylene blue (MB) dye. HRTEM, SEM, and SAED confirmed it to be spherical shaped with polycrystalline nature and chemical states being...
Preprint
Bioengineered nanoparticles display unique characteristics at the cellular, atomic, and molecular levels with their geometric shapes dictating suitable actions and use. In the present study, bioengineered and bio-compatible silver nanoparticles (AgNPs) were obtained from Thalictrum foliolosum DC leaf extract (TFLE) which served as a capping and red...