Jayant Kumar

• Ph.D
• Prof and Director Center for Advanced Materials at University of Massachusetts Lowell

Organic thermoelectric materials would be ideally suited for wearable thermoelectric devices but currently are not efficient enough for practical applications. Previous research efforts have tailored the composition, oxidation status, or doping levels of organic thin-film thermoelectrics to maximize their thermoelectric performance typically measur...

Natural and synthetic polymeric fibers are used extensively in making fabrics for a variety of civilian and military applications. Due to the durability and comfort, nyco, a 50-50% blend of nylon 66 and cotton, is used as the material of choice in many applications including military uniforms. This fabric is flammable due to the presence of cotton...

Fabric-based thermoelectrics can be seamlessly integrated into clothing so they would be ideal to power devices embedded into smart clothing. This study describes the development of thermoelectric fabrics that have their fibers covered with PEDOT:Tosylate and CuI nanocrystals. Several types of fabrics (e.g., cotton, nylon, NYCO, polyester, nomex, m...

A single-step, solvent-free microwave-assisted technique for flame retardant (FR) cotton fabric using a bio-based FR agent, phytic acid is presented. The effects of microwave power and irradiation time on FR characteristics of cotton are investigated. Self-extinguishing cotton fabric with char length of 79 mm and no afterflame is achieved within 4...

Thermoelectric composites of organic and inorganic materials exhibit significantly enhanced thermoelectric properties compared with pristine organic thermoelectrics so they might be better suited as core materials of wearable thermoelectric devices. This study describes the development of three-dimensional (3D) paper PEDOT:tosylate/CuI composites t...

Photovoltaic backsheet technology is utilized to protect the interior components of solar modules from environmental stress as well as provide electrical insulation to the module. The growing demand for solar energy and longer module service life requirements have brought backsheet performance into focus. Despite being a protective packaging materi...

Nylon is one of the most important engineering polymers used in textile, electronics, and automotive applications. In addition to good mechanical properties, flame retardancy is desirable in these applications. Nylon is typically processed at high temperatures and very few non-toxic synthetic flame-retardant (FR) additives are stable at these tempe...

In recent years, developing potent antioxidants has been a very active area of research. In this context, phenolic compounds have been evaluated for their antioxidant activity. However, the use of phenolic compounds has also been limited by poor antioxidant activity in several in vivo studies. Polymeric phenols have received much attention owing to...

The effect of one-layer polymeric barrier coatings onto flexible and thin polyethylene terephthalate (PET) film is herein examined towards the blockage of water vapor. It is observed that well-known semi-crystalline polymers such as poly(ethylene) (PE), partially chlorinated PE (47% Cl-PE), poly(propylene) (PP), and poly(vinylidene fluoride) (PVDF)...

In the quest for development of halogen-free FR additive and better understanding of the structure-flammability relationship, here we report the synthesis and characterization of a series of phenolic and benzylic succinamides, with and without aliphatic hydroxyl groups. These compounds allow for detailed investigation of the influence of these func...

A new and versatile method to covalently functionalize cellulose in cotton and Nylon/cotton (Nyco) blends with plant-based renewable material, phytic acid to impart flame retardant characteristics that is durable is presented. This involves functionalization of 1,1′-carbonyldiimidazole to the cellulose structure of cotton followed by the attachment...

Polyserotonin was enzymatically synthesized using Horseradish peroxidase (HRP) as the catalyst. This novel conjugated polymer exhibited good fluorescent properties with significantly higher Stokes shift than its monomer. The enzymatic polymerization eliminated the need for extensive purification of the product (typically necessary for the removal o...

This chapter contains sections titled: Introduction Fire Retardant Additives Based on Phosphorus and Nitrogen from Renewable Resources Natural Phenolic Compounds as Flame Retardant Additives Other FR Materials from Renewable Sources Prospects Summary Acknowledgements

The recognized drawback of utilizing metal catalysts for the synthesis of fluorescent conjugated polymers (CP) is the requirement for extensive purification to ensure complete removal of residual catalyst that would otherwise quench the fluorescence. In addition, typical synthesis of fluorescent CP involves multiple steps, monomers and solvents wit...

Aqueous vitamin C solution has been used as an environment-friendly reducing agent for tuning the thermoelectric properties of p-toluenesulfonate-doped poly(3,4-ethylenedioxythiophene) (PEDOT-Tos) films. The de-doping of the PEDOT-Tos films by aqueous vitamin C solutions led to a decrease in the electrical conductivity of the films. The measured ul...

The effect of nanoimprinted structures on the performance of organic bulk heterojunction solar cells was investigated. The nanostructures were formed over the active layer employing the soft lithographic technique. The measured incident photon-to-current efficiency revealed that the nanostructured morphology over the active layer can efficiently en...

Organometallic halide perovskite materials are attracting considerable interest for high performance photovoltaic and photodetector applications due to their exceptional opto-electronic properties and easy processing capability. The high atomic numbers (Z) of their constituents also make these materials suitable for X-ray detection. Here we report...

Utilization of renewable materials for the development of safer and nontoxic flame retardants has been of interest from environmental safety and sustainability perspective. Tannic acid (TA) is an abundantly available bio-based polyphenol that exhibits good intumescence and char forming characteristics upon being subjected to heat. Intumescence and...

The effect of pendant side groups on two-photon-absorption cross-section in a number of soluble fluorescent polythiophenes was investigated. Different side group leads to different planarity and conformation of the polymer. As the side group induced planarity of the polymer chain increases, the two-photon-absorption cross-section also increases. Th...

Enzymes, being remarkable catalysts, are capable of accepting a wide range of complex molecules as substrates and catalyze a variety of reactions with a high degree of chemo-, stereo- and regioselectivity in most of the reactions. Biocatalysis can be used in both simple and complex chemical transformations without the need for tedious protection an...

We have synthesized two novel fluorescent 3-(4-diethylaminocinnamoyl) coumarins that exhibit fluorescence quenching upon exposure to a nerve agent simulant, diethylchlorophosphate (DCP), providing a basis for rapid and sensitive DCP chemosensing. Furthermore, these coumarin derivatives display two-photon fluorescence upon illumination with near-inf...

Purpose: To fabricate organic photovoltaic (OPV) cells with nanometric active layers sensitive to ionizing radiation and measure their dosimetric characteristics in clinical x-ray beams in the diagnostic tube potential range of 60–150 kVp. Methods: Experiments were designed to optimize the detector’s x-ray response and find the best parameter comb...

Photovoltaic performance enhancement of fullerene based solar cells was achieved upon Photovoltaic performance enhancement of fullerene based solar cells was achieved upon exposure to near-infrared (NIR) laser pulses. The solar cells were fabricated with poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) under ambie...

A novel class of PDMS based polymers containing azobenzene side chains were synthesized and evaluated as coatings for quartz crystal microbalance (QCM) based sensors to detect nitroaromatic vapors. The polymers contain functional groups (p-substituted azobenzene moieties and hydroxyl groups) that can interact with compounds with large dipole moment...

Fluorescent conjugated materials exhibiting reasonable biocompatibility that are capable of interacting with biological molecules are of interest for bio-sensing and imaging applications. Traditional approaches do not allow for the synthesis of conjugated materials in the presence of biologically relevant substrates. Further conjugated polymers syn...

Fluorescent conjugated materials exhibiting reasonable biocompatibility that are capable of interacting with biological molecules are of interest for bio-sensing and imaging applications. Traditional approaches do not allow for the synthesis of conjugated materials in the presence of biologically relevant substrates. Further conjugated polymers syn...

Quaterthiophene (QT) with a 1,2,3-triazole moiety was found to have a high sensory response in solution toward a broad class of nitroaromatics, including DNT and TNT, and nitro esters, such as RDX and PETN. Fluorescence quenching in QT thin films was also high for vapors containing DNT or TNT in ppb levels. These results were unexpected based our e...

Unusually photoluminescent undoped oligomers and doped electrically conducting polymers of 4-(3-Pyrrolyl)butyric acid have been enzymatically synthesized using the oxidoreductase soybean peroxidase as a catalyst. This biocatalytic approach provides a direct route to a fluorescent-undoped oligomer of pyrrole that requires no protection/deprotection...

Thin films of environmentally safe, halogen free, anionic sodium phosphate and cationic polysiloxanes were deposited on a Nyco (1:1 nylon/cotton blend) fabric via layer-by-layer (LbL) assembly to reduce the inherent flammability of Nyco fabric. In the coating process, we used three different polysiloxane materials containing different amine groups...

We report sensitive detection of explosive materials via fluorescence quenching mechanism of a conjugated polymer Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)]. The polymer used in this investigation is highly fluorescent and can be easily processed into thin films or nanostructured fibers. We have shown that a thin film of the polymer can...

Dye-sensitized solar cells (DSSCs) were fabricated using photoanodes made from graphene-TiO2 nanocomposites. The dependence of the size of graphene sheets on the cell performance was investigated. The experimental results indicated that cells loaded with the smaller graphene sheets yielded larger enhancement. The smaller graphene sheets improved th...

We report an easy and simple approach for making silver nanotubes (NTs) using electrospinning. Silver nanoparticles were first deposited on an electrospun polymer nanofiber template by dip-coating in aqueous medium. Subsequently, selective dissolution of the polymer core led to the formation of silver NTs. Average diameter of the NTs was 250 nm and...

Polymer solar cells fabricated in air under ambient conditions are of significant current interest, because of the implications in practicality of such devices. However, only moderate performance has been obtained for the air-processed devices. Here, we report that enhanced short circuit current density (Jsc) and open circuit voltage (Voc) in air-p...

Purpose To fabricate and test nanometric organic photovoltaic (OPV) cells made of various active‐layer/electrode thicknesses and sizes; to determine the optimal material combinations and geometries suitable for dose measurements in clinical kilovoltage x‐ray beams. Methods The OPV consisted of P3HT:PCBM photoactive materials sandwiched between alu...

Sensors are devices that respond to external stimuli and convert them to a signal, which can be measured and recorded. In chemical sensors, the presence of specific chemical compounds or certain chemical reactions is detected through a variety of responses. Detection of environmentally toxic chemicals, especially metal ions, and chemicals that pres...

Curcumin is well-known for its wide range of physiological actions. It is a fluorescent polyphenol, and its optical properties could be used for sensing chemicals. Major impediment is the aggregation of curcumin in thin film, thereby, reducing the fluorescence quantum yield. Herein, we report the chemo-enzymatic polymerization of curcumin with poly...

A series of two-photon (TP) active 4-dimethylaminocinnamoyl coumarins were synthesized. These compounds exhibit red shift in absorption and considerable Stokes shift in emission spectra in comparison to the parent coumarin. Large TP absorption cross-sections were measured for all the coumarins in dilute solutions. A correlation between the chemical...

The emerald ash borer (EAB), Agrilus planipennis, is an invasive tree-killing pest in North America. Like other buprestid beetles, it has an iridescent coloring, produced by a periodically layered cuticle whose reflectance peaks at 540 nm wavelength. The males perform a visually mediated ritualistic mating flight directly onto females poised on sun...

The adverse impact of chemical and biochemical waste on the environment and human health poses a serious challenge in today's World. The best way to address these challenges is to reduce the waste by developing more efficient processes and technologies, based on the principles of "green chemistry". Some of these synthetic approaches involving the c...

We report the synthesis of a self organizable and water dispersible bis PEGylated (bis polyethyleneglycolated) curcumin (1) using an efficient synthetic method. Compound 1 forms nanoparticles on the order of 90 nm in water. Even though it forms nanoparticles, compound 1 interacts strongly with metal ions, Al+3, Cu+2, and Hg+2. Fluorescence and abso...

Polydimethylsiloxane-aromatic dianhydride copolymers (PS-Oxy-PAA and PS-DAH-PAA) were blended through several techniques with organoclays Cloisite 30B, 10A and Na+ ranging from 1 to 5 wt.%. Thermal and flame-retardant analysis revealed an in-situ blending approach was optimal, which led to the generation of a nanocomposite, PS-Oxy-PAA/30B (5 wt.%),...

Globally, certain types of halogenated flame retardant additives (FR) are becoming increasingly regulated or banned from being used in polymers. There is an immediate need for alternative non-toxic thermally stable polymers and char-forming additives. Development of non-halogenated FR for the commonly used and highly flammable thermoplastics, namel...

Two water dispersible and two-photon (TP) active polymer nanoparticles were synthesized from poly [2-(3-thienyl) ethanol n-butoxy carbonyl methyl-urethane] and poly(3,3’’’-didodecyl quarter thiophene) polymers using a simple miniemulsion technique. Strong TP fluorescence was observed from each of these nanoparticles using a femtosecond laser operat...

A highly twisted triphenylamine displays aggregation-induced enhanced emission. A solvent-specific critical molecular aggregate size, once reached, gives rapid onset of enhanced emission in polar solvent mixtures that favor quenching of solvated individual molecule excited states.

A new strategy was developed for improving basic dye sensitized solar cell (DSSC) performance, using push–pull organic triarylamines with tunable frontier energy levels as additives in the DSSC electron shuttling electrolyte solution. A significant improvement in the device performance was observed and attributed to improved dye regeneration and ho...

We observe more than two orders of magnitude enhancement of fluorescence quenching in colloidal conjugated polymer nanoparticles by nitroaromatic analytes compared to solution of the same polymer in organic solvents. This observation is surprising as the quantum efficiency of fluorescence of the polymer solution is significantly higher. The colloid...

The Emerald Ash Borer (EAB), Agrilus planipennis, is an invasive species threatening the ash trees of North America. EABs exhibit a mating behavior in which the flying male will spot a stationary female at rest, then execute a pouncing maneuver where he dives sharply onto the female. It is thought that this pouncing behavior is cued by some visual...

Through a bioreplication approach, we have fabricated artificial visual decoys for the invasive species Agrilus planipennis— commonly known as the Emerald Ash Borer (EAB). The mating behavior of this species involves an overflying EAB male pouncing on an EAB female at rest on an ash leaflet before copulating. The male spots the female on the leafle...

Two-photon active monodisperse Nile Red dye incorporated polystyrene nanoparticles were fabricated using a simple mini-emulsion technique. The nanoparticles were stable as an aqueous dispersion and emitted strong two-photon-fluorescence when excited with 800 nm laser pulses. Quadratic dependence of the fluorescence was confirmed by varying the inci...

The present invention relates to amphiphilic polymers, and micelles and compositions comprising the same, and their use in a variety of biological settings, including imaging, targeting drugs, or a combination thereof for diagnostic and therapeutic purposes.

Increasing awareness of toxicity of halogenated flame retardants (FRs) has resulted in stringent regulations that require the elimination of their use in plastics. Consequently, there is considerable interest for the development of new varieties of high performance FRs. Here, we report the synthesis of new class of polyphenol based FR additives. Pr...

Enzymatic synthesis of doped polypyrrole (PPy) complexes using oxidoreductases (specifically peroxidases) is very well established "green" methods for producing conducting polypyrrole. The importance of this approach is realized by the numerous potential opportunities of using PPy in biological applications. However, due to very high costs and low...

Attenuation characteristics of hollow, flexible, metal and metal/dielectric coated polycarbonate waveguides were investigated using an optically pumped far infrared (FIR) laser at 215 µm. The bending loss of silver coated polycarbonate waveguides were measured as a function of various bending angles, bending radii, and bore diameters. Minimal propa...

The charge transport characteristics of organic semiconductors are one of the key attributes that impacts the performance of organic electronic and optoelectronic devices in which they are utilized. For improved performance in organic photovoltaic cells, light-emitting diodes, and field-effect transistors (FETs), efficient transport of the charge c...

We report a straightforward synthetic method to generate solution processable electron transporting polymers with low band gap and wide absorption range from readily available acceptor monomers. We show the efficacy of this approach using widely used electron acceptor 2,1,3-benzothiadiazole. The polymers have absorption up to 750 nm with electron m...

Two-photon (TP) fluorescence properties of an antioxidant and anti-tumor molecule, curcumin, were investigated. The two-photon absorption (TPA) action cross-section was measured in organic solvents and found to be 6 GM in tetrahydrofuran and 2 GM in dimethyl sulfoxide. The measured TPA cross-section is comparable to that of rhodamine 6G. One-photon...

A dry single-step process for enhancing the surface area of a silicon microcantilever is described. In this process, a flat microcantilever is irradiated with ∼ 100-femto-second-long laser pulses. The silicon surface melts and rapidly cools, resulting in the formation of nanoscale pillars. The shape and size of these nanostructures can be tuned by...

Polyacrylonitrile fibers were electrospun yielding diameters in the range of 50 to 200 nm. These nanofibers were then immersed in an aqueous coating solution to deposit a continuous film of titanium dioxide on the surface. In order to shorten the coating time and optimize the metal oxide layer thickness, the fibers were surface functionalized by im...

Bulk heterojunction (BHJ) solar cells consisting of poly(3-hexylthiophene) (P3HT) as donor and cadmium selenide/zinc sulphide (CdSe/ZnS) core shell quantum dots (QDs) as acceptor have been developed. Starting from the bilayer of P3HT/QD structure a BHJ is induced using the process of thermal inter-diffusion. The absorption measurements on the bilay...

Interference effects and photosensitive materials provide a simple method to fabricate a variety of periodic nanostructures.

The emerald ash borer (EAB), Agrilus planipennis, is an invasive species of beetles threatening the ash trees of North America. The species exhibits a mating behavior in which a flying male will first spot a stationary female at rest and then execute a pouncing maneuver to dive sharply onto her. The pouncing behavior appears to be cued by some visu...

Strong two-photon-induced fluorescence was observed from a series of novel fluorescent semiconducting polymer nanoparticles using femtosecond laser pulses at 800 nm. The conjugated polymer nanoparticles were fabricated by a simple technique known as the ``mini emulsion'' technique. The quadratic dependence of the two-photon-fluorescence was confirm...

Curcumin is a polyphenol which has elicited considerable interest for its antioxidant and anti tumor properties. Although curcumin may be used as potential therapeutic drug, it is very sparingly soluble in water which makes it less bioavailable under physiological conditions. We report two approaches to make curcumin more bioavailable. The first ap...

Low-loss hollow flexible metal/dielectric coated polycarbonate waveguides have been designed and fabricated for the maximal transmission of Terahertz radiation (THz). Attenuation characteristics of Terahertz radiation in Ag/Au coated waveguides with bore diameters 4.1 mm, 3.2 mm, 2 mm were studied at 215 µm wavelength and the maximal transmission...

Over the past few years, the use of certain types of halogenated flame retardant additives such as decabromodiphenylether has come under intense scrutiny due to their toxicity, environmental persistence and bio-accumulation. There is an immediate need for the development of non-toxic alternative flame retardant materials and fire resistant polymers...

Imidazolium iodide compounds have been utilized in the electrolytes for dye sensitized solar cells (DSSC). Most of the investigations with these compounds focus on the formulation of eutectic mixtures that promote efficient dissociation and diffusion of the iodide and triiodide species. Facile alternative synthetic approaches such as click chemistr...

Nanoparticles of a regioregular and soluble polythiophene were fabricated by mini-emulsion technique. The fabricated nanoparticles were characterized by optical spectroscopy and dynamic light scattering. The fluorescence quenching of these fabricated nanoparticles with 2,4-dinitrotolune (DNT) in aqueous and organic solutions was investigated. Signi...

Two-photon fabrication of surface relief gratings on azobenzene functionalized polymer films was carried out using femtosecond laser pulses at 800 nm. The two-photon inscriptions were achieved by simply employing a relief grating as a phase mask. The relief patterns were successfully recorded with the phase mask and the near-infrared laser pulses....

An optical sensor array consisting four fluorescent polymer thin films was investigated to recognize nitro containing explosive, TNT (2,4,6-trinitro toluene) and its simulants. The fluorescence quenching behaviour in presence of these analyte vapors was measured at peak emission of fluorescent materials upon excitation at 440nm under ambient condit...

Resveratrol (3,5,4′ trihydroxy trans-stilbene) is a plant based phenolic compound. Enzymatic oligomerization of trans-resveratrol using horseradish peroxidase followed by characterization of the oligomer is presented. The oligomerization reaction was monitored using UV-Visible absorption and fluorescence spectroscopies. The oligomer exhibits strong...

A one-pot, environmentally friendly enzymatic method is described for the synthesis a polypyrrole derivative, poly(3-methylpyrrole) (poly(3-MP)) in an aqueous solvent system. The enzyme, soybean peroxidase (SBP), was shown to successfully polymerize the beta functionalized pyrrole monomer. The resulting polymer was semiconducting, thermally stable,...

Nano-particles with controllable particle size and shape are of great interest in biomedical applications (1). From the standpoint of drug carrier design with wide applicability to a variety of hydrophobic drugs, an effective strategy would be to prepare a simple copolymer having the property to form stable polymeric micelles which can entrap hydro...

Quartz Crystal Microbalance (QCM) based sensors have been used extensively to detect trace amounts of organic chemical vapors. These devices typically incorporate a polymer coating as an active layer that can bind the analytes of interest. Analyte adsorption causes a shift in the resonant frequency of the device proportional to the amount of adsorb...

A soluble thiophene copolymer having polar and non polar side groups was synthesized and its photovoltaics performance was investigated. The synthesized copolymer was characterized using Nuclear Magnetic Resonance (NMR) and optical spectroscopy. Dye sensitized solar cells were fabricated using this copolymer as sensitizer. An open-circuit voltage o...

Crosslinking of polymers using crosslinking agents has been widely utilized to further improve the mechanical and thermal properties of the polymers. We have explored various aliphatic and aromatic dicarboxylic acids such as malonic acid, glutaric acid, isophthalic acid, terephthalic acid and terephthaloyl chloride as crosslinking agents to crossli...

Polymers synthesized from naturally derived monomers are valuable since they decrease the reliance on petroleum based feed stocks. Cashew nut shell oil (CNSL) is a side-product from processing of edible Cashew nuts of Annacardium occidentale. One of the major components of CNSL is cardanol, which is a phenol derivative having an unsaturated pentade...

With the increase in popularity of enzyme catalysis, there has been a demand for the development of novel biomimetics that can emulate naturally occurring enzymes and serve as surrogate catalysts. Metal containing porphyins have been used as catalysts for mediating a number of chemical transformations. Metalloporphyrins play vital roles in catalyzi...

Optical sensing, via fluorescence quenching, of nitroaromatic vapours using polythiophenes has received limited attention due to their rather low sensory response. We hypothesized that a dipolar 1,2,3-triazole moiety can enhance the interaction of DNT and TNT with the polymer in thin films and bulky side chains can decrease the chain packing in thi...

Since decades, varieties of amphiphilic polymers have been widely investigated for improving aqueous solubility and bioavailability of the hydrophobic drugs. The upcoming approach is to develop more efficient advanced nano-carrier molecules capable of more than drug delivery. Herein, we report the design and synthesis of some novel carrier molecule...

A polymer light emitting diode (PLED) based on poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene]:CdSe/ZnS core shell uncapped quantum dots (QDs) was fabricated. It was observed that the presence of QDs in the polymer tunes the emission spectrum of the PLED as their QDs concentration increases to 10% w/w and above. It was also found that...

A facile single step strategy for the synthesis and large area patterning of silver nanoparticles via photodecomposition of a photoactive silver nitrite aliphatic amine complex was developed. Decomposition of the silver complex was facilitated using either a UV or an Argon ion laser (514.5 nm) irradiation. The synthesis was performed both in soluti...

The combined effect of a salmon deoxyribonucleic acid (DNA)-based electron blocking layer and a single walled carbon nanotube (SWCNT) composite-based electron transport layer on the performance of a poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) polymer light emitting diode (PLED) has been examined. The SWCNT network in the...

Two-photon-induced fluorescence from a soluble polythiophene containing urethane side groups has been investigated using femto-second laser pulses at 800nm. Strong two-photon fluorescence was measured in polymer solution. The quadratic dependence of the fluorescence on the excitation laser intensity confirmed the two-photon process. The measured tw...