In Situ Synthesis of Metal Nanoparticle Embedded Hybrid Soft

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In Situ Synthesis of Metal Nanoparticle Embedded Hybrid Soft Nanomaterials Kizhmuri P. Divya,† Mikhail Miroshnikov,†,# Debjit Dutta,‡ Praveen Kumar Vemula,*,‡ Pulickel M. Ajayan,§ and George John*,†,# †

Department of Chemistry and Center for Discovery and Innovation, The City College of New York, 85 St. Nicholas Terrace, New York, New York 10031, United States # Ph.D. Program in Chemistry, The Graduate Center of The City University of New York, New York, New York 10016, United States ‡ Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bellary Road, Bangalore 560065, India § Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States CONSPECTUS: The allure of integrating the tunable properties of soft nanomaterials with the unique optical and electronic properties of metal nanoparticles has led to the development of organic−inorganic hybrid nanomaterials. A promising method for the synthesis of such organic− inorganic hybrid nanomaterials is afforded by the in situ generation of metal nanoparticles within a host organic template. Due to their tunable surface morphology and porosity, soft organic materials such as gels, liquid crystals, and polymers that are derived from various synthetic or natural compounds can act as templates for the synthesis of metal nanoparticles of different shapes and sizes. This method provides stabilization to the metal nanoparticles by the organic soft material and advantageously precludes the use of external reducing or capping agents in many instances. In this Account, we exemplify the green chemistry approach for synthesizing these materials, both in the choice of gelators as soft material frameworks and in the reduction mechanisms that generate the metal nanoparticles. Established herein is the core design principle centered on conceiving multifaceted amphiphilic soft materials that possess the ability to self-assemble and reduce metal ions into nanoparticles. Furthermore, these soft materials stabilize the in situ generated metal nanoparticles and retain their self-assembly ability to generate metal nanoparticle embedded homogeneous organic−inorganic hybrid materials. We discuss a remarkable example of vegetable-based drying oils as host templates for metal ions, resulting in the synthesis of novel hybrid nanomaterials. The synthesis of metal nanoparticles via polymers and self-assembled materials fabricated via cardanol (a bioorganic monomer derived from cashew nut shell liquid) are also explored in this Account. The organic−inorganic hybrid structures were characterized by several techniques such as UV− visible spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Utilization of silver nanoparticle-based hybrid nanomaterials as an antimicrobial material is another illustration of the advantage of hybrid nanomaterials. We envision that the results summarized in this Account will help the scientific community to design and develop diverse organic−inorganic hybrid materials using environmentally benign methods and that these materials will yield advanced properties that have multifaceted applications in various research fields.

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INTRODUCTION

research is largely devoted to combining organic materials with metal nanoparticles (MNPs). Hybrid nanomaterials have recently received significant attention due to the advantageous combination of structural and catalytic properties of organic polymers and the optical, magnetic, and electrical properties of the embedded nanoparticles. Apart from free-standing polymeric films, the organic counterparts include liquid crystals, hydrogels, and self-assembled monolayers. These “soft” nanomaterials have a highly tunable surface chemistry, allowing for facile modification of functional group composition, porosity, and morphology. As a result, they operate as efficient templates

The emergence of nanoscience in the 1990s triggered revolutionary changes in scientific research. Despite the fact that nanosized copper and silver oxide particles were used in the ninth century to imbue luster in pottery, nanoparticle research has only flourished within the last few decades. In the present day, metal nanoparticles have found established applications in the biomedical, optical, and electronic fields.1−7 The unique properties of these particles, stemming from their size and shape, have attributed to their impact as components of functional materials within industry and materials science. The quest to advance these properties and enhance them for cutting-edge performance capabilities has led to the development of hybrid organic−inorganic nanomaterials.8−10 Current © XXXX American Chemical Society

Received: April 28, 2016

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DOI: 10.1021/acs.accounts.6b00201 Acc. Chem. Res. XXXX, XXX, XXX−XXX

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Accounts of Chemical Research for synthesis and add a dimension of biocompatibility that is necessary for environmental, medicinal, and green energy applications.11−14 Several methods have been developed to prepare organic−MNP hybrid materials. These methods can be categorized into two types: (1) the use of preformed MNPs that are combined with organic soft nanomaterials and (2) in situ synthesis of MNPs in the host organic material to generate hybrid materials. In the former case, the MNPs are synthesized by various techniques such as chemical etching or electrochemical methods or by using gases such as carbon monoxide as reducing agents, followed by the incorporation into organic matrices.15 The latter method involves the preparation of MNPs within the organic template by chemical or physical stimuli, which are the topic of discussion for this Account.16

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IN SITU SYNTHESIS OF METAL NANOPARTICLES IN SOFT MATERIALS TO GENERATE HYBRID MATERIALS A variety of soft material systems have been designed and developed over several years. These soft materials can be derived from synthetic or naturally occurring organic molecules including self-assembled nanotubes, nanofibers, gels, liquid crystals, and polymers. Often, the molecular self-assemblies are generated by amphiphilic molecules that arrange into various geometric structures as a result of modifications to their solubility in a medium. As the prevalence of soft nanostructures as potential templates for hybrid nanoparticle synthesis have expanded, scientists combined molecular self-assembly and coordination chemistry to design tools for the development of gel-based materials and beyond. Here, some of these materials are discussed in detail.

Figure 1. Schematic illustration of formation of aligned Cu nanoparticles from self-assembled copper-chelating amphiphiles.

Metal Nanoparticles in Self-Assembled Hydro- or Organogels

reducing agents, however, was first demonstrated by our group.26 The design strategy for such systems required a clever choice of active moieties for triggering self-assembly to form soft materials, as well as a metal reducing entity to generate MNPs. In addition, the self-assembled nanostructure should stabilize MNPs and retain its ability to form encapsulated MNP hybrid materials (Figure 2). Gelators of urea-based aryl derivatives were used as reducing and capping agents for the synthesis of GNPs (Figure 3). It has already been demonstrated that amines, such as oleylamine, can reduce Au(III) to Au(0) to form GNPs. Hence, we have utilized the terminal −NH2 group of the synthesized urea based gelators to reduce HAuCl4, which is subsequently followed by capping. A change from yellow colored solution to colorless solution, followed by the appearance of a pink hue, indicated the presence of the reduced form of gold. One of the main advantages of this system was that the morphology, as well as the bulk properties, of the gel was not changed in the presence of GNPs. In the ensuing years, several groups continued to adopt the concept of peptide gel templated synthesis of MNPs. Organogels formed from tripeptides with redox-active chemical moieties were used for the in situ formation and stabilization of gold and silver nanoparticles.27 In some cases, however, structural alterations to the gel structures were observed. Chloroauric acid undergoes reduction in the presence of vitamin C (ascorbic acid) to generate GNPs in the solution phase. In situ synthesis of GNPs using self-assembled vitamin C-based amphiphiles was later demonstrated by our group.28

Gels are one example of functional architectures in which the self-assembly of low molecular weight gelators leads to the formation of nanoscale fibers through noncovalent interactions. The fibers entangle to form a 3D network that holds a large amount of liquid, resulting in the macromolecular organization of the liquid into a solid or semisolid. Shinkai and co-workers used supramolecular organogels as templates for the preparation of various inorganic nanostructures.17−19 Similarly, transition metal nanotubes and CdS ribbons were developed using supramolecular gels as templates by Hanabusa20,21 and Stupp,22 respectively. Our group adapted metallophilic organogels to prepare assembled copper nanoparticles from copperchelating amphiphiles by using glycolipid nanotubes as templates (Figure 1).23 The amphiphile, which contains a copper chelating diaminopyridine moiety, aggregates in aqueous media to form nanotubes. Functional arms of the nanotubes were able to coordinate with Cu2+ ions when dispersed in copper chloride solution. Further Cu nanoparticles were formed by removing the nanotube templates through an annealing process at 500 °C in argon atmosphere. In 2004, Kimura et al. reported the synthesis of a physical mixture of hot gel solution with preformed alkylthiol stabilized gold nanoparticles (GNPs); further gelation resulted in GNP assembly on a fibrous gel network.24 Love et al. later reported GNP synthesis in an organogel through the diffusion of tetraoctylammonium bromide stabilized HAuCl4 toluene solution into preformed toluene gel and subsequent UV irradiation.25 The in situ preparation of GNPs using lowmolecular-weight hydrogelators in the absence of external B


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Figure 2. General scheme of design strategy and formation of hybrid nanostructures.

Figure 3. (a) Urea based gelator that forms a gel in water; (b) TEM image of hydrogel with GNPs. Reprinted with permission from ref 26. Copyright 2006 Royal Society of Chemistry.

hydrogel matrix.30 The hydrogel−GNP composites showed improved viscoelastic properties than the native hydrogel, confirmed by rheological studies. By change of pH, hydrogelating amphiphilic carboxylates were transformed to the corresponding carboxylic acids (efficient organogelators). Thus, the synthesized AuNP−hydrogel composite could be easily converted to AuNP−organogel by this simple change in the pH of the aqueous medium.

Ascorbic acid derivatives ASC8, ASC12, and ASC18 (Figure 4) were synthesized by enzyme catalysis and generated gels in various solvents. Three milligrams of ASC18 was added to a 5 mol % HAuCl4 solution in water and heated at 40−50 °C to yield a homogeneous solution. Heating of the solution resulted in a color change from the initially yellow solution to colorless, and then finally to pink. Thus, the in situ synthesis of GNPs was performed without the use of any external reducing or capping agent. The appearance of a surface plasmon band at a longer wavelength (555 nm) was confirmed by using a UV−visible spectrophotometer; this implies the presence of GNPs. Further characterization of GNP-embedded gels was done using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Das and co-workers have synthesized GNPs of different shapes via in situ reduction by a low-molecular-weight gel template of tryptophan-containing peptide amphiphiles in water. This was accomplished in the absence of external reducing or capping agents (Figure 5).29 The authors have modulated the shape of GNPs in the 3D-supramolecular hydrogel matrix by modifying the headgroup architecture of hydrogelator peptide amphiphiles. The same group has also used amino acid based amphiphilic gelators (carboxylate salts) for the in situ synthesis of gold nanoparticles (GNPs) in a

Metal Nanoparticles in Self-Assembled Liquid Crystals

Another exemplary class of template materials is self-assembled liquid crystals (LCs). LCs have a diverse array of applications; for example, they are currently being used in photonics as electronic visual displays and ferroelectric materials. Much focus has also been directed toward developing self-organizing systems of LCs. The use of LCs as templates for the synthesis of nanostructured materials and nanoparticles has been reported in the literature;31 the resulting hybrid materials possess the properties of both metal particles and soft matter. In general, the synthesis of LCs embedded with MNPs involves multiple steps including the separate synthesis of MNPs, their functionalization, and the doping of particles into LC domains.32−36 Apart from this tedious synthetic procedure, destabilization of the LC domains by the incorporation of C


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molecular weight molecules Ch11, Ch7, and Ch5 contain a cholesterol mesogenic core and aniline group to reduce HAuCl4-with different methylene chains (Figure 6). Mesogens Ch7 and Ch5 form chiral smectic A (SmA*) phase at 68.6 and 67.9 °C, respectively. The melted SmC* phase of Ch11 was confirmed from its broken fan-shaped texture with dechiralization lines. The yellow colored film obtained by drop casting a homogeneous solution of mesogen and HAuCl4 at 100 °C for 60 s turned colorless and then pink. These color changes are in accordance with initial rapid reduction of AuIII to AuI, followed by reduction of AuI to Au0. A higher melting temperature was associated with Ch11−GNP conjugates compared with Ch11 individually indicated the stabilization of the LC phase by the GNPs. Electrostatic interactions between AuCl4− and the NH3+ group of the mesogens entrap gold ions in the LC domain. This is then followed by reduction of gold ions to nanoparticles, which form well-defined 3D structures. Varying the HAuCl4 concentration yielded different shapes of GNPs including platelike structures, pyramids (triangular cross section), cubes (squares), dodecahedra (pentagons, hexagons), and spheres (circular) with sizes ranging from 12 to 35 nm. The major advantage of this approach is that shape-selective synthesis of GNPs in glass-forming liquid crystalline materials can be done in a single step without any external reducing or stabilizing agents. The effect of meta substituents on the liquid crystalline behavior and in situ MNP synthesis of cholesterol phenoxy alkanoate (CPA) mesogens was also studied in detail (Figure 7).38 Among CPAs with different substituents, all derivatives exhibited thermotropic liquid crystalline properties during the cooling cycle except for CPA−NHCOCH3; however, only CPA−NH2 showed an enantiotropic LC phase during the heating cycle. CPA−CHO showed monotropic chiral nematic

Figure 4. (a) Structure of ascorbic acid-based amphiphiles. SEM images of ASC18 hydrogels (b) without and (c) with GNPs. (d) TEM image of GNP-containing ASC18 hydrogel. (e) Absorption spectra of GNPs prepared in ASC18 hydrogel Reprinted with permission from ref 28. Copyright 2007 American Chemical Society.

MNPs presented a recurring problem. Hence, these difficulties spurred a great demand for the development of a straightforward protocol for creating homogeneously dispersed MNPs embedded in LCs. We have reported a new class of lowmolecular-weight mesogens that could reduce metal salts to nanoparticles as well as form glassy LC phases.37 The low

Figure 5. (a) Structure of tryptophan based gelators and TEM images of GNPs from the corresponding gels. (b) Transfer of GNP−hydrogel nanocomposite to GNP−organogel nanocomposite by changing the pH. Adapted with permission from refs 29 and 30. Copyright 2008 American Chemical Society and Copyright 2010 Royal Society of Chemistry. D


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Figure 6. (a) Chemical structures of amphiphile containing reducing (amine) group connected to cholesteryl mesogens. (b) Schematic diagram of LC-template-assisted alignment of GNP arrays. (c) Glass plates coated with Ch11 and HAuCl4 at 25 °C, before heating (yellow) and after heating at 100 °C followed by slow cooling to 25 °C (pink). (d) POM images of SmC* phases formed by Ch11−GNP conjugates. (e) TEM image of GNPs embedded in SmC* domains of Ch11. Reprinted with permission from ref 37. Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

triglycerides were employed. Moreover, the free radicals that were naturally generated in situ during the drying process were used as reducing agents. The most important advantage of this is that the alkyl resin itself acts as the protecting agent while fatty acids and in situ-generated aldehydes, along with other intermediates, act as stabilizing agents for the MNPs. This method follows the free-radical-induced MNP synthesis mechanism (Figure 8). Free-radicals such as LOO•, LO•, and L• (L = lipid chain) generated in situ during autoxidation of drying oils are used for the reduction of metal salts to synthesize MNPs in situ. Our group has applied this reaction toward the successful development of AgNP-embedded coatings and paints. AgNPs were explored as antimicrobial materials due to their ability to interact with bacterial cell membranes and disrupt their functionality.40 This is believed to occur through the formation of S−Ag bonds and silver catalyzed disulfide bonds in critical thiol containing enzymes, resulting in their inactivation.41−43 We have exercised the aforementioned method to generate an antimicrobial AgNPembedded drying oil that was found to be an excellent paint for coating several kinds of surfaces including wood, glass, polypropylene, poly(methyl methacrylate), polystyrene, and building walls of different materials.37 The bactericidal activity of in situ-synthesized AgNP-embedded vegetable drying oil was tested against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. It was found that the newly synthesized AgNP-embedded paint killed both kinds of bacteria. X-ray photoemission spectroscopy studies revealed that ratio of Ag0 to Ag+ in AgNPs is 7.5:1, and both silver ions and metallic silver coactively contribute to the enhanced antibacterial activity.

Figure 7. Structure of cholesterol phenoxy alkanoate (CPA) mesogens.

(N*) phase from 77.2 to 45 °C, which upon cooling transformed into SmA* phase. CPA−NH2 and CPA−CHO were found to be potential candidates for in situ synthesis of MNPs. The hybrid materials were stable for several months. We have additionally utilized the LC-forming properties of ASC18 for the in situ synthesis of GNPs to generate LC−GNP. Since the amphiphilic self-assembly acts as both the reducing agent and stabilizing agent for the GNPs in molecular gels and liquid crystals, the native morphology of the assembly was undisturbed. Green Chemistry Approach for the Synthesis of Hybrid Nanomaterials: MNP-Embedded Polymers and Coatings as Antimicrobial Materials

Vegetable-based drying oil is another kind of soft material that has been used as a host to synthesize hybrid nanomaterials incorporating metal ions.39 Unlike conventional approaches, this method of preparation is solvent-free and devoid of heating and does not require any external toxic reducing agents and stabilizers. Instead, a mixture of poly-unsaturated fatty acids, commonly derived from linoleic or linolenic acid, and their E


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Figure 8. (a) General mechanism for the free-radical-mediated autoxidation process in drying oils. (b) Schematic diagram of in situ synthesis and stabilization of MNPs in drying oils. (c) Images of commercially available drying oil and silver benzoate and chloroauric acid dissolved in drying oils (left to right). Images of paint coatings without nanoparticles (colorless), with AgNPs (yellow), and with AuNPs (pink) on glass (d) and polymer (e) surfaces. Reprinted with permission from ref 39. Copyright 2008 Nature Publishing Group.

Multiarmed Self-Assembled Systems for Generating MNP-Embedded Hybrid Material Coatings

Cardanol, a bioorganic monomer derived from cashew nut shell liquid (CNSL), has been successfully polymerized in the past. Its derivatives have also been utilized as self-assembling amphiphiles for a variety of functional materials and coatings.44,45 Drying poly(cardanyl acrylate) in the presence of HAuCl4 produced a GNP-embedded cross-linked polymer that was coated on a glass slide. This is due to the reduction of metal salts by the in situ formed free radicals. Free radicals are formed by naturally occurring cross-linking of unsaturated alkyl chains (autoxidation). However, a saturated analogue of the polymer did not undergo oxidative drying due to the absence of characteristic allylic unsaturation on the polymer side chains, which thus hindered nanoparticle synthesis.46 Poly(cardanyl acrylate) undergoes autoxidation and crosslinking upon exposure to air, UV radiation, or heat to yield insoluble transparent films. This photocuring property has inspired further research into cardanyl acrylate polymer systems, among others, as eco-friendly protective coatings.47 Our group has designed a new class of cardanol-based hybrid materials consisting of self-assembling multiarmed columnar structures. These structures potentially undergo natural crosslinking to generate polymer-like coatings, which can be utilized for in situ synthesis of embedded MNPs (Figure 9).48 The MNP embedded polymer film was prepared by drop-casting Au and Ag metal salt-containing chloroform solutions of Card-6 on glass slides. After films of Card-6 were heated at 70 °C for 7−12 h, visual color changes to pink and yellow were observed. This indicated the formation of GNPs and AgNPs, respectively. It was found that molecules Card-6 and Card-3 have the ability to form scratch-free and transparent insoluble films upon heating to 70 °C for 7−12 h or upon exposure to air for 3 days. This change was attributed to the autoxidation induced crosslinking of the unsaturated side chains, which was facilitated by

Figure 9. (a) Structure of cardanol-based multiarmed molecules. (b) Absorption spectra of thin films made from Card-6 in the presence of metal salts (i) before and (ii, iii) after the formation of MNPs, (ii) AgNPs and (iii) GNPs. Inset shows the photograph of glass slides coated with MNP embedded Card-6 films. Reprinted with permission from ref 48. Copyright 2009 Royal Society of Chemistry.

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Figure 10. (a) Photograph of pure PDMS (left) and Au-embedded (right) PDMS films depicting the color change. (b, c) TEM images of gold nanoparticles formed in the PDMS matrix. (d) TEM image of Pt nanoparticles embedded in PDMS film. Inset shows photograph of Pt-PDMS film. Reprinted with permission from ref 49. Copyright 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

the prealignment of the central aromatic ring. Free radicals including LOO•, LO•, and L• (L = cardanyl lipid chain), which are generated during the oxidative drying of the unsaturated chains of cardanol, can potentially reduce metal salts and initiate MNP growth.

but also to improve the functional properties of the materials yielded by these procedures. In this Account, we have discussed the recently emerged novel concept to generate highly homogeneous, environmentally friendly, and potentially economic organic−inorganic hybrid nanomaterials. Key components of this concept are to design versatile amphiphiles that have multiple characteristics such as having the ability to self-assemble to form soft materials while they can reduce metal ions into MNPs. Additionally, they stabilize the in situ generated MNPs and preserve their ability to form self-assembled soft materials. This process is efficient and leads to the formation of MNP-embedded homogeneous organic−inorganic hybrid materials. Importantly, it can reduce the number of manufacturing steps and eliminates the use of toxic reducing agents. Such concept has been consistent in a wide range of soft materials such as self-assembled nanotubes, hydrogels, organogels, liquid crystals, and curable polymer coatings. This new field of research aims to create smart materials without expensive and laborious synthetic procedures. The organic−inorganic hybrid materials synthesized through the hereby-discussed methodologies have found applications as optoelectronic materials, catalysts,51 sensors,52 and antibacterial53 and biomedical materials. There are several other organic−inorganic hybrid materials based on different synthetic strategies that are beyond the scope of this Account. However, we have aimed to provide an impactful account of the advantageous and novel eco-benign protocols that have been developed by our group and prominent researchers in this field.

Other Polymer-Induced Hybrid Materials

We have also accomplished a simple one-step method for synthesizing noble metal nanoparticle embedded free-standing polydimethylsiloxane (PDMS) composite films. In this method, a homogeneous mixture of metal salt (silver, gold, and platinum), silicone elastomer, and the curing agent (hardener) was prepared (Figure 10).49 The hardener cross-links the elastomer and simultaneously reduces the metal salt to form nanoparticles. Thus, the hardener acted as both a reducing and curing agent. The Young’s modulus of PDMS films containing silver nanoparticles was greater than that of pure PDMS films by a factor of 3, without significant alteration in damping properties. The uniform, transparent, and self-standing films fabricated from nanoparticle-dispersed polymers offer the advantage of preserving the optical, electrical, magnetic, and catalytic properties of embedded MNPs. This allows the use of these materials in device-oriented applications. In the mainstream synthesis, the polymer acts as the reducing agent, and electrons are transferred from the polymer backbone to a metal ion. For example, Korchev et al. reported the preparation of poly(vinyl alcohol) (PVA) matrices that are sensitive to light at 350 nm.50 PVA acts as an electron donor to sulfonated poly(ether−ether) ketone (SPEEK) in the photoreduction process. The resulting polymeric benzophenone ketyl (BPK) radicals were found to reduce Ag+ ions and generate silver nanoparticles in the polymeric film. This hybrid nanoparticle system also possessed high light sensitivity and ion exchange capabilities. The irreversible electron transfer couples with the degradation of polymer matrix simultaneously affecting the thermal and mechanical durability of the system.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest. Biographies

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Dr. Kizhmuri P. Divya received her Ph.D. in 2012 from National Institute for Interdisciplinary Science and Technology (NIIST-CSIR), Trivandrum, India, under the guidance of Dr. A. Ajayaghosh. Her work was focused on the photophysical properties of donor−acceptor− donor type fluorescent molecules. Subsequently, she moved to Georgetown University, Washington, DC, to work as a postdoctoral researcher in the group of Prof. Richard G. Weiss on the excited state properties of fluorescent guest molecules in polymer matrices and ionic liquids. Currently she is a postdoctoral fellow in Prof. George John’s laboratory at The City College of New York. Her research interests include design and synthesis of organic electrode materials for

CONCLUSIONS Modern advances in materials research have seemingly allowed for the growth of nanoscale metal particles as easily as that of planted seeds. This analogy is far less equivocal when one considers that plant-based soft materials have been successfully implemented as templates that cultivate these nanoparticles, providing them with tunable electron rich reducing groups that stimulate their growth from ions. It is a narrative that fits in accordance with our goal of implementing green chemistry not only to reduce the toxicity of established synthetic procedures G


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Accounts of Chemical Research Li-ion batteries, novel self-assembled fluorescent soft materials from renewable resources, etc.

laboratory is highly interdisciplinary and is focused on molecular design of synthetic lipids, membrane mimics, soft nanomaterials, green energy technologies, and organic materials chemistry. His group has successfully developed environmentally benign antibacterial paints, polymer coatings, molecular gel technologies, oil spill recovery materials, battery components, vegetable oil thickening agents, and trans-fat alternatives. He is the recipient of senior Fulbright Scholar to India, Tokyo University of Sciences (TUS) President Award, Pfizer visiting professorship at (IISc) Bangalore and Kerala center award.

Mr. Mikhail Miroshnikov was raised in New York City and received his bachelor’s degree in chemistry from New York University in 2012. He is currently a graduate student at City College as part of the Ph.D. Program in Chemistry at the CUNY Graduate Center. Mikhail’s research interests include a combination of materials science, organic synthesis, and polymer chemistry for the development of green battery materials from nature-derived organic compounds. Under the mentorship of Professor George John, current research projects include the discovery and synthesis of anthraquinone appended polymer electrodes and novel polymer gel electrolytes.

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ACKNOWLEDGMENTS P.A and G.J acknowledge the Hartley foundation’s funding towards the green battery project through Rice University. M.M. and K.P.D. also gratefully acknowledge the support of the Hartley Foundation. M.M. was the recipient of a fellowship award from the U.S. Department of Education Graduate Assistance in Areas of National Need (GAANN) Program in Molecular Biophysics and Biomaterials at The City College of New York (Grant PA200A120211). P.K.V. thanks the Department of Biotechnology, Government of India for Ramalingaswami ReEntry fellowship.

Dr. Debjit Dutta obtained his Masters in Chemistry from Indian Institute of Technology, Delhi, and later his Ph.D. in Chemistry from University of North Carolina at Chapel Hill (2011) where he developed a chemoselective liposome fusion strategy for generation of three-dimensional tissue structures. After two years of postdoctoral research at Columbia University, New York, he went on to do a postdoctoral stint at Dr. Praveen Vemula’s lab at Institute of Stem Cell Biology and Regenerative Medicine (inStem), Bangalore. Currently he is a postdoctoral fellow at Genome Institute of Singapore where his research work is focused on developing a three-dimensional high throughput screening platform for oral cancer drugs.

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Dr. Praveen Kumar Vemula is a faculty member at the Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bangalore, India. He is a Ramalingaswami ReEntry fellow, Dept. of Biotechnology, Govt. of India. After obtaining Ph.D. from Indian Institute of Science in 2005, he received postdoctoral training at The City College of New York and Harvard−MIT Division of Health Sciences and Technology at Harvard Medical School in affiliation with Brigham and Women’s Hospital. In 2009, the Ewing Marion Kauffman Foundation selected him as an entrepreneur fellow through whom he received formal training in translational research and entrepreneurship. He is part of two startups in Paris and Boston, which are founded based on his technologies. His lab (www.praveenlab.net) is focusing to develop self-assembled biomaterials to solve huge unmet clinical needs. The current thrust of his lab is developing “disease-responsive biomaterials” that can be used for the treatment of inflammatory diseases and improve the lifetime of transplanted organs.

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Prof. Pulickel M. Ajayan has been a pioneer in the area of nanotechnology and was involved in early work in the development of carbon nanotubes. His work has covered diverse areas of nanomaterials including nanoparticles, nanotubes, 2D materials, nanocomposites, and energy storage materials. Presently he is the Benjamin M. and Mary Greenwood Anderson professor of Engineering at Rice University in Houston, Texas, and the founding chair of the department of Materials Science and NanoEngineering. He is affiliated with several other universities around the world as visiting professor and has given over 350 invited talks at various venues and conferences. He is recipient of two Guinness book of world records. He received Docteur Honoris Causa from the Universite Catholique de of Louvain in 2014. He has also been recognized as a distinguished alumnus by his alma mater, Banaras Hindu University, and the department of materials science at Northwestern University. Prof. George John is recognized for his active research in the field of functional molecular materials from renewable resources and green nanotechnology. After receiving his Ph.D. from NIIST-CSIR in Chemistry in 1993, he held research positions in the Netherlands, Japan, and the USA before joining The City College of New York. Currently he is a Professor of Chemistry, The City College of The City University of New York (CUNY). The research in John’s H


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