Fabrication of Flexible, Conductive Polypyrrole-Graphene Quantum Dot (PPy-GQD) Nanocomposite via Electrodeposition on Carbon Fiber Mesh

Faculty Research Day 2018: Graduate Student Poster Honorable MentionCarbon fibers have recently gained popularity for their variety of applications as a working electrode material. Due to their conductive nature, high specific surface area, and chemical inertness, they prove to be an ideal material for electrodeposition of a variety of materials for future in vivo or in situ biomedical applications. Here, we use cyclic voltammetry to simultaneously polymerize polypyrrole (PPy) and integrate graphene quantum dots (GQDs), while depositing onto a carbon fiber mesh (CF). Polypyrrole has been used in a variety of applications due to it’s conductive nature and GQDs have been used for their electronic properties as well. This nanocomposite will be further characterized using SEM, TEM, Raman, cyclic voltammetry, and electrochemical impedance spectroscopy to determine structural and functional capabilities

Synthesis and Fabrication of Graphene Quantum Dots-Polypyrrole (GQDs-PPy) Nanocomposites in Bioengineering Applications as Supercapacitors and Fluorescent Probes

Graphene quantum dots (GQDs), which are edge-bound nanometer-size graphene pieces, have fascinating optical and electronic properties. These GQDs fabricated by acid treatment and chemical exfoliation of pitch carbon-fibres and this produced GQDs have 1-4 nm in size with 2D morphology. The photoluminescence of the GQDs can be tailored through varying the size of the GQDs by changing the process parameters. Due to the luminescence stability, nanosecond lifetime, biocompatibility, low toxicity, and high water solubility, these GQDs are demonstrated to be excellent probes for high contrast bioimaging and biosensing applications. Here, we reporting the fabrication of free standing GQDs-PPy hybrid electrode films by electrochemical polymerization for supercapacitor device assembly. And also we reporting the bioconjugated quantum dots (QDs) provide a new class of biological labels for evaluating biomolecular signatures (biomarkers) on intact cells and tissue specimens. In particular, the use of multicolor QD probes in immunohistochemistry or cell biology studies of proteins and peptides is considered to be the most important and clinically relevant applications

Analysis of the Structural Evolution of Graphene-CNT-Polypyrrole Nanocomposite

The following work reports the evolution of the formation of polypyrrole (PPy) chains and it's intercalation with graphene-carbon nanotubes (G-CNT) nanocomposites. Experiments were carried out to demonstrate the growth of pyrrole through polymerization and its interaction with G-CNT using Cyclic Voltammetry (CV) for 5 – 50 cycles. The interface analysis of the nanocomposite was carried out through SEM. The G-CNT-PPy nanocomposite has shown potential to be used as a supercapacitor which can be further substantiated by CV experiments

Analysis of Emergent Electronic Properties of Self-Assembling Nucleopeptides

Biomolecular structures are held together by a complex network of molecular interactions that direct assembly and stabilize structures. In order to translate the fundamental molecular interactions of biomolecules into the design of functional biomaterials, we have developed a model system that integrates nucleic acids and self- assembling peptides. These nucleopeptides serve as a small-model system for the study of the non-covalent molecular interactions involved in biomolecule self-assembly. We have scaled up and expanded the analysis of our original nucleopeptide library in order to further characterize these assembled structures. Infrared (IR) spectroscopy, Atomic Force Microscopy (AFM), and Transmission Electron Microscopy (TEM) were utilized to characterize the assembly structure and image the supramolecular morphology of the nucleopeptides. The emergent electronic properties of the nucleopeptide assemblies were analyzed by Electrical Impedance Spectroscopy (EIS). Collectively, these studies on nucleopeptide supramolecular structure assembly will contribute to the design of functional biomaterials with the potential to conduct and store electrical charge

Solar Cell with PbS Quantum Dots Sensitized TiO 2 -Multiwalled Carbon Nanotubes Composite, Sulfide-titania gel and Tin Sulfide Coated C-fabric

Novel approaches to boost quantum dot solar cell (QDSC) efficiencies are in demand. Herein, three strategies are used: (i) a hydrothermally synthesized TiO2–multiwalled carbon nanotube (MWCNT) composite instead of conventional TiO2, (ii) a counter electrode (CE) that has not been applied to QDSCs until now, namely, tin sulfide (SnS) nanoparticles (NPs) coated over a conductive carbon (C)-fabric, and (iii) a quasi-solid-state gel electrolyte composed of S2−, an inert polymer and TiO2 nanoparticles as opposed to a polysulfide solution based hole transport layer. MWCNTs by virtue of their high electrical conductivity and suitably positioned Fermi level (below the conduction bands of TiO2 and PbS) allow fast photogenerated electron injection into the external circuit, and this is confirmed by a higher efficiency of 6.3% achieved for a TiO2–MWCNT/PbS/ZnS based (champion) cell, compared to the corresponding TiO2/PbS/ZnS based cell (4.45%). Nanoscale current map analysis of TiO2 and TiO2–MWCNTs reveals the presence of narrowly spaced highly conducting domains in the latter, which equips it with an average current carrying capability greater by a few orders of magnitude. Electron transport and recombination resistances are lower and higher respectively for the TiO2–MWCNT/PbS/ZnS cell relative to the TiO2/PbS/ZnS cell, thus leading to a high performance cell. The efficacy of SnS/C-fabric as a CE is confirmed from the higher efficiency achieved in cells with this CE compared to the C-fabric based cells. Lower charge transfer and diffusional resistances, slower photovoltage decay, high electrical conductance and lower redox potential impart high catalytic activity to the SnS/C-fabric assembly for sulfide reduction and thus endow the TiO2–MWCNT/PbS/ZnS cell with a high open circuit voltage (0.9 V) and a large short circuit current density (∼20 mA cm−2). This study attempts to unravel how simple strategies can amplify QDSC performances

Differentiation Of Mesenchymal Stem Cells (Mscs) To Functional Neuron On Graphene-Polycaprolactone Nanoscaffolds

Spinal cord is an important part of the central nervous system that controls all activities of the body. It is a tubular bundle of nerve fibers and tissues connecting brain to nearly all parts of the body. Nerve cells in an adult human body do not divide and make copies of themselves. Therefore, in case of an injury or damage to any part of spinal cord causes permanent changes to strength, sensation and other body functions. The field of tissue engineering and regenerative medicine which aims to replace and repair damaged tissues, organs or cells entails for effective methods for fabricating biological scaffolds. Here we present synthesis of fibrous scaffolds by a process called electrospinning that can provide a microenvironment in-vitro for differentiation and proliferation of functional neurons from mesenchymal stem cells. These nanofibrous PCL scaffolds with graphene as filler materials are engineered in such a way so as to provide topological, biochemical as well as electrical cues that can enhance neurite extension and penetration. Poly(ε-caprolactone) (PCL) is a FDA approved synthetic biodegradable polyester extensively used in biomedical applications. Graphene, a single layer carbon crystal, based nanomaterials have recently gained considerable interest for tissue engineering applications including osteogenic, neural and differentiation in other lineages due to their favorable chemical, electrical and mechanical properties. Our final aim is that the functional tissues or organs developed in vitro shall be implanted inside body to rehabilitate the biological function that was lost due to injury, abnormality or loss

New Antimony Selenide / Nickel Oxide Photocathode Boosts the Efficiency of Graphene Quantum Dots Co-sensitized Solar Cell

A novel assembly of a photocathode and photoanode is investigated to explore their complementary effects in enhancing the photovoltaic performance of a quantum dot solar cell (QDSC). While p-type nickel oxide (NiO) has been used previously, antimony selenide (Sb2Se3) has not been used in a QDSC, especially as a component of a counter electrode (CE) architecture that doubles up as the photocathode. Here, near infrared (NIR) light absorbing Sb2Se3 nanoparticles (NPs) coated over electrodeposited NiO nanofibers on a carbon (C)-fabric substrate was employed as the highly efficient photocathode. Quasi-spherical Sb2Se3 NPs, with a band gap of 1.13 eV, upon illumination release photoexcited electrons in addition to other charge carriers at the CE to further enhance the reduction of the oxidized polysulfide. The p-type conducting behavior of Sb2Se3, coupled with a work function at 4.63 eV, also facilitate electron injection to polysulfide. The effect of graphene quantum dots (GQDs) as co-sensitizers as well as electron conduits is also investigated where a TiO2/CdS/GQDs photoanode structure in combination with a C-fabric CE delivered a power conversion efficiency (PCE) of 5.28%, which is a vast improvement over the 4.23 % that is obtained by using a TiO2/CdS pho-toanode (without GQDs) with the same CE. GQDs due to a superior conductance, impact efficiency more than Sb2Se3 NPs do. The best PCE of a TiO2/CdS/GQDs-nS2-/Sn2--Sb2Se3/NiO/C-fabric cell is 5.96% (0.11 cm2 area), which when replicated on a smaller area of 0.06 cm2, is seen to increase dramatically to 7.19%. The cell is also tested for 6 h of continuous irradiance. The rationalization for the channelized photogenerated electron movement which augments the cell performance is furnished in detail in these studies

Solar Cell with PbS Quantum Dots Sensitized TiO2-Multiwalled Carbon Nanotubes Composite, Sulfide-titania gel and Tin Sulfide Coated C-fabric

Novel approaches to boost quantum dot solar cell (QDSC) efficiencies are in demand. Here, three strategies are used: (i) a hydrothermally synthesized TiO2-multiwalled carbon nanotubes (MWCNTs) composite instead of conventional TiO2, (ii) a counter electrode (CE) that has not been applied to QDSCs till date, namely, tin sulfide (SnS) nanoparticles (NPs) coated over a conductive carbon (C)-fabric, and (iii) a quasi-solid-state gel electrolyte composed of S2-, an inert polymer and TiO2 nanoparticles as opposed to a polysulfide solution based hole transport layer. MWCNTs by the virtue of their high electrical conductivity and a suitably positioned Fermi level (below the conduction bands of TiO2 and PbS) allow fast photogenerated electron injection to the external circuit, and this is confirmed by the higher efficiency of 6.3% achieved for a TiO2-MWCNTs/PbS/ZnS based (champion) cell, compared to the corresponding TiO2/PbS/ZnS based cell (4.45%). Nanoscale current map analysis of TiO2 and TiO2-MWCNTs reveal the presence of narrowly spaced highly conducting domains in the latter, which equips it with an average current carrying capability greater by a few orders of magnitude. Electron transport and recombination resistances are lower and higher respectively for the TiO2-MWCNTs/PbS/ZnS cell relative to the TiO2/PbS/ZnS cell, thus leading to a high performance cell. The efficacy of SnS/C-fabric as a CE is confirmed from the higher efficiency achieved in cells with this CE compared to C-fabric based cells. Lower charge transfer and diffusional resistances, slower photovoltage decay, high electrical conductance and lower redox potential impart high catalytic activity to the SnS/C-fabric assembly for sulfide reduction and thus endow the TiO2-MWCNTs/PbS/ZnS cell with a high open circuit voltage (0.9 V) and a large short circuit current density (~20 mA cm-2). This study attempts to unravel how simple strategies can amplify QDSC performances

Graphene Quantum Dot Oxidation Governs Noncovalent Biopolymer Adsorption.

Graphene quantum dots (GQDs) are an allotrope of carbon with a planar surface amenable to functionalization and nanoscale dimensions that confer photoluminescence. Collectively, these properties render GQDs an advantageous platform for nanobiotechnology applications, including optical biosensing and delivery. Towards this end, noncovalent functionalization offers a route to reversibly modify and preserve the pristine GQD substrate, however, a clear paradigm has yet to be realized. Herein, we demonstrate the feasibility of noncovalent polymer adsorption to GQD surfaces, with a specific focus on single-stranded DNA (ssDNA). We study how GQD oxidation level affects the propensity for polymer adsorption by synthesizing and characterizing four types of GQD substrates ranging ~60-fold in oxidation level, then investigating noncovalent polymer association to these substrates. Adsorption of ssDNA quenches intrinsic GQD fluorescence by 31.5% for low-oxidation GQDs and enables aqueous dispersion of otherwise insoluble no-oxidation GQDs. ssDNA-GQD complexation is confirmed by atomic force microscopy, by inducing ssDNA desorption, and with molecular dynamics simulations. ssDNA is determined to adsorb strongly to no-oxidation GQDs, weakly to low-oxidation GQDs, and not at all for heavily oxidized GQDs. Finally, we reveal the generality of the adsorption platform and assess how the GQD system is tunable by modifying polymer sequence and type

A structural study of new tetrakis(1H-pyrazol-1-yl)methanes

Tetrakis(1H-pyrazol-1-yl)methanes are very rare compounds of which only two are known: the unsubstituted 1 obtained classically by Hückel in 1937 from carbon tetrachloride and prepared again several times and the 3,5-dimethyl substituted 2 obtained serendipitously by Pombeiro in 2009. We have now extended this group to include four new derivatives 8, 9, 11 and 12 bearing methyl groups. The X-ray crystal structure of the four compounds has been determined. They have been studied by NMR both in solution (H, C, N) and in the solid state (C and N). DFT calculations of the six compounds (geometries, energies and absolute shieldings) have been used to discuss the experimental observations.We thank Dr. Duane Choquesillo-Lazarte (LEC, IACT-CSIC) for compound 12 X-ray data collection. This work was carried out with financial support from the Ministerio de Ciencia, Innovación y Universidades (Project PGC2018-094644-B-C22) and Direccion General de Investigacion en Innovacion de la Comunidad de Madrid (PS2018/EMT-4329 AIRTEC-CM). Computer, storage and other resources from the CTI (CSIC) are gratefully acknowledged. Thanks are also due to University of Aveiro and FCT/MEC for the financial support of the QOPNA research unit (FCTUID/QUI/00062/2019) through national founds and, where applicable, co-financed by the FEDER, within the PT2020 Partnership, and also to the Portuguese NMR network. Support from the UNED is also greatly acknowledge