Improved Photoelectrochemical Cell Performance of Tin Oxide with Functionalized Multiwalled Carbon Nanotubes–Cadmium Selenide Sensitizer

Bhande, Sambhaji S.,Ambade, Rohan B.,Shinde, Dipak V.,Ambade, Swapnil B.,Patil, Supriya A.,Naushad, Mu.,Mane, Rajaram S.,Alothman, Z. A.,Lee, Soo-Hyoung,Han, Sung-Hwan American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.45

<P>Here we report functionalized multiwalled carbon nanotubes (<I>f</I>-MWCNTs)–CdSe nanocrystals (NCs) as photosensitizer in photoelectrochemical cells, where <I>f</I>-MWCNTs were uniformly coated with CdSe NCs onto SnO<SUB>2</SUB> upright standing nanosheets by using a simple electrodeposition method. The resultant blended photoanodes demonstrate extraordinary electrochemical properties including higher Stern–Volmer constant, higher absorbance, and positive quenching, etc., caused by more accessibility of CdSe NCs compared with pristine SnO<SUB>2</SUB>–CdSe photoanode. Atomic and weight percent changes of carbon with <I>f</I>-MWCNTs blending concentrations were confirmed from the energy dispersive X-ray analysis. The morphology images show a uniform coverage of CdSe NCs over <I>f</I>-MWCNTs forming a core–shell type structure as a blend. Compared to pristine CdSe, photoanode with <I>f</I>-MWCNTs demonstrated a 257% increase in overall power conversion efficiency. Obtained results were corroborated by the electrochemical impedance analysis. Higher scattering, more accessibility, and hierarchical structure of SnO<SUB>2</SUB>-<I>f</I>-MWCNTs-blend–CdSe NCs photoanode is responsible for higher (a) electron mobility (6.89 × 10<SUP>–4</SUP> to 10.89 × 10<SUP>–4</SUP> cm<SUP>2</SUP> V<SUP>–1</SUP> S<SUP>1–</SUP>), (b) diffusion length (27 × 10<SUP>–6</SUP>), (c) average electron lifetime (32.2 ms), and transit time (1.15 ms).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-45/acsami.5b05385/production/images/medium/am-2015-05385e_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b05385'>ACS Electronic Supporting Info</A></P>

Controlled growth of polythiophene nanofibers in TiO2 nanotube arrays for supercapacitor applications

Ambade, R.,Ambade, S.,Shrestha, N.,Salunkhe, R.,Lee, W.,Bagde, S.,Kim, J.,Stadler, F.,Yamauchi, Y.,Lee, S. H. Royal Society of Chemistry 2017 Journal of materials chemistry. A, Materials for e Vol.5 No.1

<P>One-dimensional (1D) nanostructured materials have attracted intense interest because they are superior for applications when compared to their bulk counterparts, owing to their unique and fascinating properties. We thus demonstrate the development of conducting 1D polythiophene (PTh) nanofibers in hollow TiO2 nanotube arrays (TNTs) by controlling nucleation and growth during the electropolymerization of the thiophene monomer. The progression of nanofiber (NF) formation in the hollow interiors of the TNTs follows a three-dimensional instantaneous nucleation and growth mode, in which the polymer grows at a rate that does not allow for the build-up of the polymer on new polymerization sites, but only on existing ones. The formation of highly conductive dienes of PTh is confirmed, with increased conjugation in PTh NFs grown in the confined matrix of TNTs. These 1D PTh-TNT NFs show potential as a promising supercapacitor electrode material, exhibiting a high specific capacitance of 1052 F g(-1), which clearly highlights their importance as potential next-generation charge storage entities.</P>

Triple-tyrosine kinase inhibition attenuates pulmonary arterial hypertension and neointimal formation

Ambade, Anjira S.,Jung, Birgit,Lee, Dongwon,Doods, Henri,Wu, Dongmei Elsevier 2019 Translational research Vol.203 No.-

<P>The present study examined the effects of simultaneous inhibition of vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) receptor signaling with BIBF1000, a novel triple tyrosine kinase inhibitor on preventing and reversing the progression of severe pulmonary arterial hypertension (PAH) in an experimental model in rats. Left pneumonectomized male Wistar rats were injected with monocrotaline to induce PAH. Treatment with BIBF1000 from day 1 to day 21 after monocrotaline injection attenuated PAH development, as evidenced by lower values for pulmonary artery pressure (mPAP), right ventricular pressure (RVSP), pulmonary arterial neointimal formation, and the ratio of right ventricular weight to left ventricular and septum weight [RV/(LV+S)] on day 21 compared to control rats. Treatment with BIBF1000 from day 21 to day 42 after monocrotaline injection reversed established PAH as shown by normalized values for mPAP and RVSP, RV/(LV+S) ratio, pulmonary arterial occlusion scores, levels of heart and lung fibrosis, as well as improved survival. Treatment with BIBF1000 reduced inflammatory cell recruitment in bronchoalveolar lavage and lung tissues, reduced CD-68 positive macrophages and expression of proliferating cell nuclear antigen in the perivascular areas, and reduced TNF-α and growth factor productions, and inhibited the phosphorylation of AKT and GSK3β in lungs. In addition, BIBF1000 inhibited pulmonary artery smooth muscle cells migration and proliferation from rat pulmonary artery explant cultures. Simultaneous inhibition of VEGF, PDGF, and FGF receptor signaling by BIBF1000 prevents and reverses the progression of severe pulmonary arterial hypertension and vascular remodeling in this experimental model.</P>

Low-Temperature Solution-Processed Thiophene-Sulfur-Doped Planar ZnO Nanorods as Electron-Transporting Layers for Enhanced Performance of Organic Solar Cells

Ambade, Swapnil B.,Ambade, Rohan B.,Bagde, Sushil S.,Eom, Seung Hun,Mane, Rajaram S.,Shin, Won Suk,Lee, Soo-Hyoung American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.4

<P>1-D ZnO represents a fascinating class of nanostructures that are significant to optoelectronics. In this work, we investigated the use of an eco-friendly, metal free in situ doping through a pure thiophene-sulfur (5) on low temperature processed (<95 degrees C) and annealed (<170 degrees C), planar 1-D ZnO nanorods (ZnRs) spin-coated as a hole blocking and electron transporting layer (ETL) for inverted organic solar cells (iOSCs). The TEM, HRTEM, XPS, FT-IR, EDS and Raman studies clearly reveal that the thiophene-S (Thi-S) atom is incorporated on planar ZnRs. The investigations in electrical properties suggest the enhancement in conductivity after Thi-S doping on 1-D ZnRs. The iOSCs of poly.(3-hexylthiophene-2,5-diyl) and phenyl-C-61-butyric acid methyl ester (P3HT: PC60BM) photoactive layer containing thiophene-S doped planar ZnRs (Thi-S-PZnRs) as ETL exhibits power conversion efficiency (PCE) of 3.68% under simulated AM 1.5 G, 100 mW cm(-2) illumination. The similar to 47% enhancement in PCE compared with pristine planar ZnRs (PCE = 2.38%) ETL is attributed to a combination of desirable energy level alignment, morphological modification, increased conductivity and doping effect. The universality of Thi-S-PZnRs ETL is demonstrated by the highest PCE of 8.15% in contrast to 6.50% exhibited by the iOSCs of ZnRs ETL for the photoactive layer comprising of poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b;4,5-b]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] : phenyl-C71-butyric acid methyl ester (PTB7-Th: PCB71M). This enhancement in PCE is observed to be driven mainly through improved photovoltaic parameters like fill factor (ff) as well as photocurrent density (J(sc)), which are assigned to increased conductivity, exciton dissociation, and effective charge extraction, while; better ohmic contact, reduced charge recombination, and low leakage current density resulted in increased Voc.</P>

Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells

Ambade, S.,Ambade, R.,Eom, S.,Baek, M. J.,Bagde, S.,Mane, R.,Lee, S. H. Royal Society of Chemistry 2016 Nanoscale Vol.8 No.9

<P>In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy) acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th: PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.</P>

Development of highly transparent seedless ZnO nanorods engineered for inverted polymer solar cells.

Ambade, Swapnil B,Ambade, Rohan B,Lee, Wonjoo,Mane, Rajaram S,Yoon, Sung Cheol,Lee, Soo-Hyoung RSC Pub 2014 Nanoscale Vol.6 No.20

<P>This work reports on inverted polymer solar cells (IPSCs) based on highly transparent (>95%), hydrophobic, seedless ZnO nanorods (NRs) as cathode buffers with extremely enhanced electrical characteristics. The transparent NR suspension with stability for more than a year is achieved by adding a small amount of 2-(2-methoxyethoxy) acetic acid (MEA). The ability of the stable nanorod suspension to easily spin-coat is certainly an advance to the fabrication of films over large areas and to replace the conventional seeding method to grow one-dimensional nanostructures for use in optoelectronic devices. We observe a strong correlation between the photovoltaic performance and the transparency of ZnO NRs. IPSCs using poly-3-hexylthiophene (P3HT) and [6,6]-phenyl C60 butyric acid methyl ester (PCBM) mixtures in the active layer and transparent (MEA-capped) ZnO NRs as cathode buffers exhibit a power conversion efficiency of 3.24% under simulated AM 1.5G, 100 mW cm(-2) illumination.</P>

Interfacial Engineering Importance of Bilayered ZnO Cathode Buffer on the Photovoltaic Performance of Inverted Organic Solar Cells.

Ambade, Rohan B,Ambade, Swapnil B,Mane, Rajaram S,Lee, Soo-Hyoung American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.15

<P>The role of cathode buffer layer (CBL) is crucial in determining the power conversion efficiency (PCE) of inverted organic solar cells (IOSCs). The hallmarks of a promising CBL include high transparency, ideal energy levels, and tendency to offer good interfacial contact with the organic bulk-heterojunction (BHJ) layers. Zinc oxide (ZnO), with its ability to form numerous morphologies in juxtaposition to its excellent electron affinity, solution processability, and good transparency is an ideal CBL material for IOSCs. Technically, when CBL is sandwiched between the BHJ active layer and the indium-tin-oxide (ITO) cathode, it performs two functions, namely, electron collection from the photoactive layer that is effectively carried out by morphologies like nanoparticles or nanoridges obtained by ZnO sol-gel (ZnO SG) method through an accumulation of individual nanoparticles and, second, transport of collected electrons toward the cathode, which is more effectively manifested by one-dimensional (1D) nanostructures like ZnO nanorods (ZnO NRs). This work presents the use of bilayered ZnO CBL in IOSCs of poly(3-hexylthiophene) (P3HT)/[6, 6]-phenyl-C60-butyric acid methyl ester (PCBM) to overcome the limitations offered by a conventionally used single layer CBL. We found that the PCE of IOSCs with an appropriate bilayer CBL comprising of ZnO NRs/ZnO SG is 18.21% higher than those containing ZnO SG/ZnO NRs. We believe that, in bilayer ZnO NRs/ZnO SG, ZnO SG collects electrons effectively from photoactive layer while ZnO NRs transport them further to ITO resulting significant increase in the photocurrent to achieve highest PCE of 3.70%. The enhancement in performance was obtained through improved interfacial engineering, enhanced electrical properties, and reduced surface/bulk defects in bilayer ZnO NRs/ZnO SG. This study demonstrates that the novel bilayer ZnO CBL approach of electron collection/transport would overcome crucial interfacial recombination issues and contribute in enhancing PCE of IOSCs.</P>

Stereospecific growth of densely populated rutile mesoporous TiO₂ nanoplate films: a facile low temperature chemical synthesis approach

Lee, Go-Woon,Ambade, Swapnil B,Cho, Young-Jin,Mane, Rajaram S,Shashikala, V,Yadav, Jyotiprakash,Gaikwad, Rajendra S,Lee, Soo-Hyoung,Jung, Kwang-Deog,Han, Sung-Hwan,Joo, Oh-Shim IOP Pub 2010 Nanotechnology Vol.21 No.10

<P>We report for the first time, using a simple and environmentally benign chemical method, the low temperature synthesis of densely populated upright-standing rutile TiO<SUB>2</SUB> nanoplate films onto a glass substrate from a mixture of titanium trichloride, hydrogen peroxide and thiourea in triply distilled water. The rutile TiO<SUB>2</SUB> nanoplate films (the phase is confirmed from x-ray diffraction analysis, selected area electron diffraction, energy-dispersive x-ray analysis, and Raman shift) are 20–35 nm wide and 100–120 nm long. The chemical reaction kinetics for the growth of these upright-standing TiO<SUB>2</SUB> nanoplate films is also interpreted. Films of TiO<SUB>2</SUB> nanoplates are optically transparent in the visible region with a sharp absorption edge close to 350 nm, confirming an indirect band gap energy of 3.12 eV. The Brunauer–Emmet–Teller surface area, Barret–Joyner–Halenda pore volume and pore diameter, obtained from N<SUB>2</SUB> physisorption studies, are 82 m<SUP>2</SUP> g<SUP> − 1</SUP>, 0.0964 cm<SUP>3</SUP> g<SUP> − 1</SUP> and 3.5 nm, respectively, confirming the mesoporosity of scratched rutile TiO<SUB>2</SUB> nanoplate powder that would be ideal for the direct fabrication of nanoscaled devices including upcoming dye-sensitized solar cells and gas sensors. </P>