Chemical synthesis of p-type nanocrystalline copper selenide thin films for heterojunction solar cells

Nanocrystalline thin films of copper selenide have been grown on glass and tin doped-indium oxide substrates using chemical method. At ambient temperature, golden films have been synthesized and annealed at 200 °C for 1 h and were examined for their structural, surface morphological and optical properties by means of X-ray diffraction (XRD), scanning electron microscopy and UV-vis spectrophotometry techniques, respectively. Cu_2−xSe phase was confirmed by XRD pattern and spherical grains of 30 ± 4 - 40 ± 4 nm in size aggregated over about 130 ± 10 nm islands were seen by SEM images. Effect of annealing on crystallinity improvement, band edge shift and photoelectrochemical performance (under 80 mW/cm² light intensity and in lithium iodide electrolyte) has been studied and reported. Observed p-type electrical conductivity in copper selenide thin films make it a suitable candidate for heterojunction solar cells.     

A scheme for sequential separation of thorium,lanthanides, uranium in geo-materials and their ICP-OES determination

Journal of Radioanalytical and Nuclear Chemistry - Neutral complexes of thorium and lanthanides with 2,3-dihydroxynaphthalene and anionic complexes of uranium with the same chelating agent in...     

A simple CdS nanoparticles cascading approach for boosting N3 dye/ZnO nanoplates DSSCs overall performance

Enhanced photosensitization in presence of CdS nanoparticles is achieved in electrochemically deposited ZnO nanoplates and N3 loaded dye-sensitized solar cells. Chemically embedded CdS nanoparticles act as a sandwiching layer between ZnO nanoplates and dye molecules by overcoming current limiting serious Zn²⁺/dye insulating complex formation and CdS photo-corrosion issues. The X-ray diffraction and the scanning electron microscopy confirm the ZnO with vertically aligned nanoplates, perpendicular to the substrate surface. Amorphous CdS is monitored using electron dispersive X-ray analysis. The low and high resolution transmission electron microscope images confirm the presence of CdS nanoparticles over ZnO nanoplates which later is supported by an increase in optical absorbance and shift in band edge. About 400% increase in solar conversion efficiency with this cascade arrangement is achieved when compared with without CdS which could be fascinating while designing solid state solar cells in presence of suitable p-type layer.     

Addition of multiwalled carbon nanotube and graphene nanosheet in cobalt oxide film for enhancement of capacitance in electrochemical capacitors

In order to enhance the capacitance of electrochemical capacitors, multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets (GNS) were added to cobalt oxide (Co₃O₄) paste. The composite film based on Co₃O₄/MWCNT/GNS (95:4:1 wt%) exhibited a capacitance of 294 F/g while the capacitance of Co₃O₄/MWCNT (95:5 wt%) and pure Co₃O₄ film is 205 and 163 F/g, respectively. The enhanced capacitance of Co₃O₄/MWCNT/GNS composite film was attributed to the electrochemical contributions of the Co₃O₄ nanoparticle attached to the GNS as well as their significantly increased specific surface areas by MWCNTs. Furthermore, the composite films showed faradaic redox capacitive behavior to double-layer capacitive behavior due to the different nanostructures of the composites.     

A modified method for the determination of uranium in Nb/Ta minerals by LED fluorimetry

A modified LED fluorimetry determination of uranium in Nb/Ta minerals has been developed. The mineral is brought into solution by fusion with mixed phosphate flux (NaH₂PO₄, H₂O and Na₂HPO₄). Iron quenches uranium fluorescence when it is present above the ratio of (iron to uranium) 100. Uranium is separated in ethyl acetate by solvent extraction and then stripped back into pyrophosphate buffer (pH ~ 7) prior to its LED fluorimetry determination. This modified method has been applied for the determination of uranium in synthetic mixtures and Nb/Ta minerals including Certified Reference Materials (X1807) with high degree of accuracy and precision.

     

Orthogonally Self‐Assembled Multifunctional Block Copolymers

We report the synthesis of telechelic poly(norbornene) and poly(cyclooctene) homopolymers by ring‐opening metathesis polymerization (ROMP) and their subsequent functionalization and block copolymer formation based on noncovalent interactions. Whereas all the poly(norbornene)s contain either a metal complex or a hydrogen‐bonding moiety along the polymer side‐chains, together with a single hydrogen‐bonding‐based molecular recognition moiety at one terminal end of the polymer chain. These homopolymers allow for the formation of side‐chain‐functionalized AB and ABA block copolymers through self‐assembly. The orthogonal natures of all side‐ and main‐chain self‐assembly events were demonstrated by ¹H NMR spectroscopy and isothermal titration calorimetry. The resulting fully functionalized block copolymers are the first copolymers combining both side‐ and main‐chain self‐assembly, thereby providing a high degree of control over copolymer functionalization and architecture and bringing synthetic materials one step closer to the dynamic self‐assembly structures found in nature.     

Self-assembly of facially amphiphilic dendrimers on surfaces

Facially amphiphilic dendrimers have been shown to provide significant difference in surface behavior due to subtle changes in structure. The monodendrons are capable of providing hydrophobic surfaces, while the didendrons provide superhydrophobic surfaces. This provides an example of how a molecular level change could result in significant changes in surface behavior. This difference is attributed to the conformational differences exhibited by these dendrimers on surfaces.     

An efficient route for the synthesis of hyperbranched polymers and dendritic building blocks based on urea linkages

A highly efficient synthetic route, based on the quantitative reaction between amine and isocyanate functionalities, was used successfully for the synthesis of hyperbranched polymers and dendritic building blocks based on urea linkages. The thermal decomposition of 3,5‐diamino benzoyl azide or 5‐amino isophthaloyl azide generated in situ the corresponding phenyl isocyanates, which were then polymerized to give wholly aromatic hyperbranched polyureas. Hyperbranched polyurea with amine chain ends was soluble in common organic solvents. The degree of branching, as calculated with ¹H NMR, was 0.55. Diethyl 5‐amino isophthalate and Boc‐protected 5‐amino isophthaloyl azide were used for the successful stepwise synthesis of dendritic wedges based on urea linkages. The thermal generation of the isocyanate functionality with gaseous nitrogen as the side product and its quantitative reaction with amine groups were the salient features of this convergent synthesis. This eliminated the use of chromatographic purification, an inherent part of other convergent growth approaches, and made it a very efficient synthetic route for the synthesis of dendritic wedges. The products were characterized by ¹H NMR, ¹³C NMR, and electron spray mass spectroscopy (ESMS) techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1295–1304, 2001     

A novel HMP-2 dye of high extinction coefficient designed for enhancing the performance of ZnO platelets

Newly designed cis-[Ru(H₂dcbpy) (L) (NCS)₂ (HMP-2), where L is 4-(4-(N,N-di-(p-hexyloxyphenyl)-amino)styryl)-4′-methyl-2,2′-bipyridine, sensitizing dye of high extinction coefficient than the routinely preferred ruthenium (II) cis-di(thiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylic acid) (N3) sensitizing dye is explored. Electrochemically synthesized ZnO (plates of 4–5 μm in height and 100–150 nm in width) electrodes are dipped intentionally in N3 and HMP-2 dyes for 20 h so as to observe large surface agglomeration effect for ZnO/N3 system. Due to the local inhomogeneity resulting from the Zn²⁺/dye complex layer formed between ZnO platelets and N3 dye, its solar-to-electrical conversion efficiency is inferior than aggregation-free ZnO/HMP-2.     

Main-chain supramolecular block copolymers

Block copolymers are key building blocks for a variety of applications ranging from electronic devices to drug delivery. The material properties of block copolymers can be tuned and potentially improved by introducing noncovalent interactions in place of covalent linkages between polymeric blocks resulting in the formation of supramolecular block copolymers. Such materials combine the microphase separation behavior inherent to block copolymers with the responsiveness of supramolecular materials thereby affording dynamic and reversible materials. This tutorial review covers recent advances in main-chain supramolecular block copolymers and describes the design principles, synthetic approaches, advantages, and potential applications.