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Surface pressure versus mean molecular area isotherms of Langmuir films of a hybrid diblock copolymer of poly(ethylene glycol) (PEG) and poly(methacrylo polyhedral oligomeric silsesquioxane) P(MA-POSS) together with Brewster angle microscopy reveal details of the phase transitions. The formation of a periodic wrinkling pattern in collapsed films is observed by epifluorescence microscopy after applying several compression-expansion cycles above the surface pressure of ≈18 mN/m. The wrinkle formation is reversible upon compression and expansion of the Langmuir films. Two distinct orientations of POSS molecules are assumed in Langmuir films upon compression, vertically for chains close to the water surface and horizontally orientated upper layers with significant amounts of PEG in between them. Thus, the wrinkling forms mainly in the top stiffer MA-POSS blocks above a certain compressional stress. The wrinkles disappear during the Langmuir-Blodgett (LB) transfer. Nevertheless, atomic force microscopy and grazing incidence wide-angle X-ray scattering experiments reveal the formation of highly ordered POSS molecules in LB films.

In this study, amidoxime-functionalized silica decorated with copper (AFS-Cu) was fabricated and tested for its catalytic application. Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were employed to characterize its structure and morphology. The application of AFS-Cu as a catalyst for the catalytic reduction of methylene blue (MB) in aqueous media using NaBH4 as reductant was evaluated. The ability to reuse as well as the effect of catalyst dose and pH of solution on the catalytic activity was investigated. The reduction of MB followed pseudo-first-order kinetics and the rate constant (k) was 0.6224 min(-1). AFS-Cu was found to be a highly effective catalyst for MB reduction reaction and can be easily recovered and reused several times with no appreciable loss of catalytic activity.

Background: Germin-like Proteins (GLPs) play an important role in various stresses. Rice contains 43 GLPs, among which many remain functionally unexplored. The computational analysis will provide significant insight into their function. Objective: To find various structural properties, functional importance, phylogeny and expression pattern of all OsGLPs using various bioinformatics tools. Methods: Physiochemical properties, sub-cellular localization, domain composition, Nglycosylation and Phosphorylation sites, and 3D structural models of the OsGLPs were predicted using various bioinformatics tools. Functional analysis was carried out with the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) and Blast2GO servers. The expression profile of the OsGLPs was predicted by retrieving the data for expression values from tissuespecific and hormonal stressed array libraries of RiceXPro. Their phylogenetic relationship was computed using Molecular and Evolutionary Genetic Analysis (MEGA6) tool. Results: Most of the OsGLPs are stable in the cellular environment with a prominent expression in the extracellular region (57%) and plasma membrane (33%). Besides, 3 basic cupin domains, 7 more were reported, among which NTTNKVGSNVTLINV, FLLAALLALASWQAI, and MASSSF were common to 99% of the sequences, related to bacterial pathogenicity, peroxidase activity, and peptide signal activity, respectively. Structurally, OsGLPs are similar but functionally they are diverse with novel enzymatic activities of oxalate decarboxylase, lyase, peroxidase, and oxidoreductase. Expression analysis revealed prominent activities in the root, endosperm, and leaves. OsGLPs were strongly expressed by abscisic acid, auxin, gibberellin, cytokinin, and brassinosteroid. Phylogenetically they showed polyphyletic origin with a narrow genetic background of 0.05%. OsGLPs of chromosome 3, 8, and 12 are functionally more important due to their defensive role against various stresses through co-expression strategy. Conclusion: The analysis will help to utilize OsGLPs in future food programs.

A photoactive nanohybrid material consisting of pyrocatechol violet, carminic acid and dithizone dyes functionalized silver and neodymium-doped TiO

Considering the great importance of nanocomposite based photo-active nanomaterials for a variety of elec-tronics, photonics and photovoltaics application, it is always worth considering to synthesize new hetreos-tructure. This paper describes the sol-gel and hydrothermal synthesis of metal (holmium, barium, and cadmium) doped TiO2/CdS nanocomposites for photoanode applications. Various characterization techniques, including XRD, FTIR, UV-VIS, EDX, and SEM were used to examine the synthesized heterostructures. The band gap of pure TiO2 NPs is 3.10 eV, which was effectively decreased to 2.16 eV by doping and coupling with CdS. The nano-material's crystallinity, crystallite size, morphology and elemental composition were determined by XRD, SEM and EDX, respectively. As sensitizers, the organic dyes dithizone, carminic acid, and pyrocatechol violet were used. FTIR was used to analyze the effective dye grafting on the surface of nanomaterials. In the presence of hole conducting P3HT polymer as solid state electrolyte, the sensitized materials were evaluated for solid state dye -sensitized solar cells. Compared to the reference device, Cd-TiO2/CdS photosensitized using Pyrocatechol violet dye demonstrated the highest efficiency of 2.68% (0.82%). Other parameters of this device, including open circuit voltage (Voc) and short circuit current (Jsc), were determined to be 16.97 mA cm2 and 0.41V, respectively., Higher education commission of Pakistan; [6169/Federal/NRPU/R D/HEC/16], We are greatly appreciative to Higher education commission of Pakistan under project No-6169/Federal/NRPU/R & D/HEC/16 for financial support and Quaid-i-Azam University, Islamabad, for providing laboratory and other facilities.

A photoactive nanohybrid material consisting of pyrocatechol violet, carminic acid and dithizone dyes functionalized silver and neodymium-doped TiO2/ZnO nanostructured materials is reported here, as photoactive blend, for solid-state dye sensitized solar cell. First of all we synthesized metals (silver, neodymium) doped (TiO2) Titanium oxide nanoparticles and their nanocomposites (TiO2/ZnO, M-TiO2/ZnO) using the sol-gel and reflux technique, respectively. The synthesized samples were then characterized by UV-Visible spectroscopy, X-Ray diffraction Analysis (XRD), Scanning electron microscopy (SEM), Energy dispersive X-Ray Analysis (EDX), and Fourier Transform infrared spectroscopy (FTIR). Optical studies were done through UV-Visible spectroscopy and the absorption spectra were used to calculate band gaps. The value of the energy gap for TiO2 nanoparticles is 3.10 eV which was gradually tuned to 2.47 eV after incorporating metals (Ag and Nd) and forming respective nanocomposites. X-Ray diffraction Analysis (XRD) patterns revealed the purity and crystallinity in samples. Scanning electron microscopy (SEM) confirmed the irregular morphology (nanorods and spherical shaped) of ZnO and TiO2 nanostructures respectively. The elemental composition of nanomaterials was successfully investigated using energy dispersive X-ray analysis (EDX). In the absence of any impurities, Fourier Transform infrared spectroscopy (FTIR) was used to identify the functional groups in synthesized material. For device fabrication, a solid-state electrolyte, P3HT, a hole conducting polymer was used. Characterization of fabricated solar cells was done using I-V measurements. Under simulated solar irradiation, the DSSC based on pyrocate-chol violet sensitized neodymium doped TiO2/ZnO nanohybrid materials exhibited the best PCE (power conversion efficiency) of 2.38 % and significantly improved Jsc (short circuit current density) of 15.68 mA/ cm2 as compared to carminic acid and dithizone in photovoltaic measurements. The improved power conversion efficiency of this device is ascribed to the particle size, increased dye adsorption, increased surface area and thus improved short circuit current density (Jsc). (c) 2022 Published by Elsevier B.V., Quaid-i-Azam University, Islamabad [6169/Federal//NRPU/RD/HEC/16], We are highly thankful to Higher education commission of Pakistan under project No-6169/Federal//NRPU/R & D/HEC/16 for financial support and Quaid-i-Azam University, Islamabad, for providing laboratory and other facilities.

The odd–even effect of a homologous series of two poly(ethylene oxide) chains separated by (CH2)n spacers and joined by two 1,2,3-triazole rings with 2 ≤ n ≤ 8 (PEO11-TR-(CH2)n-TR-PEO11) is reporte...

The Langmuir film formation of poly(ethylene glycol) (PEG)- and poly(methacrylo polyhedral oligomeric silsesquioxane) P(MA-POSS)-based diblock copolymers (PEG5k-b-P(MA-POSS)x) at the air/water interface is investigated. While the Langmuir film formed by the PEG5k collapses at π ≈ 8 mN m−1, the PEG5k-b-P(MA-POSS)x forms a stable film on the water surface revealing various phase transitions in surface pressure vs mean molecular area (π-mmA) isotherm—manifested by various pseudo-plateaus during compression. At higher surface coverage, the π-mmA isotherm exhibits a phase transition that is attributed to the transformation of the P(MA-POSS) monolayer into a multilayer film that is confirmed by AFM measurements of the Langmuir-Blodgett films fabricated before and after the phase transition and direct infrared reflection absorption spectroscopy of the Langmuir film during compression. At a still higher surface pressure, another pseudo-plateau is observed that is assigned to the ultimate film collapse as verified by the Brewster angle microscopy.

ZnO nanorods doped with different concentrations of Ag and Nd (1–7%) were synthesized by hydrothermal method. In this article we describe the synthesis, characterization and applications of pristine ZnO, Ag-doped ZnO and Nd-doped ZnO nanorods in hybrid bulk heterojunction solar cells. Their optical, structural, and morphological properties were analyzed by using UV–Visible spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Energy dispersive X-ray spectroscopy (EDX). The X-ray diffraction analysis reveals that the pristine and doped ZnO nanorods were crystallized in a hexagonal wurtzite structure. SEM images supplemented with EDX were used to explore the morphology, size and chemical composition of pristine ZnO, Ag-doped ZnO and Nd-doped ZnO samples. UV visible absorption spectra showed that bathochromic shift occurred when ZnO nanorods were doped with Ag and Nd up to a certain limit of dopant concentration. Doped ZnO nanorods were found more conducting than prisitne ZnO nanorods. This work also represents the chemical modification of pristine ZnO, Ag-doped ZnO, and Nd-doped ZnO nanorods with a bromopyrogallol red dye (Br-PGR) which is not reported yet. The pristine and doped samples were sensitized with Br-PGR and the material so sensitized was tested in solar cell. The optical properties of grafted samples were thoroughly studied by using UV–visible spectroscopy. The Nano-hybrid material was tested as a photoactive blend of the DSSCs and their current-voltage measurements (I-V) were performed to examine the effect of pristine and doped ZnO nanorods on the performance of solar cells. Moreover current voltage (I-V) measurements confirmed the boosting of efficiency in pristine and doped ZnO nanorods based DSSCs owing to their sensitization with Br-PGR. Maximum power conversion efficiency of 1% was recorded for Ag-doped ZnO nanorods.

Cadmium oxide nanoparticles (NPs) were successfully synthesized through the simple and low-cost sol–gel method. The optical, morphological, compositional, and structural properties of as-synthesized NPs were investigated by ultraviolet–visible (UV/Vis) spectroscopy, fluorescence spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analysis. Absorption spectra of CdO NPs were used for band gaps calculation, which was found to be 2.11 eV. The XRD pattern was used to investigate the purity and crystalline nature of NPs. Morphology and elemental composition were investigated by using SEM and energy-dispersive X-ray spectroscopy (EDX), respectively. FTIR assisted in identifying the functional groups and grafting of the dye on the surface of NPs. These CdO nanoparticles were photosensitized with Ru (II) based Z907 dye. Z907 dye was employed to extend the absorption spectrum of the material to the visible region of the solar spectrum so as to harvest the maximum amount of solar influx on the surface of earth. The energy level diagram revealed that the interaction among the constituents of the nanohybrid assembly permitted the flow of the electron in a cascade manner from dye to CdO nanoparticles. The synthesized photoactive nanohybrid material was thoroughly blended with poly (3-hexylthiophene), a solid electrolyte, and I–V measurements under simulated radiations 1000 W/m2 (AM 1.5) were recorded. A maximum induced photon to the current conversion efficiency of 0.60% was achieved.

We have used Cu(I)-catalyzed azide–alkyne cycloaddition to synthesize a new series of poly(ethylene oxide)s having in the center of their chains two 1,2,3-triazole (TR) rings separated by (CH2)n spacers with 2 ≤ n ≤ 4 (PEO11-TR-(CH2)n-TR-PEO11). The degree of crystallinity obtained by temperature-dependent WAXS measurements indicates that only one out of the two PEO11 chains of the three polymers forms a 72 helix upon cooling to −10 °C and crystallizes into a monoclinic unit cell known from PEO homopolymer. A solid-state phase transition occurs for all samples during heating below their melting temperature. Solid-state 13C MAS cross-polarization and single-pulse NMR spectroscopy indicate the complete incorporation of the chain defects into the PEO crystals (PEO-TR phase) during this transition. The 2D WAXS pattern of an oriented PEO11-TR-(CH2)2-TR-PEO11 sample generates a structural model where the crystal lattice of the initial PEO phase becomes highly distorted during the solid-state phase transition du...

Well-defined amphiphilic comb-like pentablock copolymers based on Pluronic L64 (PEO13-b-PPO30-b-PEO13) and poly(ethylene glycol)methyl ether methacrylate (PEGMA) have been successfully synthesized via atom transfer radical polymerization (ATRP). The L64 is transformed into ATRP macroinitiator and chain extended with PEGMA under typical ATRP conditions to achieve comb-like pentablock copolymers of various compositions. Due to their amphiphilic nature, the block copolymers could form self-assembled structures in aqueous solutions as confirmed by dynamic light scattering. At higher PEGMA content in the synthesized copolymer, however, the critical aggregation concentration (CAC) is less pronounced that could be attributed to the increased hydrophilicity and steric hindrance of PEG side chains of the PEGMA, thus preventing the formation of well-defined micellar aggregates, and probably leads to open-shell aggregation mechanism. The lower critical solution temperature (LCST) of the synthesized block copolymers is found higher than the neat L64 and increased with increasing the PEGMA content. Further, tuning the clouding behavior could be achieved with inorganic additives (KBr and K2SO4). The influence of SO42− and Br1− on LCST is according to their position in Hofmeister series. Interestingly, the effect of additives is more pronounced above the CAC of the copolymer, suggesting that the nanoaggregates in solution induce the macrophase separation.

In the present work we report the development of a novel electrochemical sensor associated with high sensitivity, selectivity, cost affordability and fast sensing ability. We used 1-phenyl-N-(pyridin-2-ylmethyl)ethanamine (PPE) as a recognition layer over the surface of glassy carbon electrode for the trace level detection of mercuric (Hg2+) and cadmium (Cd2+) ions. The effects of pH, temperature, concentration of the modifier, accumulation time, deposition potential and supporting electrolytes were examined to optimize conditions for achieving the best sensing response of the analytes. The designed sensors demonstrated good percentage recovery, remarkable electrocatalytic activity and excellent discrimination ability for the target analytes in the presence of interfering metal ions. The wide linearity range and quite lower detection limits of 0.1 nM and 0.8 nM for Hg+2 and Cd+2 ions suggested the promising candidature of the designed sensor for monitoring heavy metal ions in aqueous systems.

In this research work, bare ZnS, ZnS reduced graphene oxide (ZnS/rGO) and Cadmium doped ZnS reduced graphene oxide (Zn1−XCdXS/rGO) decorated nanocomposites were successfully synthesized through facile coprecipitation method. Optical and morphological analysis of these synthesized nanomaterials were done by using UV-Visible, florescence spectroscopy, X-Ray diffraction spectroscopy (XRD), Field emission scanning electron microscopy (FESEM), Elemental dispersive X-Ray analysis (EDX), Transmission electron microscopy (TEM), Fourier transform infra-red (FT-IR) and Raman spectroscopy. The band gap values were calculated from the optical absorption spectra. The study reveals that the band gap of ZnS (3.96 eV) was effectively tuned up to 2.99 eV by coupling with reduced graphene oxide. The phase purity, crystalline nature,morphology, functional groups detection, elemental composition of the samples were confirmed through XRD, FESEM,TEM,FTIR and EDX respectively. The Z907 dye grafted nanomaterials were combined P3HT (hole conducting polymer) to make a photoactive blend for dye sensitized solar cell. The fabricated cells were then investigated by using current –voltage (I-V) measurements. I-V measurements revealed that the photoconductive ability of ZnS nanoparticles has been significantly enhanced on the formation of its ZnS/rGO and Zn1−XCdXS/rGO decorated nanocomposites. Boost in efficiency of about 64% and 83% in comparison to reference device has been observed for Ru/ZnS/rGO-P3HT (0.466%) and Ru/Zn1−XCdXS/rGO-P3HT (0.522%). Enhanced Jsc and Voc values of these synthesized composites presented them as ground materials for further research by interface engineering to enhance their efficiency in SSDSSCs.

Poly(glycerol adipate) (PGA) was synthesized by enzymatic polymerization and grafted with different amounts of oleoyl chloride. A series of graft copolymers PGA-g-Ox was obtained where O represents the oleate side chains and x is the degree of grafting (mol% of the pendant OH groups of PGA esterified) ranging from 11 to 90. Small angle X-ray scattering (SAXS) data revealed nanophase separation of the oleate side chains into nanodomains in bulk and wide angle X-ray scattering (WAXS) profiles showed a broad halo, reflecting the amorphous nature of the synthesized graft polymers. Glycerol monooleate (GMO), an amphiphilic lipid with one hydrophobic oleate tail and a glycerol hydrophilic head group, self-assembles into various liquid crystalline phases in the presence of water. Since oleate chains are integral part of both GMO and the graft copolymers, a certain degree of miscibility can be expected influencing the self-assembly behavior. Using SAXS for phase identification, systematic studies were carried out at room temperature on the ternary system of GMO/PGA-g-O22/water and the ternary phase diagram was constructed. The addition of polymer did influence the phase behavior of the GMO/water system. The water in the lamellar and cubic mesophases was partially replaced by PGA-g-O22. Furthermore, keeping the GMO/water ratio constant at 1:1, the addition of PGA-g-O22 lead to swelling of the water channels in the inverse bicontinuous Pn3m cubic phase. Preliminary investigations on the potential application of PGA-g-O22 as a stabilizer of structured nanoparticles in aqueous dispersions were carried out employing different transmission electron microscopy techniques.

As a membrane-mimetic system, detergent micelles are popularly used to extract membrane proteins from lipid environments and to maintain their solubility and stability in an aqueous medium. However, many membrane proteins encapsulated in conventional detergents tend to undergo structural degradation during extraction and purification, thus necessitating the development of new agents with enhanced properties. In the current study, two classes of new amphiphiles are introduced, resorcinarene-based glucoside and maltoside amphiphiles (designated RGAs and RMAs, respectively), for which the alkyl chains are facially segregated from the carbohydrate head groups. Of these facial amphiphiles, two RGAs (RGA-C11 and RGA-C13) conferred markedly enhanced stability to four tested membrane proteins compared to a gold-standard conventional detergent. The relatively high water solubility and micellar stability of the RGAs compared to the RMAs, along with their generally favourable behaviours for membrane protein stabilisation described here, are likely to be, at least in part, a result of the high conformational flexibility of these glucosides. This study suggests that flexibility could be an important factor in determining the suitability of new detergents for membrane protein studies.

A new series of well-defined amphiphilic hybrid polymers of tadpole-shaped architecture with polyhedral oligomeric silsesquioxane (POSS) nanocage as the hydrophobic head and poly(glycerol methacrylate) (PGMA) as the hydrophilic tail (POSS-PGMA) has been synthesized via atom transfer radical polymerization (ATRP). The aminopropylIsobutyl POSS, a monofunctional POSS nanocage, was transformed into ATRP initiator by treating with 2-bromoisobutyrylbromide. The POSS-PGMA was achieved in two steps. First, solketal methacrylate (SMA) (the precursor monomer for GMA), synthesized by reacting solketal with methacryloyl chloride, was polymerized under typical ATRP conditions with THF as the solvent at 40 °C, employing the synthesized POSS based initiator, and CuCl/N,N,N,N,N-pentamethyldiethylenetriamine as the catalyst system. The size exclusion chromatography (SEC) chromatograms reveal monomodal molecular weight distributions and narrow polydispersity indices; suggesting that well-defined tadpole-shaped hybrid polymers have been achieved. This further confirms that the monofunctional POSS initiator is able to affectively polymerize SMA in a controlled fashion under ATRP conditions. In the second step, the obtained POSS-PSMA was transformed into amphiphilic POSS-PGMA by acid hydrolysis. The successful transformation could be verified by 1H NMR and FTIR spectroscopy. Finally, because of the amphiphilic nature, the obtained POSS-PGMA could self-assemble when dispersed in water as confirmed by measuring the critical aggregation concentration (CAC) by fluorescence spectroscopy, using pyrene as the fluorescence probe. The CAC was found to increase with increasing the PGMA chain length. The large hydrodynamic size of the self-assembled structures, as determined by the laser light scattering data, however, suggests that the aggregates are not of typical core-shell type micelles.

TiO2 nanoparticles doped with various concentrations of selected transition metals (2–8% Cu, Ni and Cr) were synthesized by sol–gel method. These nanoparticles were characterized using UV–Visible, fluorescence, transmission and scanning electron microscopies to investigate their optical and morphological properties. Direct band of pure TiO2 (3.9 eV) was significantly reduced to 2.9, 3.4 and 3.6 eV for Cu, Ni and Cr doped samples respectively. Higher dopant concentrations induced the widening of the band gap according to the Burstein–Moss phenomenon. X-ray diffraction (XRD) spectroscopy established the retention of anatase phase in the synthesized doped materials. X-ray photoelectron spectroscopy (XPS) was used to determine the oxidation state and chemical environment of each kind of dopant ions in the crystal structure. XPS results confirmed the substitution of Ti4+ ions by transition metal ions. Reduction of Ti4+ to Ti3+ state was observed for charge compensation in the crystal structure as a result of foreign ion incorporation. Keywords: Doping, Bathochromic shift, Burstein–Moss effect, Carrier concentration

Due to its unique nanocage-like architecture and properties, polyhedral oligomeric silsesquioxane (POSS) has received tremendous attention from researchers in areas ranging from material science and engineering to biomedical fields. This has created opportunities for the applications of POSS in non-traditional areas such as nanomedicines, Li-ion batteries, and many more. Thanks to the recent advances in polymer chemistry, the POSS molecules have been successfully incorporated into well-defined organic polymeric structures leading to the creation of a plethora of well-defined hybrid nano architectures with novel properties and applications. POSS nanocage is typically a strongly hydrophobic entity, and since recently, its integration into amphiphilic macromolecular design has been a fascinating area of research activity with many interesting studies ranging from academic research to practical applications. This article encompasses new ideas and research work carried out over the last several years in this relatively new area of water soluble/amphiphilic hybrids with a focus on their synthesis, self-assembly, and applications. In this article, for convenience of the readers, various POSS based amphiphilic polymers have been grouped into telechelic, hemitelechelic, esotelechelic, block copolymers, random copolymers, and star-like polymers. Their synthesis, self-assembly, particularly in aqueous medium, and their potential applications in various fields are thoroughly reviewed.

Direct imprinting of metals is predominantly achieved by using polydimethylsiloxane (PDMS) molds to pattern metal nanoparticles and subsequently melting them to form continuous structures. Although such a combination can successfully imprint metals, the yield and reproducibility are usually low when sub-100 nm features over large areas are desired. In this work, we demonstrate a simple method involving the addition of a cross-linker ethylene glycol dimethacrylate (EDMA) to a palladium metal precursor, and its in situ free radical polymerization during imprinting, which not only dramatically increases the yield to ∼100% but also enables high reproducibility. Palladium mercaptide resist was formed by dissolving acetoxy(benzylthio)palladium, EDMA and azobis-(isobutyronitrile) in an organic solvent mixture. The resist underwent polymerization when imprinted using a silicon mold at 120 °C with pressures as low as 30 bar. Polymerization rigidly shapes the imprinted patterns, traps the metal atoms, reduces the surface energy and strengthens the structures, thereby giving ∼100% yield after demolding. Heat-treatment of the imprinted structures at 330 °C resulted in the loss of organics and their subsequent shrinkage without the loss of integrity or aspect ratio and converted them to palladium nanostructures as small as ∼35 nm wide, over areas >1 cm × 1 cm. With suitable precursors, our technique can potentially be extended to pattern noble metals such as platinum, gold and silver.

A photo-active nano-hybrid material consisting of titania nanoparticles, carminic acid, and sulphonic acid functionalized porphyrin is reported here. In an attempt to extend the absorption spectrum of titania to visible region by co-adsorbing carminic acid and sulphonic acid functionalized porphyrin on its surface. Interesting changes in the UV-visible and fluorescence spectra were noticed. The adsorption of carminic acid resulted in the formation of charge transfer complex with titania nanoparticles. This was confirmed by the electronic absorption and fluorescence emission spectroscopies. Chemisorption of porphyrin on the carminic acid functionalized titania further boosted the charge transfer effect. This was noticed by the increase in intensity and width of the charge transfer absorption and emission bands. Energy level diagram showed that the interaction among the constituents of the nano-hybrid assembly permitted the flow of electron in a cascade manner from carminic acid to TiO2.This also allowed direct flow of electrons either from carminic acid or porphyrin toward titania. The material was used as an active blend in hybrid bulk heterojunction solar cells. Co-functionalized TiO2-based devices were found 3.5 times more efficient than the reference device but morphology of the device proved a major setback.

The synthesis and characterization of amphiphilic pentablock copolymers based on Pluronic® L64 (PEO13-PPO30-PEO13) and poly(methyl methacrylate) (PMMA), synthesized via atom transfer radical polymerization (ATRP) is reported. The L64 is first transformed into a bifunctional ATRP macroinitiator which was subsequently chain extended with MMA by ATRP to afford PMMA-b-L64-b-PMMA pentablock copolymers. The chemical structure of the synthesized amphiphilic block copolymers is characterized by FTIR, 1H NMR spectroscopy, and gel permeation chromatography (GPC). The GPC profiles of the block copolymers clearly show an increase in molar mass after the ATRP of MMA and monomodal molecular weight distributions for all the samples. Finally, preliminary studies on their aggregation behavior in aqueous solution have also been investigated by measuring the scattering light intensity as function of block copolymer concentration to estimate the critical aggregation concentration (CAC). The CAC decreases with increasing of hydrophobic content in copolymer, i.e., ∼25 and ∼15 mg/mL, respectively, is estimated for the pure L64 and PMMA13-b-L64-b-PMMA13. Further, with increase in temperature, the CAC is found to decrease that is attributed to the dehydration of the PEO segments at higher temperatures.

Detergents are an absolute requirement for studying the structure of membrane proteins. However, many conventional detergents fail to stabilise denaturation-sensitive membrane proteins, such as eukaryotic proteins and membrane protein complexes. New amphipathic agents with enhanced efficacy in stabilising membrane proteins will be helpful in overcoming the barriers to studying membrane protein structures. We have prepared a number of deoxycholate-based amphiphiles with carbohydrate head groups, designated deoxycholate-based glycosides (DCGs). These DCGs are the hydrophilic variants of previously reported deoxycholate-based N-oxides (DCAOs). Membrane proteins in these agents, particularly the branched diglucoside-bearing amphiphiles DCG-1 and DCG-2, displayed favourable behaviour compared to previously reported parent compounds (DCAOs) and conventional detergents (LDAO and DDM). Given their excellent properties, these agents should have significant potential for membrane protein studies.

The influence of hydrophobic modification with fatty acids of various lengths on the behavior of poly(glycerol adipate) (PGA) at the air/water interface is investigated. The Langmuir isotherm of unmodified PGA reveals a liquid expanded (LE) phase followed by film collapse as indicated by the plateau starting at πc (collapse pressure) ∼13 mN/m. The film stability increases significantly by grafting fatty acids to the PGA backbone; PGA-graft-acyl. However, it tends to decrease again for higher degree of substitution due to the decreasing number of pendant hydroxyl groups on PGA backbone, which stabilize the monolayer by forming hydrogen bonds with water molecules. For samples with higher degree of substitutions, the LE phase could not be detected in the Langmuir isotherm which only shows a sharp increase in surface pressure, corresponding to the liquid condensed (LC) phase, followed by the film collapse. Atomic force microscopy images of the Langmuir–Blodgett films depict the formation of 3D nuclei of different heights at surface pressure, π > πc and the Brewster angle microscopy images reveal the formation of buckles in the collapse region for PGA-graft-tridecyl films. The formation of a solid phase in the Langmuir film is observed only for PGA grafted with longer alkyl side chains, including, heptadecyl and heneicosanyl. Overall, it is observed that with increasing length of the acyl chains the stability and compressibility of the film on the water surface increases because of enhanced coherence between the alkyl side chains that overcomes the obstruction effect of the PGA backbone.

We report for the first time charge-transfer complex formation at the interface of carminic acid and cadmium sulfide (CdS) nanoparticles. The complex formation was confirmed by ultraviolet–visible (UV–vis) and fluorescence emission spectroscopy. Cadmium sulfide nanoparticles were synthesized by the wet chemical method and characterized by UV–vis spectroscopy, x-ray diffraction and transmission electron microscopy. Carminic acid, in different concentrations, was chemisorbed on the surface of CdS nanoparticles. Grafting of carminic acid on CdS was confirmed by Fourier transform infrared spectroscopy. Energy levels of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals (LUMO) of both carminic acid and CdS nanoparticles matched well for the injection of electron from LUMO of carminic acid to the conduction band of cadmium sulfide. The photoactive nanohybrid material was used in dye-sensitized solar cells. The efficiency of carminic acid functionalized CdS nanoparticles was found to be double the value obtained for the reference device and remained constant over a certain concentration range owing to the complex formation at the interface. However, raising the concentration of carminic acid beyond 2.5 × 10−5 M resulted in a decrease in efficiency. This was ascribed to charge recombination due to the presence of ungrafted carminic acid molecules.

The behavior of a series of amphiphilic triblock copolymers of poly(ethylene oxide) (PEO) and poly(isobutylene) (PIB); including both symmetric (same degree of polymerization (DP) of the terminal PEO blocks) PEOm-b-PIBn-b-PEOm and non-symmetric (different DP of the terminal PEO blocks) PEOm-b-PIBn-b-PEOz, is investigated at the air/water interface by measuring surface pressure vs mean molecular area isotherms (π vs mmA), Langmuir–Blodgett (LB) technique, and infrared reflection–absorption spectroscopy (IRRAS). The block copolymer (PEO32-b-PIB160-b-PEO32) with longer PEO segments forms a stable monolayer and the isotherm reveals a pseudo-plateau starting at π ∼ 5.7 mN/m, also observed in the IRRAS, which is assigned to the pancake-to-brush transition related to the PEO dissolution into the subphase and subsequent PEO brush dehydration. Another plateau is observed at π ∼ 40 mN/m, which is attributed to the film collapse due to multilayer formation. The pancake-to-brush transition could not be observed for samples with smaller PEO chains. The isotherms for block copolymers, with short PEO chains, both symmetric (PEO3-b-PIBn-b-PEO3) and non-symmetric (PEO12-b-PIBn-b-PEO3), reveal another transition at π ∼ 20–25 mN/m. This is interpreted to be due to the conformational transition from a folded state where the middle PIB block is anchored to the water surface at both ends by the terminal hydrophilic segments to an unfolded state with PIB anchored to the water surface at one end. It is assumed that this transition involves the removal of PEO3 chains from the water surface in case of non-symmetric PEO12-b-PIB85-b-PEO3 and in case of symmetric, probably one PEO3 of each PEO3-b-PIB85-b-PEO3 chain. Because of the weaker interaction of the short PEO3 chains with the water surface as compared with the relatively longer PEO12 chains, the film of PEO3-b-PIB85-b-PEO3 collapses at much lower surface pressure after the transition as compared with the PEO12-b-PIB85-b-PEO3. The AFM images reveal the formation of microdomains of almost uniform height (6–7 nm) in LB films of PEO3-b-PIB85-b-PEO3 and PEO12-b-PIB85-b-PEO3 after transferring onto silicon surfaces. These domains are assumed to be the mesomorphic domains of ordered and folded PIB chains.

High-resolution membrane protein structures are essential for understanding the molecular basis of diverse biological events and important in drug development. Detergents are usually used to extract these bio-macromolecules from the membranes and maintain them in a soluble and stable state in aqueous solutions for downstream characterization. However, many eukaryotic membrane proteins solubilized in conventional detergents tend to undergo structural degradation, necessitating the development of new amphiphilic agents with enhanced properties. In this study, we designed and synthesized a novel class of glucoside amphiphiles, designated tandem malonate-based glucosides (TMGs). A few TMG agents proved effective at both stabilizing a range of membrane proteins and extracting proteins from the membrane environment. These favourable characteristics, along with synthetic convenience, indicate that these agents have potential in membrane protein research.

It is demonstrated that stable Langmuir films of poly(ethylene oxide) (PEO) can be formed up to surface pressures of 30 mN m(-1) when potassium carbonate K2CO3 is added to the aqueous subphase. Generally, PEO homopolymer cannot stay on the water surface at a surface pressure ≥10 mN m(-1) due to its high water solubility. To prepare stable monolayer films, PEO can be modified with hydrophobic moieties. However, by exploiting the salting out effect by adding certain salts (K2CO3 or MgSO4) into the aqueous subphase, not only very stable films but also unusual self-organization can be achieved by the PEO homopolymer on the surface of the aqueous solution. Thus, a series of OH-terminated PEOs is found to form a stable monolayer at K2CO3 concentrations of 2 M and above in the aqueous subphase, and the stability of the film increases with an increase in K2CO3 concentration. Hysteresis experiments are also carried out. During the phase transition induced by progressive compression, self-organization into well-defined domains with sizes in the micrometer range are observed, and with further compression and holding of the film for 30 min and above the microdomains transform into a crystalline morphology as visualized by Brewster angle microscopy.

To control the influence of supercooling on the preparation of poly(vinyl alcohol) (PVA) cryogel, various biocompatible ice nucleating agents, including, two fatty alcohols, and eight different amino acids are investigated for their ice nucleating efficiency in PVA aqueous solutions. The L-aspartic acid is found to be the most efficient ice nucleating agent with the ability to induce freezing at ∼−5.5 °C in 8.3 wt% aqueous PVA solution as compared to ∼−20 °C without L-aspartic acid. The PVA cryogels are prepared with L-aspartic acid as the heterogeneous ice nucleating agent and investigated for their rheological properties. Finally, it is found that freezing temperature close to the sol–gel transition temperature produces cryogel with the high tack important for various biomedical applications.

Polyhedral oligomeric silsesquioxane (POSS) compounds consist of unique three-dimensional nanocages with a general composition of (RSiO1.5)n, where R groups are organic moieties for enhanced physical and chemical compatibility of inorganic POSS frameworks with organic systems. Due to their unique size, structure and properties there has been tremendous progress over the last decade or so in the chemistry and applications of POSSs in various fields of materials, nanoscience and nanotechnology. Advances in synthetic polymer chemistry, particularly the advent of ‘controlled’ radical polymerization (CRP), namely atom transfer radical polymerization, reversible addition–fragmentation chain transfer and nitroxide-mediated polymerization, have enabled polymer chemists to integrate inorganic POSS nanocages into well-defined copolymers of almost any architecture, thus generating nanostructured materials with controlled molar masses and compositions, and well-defined and tunable morphologies. Thus, these new strategies of employing POSS nanocages in polymer chemistry could lead to potential new applications in various areas of nanoscience and nanotechnology. The present paper covers recent trends and developments over the last five years or so in POSS-based nanostructured materials via CRP. Also included is the combined CRP and ‘click’ chemistry approach to achieve POSS-containing well-defined hybrid copolymers. © 2014 Society of Chemical Industry

The synthesis and subsequent self-assembly of novel, random-type amphiphilic pH-responsive hybrid copolymers, having acrylic acid as pH-responsive hydrophilic and acrylate-polyhedral oligomeric silsesquioxane (POSS) as hydrophobic constituents are reported. The synthesis was carried out in two steps: first, t-butylacrylate and acrylate-POSS are copolymerized by ATRP, followed by the acid hydrolysis of t-butyl acrylate constituents of the synthesized poly(t-butylacrylate)-co-poly(acrylate-POSS) copolymers to achieve poly(acrylic acid)-co-poly(acrylate-POSS). It was found that POSS is a powerful hydrophobic unit. With very low POSS concentration in the copolymers, i.e., one POSS unit per 40 to 110 acrylic acid repeat units, the obtained amphiphilic hybrid copolymers could self-assemble in aqueous solution to form nanoaggregates, as revealed by the laser light scattering and fluorescence studies on the aqueous solutions of the obtained copolymers. The formation of hydrophobic core in the self-assembled aggregates is verified by the solubilization of pyrene (used as probe in fluorescence measurements) in aqueous solution of the copolymers. In addition to pH-dependent self-assembly behavior, it is also demonstrated that the particle size and aggregation number of the aggregates can be tuned simply by varying the composition of the copolymer, i.e., by changing the molar ratio of poly(acrylic acid) to poly(acrylate-POSS) in the copolymer. Finally, preliminary results on the influence of salt (NaCl) on the self-assembly of poly(acrylic acid)-co-poly(acrylate-POSS) in aqueous solution are also presented.

We demonstrate the formation of stable hybrid nanoparticles in solution through self-assembly driven by the stereocomplexation between enantiomeric poly(lactide) (PLA) chains in organic–inorganic hybrid diblock copolymers. The well-defined hybrid diblock copolymers (PLLA-b-P(MA-POSS) and PDLA-b-P(MA-POSS)) are synthesized via atom transfer radical polymerization of methacrylisobutyl POSS (MA-POSS) using either PLLA or PDLA as a macroinitiator. The structure of the block copolymers is confirmed by 1H NMR and GPC. The mixture of PLLA-b-P(MA-POSS) and PDLA-b-P(MA-POSS) in THF solution resulted in the formation of self-assembled nanoparticles as confirmed by the light scattering data. It is further verified that the only driving force for self-assembly in THF solution is the ‘stereocomplexation’ between the PLLA and PDLA blocks as no aggregation could be observed in THF solutions of homochiral polylactides at low concentration (∼1 mg mL−1). A solution mixture of 50:50 weight% of PLLA-b-P(MA-POSS) and PDLA-b-P(MA-POSS) for all the samples yields the best stereocomplexation results in terms of particles size and aggregation numbers. For a given composition, the size of the stereocomplexed hybrid nanoparticles, however, decreases with the increasing length of the (MA-POSS) block in the copolymer. As an example, for a 50:50 weight% mixture, the mean hydrodynamic radius Rh and apparent aggregation number Nagg of the particles decreased from 220 nm and 890, respectively, to 72 nm and 290, when the degree of polymerization of P(MA-POSS) increased from ∼2 to 11–12. It is assumed that the bulky POSS nanocages of P(MA-POSS) in the PLA-b-P(MA-POSS) block copolymer sterically hinder the formation of larger nanoparticles by block copolymers with longer P(MA-POSS) blocks. The stereocomplexed nanoparticles remain stable over 30 days and are not sensitive to dilution, suggesting the formation of stable hybrid nanoparticles dispersion. In contrast, the homopolymer mixture of PLLA and PDLA turned cloudy and was no longer stable after 12 days due to the formation of larger macroscopic aggregates. This interesting finding opens up new opportunities to tune the size and stability of the stereocomplexed nanoparticles in solution by manipulating the block length of the inorganic P(MA-POSS) segment.