Self-Assembly of Biopolymers on Colloidal Particles via Hydrogen Bonding

Fabrication of multilayer microcapsules via layer-by-layer approach through hydrogen bonding has attracted enormous interest due to its strong response to pH. In this communication, we have prepared hydrogen-bonded multilayer microcapsule without using any cross-linking agent by using DNA base pair (adenine and thymine) modified biocompatible polymers. The growth of the self-assembly on colloidal (melamine formaldehyde; MF) particles has been monitored with zeta potential measurement. The capsules were obtained on dissolution of MF particles at 0.1N HCl. The capsules were characterized with scanning electron microscopy. Moreover, we have observed the salt induced microscopic change in self-assembly of this system on the surface of colloidal particles

Self-Assembly and Catalytic Activity of Metal Nanoparticles Immobilized in Polymer Membrane Prepared via Layer-by-Layer Approach

Densely packed nanoparticles distributed in a stable and robust thin film is a highly preferred system for utilizing the various applications of nanoparticles. Here, we report covalent bond mediated layer-by-layer (LbL) self-assembled thin films of nanoparticles embedded in polymer membrane. Polymer with complementary functional group is utilized for fabrication of thin film via covalent bonding. UV–visible spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to monitor the growth of LbL thin film. Subsequently, the composite thin film is used for catalysis of an organic electron transfer reaction of <i>p</i>-nitrophenol to <i>p</i>-aminophenol by sodium borohydride. The catalytic activity of these composite films is assayed multiple times, proving its applicability as a catalyst. The kinetic data obtained by monitoring reduction of <i>p</i>-nitrophenol suggest that the reaction rates are directly related to the sizes of the nanoparticle and porosity of the membrane

Enhancing Surface Coverage and Growth in Layer-by-Layer Assembly of Protein Nanoparticles

Thin films of bovine serum albumin (BSA) nanoparticles are fabricated via layer-by-layer assembly. The surface of BSA nanoparticles have two oppositely acting functional groups on the surface: amine (NH₂) and carboxylate (COO^–). The protonation and deprotonation of these functional groups at different pH vary the charge density on the particle surface, and entirely different growth can be observed by varying the nature of the complementary polymer and the pH of the particles. The complementary polymers used in this study are poly­(dimethyldiallylammonium chloride) (PDDAC) and poly­(acrylic acid) (PAA). The assembly of BSA nanoparticles based on electrostatic interaction with PDDAC suffers from the poor loading of the nanoparticles. The assembly with PAA aided by a hydrogen bonding interaction shows tremendous improvement in the growth of the assembly over PDDAC. Moreover, the pH of the BSA nanoparticles was observed to affect the loading of nanoparticles in the LbL assembly with PAA significantly

Fluoranthene-Based Molecules as Electron Transport and Blue Fluorescent Materials for Organic Light-Emitting Diodes

Herein we report the synthesis, characterization, and potential application of bis­(4-(7,9,10-triphenylfluoranthen-8-yl)­phenyl)­sulfone (TPFDPSO2) and 2,8-bis­(7,9,10-triphenylfluoranthen-8-yl)­dibenzo­[<i>b</i>,<i>d</i>]­thiophene 5,5-dioxide (TPFDBTO2) as electron transport as well as light-emitting materials. These fluoranthene derivatives were synthesized by oxidation of their corresponding parent sulfide compounds, which were prepared via Diels–Alder reaction. These materials exhibit deep blue fluorescence emission in both solution and thin film, high photoluminescence quantum yield (PLQY), thermal and electrochemical stability over a wide potential range. Hole- and electron-only devices were fabricated to study the charge transport characteristics, and predominant electron transport property comparable with that of a well-known electron transport material, Alq₃, was observed. Furthermore, bilayer electroluminescent devices were fabricated utilizing these fluoranthene derivatives as electron transport as well as emitting layer, and device performance was compared with that of their parent sulfide molecules. The electroluminescence (EL) devices fabricated with these molecules displayed bright sky blue color emission and 5-fold improvement in external quantum efficiency (EQE) with respect to their parent compounds

Fluoranthene Based Derivatives for Detection of Trace Explosive Nitroaromatics

A series of fluoranthene derivatives (<b>F1</b>–<b>F5</b>) varied with nature and type of substituents were synthesized <i>via</i> Diels–Alder reaction followed by <i>in situ</i> decarbonylation. The solid state structures have been established through single crystal X-ray diffraction (XRD). The presence of extended conjugation and having two alkyloxy chains on phenyl rings induces flexibility to orient opposite to each other and interacts with another fluoranthene unit with weak π–π interactions and show unique supramolecular arrangements. The envisaged photophysical and DFT studies demonstrated that HOMO–LUMO levels were effectively tuned by different substituents with an optical band gap from 3.44 to 3.88 eV provoked to examine as sensitive fluorescent chemosensors for the detection of nitroaromatic compounds (NACs). The sensitivity toward the detection of NACs was evaluated through fluorescence quenching in solution (aqueous and non-aqueous) and solid state (vapor and contact mode). Fluorescence studies demonstrated that electron transfer occurs from the electron rich fluoranthene fluorophores to the electron deficient NACs by the dominant static quenching mechanism and the quenching process is reversible. It was found that the detection sensitivity increases with extent of conjugation on fluoranthene unit. The contact mode approach using thin layer silica chromatographic plates exhibits a femtogram (1.15 fg/cm²) detection limit for trinitrotoluene (TNT) and picric acid (PA), while the solution state fluorescence quenching shows for PA detection at the 2–20 ppb level. The sensing performance of fluoranthene thin films to NACs in aqueous solution reveals that fluorophores are highly selective towards the detection of PA. The smart performances of thin film fluorophores with high photostability have great advantage than those of conjugated polymers with superior sensitive detection of PA in groundwater

Layer-by-Layer Assembled Thin Film of Albumin Nanoparticles for Delivery of Doxorubicin

Protein nanoparticles (NPs) have found significant applications in drug delivery due to their inherent biocompatibility, which is attributed to their natural origin. In this study, bovine serum abumin (BSA) nanoparticles were introduced in multilayer thin film via layer-by-layer self-assembly for localized delivery of the anticancer drug Doxorubicin (Dox). BSA nanoparticles (∼100 nm) show a high negative zeta potential in aqueous medium (−55 mV) and form a stable dispersion in water without agglomeration for a long period. Hence, BSA NPs can be assembled on a substrate via layer-by-layer approach using a positively charged polyelectrolyte (chitosan in acidic medium). The protein nature of these BSA nanoparticles ensures the biocompatibility of the film, whereas the availability of functional groups on this protein allows one to tune the property of the self-assembly to have a pH-dependent drug release profile. The growth of multilayer thin film was monitored by UV–visible spectroscopy, and the films were further characterized by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The drug release kinetics of these BSA nanoparticles and their self-assembled thin film has been compared at a physiological pH of 7.4 and an acidic pH of 6.4

Fluoranthene Based Derivatives for Detection of Trace Explosive Nitroaromatics

A series of fluoranthene derivatives (<b>F1</b>–<b>F5</b>) varied with nature and type of substituents were synthesized <i>via</i> Diels–Alder reaction followed by <i>in situ</i> decarbonylation. The solid state structures have been established through single crystal X-ray diffraction (XRD). The presence of extended conjugation and having two alkyloxy chains on phenyl rings induces flexibility to orient opposite to each other and interacts with another fluoranthene unit with weak π–π interactions and show unique supramolecular arrangements. The envisaged photophysical and DFT studies demonstrated that HOMO–LUMO levels were effectively tuned by different substituents with an optical band gap from 3.44 to 3.88 eV provoked to examine as sensitive fluorescent chemosensors for the detection of nitroaromatic compounds (NACs). The sensitivity toward the detection of NACs was evaluated through fluorescence quenching in solution (aqueous and non-aqueous) and solid state (vapor and contact mode). Fluorescence studies demonstrated that electron transfer occurs from the electron rich fluoranthene fluorophores to the electron deficient NACs by the dominant static quenching mechanism and the quenching process is reversible. It was found that the detection sensitivity increases with extent of conjugation on fluoranthene unit. The contact mode approach using thin layer silica chromatographic plates exhibits a femtogram (1.15 fg/cm²) detection limit for trinitrotoluene (TNT) and picric acid (PA), while the solution state fluorescence quenching shows for PA detection at the 2–20 ppb level. The sensing performance of fluoranthene thin films to NACs in aqueous solution reveals that fluorophores are highly selective towards the detection of PA. The smart performances of thin film fluorophores with high photostability have great advantage than those of conjugated polymers with superior sensitive detection of PA in groundwater

Correlation between Optical Properties and Nanomorphology of Fluoranthene-Based Conjugated Copolymer

Nanoparticles of conjugated polymers are receiving attention due to their interesting optical properties. Here we report nanoparticles of fluoranthene-based conjugated copolymer prepared by the Suzuki coupling reaction. The copolymer forms nanoparticles by the spontaneous self-assembly after evaporation of organic solvent. The mean diameter of the nanoparticles can be manipulated by varying solvent composition. We investigated the parameters that govern the nanostructured morphology of polymer by systematic variation of good and poor solvent. The UV–vis and time-resolved fluorescence spectroscopy measurement reveal the use of poor solvent in the organization of nanostructures. Furthermore, transmission electron microscopy highlights the importance of rigidity of the polymer backbone in morphological development

Screening of Rubiaceae and Apocynaceae extracts for mosquito larvicidal potential

<div><p>Rubiaceae and Apocynaceae families are well known for the expression of cyclotides having insecticidal properties. Leaves and flowers extracts of plants from the families Rubiaceae (<i>Ixora coccinea</i>) and Apocynaceae (<i>Allamanda violacea</i>) were evaluated for mosquito larvicidal effect against early IVth instars of <i>Aedes aegypti</i> and <i>Anopheles stephensi</i>. Two forms of plant extracts, one untreated and the other treated with heat and proteolytic enzyme were used for assay. After primary assay, the extract showing more than 50% inhibition was further used for quantification purpose. LC₅₀ and LC₉₀ values of all the extracts were found to be reduced with the treated form. Phytochemical analysis of plant extracts was performed. Primary confirmation for the presence of cyclotides was done by Lowry test, thin layer chromatography and haemolytic assay. This novel approach merits use of plant extracts in mosquito control programmes.</p></div

Influence of Side-Chain on Structural Order and Photophysical Properties in Thiophene Based Diketopyrrolopyrroles: A Systematic Study

In this work, we have synthesized a series of TDPP derivatives with different alkyl groups such as <i>n</i>-hexyl (−C₆H₁₃) <b>3a</b>, 2-ethylhexyl (-(2-C₂H₅)­C₆H₁₂) <b>3b</b>, triethylene glycol mono methyl ether (-(CH₂CH₂O)_<b>3c</b>H₃, TEG) <b>3c</b>, and octadodecyl (-(8-C₈H₁₇)­C₁₂H₂₂) <b>3d</b>. <i>N</i>,<i>N</i> dialkylation of thiophene-diketopyrrolopyrrole (TDPP, <b>1</b>) strongly influences its solubility, solid state packing, and structural order. These materials allow us to explicitly study the influence of alkyl chain on solid state packing and photophysical properties. TDPP moiety containing two different alkyl groups <b>3e</b> (TEG and 2-ethylhexyl) and <b>3f</b> (TEG and <i>n</i>-hexyl) were synthesized for the first time. The absorption spectra of all derivatives exhibited a red shift in solid state when compared to their solution spectra. The type of alkyl chains leads to change in the optical band gaps in solid state. The fluorescence study reveals that TDPP derivatives have strong π–π interaction in the solid state and the extent of bathochromic shift is due to combination of intramolecular interaction and formation of aggregates in solid state. This behavior strongly depends on the nature of alkyl chain. The presence of strong C–H···O inter chain interactions and CH−π interactions in solid state exhibits strong influence on the photophysical properties of TDPP chromophore