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An exceptional Zinc(II)-organic framework with the formula [{Zn( L 4-py )(bdc)}·DMF] n ( Zn-MOF ) has been constructed solvothermally using a novel linker L 4-py {2,7-bis(3-(pyridin-4-ylethynyl)phenyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2 H ,7 H )-tetraone}, coligand H 2 bdc (1,4-benzenedicarboxylic acid), and ZnBF 4 · x H 2 O. The ligand L 4-py has been fabricated after functionalization of NDA (1,4,5,8-naphthalenetetracarboxylic dianhydride) core with 3-(pyridin-4-ylethynyl)phenyl group. The single-crystal X-ray analysis reveals that Zn-MOF exhibits a comprehensive three-dimensional (3D) framework architecture and features (4)-connected uninodal dia ; 4/6/c1; sqc6 topology with point symbol {6 6 } and two-dimensional (2D) + 2D, parallel polycatenation. Notably, Zn-MOF displayed excellent fluorescence phenomenon and stability in water as well as in methanol solvents and was harnessed as a versatile sensor, demonstrating selective and sensitive molecular recognition of flame retardants and antibiotics. Notably, Zn-MOF displayed 57 and 49.5% quenching efficiency for the flame-retardant pentabromophenol (PBP) and 3,3',5,5'-tetrabromobisphenol A (TBPA), respectively. Whereas an outstanding 90% quenching efficiency was observed for antibiotics, tetracycline (TC) and secnidazole (SD). The mechanistic investigations of this luminescence quenching suggest that this might be primarily occurring via the Fourier resonance energy transfer (FRET) and photoinduced electron transfer (PET) mechanisms, which might be assisted by the competitive absorption and host-guest interactions. The π-electron-rich framework structure of sensor Zn-MOF activates this mechanism.

Synthesis and structural depiction of two new metal-organic frameworks (MOFs), namely, [{Zn( L )(oba)}·4H 2 O] α (Zn-MOF -1 ) and [{Cd 1/2 ( L ) 1/2 (nipa) 1/2 (H 2 O) 1/2 }·(DMF) 1/2 (H 2 O)] α (Cd-MOF -2 ) (where L = N 2 , N 6 -di(pyridin-4-yl)naphthalene-2,6-dicarboxamide, 4,4'-H 2 oba = 4,4'-oxybisbenzoic acid, and 5-H 2 nipa = 5-nitroisophthalic acid) are reported. Both Zn-MOF- 1 and Cd-MOF- 2 have been prepared by reacting ligand L and coligand 4,4'-H 2 oba or 5-H 2 nipa with the respective dihydrates of Zn(OAc) 2 and Cd(OAc) 2 (OAc = acetate). Crystal structure X-ray analysis discloses that Zn-MOF -1 displays an overall 2D → 3D interpenetrated framework structure. The topological analysis by ToposPro suggests a (4)-connected uninodal sql topology with a point symbol of {4 4 ·6 2 } having 2D + 2D parallel polycatenation. However, crystal packing of Cd-MOF -2 adapted a porous framework architecture and was topologically simplified as (3,4)-connected binodal 2D net. In addition, both Zn-MOF -1 and Cd-MOF -2 were proved to be multifunctional materials for the recognition of organic amines and in the fixation of CO 2 to cyclic carbonates. Remarkably, Zn-MOF- 1 and Cd-MOF- 2 showed very good fluorescence stability in aqueous media and have shown 98 and 97% quenching efficiencies, respectively, for 4-aminobenzoic acid (4-ABA), among all of the researched amines. The mechanistic study of organic amines recognition proposed that fluorescence quenching happened mainly through hydrogen-bonding and π-π stacking interactions. Additionally, cycloaddition of CO 2 to epoxide in the presence of Zn-MOF- 1 and Cd-MOF- 2 afforded up to 96% of cyclic carbonate within 24 h. Both Zn-MOF- 1 and Cd-MOF- 2 exhibited recyclability for up to five cycles without noticing an appreciable loss in their sensing or catalytic efficiency.

We report the synthesis and structural characterization of two coordination polymers (CPs), namely; [{Zn(L)(DMF) 4 } ⋅ 2BF 4 ] α (1) and [{Cd(L) 2 (Cl) 2 } ⋅ 2H 2 O] α (2) (where L=N 2 ,N 6 -di(pyridin-4-yl)naphthalene-2,6-dicarboxamide). Crystal packing of 1 reveals the existence of channels running along the b- and c-axis filled by the ligated DMF and lattice anions, respectively. Whereas, crystal packing of 2 reveals that the metallacycles of each 1D chain are intercalating into the groove of adjacent metallacycles resulting in the stacking of 1D loop-chains to form a sheet-like architecture. In addition, both 1 and 2 were exploited as multifunctional materials for the detection of nitroaromatic compounds (NACs) as well as a catalyst in the ipso-hydroxylation of aryl/heteroarylboronic acids. Remarkably, 1 and 2 showed high fluorescence stability in an aqueous medium and displayed a maximum 88% and 97% quenching efficiency for 4-NPH, respectively among all the investigated NACs. The mechanistic investigation of NACs recognition suggested that the fluorescence quenching occurred via electron as well as energy transfer process. Furthermore, the ipso-hydroxylation of aryl/heteroarylboronic acids in presence of 1 and 2 gave up to 99% desired product yield within 15 min in our established protocol. In both cases, 1 and 2 are recyclable upto five cycles without any significant loss in their efficiency., (© 2021 Wiley-VCH GmbH.)

Fluorescence quenching based immunoassay format for the detection of a trace amount of some nitro-explosives with a high degree of selectivity is reported in this study. The immunoassay comprises anti-explosive antibodies functionalized microtitre strips specific to the targeted explosives, pentaerythritol tetranitrate (PETN), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and 2,4,6-trinitrotoluene (TNT). UV induced photolysis of nitro-explosive bound to targeted antibodies generates primarily nitrite ions which after the quick reaction with the detector molecule, 2,3-diaminonaphthalene (DAN), a fluorophore, quenches its fluorescence intensity, however, proportionately undergo cyclization to produce a highly fluorescent product, 2,3-naphthotriazole (NAT). The synthesized product, NAT, was verified using various chromatographic and spectrophotometric techniques. This newly developed antibody-based detection method, utilizing DAN dye, demonstrated a high selectivity towards PETN, RDX, and TNT. This method can be used as an economical testing kit for direct quantification of explosives, implying the great potential for quick, low-cost trace detection of explosives., (Copyright © 2019. Published by Elsevier B.V.)

A new immunoassay format using thermally induced defragmentation of some nitro-explosives with a high degree of selectivity is reported. Specific antibodies against three widely used explosives, 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and pentaerythritol tetranitrate (PETN) were generated by designing suitable haptens using geometry optimization modules. These in-house generated antibodies were used in a newly developed thermal mediated immunochemical biosensing technique which involves the binding of specific antibodies to respective nitro-explosives on a microtiter strip, resulting in the formation of specific immunocomplex. Heating the specific immuno-complex formed on microtiter wells resulted in thermal lysis of nitro-explosives to generate nitrite ions. These ions react with Griess reagent to form a colored chromophore which correlates the concentration of individual explosive in the sample. The present work fulfills the need for an improved explosive detecting system that is highly specific and capable of quickly determining the presence of nitrate containing explosives from a mixture pool., (Copyright © 2018. Published by Elsevier B.V.)

The utilization of selenium nanomaterials (Se Nps) in material and biological science is quickly growing, crafting an imperative need for toxicological evaluation of the exposure prospective and environmental consequences of Se Nps. The combination of quantitative multi-assay approach into environmental toxicological analysis has provided novel opportunities to build up effective markers and scrutinize the means of venomous nature of Se Nps in the current study. In the present work, we analyzed the toxicological effect of bare and surface functionalized Se Nps by using multi assay viz. seed germination studies as a function of concentration of SeNps and by using antifungal assays. The influence of SeNps on bacterial activities were also investigated by using the S. aureus, E. coli, P. aeruginosa and S. typhi bacterial strains as widespread marker species for antibacterial studies. The ocular assessment of chlorophyll content was maximum for Brij coated Se NPs (98%) as compared to bare (20%), SDS (45%) and CTAB (38%) coated SeNps. The existence of chromosomal aberrations in root meristems of A. cepa(A. cepa) with computed MI values of 16, 25, 33 and 52% for bare, CTAB, SDS and Brij coated particles has indicated the genotoxic effects of SeNps. The biocompatible nature of Brij coated Se Nps was observed from the faster mobility of DNA in gel electrophoresis studies. The investigational studies in the current work appraise the toxicity and measure the competence of obtained data to characterize possibilities of probable threats, prominence of data requirement and breaches that must be filled to diminish the ambiguities about the safe use of Se Nps., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Recent advancement in nanoscience and nanotechnology has witnessed numerous triumphs of zinc oxide (ZnO) nanomaterials due to their various exotic and multifunctional properties and wide applications. As a remarkable and functional material, ZnO has attracted extensive scientific and technological attention, as it combines different properties such as high specific surface area, biocompatibility, electrochemical activities, chemical and photochemical stability, high-electron communicating features, non-toxicity, ease of syntheses, and so on. Because of its various interesting properties, ZnO nanomaterials have been used for various applications ranging from electronics to optoelectronics, sensing to biomedical and environmental applications. Further, due to the high electrochemical activities and electron communication features, ZnO nanomaterials are considered as excellent candidates for electrochemical sensors. The present review meticulously introduces the current advancements of ZnO nanomaterial-based chemical sensors. Various operational factors such as the effect of size, morphologies, compositions and their respective working mechanisms along with the selectivity, sensitivity, detection limit, stability, etc., are discussed in this article., Competing Interests: The authors declare no conflict of interest.

A simple and efficient method has been described to synthesize the hitherto unknown imidazo[1,2-a]pyridine selenides (5a-l) by reaction of 2-chloroimidazo [1,2-a]pyridines with aryl/heteroaryl selenols, generated in situ by reduction of various diselenides with hypophosphorous acid. The crystal structures of 3-nitro-2-(phenylselanyl)-imidazo[1,2-a]pyridine (5a), 2-(mesitylselanyl)-3-nitro-imidazo[1,2-a]pyridine (5d) and 3-nitro-2-(pyridin-2-ylselanyl)-imidazo[1,2-a]pyridine (5e) were confirmed by X-ray crystallography and the DFT calculations were performed to determine various structural parameters which were correlated with the X-ray crystal structures. The synthesized compounds were subjected to antimicrobial evaluation and it was found that compounds 5a and 5j were active against gram negative bacterium Escherichia coli whereas compound 5e was active against different fungal strains. Time kill assay was performed to understand the microbial activity of synthesized organoselenium compounds and the toxicity of these compounds was evaluated against human cell lines. Synergistic effects of active compounds 5a and 5e were tested with existing antibiotic drugs which exhibited that the antibiotic combination with synthesized organoselenium compounds efficiently enhanced the antimicrobial activity., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

In the title compound, C11H9NO2Se, the pyridine and phenyl rings are almost perpendicular, with the dihedral angle between their mean planes being 79.16 (7)°. In the crystal, the mol-ecules pack so as to form ruffled sheets in the (110) plane connected by weak C-H⋯O inter-actions. In addition, there are weak π-π inter-actions between the mean planes of both the phenyl [centroid-centroid perpendicular distance of 3.591 (2) Å and slippage of 1.854 (2) Å] and pyridine rings [centroid-centroid perpendicular distance of 3.348 (2) Å and slippage of 1.854 (2) Å].

Highly luminescent water soluble CdTe quantum dots (QDs) were synthesized and conjugated with anti-HbA1c antibody to generate specific nanobioprobe. A sandwich immunoassay model was employed using capture HbA1c antibody as a specific receptor molecule and the QD-labeled secondary antibody as a dual (fluorescence cum electrochemical) tracer to quantify the concentration of HbA1c. A linear increase in current was observed for HbA1c analytical standards with a R(2) value of 0.990 and coefficient of variance ~5%. A comparison between HPLC and dual immunoassay for clinical samples showed a correlation coefficient of 89% and 96% for fluorescence and electrochemical detection methods respectively. The QD-based immunoassay shows great promise for rapid reproducible and cost effective analysis of HbA1c in clinical samples., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements for determination of specific diabetic biomarker glycated hemoglobin (HbA1c) using functionalised gold nanoparticles as bioprobes is reported. The assay exhibited an excellent sensitivity based on absorbance and zeta potential measurements showing the dynamic response range from 0.001-0.004 mg mL(-1) for HbA1c with a detection limit of 0.0015 mg mL(-1).

The use of multiple drug regimes for the treatment of tuberculosis is restricted because of the degradation of Rifampicin in the presence of Isoniazid. In the present report, the microemulsion comprising Tween 80/ethanol/oleic acid/Buffer (pH 7.4) has been investigated for encapsulating Rifampicin (RIF), Isoniazid (INH), and Pyrazinamide (PZA) in different combinations. The main idea is to use the compartment of different domains of microemulsion for encapsulating drugs of different solubilties. The structural changes in the microstructure of microemulsion have been investigated in the light of the changes occurring in the presence of ATDs (anti-Tb drugs) in binary or ternary mixtures through conductivity and viscosity. Optical microscopy and (1)H NMR helped in estimating the shape and location of ATDs in microemulsion system. Electronic spectroscopy has been utilized qualitatively and quantitatively for understanding the stability and release of RIF from the composed formulation with various binary or ternary mixtures. Dissolution and release kinetics have been carried out to get an idea on the release of drugs from microemulsion formulation. ATDs in single and mixed drug formulations followed non-Fickian release behavior except for RIF in pH 7.4 release medium. The investigations employed have given us a fair success to predict not only the stability but also the release mechanism of ATDs in single and mixed drug formulations., (2009 Wiley-Liss, Inc. and the American Pharmacists Association)

The microemulsion composed of oleic acid, phosphate buffer, ethanol, and Tween (20, 40, 60, and 80) has been investigated in the presence of antitubercular drugs of extremely different solubilities, viz. isoniazid (INH), pyrazinamide (PZA), and rifampicin (RIF). The phase behavior showing the realm of existence of microemulsion has been delineated at constant surfactant/co-surfactant ratio (K (m) = 0.55) with maximum isotropic region resulting in the case of Tween 80. The changes in the microstructure of Tween 80-based microemulsion in the presence of anti-TB drugs have been established using conductivty (sigma) and viscosity (eta) behavior. The optical microscopic images of the system help in understanding the effect of dilution and presence of drug on the structure of microemulsion. Partition coefficient, particle size analysis, and spectroscopic studies (UV-visible, Fourier transform infrared, and 1H NMR) have been performed to evaluate the location of a drug in the colloidal formulation. To compare the release of RIF, PZA, and INH from Tween 80 formulation, the dissolution studies have been carried out. It shows that the release of drugs follow the order INH>PZA>RIF. The kinetics of the release of drug has been analyzed using the Korsmeyer and Peppas equation. The results have given a fair success to predict that the release of PZA and INH from Tween 80 microemulsion is non-Fickian, whereas RIF is found to follow a Fickian mechanism.

In this study, we have monitored the formation of CdS and HgS nanoparticles (NPs) using a precipitation method in the presence of surface-active agents. Three surfactants were tested to analyze the dependence of various parameters such as size, growth rate, photoluminescence (PL) emission and polydispersity of NPs on surfactant structure. Optical absorption spectroscopy was mainly used to estimate the optical bandgap and the size of NPs. The surfactant-induced quenching of PL intensity was found to be consistent with the different tendencies of the surfactants to act as Lewis acids towards these surfaces. The time-evolution of the absorbance suggested that the nucleation and growth rates markedly vary in a first-order fashion w.r.t. Cd(2+) and Hg(2+) salt concentration in excess of sulfide ions. The differences in the stabilization ability of the surfactants are discussed in reference to their structure-dependent adsorption behavior onto the particles. The comparative aspects of the different properties of CdS and HgS NPs prepared with identical methodology are presented in terms of metal cation-surfactant interactions. Changes in UV-vis and PL spectra during nucleation and growth of NPs were used to establish the possible mechanisms for the adsorption of surfactant molecules on the particle surface to restrict the unlimited growth.

A U-type microemulsion of Brij 96 has been characterized with respect to the change in cosurfactant, oil chain length on dilution, water solubility, and water solubilization capacity. The phase behavior of the systems has been mapped with different oils. Several techniques, viz., conductivity, optical microscopy, dilution method, absorption, and FT-IR spectroscopy, have been used for microemulsion analysis. The equilibrium within the microemulsion droplets and liquid crystals has been visualized using optical microscopy. The microemulsions have evidenced volume-induced conductance percolation in all the cosurfactants (n2-n6 alcohols). The energetics of transfer of alcohol from the bulk oil to the interface has been determined through dilution method. To gain insight into the microenvironment of microemulsion, two optical probes, hydrophilic (Methyl orange) and hydrophobic (Nile red), have been utilized in absorption spectroscopy. Lastly, FT-IR has been explored to observe the state and dissolution behavior of water with increasing weight fraction.

We exploited the added degree of compositional freedom provided by mixed AOT/lecithin surfactants in reverse isooctane microemulsion to demonstrate that a small amount of added lecithin significantly enhances the solubility of organodiselenides over that in AOT reverse isooctane microemulsions alone. Conductivity results show that the added lecithin significantly increases the solubility of four different organodiselenides and raises the temperature required to induce percolation. FTIR, (1)H NMR, and UV-visible techniques were utilized to gain insight into the interactions of organodiselenides, AOT and lecithin headgroups with water in the micellar core. The information obtained from these experiments was used to design a novel synthetic route for preparing 4-chloro-2-(naphthalen-2-ylselanyl) pyrimidine in reverse microemulsion.

Spectral and physiochemical behavior of water/sodium bis-(2-ethylhexyl)sulfosuccinate (AOT)/isooctane (ME-I) and water/AOT+lecithin (LC)/isooctane (ME-II) microemulsions has been investigated in the presence of organodiselenides. It was found that the OH, CO and C-O-C FTIR stretching frequency of the formulated microemulsions change with the addition of organodiselenides. Interaction with Acridine Orange (AO) indicates organodiselenide presence at the interface. Estimates of the micropolarities of the microemulsions at different water contents were carried out in terms of an empirical polarity parameter E(T)(30). The values increase with the increase in omega = [H(2)O]/[surfactant]. The emission spectra of AO reveal the quenching capacities of the added organodiselenides. The temperature induced percolation process has also been studied. The results indicate a subsequent increase in solubilization of organodiselenide in ME-II as compared to ME-I.

Colloidal nanodispersions of ZnS have been prepared using aqueous micellar solution of two cationic surfactants of trimethylammonium/pyridinium series with different head groups i.e., cetyltrimethylammonium chloride (CTAC) and cetyltrimethylpyridinium chloride (CPyC). The role of these surfactants in controlling size, agglomeration behavior and photophysical properties of ZnS nanoparticles has been discussed. UV-visible spectroscopy has been carried out for determination of optical band gap and size of ZnS nanoparticles. Transmission electron microscopy and dynamic light scattering were used to measure sizes and size distribution of ZnS nanoparticles. Powder X-ray analysis (Powder XRD) reveals the cubic structure of nanocrystallite in powdered sample. The photoluminescence emission band exhibits red shift for ZnS nanoparticles in CTAC compared to those in CPyC. The aggregation behavior in two surfactants has been compared using turbidity measurements after redispersing the nanoparticles in water. In situ evolution and growth of ZnS nanoparticles in two different surfactants have been compared through time-dependent absorption behavior and UV irradiation studies. Electrical conductivity measurements reveal that CPyC micelles better stabilize the nanoparticles than that of CTAC. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11671-009-9377-8) contains supplementary material, which is available to authorized users.

This study investigated the water solubility enhancements of organochalcogen compounds, viz. bis(diphenylmethyl)diselenide [(C6H5)2CHSe]2 and 3,3'-dibromo-4,4'-dimethyl-2-dipyridyl diselenide [C12H10N2Se2Br2] in micellar media. Two cationic and one nonionic surfactants possessing the same hydrocarbon tail, namely hexadecyltrimethylammonium bromide (C16Br), hexadecyltrimethylammonium chloride (C16Cl), and polyoxyethylene(20)mono-n-hexadecyl ether (Brij 58), in their single as well as equimolar binary and ternary mixed states have been used. Solubilization capacity has been evaluated in terms of the molar solubilization ratio and the micelle water partition coefficients. The association constants between the solubilizate molecules and that of micelle and the average number of solubilizate molecules per micelle have also been quantified. The results showed that cationic surfactants exhibit less solubilization as compared to nonionic surfactant. The mixing effects of surfactants on micelle formation and solubilization efficiencies have also been discussed. It has been observed that cationic-nonionic binary combinations showed better solubilization capacity as compared to pure cationic, nonionic, or cationic-cationic binary mixtures. An equimolar cationic-cationic-nonionic ternary surfactant system provides higher solubilization than cationic-cationic but lowers than their cationic-nonionic counterpart. In addition, Fourier transform infrared has been employed with fair success to predict the information regarding the aggregates and the mechanism of docking of the surfactant and the chalcogenides in the system. The analysis has provided valuable information for the selection of mixed surfactants for solubilizing water-insoluble compounds. Certainly the solubilization ability of these surfactants is not simply related to molar capacity. The results give sufficient encouragement to warrant more detailed investigation of the features of surfactant properties that affect solubilization.

The influence of various water-glycol mixed solvents on the self-assembly of 1-hexadecylpyridinium chloride (CPyCl) was investigated using electrical conductivity and spectroscopic measurements. Temperature studies were performed in aqueous mixtures of ethylene, diethylene, triethylene and tetraethylene glycols (abbreviated as EG, DEG, TEG and TeEG, respectively). The correlation among critical micellization concentration (cmc) and degree of ionization (beta) was discussed in term of thermodynamic parameters or the changes in the Gibbs free energy, enthalpy and entropy upon micelle formation (DeltaG(m)(0), DeltaH(m)(0) and DeltaS(m)(0)). The differences in the Gibbs energies of micellization of CPyCl between water and binary solvents were determined to evaluate the influence of the cosolvent. This study allowed us to conclude that the ability of glycols to act, as a structure breaker and its interaction with the surfactant hydrophilic groups are the controlling factors of the micellization process. The effect of cosolvents on the size of the aggregates was analyzed by means of density measurements. Micellar micropolarity and solute solvent parameters were examined spectrophotometrically using methyl orange (MO) as a probe. The increase in micellar microviscosity was revealed from fluorescence measurements. The mechanism of docking of surfactant and the probe molecules in the system were obtained by using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy.

Synthesis of semiconductor nanoparticles with new photophysical properties is an area of special interest. Here, we report synthesis of ZnS nanoparticles in aqueous micellar solution of Cetyltrimethylammonium bromide (CTAB). The size of ZnS nanodispersions in aqueous micellar solution has been calculated using UV-vis spectroscopy, XRD, SAXS, and TEM measurements. The nanoparticles are found to be polydispersed in the size range 6-15 nm. Surface passivation by surfactant molecules has been studied using FTIR and fluorescence spectroscopy. The nanoparticles have been better stabilized using CTAB concentration above 1 mM. Furthermore, room temperature absorption and fluorescence emission of powdered ZnS nanoparticles after redispersion in water have also been investigated and compared with that in aqueous micellar solution. Time-dependent absorption behavior reveals that the formation of ZnS nanoparticles depends on CTAB concentration and was complete within 25 min.

The effect of the addition of cyclodextrins (CD) viz., alpha-, beta-, HPbeta- and gamma-CD to the aqueous solutions of the most widely prescribed anti-inflammatory drug, diclofenac sodium (DS), has been fully investigated by means of spectroscopic (UV-vis, steady-state fluorescence, (1)H NMR and ROESY) and thermodynamic (conductivity) techniques. The global picture of the results indicates that diclofenac sodium penetrates the CD cavity. The apparent association constants for all the inclusion complexes were estimated from fluorescence data. Conductivity measurements of aqueous solutions of diclofenac sodium were performed both as a function of DS concentration and CD concentration, at different temperatures ranging from 15 to 40 degrees C. Results suggested the existence of 1:1 complex between DS and CD. The thermodynamics of the system was discussed in terms of change in Gibbs free energy. Free energy of the DS/W system was found to decrease on addition of cyclodextrin, which points towards the energetically favorable interactions between drug and cyclodextrin molecules in solution phase. (1)H NMR chemical shift changes and ROESY spectra provide powerful means for probing CD:DS interactions.

In this work, an attempt has been made to synthesize well-distributed stable selenium (Se) particles of nanosize dimensions via an aqueous micellar solution by the assistance of surfactants of two different polarities (anionic, sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and cationic, hexadecyltrimethylammonium bromide (CTAB)). The morphology of the particles was examined with transmission electron microscopy (TEM). X-ray analysis reveals that the particles have a monoclinic structure. The band gap of the particles was determined from UV-visible optical spectroscopic results. The size variation was estimated by employing a quantum confinement effect equation. The evolution of the selenium nanoparticles in AOT and CTAB micellar media was corroborated with the time-dependent absorption spectra. The influence of hydrazine hydrate concentrations on the formation kinetics of Se nanoparticles was also investigated. The capping ability of the surfactants has been quantitatively evaluated from Fourier transform infrared (FTIR) studies.

We report a novel strategy for the synthesis of aqueous stable, carboxylated gold nanoparticles (GNPs) by using glutamic acid as the reducing agent. The ratio of chloroaurate ions, AuCl(-)(4) to glutamic acid was optimized in the reaction medium to obtain monodispersed GNPs. Glutamic acid reduced gold nanoparticles were characterized by UV-visible, FTIR, dynamic light scattering and transmission electron microscopy, which demonstrated high stability in aqueous solution over a period of time indicating stabilization via surface-bound amino acid. Functionalized nanoparticles were conjugated with protein molecules through electrostatic attraction between the surface-terminated negatively charged carboxylate groups (COO(-)) of glutamic acid and the positively charged amino groups (NH(+)(3)) of the protein. The conjugation efficiency of the GNP:protein conjugates was confirmed qualitatively and quantitatively through gel electrophoresis and critical flocculation concentration analysis. The interaction between functionalized GNPs with protein molecules was investigated using fluorescence spectroscopy showing the fluorescence quenching of the tryptophan residues of protein molecules after conjugation. Circular dichroism (CD) studies of the conjugates confirmed that the protein undergoes a more flexible conformational state on the boundary surface of GNPs after conjugation. There was substantial conformational transition from alpha-helix to beta-sheet structure after conjugation of protein to GNPs.

In this work, we report the effect of concentration of bovine serum albumin (BSA) on the micellization of a cationic surfactant, dodecyldimethylethylammonium bromide (DDAB). Several samples covering a wide range of concentrations of protein and surfactant have been investigated. The interactions between the moieties are investigated by measuring fluorescence quenching of BSA molecules. The aggregation number of DDAB micelles is found to be small in the presence of BSA. The formation of DDAB-BSA complex is confirmed by FTIR. Absorbance spectroscopy indicates that at higher concentration, the conformational stability of BSA in DDAB is higher. The viscosity data for protein-surfactant systems confirm conformational changes in protein chains induced by the surfactant. The cmc values for DDAB increase with increasing concentration of BSA. At higher temperatures the micellization-complexation becomes enthalpy-dominated.

Conductivity, static fluorescence and (1)H NMR measurements have been carried out to study the micellar behavior of aqueous solutions of dodecyldimethylethylammonium bromide (DDAB), dodecyltrimethylammonium chloride (DTAC) and tetradecyltrimethylammonium chloride (TDAC) in absence and presence of alpha-cyclodextrin (alpha-CD), beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HPbeta-CD) and gamma-cyclodextrin (gamma-CD). The conductivity measurements were carried out at 298.15 K. The influence of cyclodextrins on the micellar parameters, such as cmc* (apparent critical micellar concentration), beta (degree of ionization) have been analyzed. Thermodynamics of the systems was discussed in terms of the change in standard free energy of micellization, DeltaG(m)(0). Micellization was found to be less spontaneous in presence of cyclodextrins. The fluorescence intensity of the surfactant solutions is enhanced by the addition of cyclodextrins. The association constants obtained from conductivity and fluorescence data suggest the binding of gamma-CD with the surfactants to be strongest among all the cyclodextrins used. (1)H NMR chemical shift changes provide powerful means for probing the cyclodextrin-micellar interactions and inclusion of surfactant is shown by the change in the chemical shift of some of the guest and host protons in comparison with the chemical shifts of the same protons in the free compounds.

The aggregation behavior of cetylpyridinium chloride (CPyCl) in N,N-dimethylformamide (DMF)-water mixed solvents was investigated using electrical conductivity and spectroscopic techniques. Micellar and thermodynamic parameters (DeltaG(m)(0), DeltaH(m)(0), DeltaS(m)(0) and Delta(m)C(p)(0)) were obtained from the temperature dependence of critical micelle concentrations in various aqueous mixtures of DMF. The differences in the Gibbs energies of micellization of CPyCl between water and binary solvents were determined to evaluate the influence of the cosolvent. The effect of cosolvent on the Krafft temperature (K(T)) and on the aggregation number was also analyzed. Micellar micropolarity was examined spectrophotometrically using two different probes, methyl orange (MO) and methylene blue (MB), and was found to increase with DMF addition, accompanied by an enhanced solvation. The mechanism of docking of surfactant and the probe molecules in the system were obtained by using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy.

In this work, we report the size tunable synthesis of water-dispersed gold nanoparticles by using octadecylamine (ODA) as the reducing agent, that electrostatically complexes with the chloroaurate ions, reduces them, and subsequently caps the gold nanoparticles. Amine-capped gold nanoparticles, thus formed, were subsequently coordinated with a secondary monolayer of an anionic surfactant, sodium bis(2-ethylhexyl)-sulfosuccinate (AOT) which helps in providing sufficient hydrophilicity to the gold nanoparticles. Functionalized gold nanoparticles were characterized by UV-vis, IR spectrophotometric, dynamic light scattering, zeta-potential and transmission electron microscopic techniques, which demonstrated high stability of gold nanoparticles in aqueous media, indicating stabilization via bilayers of ODA and AOT. The gold nanoparticles were further conjugated with a protein (bovine serum albumin) and the interaction was investigated by circular dichroism studies as well as by measuring the fluorescence quenching of the tryptophan residues of protein molecules after the binding of nanoparticles to specific sites of the protein. The binding constant and the stoichiometry values indicated that the particles with larger core size are less site-specific but show higher binding affinity with protein molecules. The use of a bio-compatible synthetic process and the stabilization of the gold nanoparticles by ODA and AOT are interesting from the point of view of making bioprobes for life science applications.

Purpose: The purpose of present study is to formulate microemulsion composed of oleic acid, phosphate buffer, Tween 80, ethanol and to investigate its potential as drug delivery system for an antitubercular drug isoniazid., Materials and Methods: The pseudo-ternary phase diagram (Gibbs Triangle) was delineated at constant surfactant/co-surfactant ratio (Km 0.55). Changes in the microstructure were established using conductivity (sigma), viscosity (eta), surface tension (gamma) and density measurements. Dissolution studies and particle size analysis were carried out to understand the release of isoniazid from the microemulsion formulation. Further, partitioning studies and spectroscopic analysis (FT-IR and (1)H NMR) was performed to evaluate the location of drug in the colloidal formulation., Results: Physico-chemical analysis of microemulsion system showed the occurrence of structural changes from water-in-oil to oil-in-water microemulsion. It has been observed that the microemulsion remained stable after the incorporation of isoniazid (in terms of optical texture, pH and phase separation). The changes in the microstructure of the microemulsion after incorporation of drug was analyzed on the basis of partition studies of isoniazid in microemulsion components and various parameters viz pH, sigma, eta,gamma. In addition, the particle size analysis indicates that the microemulsion changes into o/w emulsion at infinite dilution. The spectroscopic studies revealed that most of the drug molecules are present in the continuum region of an o/w microemulsion. Dissolution studies infer that a controlled release of drug is expected from o/w emulsion droplet. In the present system the release of isoniazid from microemulsion was found to be non-Fickian., Conclusion: The present Tween based microemulsion appears beneficial for the delivery of the isoniazid in terms of easy preparation, stability, low cost, sustained and controlled release of a highly water soluble drug.

The purpose of present study was to formulate microemulsion composed of oleic acid+phosphate buffer (PB)+Tween 80+ethanol and to investigate its potential as drug delivery system for an antitubercular drug rifampicin. The pseudo-ternary phase diagram has been delineated at constant surfactant/cosurfactant ratio (K(m) 0.55). Conductivity (sigma) and viscosity (keta) studies with variation in Phi (weight fraction of aqueous phase) and omega (molar concentration ratio) show the occurrence of structural changes from water-in-oil (w/o) microemulsion to oil-in-water (o/w). Along with the solubility and partition studies of rifampicin in microemulsion components, the changes in the microstructure of the microemulsion after incorporation of drug have been evaluated using pH, sigma and keta studies. The results have shown that the microemulsion remained stable after the incorporation of rifampicin (in terms of optical texture and phase separation). In addition, the particle size analysis indicates that the microemulsion changes into o/w emulsion at infinite dilution. Dissolution studies infer that a controlled release of rifampicin is expected from o/w emulsion droplet.

The well-characterized, monodisperse nature of reverse micelles formed by sodium bis-(2-ethylhexyl)sulfosuccinate/water/isooctane and their usefulness in assimilating compounds of varied interests have been exploited to investigate the effect of acetyl modified amino acids (MAA) viz., N-acetyl-L-glycine (NAG), N-acetyl-L-aspartic acid (NAA) and N-acetyl-L-cysteine (NAC), on the water pool and physiochemical properties. Non-invasive techniques such as FTIR and UV-vis absorption spectroscopy have been employed to analyze the interactions of MAA with core water and the AOT headgroup. The micropolarities on both sides of AOT interface have further been investigated by UV-vis absorption probes, methyl orange (MO) and methylene blue (MB). The dynamics of water and temperature induced percolation process have also been studied. The MAA molecules have been found to assist the process with the increase in water content where as a contrary behavior has been observed with the increase in temperature. Conductivity results have been further rationalized in terms of scaling equations, which delineate the dynamic nature of the percolation process. The results have also been analyzed in the light of activation energy of the percolation process and thermodynamics of droplet clustering.

A novel method for the preparation of hitherto unknown symmetrical bis(2-halo-3-pyridyl) dichalcogenides (E = S, Se and Te) by the oxidation of intermediate 2-halo-3-pyridyl chalcogenolate, prepared by lithiation of 2-halo pyridines using lithium diisopropylamine is being reported. All the newly synthesized compounds have been characterized through elemental analysis employing various spectroscopic techniques, namely, NMR ((1)H, (13)C, (77)Se), infrared, mass spectrometry, and X-ray crystal structures in representative cases.

The course of temperature percolation in a w/o microemulsion system comprising water/bis(2-ethylhexyl) sulfosuccinate sodium, AOT/isooctane affected by the presence of additives has been investigated. Additives, viz., organic derivatives of chalcogens including dipyridyl diselenide (Py2Se2), diphenyl diselenide (Ph2Se2), and dipyridyl ditelluride (Py2Te2), have been assimilated in the reverse micellar system. Formulations have been studied in terms of (i) the concentration variation of additives, (ii) the change in omega (= [H2O]/[AOT]), and (iii) the change in the nonpolar continuum, S (= [oil]/[AOT]). Phenyl derivatives hinder the percolation, whereas the pyridyl derivative in moderate amounts favors the phenomenon. The estimated values of the critical exponents are lower than those predicted by the dynamic percolation theory. The association model has been implemented to access the thermodynamic parameters of droplet clustering. Pyridyl compounds are expected to alter the rigidity of the surfactant monolayer, which could help to promote the attractive interdroplet interaction. FT-IR spectroscopy has been used to elucidate the changes occurring in the core water in the presence of organic derivatives of chalcogens as the droplet size is increased. Results have been rationalized in terms of the alteration in the physicochemical behavior of the water/AOT/isooctane microemulsion in the presence of additives.