Search

Abstract: Polymers either serve as shielding or capping agents to restrict the nanoparticle size. This study demonstrates the polymer depositions and their effects in synthesis and sharp stabilization of gold nanoparticles (AuNPs) and to develop gold/silver nanoalloys (Au/Ag nanoalloys). Effects of different polymers are tested to justify their role in synthesis and stability of phloroglucinol (PG) coated AuNPs and Au/Ag nanoalloys. Cationic and anionic i.e. [Polydiallyldimethylammonium]+ (PDDA), [Polyethyleneimine]+ (PEI), [Polystyrene sulfonate]2− (PSS) and neutral polymer Polychlorotriflouroethylene (PCTFE) produce praiseworthy stable AuNPs and Au/Ag nanoalloy. To prove polymer effects characterization protocols including UV–vis, Fluorescence (PL), IR and AFM imaging are performed to fully investigate the mechanism and size characteristics of these nanoparticles/nanoalloys. In this study sharp size controlling/sheilding effects were observed particularly with cationic polymers simply through the favorable electrostatic interactions with the terminal ends of PG Potent/significant detection of doxorubicin (DOX, an antileukemic agent) via fluorescence resonance energy transfer (FRET) between PEI shielded AuNPs (AuNPEI) and DOX was achieved upto 10pM level, while PDDA protected AuNPs facilitated the detection of ascorbic acid based on fluorescence enhancement effects in wide range (10–200nM) and with detection limit of 200pM. Similarly sensing performance of PEI stabilized Au/Ag nanoalloys on addition of halides (Cl−, Br-, I−) is evaluated through red shifted SPR along with continuous increase in absorbance and also through AFM. Moreover the addition of halide ions also helped the regeneration of AuNPs by taking away silver from the Au/Ag nanoalloys enabling their detections upto subnanomolar levels. [Copyright &y& Elsevier]

The bioassay-guided fractionation of Daphne retusa Hemsl. has led to the isolation of a new aryl tetrahydronaphthalene lignan derivative named as daphnretusic acid (1), along with six new source compounds such as 5,7-dihydroxyflavone (2), 7-hydroxyflavone (3), 6-methoxyflavone (4), (+) pinoresinol (5), (+) sesamin (6), and β-sitosterol-3-O-β-D-glucopyranoside (7). Their structures were elucidated by 1H NMR, 13C NMR, 1D, 2D NMR, UV, IR, and EIMS analyses. All the fractions (n-hexane, CHCl3, AcOEt, CH3OH, and water) and pure compounds (1–7) were subjected to the assay of urease and α-chymotrypsin inhibitory activities. Chloroform and methanol soluble fractions showed moderate urease inhibition. Compound 2 exhibited significant urease inhibition with IC50 value 60.4 ± 0.72 μM, whereas compounds 1 and 3–7 remained inactive during urease inhibition and α-chymotrypsin bioassays. [ABSTRACT FROM AUTHOR]

Current research efforts have demonstrated the facile hydrothermal oxidative synthetic route to develop highly fluorescent boron/nitrogen co-doped carbon nanodots (CNDs). During this process, N-(4-hydroxyphenyl)glycine served as a source of N doping and a carbon precursor as well, while boric acid H3BO3 is used as an oxidizing agent in the N2 environment. Surface passivation through ultrasonic treatment of CNDs was performed to induce modifications by using various surface passivating agents. Polyethyleneimine (PEI) remarkably enhanced the fluorescence performance and monodispersity of polymerized carbon nanodots (P-CNDs) in aqueous phase with an enhanced quantum yield of 23.71%, along with an increase in size from ~3 nm to ~200 nm. For characterization of CNDs and P-CNDs, UV, infrared, photoluminescence, transmission electron microscopy, x-ray photoelectron spectra, and atomic force microscopy techniques were utilized. Application potentials of synthesized P-CNDs were developed via introduction of protoporphyrin (PPD, a photosensitizer) which has great doping affinity with polymer PEI to switch-off the fluorescence of P-CNDs, leading to the production of dye-doped nanoprobes. Fluorescence resonance energy transfer (FRET) was also observed during dye-doping, and PPD was detected with a limit of detection (LOD, 3s) of 15 pM. The fluorescence recovery of this switched-off nanoprobe was made possible by using Sudan red III (carcinogenic dye), which was oxidized by PPD doped in P-CNDs. Sudan red III was detected in the concentration range of 9.9 pM-0.37 nM. Meanwhile, it was also confirmed that the dye-doped nanoprobe is highly selective and exceptionally sensitive to detect this carcinogenic agent in commercial products with a LOD (3σ) of 90 fM. [ABSTRACT FROM AUTHOR]

Abstract: New dimeric and a trimeric coumarin glucosides namely Daphneretusin A (1) Daphneretusin B (2) along with three known oligomers (3–5) were obtained as a result of bioassay guided fractionation of Daphne retusa Hemsl. Fractions (n-hexane, CHCl3, AcOEt, CH3OH and water) exhibited potent radical scavenging activity in relevant non-physiological bioassays. The structures of isolated compounds were elucidated by UV, IR, EIMS, FAB-MS, 1D, and 2D NMR spectroscopic analysis. [Copyright &y& Elsevier]

Herein, we demonstrate a hydrothermal route to the one-pot synthesis of polymeric mesoporous silica microcubes (P@MSMCs) for the adsorption of heavy metal ions. During the synthesis of P@MSMCs from column silica gel, the roles and combination of the polymer and an etchant were characterized. Moreover, the porosity of P@MSMCs was tailored by adjusting the reaction temperature between 75 °C and 200 °C. The characterization through UV, FTIR, FESEM, XRD, BET, and EDX techniques exhibited that P@MSMCs have a well-ordered mesoporous structure with cubic morphology. The P@MSMCs had a diameter of 2 μm, with an average pore volume and pore size of 0.69 cm3 g−1 and 10.08 nm, respectively. The results indicated that the P@MSMCs have excellent adsorption capacity for Ag(I), Ti(IV), and Zn(II) due to the formation of an aggregated complex. These aggregations led to affordable density difference-based separation of these metal ions through centrifugation, filtration or simple decantation. The removal efficiencies for Ag(I), Ti(IV), and Zn(II) were observed to be 520, 720, and 850 mg g−1, respectively. The kinetic studies demonstrated that the adsorption performance fitted well to the pseudo-second-order kinetic model. The as-synthesized P@MSMCs were stable in the wide pH range of 4–8. Significantly, the recycling or reuse results displayed effective adsorption performance of these P@MSMCs for up to 5 cycles. The adsorption results obtained herein will promote the development of similar strategies for the removal of heavy metal ions from natural water. [ABSTRACT FROM AUTHOR]

In this article, we have synthesized two energetic polyoxometalates(POMs) based ionic liquids. FT-IR, SEM, Electrochemical Impedance Spectroscopy(EIS), Optical Imaging Microscopy(OIM), Rheological analysis, 1HNMR and TGA techniques were used to characterize the corresponding ionic liquids. The acid resistant V@POM-IL and W@POM-IL were used for coating of coin samples. The uncoated coins have shown corrosion with holes production when treated with HCl but POM based ionic liquid coated coins have shown resistant against corrosion and no cracking or hole making was noticed. TGA results of W@POM-IL have shown the minimum weight loss (4.3%) and V@POM-IL has maximum weight loss (9.2%) at highest temperature (500 0C). The corrosion results have shown that un-coated coin has lost weight of 10.67% and coated coins with V@POM-IL and W@POM-IL lost weight with 2.67% and 0.67% respectively. Electrochemical impedance measurement (EIS) has charge transfer ratio of 7.03, 5.23 and 3.78 Ω for W@POM-IL, V@POM-IL and uncoated coin respectively. Rheological analysis with highest elastic modulus (103 Pa) and viscous modulus (103 Pa) of W@POM-IL has given best coating properties. [Display omitted] Corrosion is globally a serious problem for metallic structure and materials in recent decades. When there is interaction between acid and metallic structure, a large amount of corrosion produced. Herein, we have synthesized two energetic polyoxometalates (POMs) based ionic liquids by ion exchange method of smaller cations with larger cations tetraalkyl ammonium (C n H 2 n +1) 4 N+ (n = 7). FT-IR, SEM, Electrochemical Impedance Spectroscopy (EIS), Optical Imaging Microscopy(OIM), Rheological analysis, 1HNMR and TGA techniques were used to characterize the corresponding ionic liquids. Metals can easily be protected by using hydrophobic polyoxometalate-ionic liquids (POM-ILs). At room-temperature the metallic coins were coated with W17@POM-IL andV 3 W 15 @POM-IL, comprising of Dawson anions and quaternary tetraheptylammonium cations (Q7). The acid resistant V 3 W 15 @POM-IL and W 17 @POM-IL were used for coating of coins samples. The un-coated coins have shown corrosion with holes production when treated with HCl while POM-ionic liquid coated coins expressed excellent resistant against corrosion and obviously, no cracking was observed. TGA results of W 17 @POM-IL revealed minimum weight loss of 4.3% and V 3 W 15 @POM-IL has maximum weight loss (9.2%) at highest temperature (500 °C). We have analyzed from the results that coins without coating of POM-ILs have demonstrated the weight loss of 14.3% while the coins coated with V 3 W 15 @POM-IL and W 17 @POM-ILs expressed less weight lost with 3.7% and 1.7% respectively. Furthermore, electrochemical impedance measurement (EIS) has charge transfer ratio of 7.03 Ω, 5.23 Ω and 3.78 Ω for W 17 @POM-IL, V 3 W 15 @POM-IL and un-coated coins respectively. Rheological analysis with highest elastic modulus (103 Pa) and viscous modulus (103 Pa) of W 17 @POM-IL has given best coating properties. Hence, the POM-ILs have variety of applications as coherent, adherent, chemical stability. Comparison of V 3 W 15 @POM-IL with W 17 @POM-IL inferring us that later is best for protection of metal coins against corrosion and damage production with highest thermal stability. [ABSTRACT FROM AUTHOR]