Keywords : Fluorescence

Synthesis of Rod-coil Molecules bearing Oligo-Phenylene Vinylene Motifs: Effect of PEO Chain Lengths on the Evolution of Nanostructures Morphology and their Photophysical Properties

Chetan J. Bhongale; Rahul Chaudhari;Yashwant Pandit

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 731-736
DOI: 10.5185/amlett.2019.0024

The applications of nano-dispersed organic conjugated active compounds or materials as well as current research is concerned mainly with optimization and control of the optical properties, by particle size and supramolecular structure of the particles. The aromatic macromolecules consisting of conjugated rigid rod segment and hydrophilic flexible chain as coil in aqueous solution can aggregate into a variety of supramolecular structures through mutual interaction between aromatic rod and hydrophilic chains of molecules and water. Here we report the synthesis of newer oligo phenylene vinylene (OPV) based rod-coil molecules with varying chain-length polyethylene oxide (PEO) repeating units (n = 8, 17, 45). Formation and photophysical properties of their nanostructures in water are studied comparatively. The nanostructures evolution of these molecules is observed with simple reprecipitation method. The stable nanostructures were formed without addition of any surfactants. The fabricated nanostructures ultimately give the materials with ‘controlled’ aggregation induced enhanced photophysical properties. The self-assembly of such OPV type rod molecules in water without adding any surfactants, therefore, can provide a strategy for the construction of well-defined and stable nanostructures with certain chemical functionalities and physical properties as advanced materials for photonic, electronic and biological applications. Copyright © VBRI Press.

Facile synthesis of graphene quantum dots based on electrochemical method and their application for specific Fe3+ detection

Yang Fu; Runze Liu; Jinfang Zhi

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 614-618
DOI: 10.5185/amlett.2018.2052

A novel electrochemical strategy for economical, environmental-friendly, simple and facile synthesis of glycine functionalized graphene quantum dots (GQDs) based on direct exfoliation and oxidation from graphite rods was reported. The average diameter of as-synthesized GQDs is 30 nm. Due to the rich nitrogen and oxygen functional groups on the surface of GQDs, the GQDs dispersion was bright yellow and further applied in selective detection of ferric ion (Fe 3+ ). A sensor based on photoluminescence quenching of GQDs after adding Fe 3+  has a limit of detection of 3.09 μM, which is lower than the maximum level (0.3 mg/L, equivalent to 5.4 µM) of Fe 3+ permitted in drinking water by the U.S. Environmental Protection Agency (EPA). The fluorescent sensor has a wide linear range of 10–150 μM. Moreover, due to the low cytotoxicity of as-prepared GQDs, this study may provide a new analytical platform for further applications of GQDs in real environmental and biological system.

Conjugate-like addition of soft nucleophiles to 8-alkenylBODIPYs

Enrique Alvarado-Martínez; Eduardo Peña-Cabrera

Advanced Materials Letters, 2018, Volume 9, Issue 6, Pages 426-431
DOI: 10.5185/amlett.2018.1859

Meso-phenylethenylBODIPY 8 was prepared using the Liebeskind-Srogl cross-coupling reaction. The reactivity of 8 was evaluated in the addition of soft nucleophiles observing that, in all the cases studied, the addition took place exclusively at the b-alkene position with good chemical yields under mild conditions. While the starting BODIPY 8 was non-emissive, all of the adducts were highly fluorescent in MeOH, except for meso-coumarinBODIPY 11. However, when the fluorescence of 11 was measured in EtOAc, a 41-fold increase was observed. This behaviour was explained in terms of a photoinduced electron-transfer phenomenon. 

Streptavidin conjugated ZnO nanoparticles for early detection of HIV infection

L. A. Avinash Chunduri; Aditya Kurdekar; Bulagonda Eswarappa Pradeep; Mohan Kumar Haleyurgirisetty; Venkataramaniah K; Indira K. Hewlett

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 472-480
DOI: 10.5185/amlett.2017.6579

Streptavidin labelled fluorescent ZnO nanoparticles have been surface engineered to develop a fluorescent ZnO nanoparticle linked immunoassay (FZLIA) for the sensitive detection of HIV infection. ZnO nanoparticles were synthesized by a single step chemical precipitation method. Cysteine was used to graft carboxyl groups on to the surface of nanoparticles in a single step. Cysteine capped ZnO nanoparticles exhibited fluorescence at 546 nm when excited with 358 nm and FESEM confirmed the particle size to be 50-70 nm. FTIR and TGA confirmed the functionalisation of carboxyl groups by cysteine. The amount of cysteine grafted on the ZnO nanoparticles calculated as 68.1% from TGA analysis indicated the presence of large amount of carboxyl groups. ZnO nanoparticles were conjugated to streptavidin and the same were deployed as fluorescent probes in the development of the FZLIA platform for the early and accurate detection of HIV infection. The linear dose dependent detection range was from 25 pg/mL to 1000 pg/mL. HIV positive and HIV negative plasma samples were tested using FZLIA for the presence of HIV-1 p24 antigen. This immunoassay exhibited no false positive and false negative results with the clinical samples tested. This highly sensitive HIV-1 p24 antigen assay may be useful to improve blood safety by reducing the antibody negative window period in blood donors in resource limited settings where nucleic acid testing is not practical or feasible. This technology can be transferred to a lab-on-chip platform for use in resource limited settings and can also be easily adopted for the detection of other antigens.

Interaction Of Bovine Serum Albumin With Synthetic Spiropyrimidines

Swarup Roy; K.C. Majumdar;Tapan Kumar Das; Sudipta Ponra; Tapas Ghosh

Advanced Materials Letters, 2016, Volume 7, Issue 1, Pages 65-70
DOI: 10.5185/amlett.2016.6081

Study of interaction between synthetic spiropyrimidines (SP) with bovine serum albumin (BSA) was investigated by spectroscopy. The fluorescence of BSA was quenched by SP by means of static quenching mechanism. Using Stern–Volmer analysis of the fluorescence quenching data number of binding sites (n) and binding constants (K) at different temperatures were computed. The thermodynamic parameters enthalpy change (ΔH) and entropy change (ΔS) were calculated using Van’t Hoff equation (ΔH = -95.16 kJ/mol and ΔS = -251.49 J/mol/ K) and the results clearly indicated binding process is enthalpy-driven but entropically disfavored. The weak force van der Waals interaction and hydrogen bonding is responsible for BSA-SP complexation. Synchronous fluorescence, UV-Vis and circular dichroism (CD) spectra proposed possibility of alteration in conformation of BSA in the presence of SP. Using Forster’s non-radiation energy transfer (FRET) theory distance between the donor and the acceptor were found to be <7 nm.  

A Review On CdSe Quantum Dots In Sensing

Pragati Malik; Jyoti Singh; Rita Kakkar

Advanced Materials Letters, 2014, Volume 5, Issue 11, Pages 612-628
DOI: 10.5185/amlett.2014.4562

The primary aim of this review is to survey the literature on the ion sensing ability of quantum dots. Sensing of both cations and anions is important, since both play significant roles in various ecological and biological processes, which makes it important to ensure their concentration at balanced level. Contamination by heavy metal ions and various anions poses a serious threat to humans, aquatic organisms, and to the environment; therefore detection of these ions (in presence of other cations and anions), which are the major cause of environmental pollution is of immense significance at the present time. Owing to their enhanced fluorescence properties and photostability, QDs offer tremendous scope to be used for ion sensing. They offer several advantages over traditional chemical fluorophores. This review throws light on the mechanism adopted by CdSe QDs to act as flourophores. Owing to their enhanced photoluminescence properties, QDs offer selective and sensitive determination of various ions, which is a function of the capping on the surface of the QD nanosensor, i.e. it is possible to tune their sensing ability by changing the capping layer, which influences the QD's interaction with various analytes. Hence, these quantum dots may prove promising candidates in future for sensing approximately all types of analytes.