Showing papers by "Edamana Prasad published in 2017"

H-Bonding controls the emission properties of functionalized carbon nano-dots

Abstract: Bathochromic and hypsochromic shifts in the photo-luminescent spectra of doped and functionalized carbon nano-dots (CDs) arise due to the complex interaction between CDs and the solvent molecules around them. Nitrogen-functionalized carbon nano-dots (N-CDs) were synthesized from citric acid and urea using microwave assisted hydrothermal methods. Optical studies (absorption and photoluminescence) from the as-synthesized N-CDs were carried out in polar protic, aprotic and non-polar solvents. When excited at 355 nm, blue photoluminescence (PL) was observed from the N-CDs dispersed in polar aprotic solvents while green emission was observed in polar protic solvents. In addition to the general solvent effect, the analysis of the luminescence spectra in protic solvents suggests that hydrogen bonding plays a crucial role in regulating the photophysical characteristics of the system. Temperature dependent PL studies and time correlated single photon counting experiments in various solvent dispersions of N-CDs support the role of hydrogen bonding. This indicates that these results depend on the specific interactions observed from the N-CDs and can be thought of as the primary driving force which is then followed by solvent properties like dipole moments. Both the Lippert-Mataga model and Kamlet-Taft parameters were used to support the photophysical properties observed from N-CDs.

In vitro study of a glucose attached poly(aryl ether) dendron based gel as a drug carrier for a local anaesthetic

Abstract: Herein, we describe the design, synthesis and drug release kinetics of a low molecular weight gel based on an aryl ether dendron, under in vitro conditions. The first generation dendron self-assembles and forms gels, resulting in a robust three-dimensional fibrous network, to facilitate controlled release of molecules. While aryl ether dendrons are known for their enhanced self-assembling propensity, these systems have not been used for drug release studies. The self-assembled system was characterized using SEM, TEM, rheology and PXRD experiments. In vitro cytotoxicity of the dendron gel was studied and the results show that the dendron gel is biocompatible. The effect of gel leaching and the exposure time on NIH/3T3 cells is also studied. Further, the gel based on poly aryl ether dendron derivative (D1) is capable of entrapping model hydrophilic dyes and a local anaesthetic drug (prilocaine hydrochloride), where the D1 gel could effectively entrap about 1.5 mg of prilocaine hydrochloride per 5 mg of gelator. The in vitro drug release suggests that the release kinetics is inversely proportional to the gelator wt%, and the lowest release rate obtained is 1.75 min−n with 0.7 gelator wt%. The release profiles of prilocaine hydrochloride are fitted with the Peppas–Korsmeyer model, and the results depict a non-Fickian diffusion mechanism. These studies indicate that the poly aryl ether dendron based gel shows desirable characteristics and also displays promising possibilities of expanding dendron based drug delivery systems for transdermal applications.

Self-Assembly-Directed Aerogel and Membrane Formation from a Magnetic Composite: An Approach to Developing Multifunctional Materials

Abstract: Herein, we report the preparation of an aerogel and a membrane from a magnetic composite material by tuning the self-assembly at the molecular level. The gel exhibits an excellent oil absorption property, and the membrane shows a remarkable autonomous self-healing property. The composite is formed from an organosilicon-modified poly(amidoamine) (PAMAM) dendrimer, which is linked with iron oxide nanoparticles and poly(vinyl alcohol). Upon the addition of a cross-linker (formaldehyde), the system undergoes a fast self-assembly and gelation process. The aerogel, obtained after drying of the hydrogel, was modified with 1- bromohexadecane at room temperature and utilized for the removal of oil from water with 22.9 g/g absorption capacity. Intriguingly, the same system forms a membrane with 97% autonomous self-healing ability, in the absence of the cross-linker. The membrane was used to remove the salt content from water with an efficiency of 85%. The control experiments suggest that the presence of the magnetic material (iron oxide) plays a key role in the formation of both the aerogel and membrane.

Long lived charge separated states in vinylbenzonitrile substituted derivatives of pyrene and anthracene

Abstract: The present study investigates the photophysical properties of two highly conjugated pyrene and anthracene derivatives viz ( E )-4-(2-(pyren-1-yl) vinyl) benzonitrile (PyCN) and ( E )-4-(2-(anthracen-9-yl) vinyl) benzonitrile (AnCN) in the presence and absence of electron donors such as N , N -diethylaniline (DEA) and N , N -diphenylamine (DPA). The observed rates of back electron transfer (BET) in the case of PyCN-DEA and AnCN-DEA are 1.3 × 10 5 and 4.8 × 10 4 s −1 , respectively, which are 3–4 orders of magnitude lower compared to the well-known pyrene–amine and anthracene–amine systems. Mechanistic investigations indicate that the donor-acceptor systems undergo different pathways in presence of tertiary and the secondary amine. The results indicate that the design strategy is highly efficient in reducing the rate of back electron transfer, which results in long lived charge-separated excited states.

Copper‐Catalyzed Chelation‐Assisted Synthesis of Unsymmetrical Aliphatic Azo Compounds

Abstract: An unprecedented and convenient synthetic approach to a new class of unsymmetrical azo compounds is developed through a chelation-assisted copper-catalysis using cheap commercial reagents. The reactions proceed rapidly at room temperature (typically one hour) and were performed in aqueous medium as well as in solvent-free conditions, delivering structurally diverse alkyl aryl azo compounds in good yields. It has been observed that these novel pyridine hinged azo derivatives exhibit “turn on” fluorescence response in the presence of copper(II) ion in aqueous medium.

Dinuclear cobalt(II) complexes with double phosphate ester bridges and tetradentate ligands having anisole or quinoline appendages

Abstract: Phosphate esters provide a rigid and stable polymeric backbone in nucleic acids Metal complexes with phosphate ester groups have been synthesized as structural and spectroscopic models of phosphate-containing enzymes Dinucleating ligands are used extensively to synthesize model complexes since they provide the support required to stabilize such complexes The crystal structures of two dinuclear CoII complexes, namely bis(μ-diphenyl phosphato-κ2O:O')bis({2-methoxy-N,N-bis[(pyridin-2-yl)methyl]aniline-κ4N,N',N'',O}cobalt(II)) bis(perchlorate), [Co(C12H10O4P)2(C19H19N3O)2](ClO4)2, and bis(μ-diphenyl phosphato-κ2O:O')bis({N,N-bis[(pyridin-2-yl)methyl]quinolin-8-amine-κ4N,N',N'',O}cobalt(II)) bis(perchlorate), [Co(C12H10O4P)2(C21H18N4)2](ClO4)2, with tetradentate 2-methoxy-N,N-bis[(pyridin-2-yl)methyl]aniline (L1) and N,N-bis[(pyridin-2-yl)methyl]quinolin-8-amine (L2) ligands are reported The complexes have similar structures, with distorted octahedral geometries around the metal centres Both are centrosymmetric (Z' = 05), with the CoII centres doubly bridged by diphenyl phosphate ester groups A number of aromatic-aromatic interactions are present and differ between the two complexes as the anisole group in L1 is replaced by a quinoline group in L2 A detailed study of these interactions is presented

Method and apparatus for producing hydrogen gas from water

Abstract: Embodiments herein provide a method for producing hydrogen gas from water. The method includes providing aluminum salt to the water to remove mercury from the water and producing hydrogen gas from the water by reacting the water with aluminum amalgam. The method can be used to produce hydrogen gas from pure water, tap water and salt water.