Edamana Prasad

Bio: Edamana Prasad is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Dendrimer & Ether. The author has an hindex of 27, co-authored 100 publications receiving 2263 citations. Previous affiliations of Edamana Prasad include Texas Tech University & Indian Institutes of Technology.

5FU encapsulated polyglycerol sebacate nanoparticles as anti-cancer drug carriers

Abstract: The majority of anti-cancer drugs fail to reach clinical trials due to their low water solubility. A biocompatible drug delivery system that encapsulates and efficiently delivers hydrophobic drugs to the target site is the need of the hour. This study addresses the issue by focusing on a polymeric polyglycerol sebacate (PGS) nanoparticles loaded with 5-fluorouracil (5FU), a primary line chemotherapy drug for many types of cancers. The generated nanoparticle (PGS-NP) was biocompatible and had minimal cytotoxicity against the MDA-MB-231 and A549 cell lines, even at a high concentration of 100 μg mL−1. The cell viability post treatment with PGS nanoparticles encapsulated with 5FU (PGS-5FU) decreased to as low as around 40% whereas, in the case of treatment with 5FU, the viability percentage increased. The nanoparticles also showed controlled drug release when encapsulated with 5FU. This striking observation suggested that these nanoparticles can improve the efficacy of drug delivery to tumor sites. Apoptosis assay and caspase-3 activity quantification supported these data wherein PGS-5FU treatment showed almost three times caspase-3 activity as compared to control cells. Additionally, throughout all the experiments, MDA-MB-231 cells were more sensitive to PGS-5FU than A549 cells, indicating that these nanoparticles are ideal for breast cancer treatment. In summary, 5FU encapsulated PGS nanoparticles are a potential drug carrier to deliver 5FU efficiently to cancer cells.

Diffusion of Solvent-Separated Ion Pairs Controls Back Electron Transfer Rate in Graphene Quantum Dots

Abstract: In the present study, the stability of the photogenerated, solvent-separated charged states of graphene quantum dots (GQDs) in the presence of N,N-diethylaniline (DEA) has been evaluated in a series of organic solvents. The results indicate that the rate constant for back electron transfer (kBET) from GQD radical anion to DEA radical cation is diffusion-controlled. As a result of the diffusion-controlled back electron transfer (BET), kBET exhibits an inverse exponential relation to (a) the viscosity coefficient (η) of the solvent and (b) the average radius of the graphene quantum dots. An analytical expression for the diffusion-controlled back electron transfer rate constant has been formulated. The dependence of kBET on the diffusion of solvent-separated ion pairs has been evaluated for the first time for quantum dot systems and the results provide an efficient method for enhancing the lifetime of the photogenerated charge-separated states from graphene quantum dots. The present findings can potentially ...

Solvation-Controlled Emission of Divalent Europium Salts

Abstract: Coordination-environment-dependent tuning of luminescence of divalent europium is an emerging topic of research. While it has been extensively demonstrated in the solid state, recent reports indicate similar findings in solution, where emission properties were tuned by altering different ligands and counter anions. In the present study, we demonstrate that differences in solvation shells alter the luminescence properties of divalent europium. Steady-state emission measurements indicate that the emission maxima of EuII salts in dimethoxyethane is red-shifted compared to the maxima in tetrahydrofuran. This shifting was confirmed with three different EuII salts: EuI2, EuBr2, and Eu(OTf)2. UV–visible spectroscopic measurements indicate a marginal difference in absorption spectra of EuII salts in tetrahydrofuran and dimethoxyethane, ruling out the possibility that a difference in ground-state geometry is responsible for the solvation-induced emission shift. Time-dependent density functional theory studies further support this conclusion. Relaxation of the excited state in dimethoxyethane is a postulated mechanism behind the red-shifted emission. The current study demonstrates a straight-forward path toward tuning the emission properties of EuII without altering light absorption.

Conducting and superhydrophobic hybrid 2D material from coronene and pyrene

Abstract: Graphdiyne, a recent addition to the family of 2D covalent organic nanosheet structures, is known for its structural stability and potential applications in catalysis, sensors, electronics and optoelectronics. The design and synthesis of graphdiyne analogues with well-defined structures and useful applications remains a challenging task for materials chemists. Herein, we report a novel, well-defined 2D nanosheet from a coronene–pyrene hybrid 2D material (COPY), with extended π conjugation through acetylenic linkages. The bulk synthesis of the polymeric network has been realized via Sonogashira coupling of 1,4,7,10-tetrabromocoronene and 1,3,6,8-tetraethynylpyrene. The nanosheet is characterized using HR-SEM, TEM, AFM, FT-IR, Raman, XRD and XPS techniques. Electrostatic potential mapping of COPY reveals complete π electron delocalization over the 2D framework with a relatively high electro-negative potential at the acetylenic linkages. Computational study reveals the high planarity of the structure as a result of Cs point group symmetry and the material has a tunable bandgap with respect to the number of coronene and pyrene rings. Extended conjugation in the material accounts for the significant electrical conductivity (1.16 × 10−3 S m−1) that is one order of magnitude higher than that of graphdiyne and comparable to the previously reported pyrediyne (a graphdiyne analogue). The large surface area and porous nature of the material were utilized for oil–water separation by incorporating melamine sponge and cotton fabric. The COPY-incorporated cotton fabric exhibited an oil–water separation efficiency of 95.5%. More importantly, the COPY in the melamine sponge exhibited superhydrophobicity with a contact angle of 154.4°. The oil–water separation efficiency, significant electrical conductivity and superhydrophobicity of the material suggest that COPY can be a valuable candidate in the field of water repellency, anti-corrosion and biosensing.

Principles Of Fluorescence Spectroscopy

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Self-Healing Hydrogels

Abstract: Over the past few years, there has been a great deal of interest in the development of hydrogel materials with tunable structural, mechanical, and rheological properties, which exhibit rapid and autonomous self-healing and self-recovery for utilization in a broad range of applications, from soft robotics to tissue engineering. However, self-healing hydrogels generally either possess mechanically robust or rapid self-healing properties but not both. Hence, the development of a mechanically robust hydrogel material with autonomous self-healing on the time scale of seconds is yet to be fully realized. Here, the current advances in the development of autonomous self-healing hydrogels are reviewed. Specifically, methods to test self-healing efficiencies and recoveries, mechanisms of autonomous self-healing, and mechanically robust hydrogels are presented. The trends indicate that hydrogels that self-heal better also achieve self-healing faster, as compared to gels that only partially self-heal. Recommendations to guide future development of self-healing hydrogels are offered and the potential relevance of self-healing hydrogels to the exciting research areas of 3D/4D printing, soft robotics, and assisted health technologies is highlighted.

Fluorescence and colorimetric chemosensors for fluoride-ion detection.

Abstract: Detection Ying Zhou,†,‡ Jun Feng Zhang, and Juyoung Yoon*,† †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea ‡Key Laboratory of Medicinal Chemistry for Natural Resource, School of Chemical Science and Technology, Yunnan University, Kunming, 650091, P. R. China College of Chemistry and Chemical Engineering, Yunnan Normal University, Kunming 650500, P. R. China

The dry-style antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography: a superhydrophobic state with high adhesive force

Abstract: Fogging occurs when moisture condensation takes the form of accumulated droplets with diameters larger than 190 nm or half of the shortest wavelength (380 nm) of visible light. This problem may be effectively addressed by changing the affinity of a material’s surface for water, which can be accomplished via two approaches: i) the superhydrophilic approach, with a water contact angle (CA) less than 5°, and ii) the superhydrophobic approach, with a water CA greater than 150°, and extremely low CA hysteresis. To date, all techniques reported belong to the former category, as they are intended for applications in optical transparent coatings. A well-known example is the use of photocatalytic TiO2 nanoparticle coatings that become superhydrophilic under UV irradiation. Very recently, a capillary effect was skillfully adopted to achieve superhydrophilic properties by constructing 3D nanoporous structures from layer-by-layer assembled nanoparticles. The key to these two “wet”-style antifogging strategies is for micrometer-sized fog drops to rapidly spread into a uniform thin film, which can prevent light scattering and reflection from nucleated droplets. Optical transparency is not an intrinsic property of antifogging coatings even though recently developed antifogging coatings are almost transparent, and the transparency could be achieved by further tuning the nanoparticle size and film thickness. To our knowledge, the antifogging coatings may also be applied to many fields that do not require optical transparency, including, for example, paints for inhibiting swelling and peeling issues and metal surfaces for preventing corrosion. These types of issues, which are caused by adsorption of moisture, are hard to solve by the superhydrophilic approach because of its inherently “wet” nature. Thus, a “dry”-style antifogging strategy, which consists of a novel superhydrophobic technique that can prevent moisture or microscale fog drops from nucleating on a surface, is desired. Recent bionic researches have revealed that the self-cleaning ability of lotus leaves and the striking ability of a water-strider’s legs to walk on water can be attributed to the ideal superhydrophobicity of their surfaces, induced by special microand nanostructures. To date, the biomimetic fabrication of superhydrophobic microand/or nanostructures has attracted considerable interest, and these types of materials can be used for such applications as self-cleaning coatings and stain-resistant textiles. Although a superhydrophobic technique inspired by lotus leaves is expected to be able to solve such fogging problems because the water droplets can not remain on the surface, there are no reports of such antifogging coatings. Very recently, researchers from General Motors have reported that the surfaces of lotus leaves become wet with moisture because the size of the fog drops are at the microscale—so small that they can be easily trapped in the interspaces among micropapillae. Thus, lotuslike surface microstructures are unsuitable for superhydrophobic antifogging coatings, and a new inspiration from nature is desired for solving this problem. In this communication, we report a novel, biological, superhydrophobic antifogging strategy. It was found that the compound eyes of the mosquito C. pipiens possess ideal superhydrophobic properties that provide an effective protective mechanism for maintaining clear vision in a humid habitat. Our research indicates that this unique property is attributed to the smart design of elaborate microand nanostructures: hexagonally non-close-packed (ncp) nipples at the nanoscale prevent microscale fog drops from condensing on the ommatidia surface, and hexagonally close-packed (hcp) ommatidia at the microscale could efficiently prevent fog drops from being trapped in the voids between the ommatidia. We also fabricated artificial compound eyes by using soft lithography and investigated the effects of microand nanostructures on the surface hydrophobicity. These findings could be used to develop novel superhydrophobic antifogging coatings in the near future. It is known that mosquitoes possess excellent vision, which they exploit to locate various resources such as mates, hosts, and resting sites in a watery and dim habitat. To better understand such remarkable abilities, we first investigated the interaction between moisture and the eye surface. An ultrasonic humidifier was used to regulate the relative humidity of the atmosphere and mimic a mist composed of numerous tiny water droplets with diameters less than 10 lm. As the fog was C O M M U N IC A IO N