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.

Transitions in unmodified and modified bitumen using FTIR spectroscopy

Abstract: The transitions in bitumen in the temperature range of 25–75 °C are normally investigated using rheological tools. Considering the complex response of the material in such temperature range, it will be helpful if the precise nature of the material is investigated at the macromolecular level also. In this study, an attempt is made to use FTIR spectroscopy to identify the thermal transitions in unmodified and three modified bitumen. The changes in peak position and intensity of the C–H stretching vibration at 2953, 2923 and 2853 cm−1 were analyzed. Transitions, predominantly solid–solid in nature were identified in the temperature range of 35–65 °C which can be attributed to the change in conformation of the crystalline fraction. While certain peaks distinguished the effect of modification and aging, few other peaks indicated multiple transitions in the solid state of the material. The degree of crystallinity, also calculated from the FTIR spectra, indicated changes in the conformation of the material in the temperature range of 45–55 °C.

Room temperature anthracene excimer emission from self-assembled (aminomethyl)anthracene derivatives in plastic crystalline phase

Abstract: A series of (aminomethyl)anthracene (AMA) derivatives with single alkyl chain substituent (octyl, dodecyl, octadecyl and p-butylaniline) were synthesized and self-assembly of the compounds was analyzed in dichloromethane and solid thin film. Upon heat treatment of the solid thin films, the AMA derivatives exhibit plastic crystalline phase which can be preserved in a glassy state through rapid cooling of the system to room temperature. In the glassy state, the AMA derivatives are arranged in rectangular discotic columnar fashion, where the face-to-face distance between two anthracene moieties is 3.9 A. Steady state and time resolved fluorescence studies were carried out in dichloromethane, which indicate that a fraction of the AMA derivatives form anthracene excimer, upon excitation at 360 nm. Conversely, photoexcitation of the solid thin film at 360 nm leads to the exclusive formation of anthracene excimers due to the close proximity of anthracene units in the discotic columnar arrangement. Furthermore, the self-assembled AMA derivatives were utilized as effective templates for in situ prepared Ag nanoparticles. While the AMA derivatives stabilize the Ag nanoparticles effectively, the excimer emission intensity was quenched in the presence of silver nanoparticles. The experimental results from the present study provide a unique approach for generating anthracene excimer emission from solid thin films at room temperature, which is a rare observation.

Architecting pyrediyne nanowalls with improved inter-molecular interactions, electronic features and transport characteristics

Abstract: Synthesizing graphdiyne analogues with a well-defined structure and desirable band gap is a challenging task. Herein, we present a novel, well-defined and highly structured crystalline π-conjugated nanowall framework, called pyrediyne (pyrene + diyne = pyrediyne), with large in-plane periodicity. The bulk synthesis of the two-dimensional (2D) ultrathin polymeric framework of pyrediyne is achieved via a modified-Glaser–Hay coupling reaction using 1,3,6,8-tetraethynylpyrene. The ultrathin π-conjugated crystalline pyrediyne nanowall is well characterized by Raman, SEM, AFM, HR-TEM and XPS techniques. Electronic structure information reveals the π-conjugated framework to be completely planar with a Cs point group, where a tunable band gap of Eg ∼ 1.17 eV can be achieved depending on the number of pyrene units. The electrostatic potential maps reveal complete π-delocalization of the electron cloud throughout the framework with a high electronegative potential at the acetylenic linkages. This through-bond charge coupling via the conjugated network in conjunction with the charge delocalization via the π⋯π interactions in space accounts for the significant electrical conductivity {σ = 1.23(±0.1) × 10−3 S m−1} of the organic material.

Orange red emitting naphthalene diimide derivative containing dendritic wedges: aggregation induced emission (AIE) and detection of picric acid (PA)

Abstract: Herein we report the synthesis, characterization and photophysical properties of novel naphthalene diimide (NDI) derivatives containing naphthalene units which are covalently attached to either end of the NDI. The self-assembly of such ‘Donor–Acceptor–Donor’ dendritic wedges shows aggregation induced emission (AIE), which in turn results in bright orange red emission from the NDI system, in aqueous medium and solid state. The structure of self-assembly has been analyzed using X-ray diffraction, variable temperature IR and NMR spectroscopy, scanning and transmission electron microscopy, steady state and time resolved emission spectroscopy. The results suggest that the emission quantum yields in the solid state vary inversely proportional to the number of donor units (naphthalene) attached to the NDI core. The NDI derivatives have been utilized to prepare organic nanoparticles (ONPs) in suitable solvent mixtures. Further, the ONPs as well as the solid thin film formed from the NDI derivative were utilized for the detection of picric aid through fluorescence quenching experiments, with a detection limit of 0.90 ppm.

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