Thalappil Pradeep

Bio: Thalappil Pradeep is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Cluster (physics) & Mass spectrometry. The author has an hindex of 76, co-authored 581 publications receiving 24664 citations. Previous affiliations of Thalappil Pradeep include DST Systems & Lawrence Berkeley National Laboratory.

Reply to “Comments on Electric‐Field‐Assisted Growth of Highly Uniform and Oriented Gold Nanotriangles on Conducting Glass Substrates”

Abstract: 2009 WILEY-VCH Verlag Gmb We appreciate the comments of Diao et al. on our recently published paper, which describes the characterization of gold nanotriangles (NTs) using optical absorption spectroscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD). AFM images of the NTs, which confirmed their morphology, were provided, but scanning electron microscopy (SEM) images were not. Here SEM, AFM, and optical images are presented, which suggest that NTs are indeed formed. Each comment has been addressed below. It is well known that artifacts––caused particularly by blunt tips––can appear in AFM measurements. However, after considering the following facts, we are convinced that NTs were genuinely observed. In order to confirm the formation of the NTs, samples were imaged using dynamic force microscopy (DFM, a non-contact AFM technique) at the facilities of another research group (Seiko SPA-400); the results were confirmed for both the parent and the NT surfaces. Various control measurements were performed. Figure 1a–c show AFM images recorded at various stages of growth. NTs of varying size as well as spherical particles can be seen. The particle size increases with the evolution of reaction time. Note that a blunt tip could not have produced images of spherical particles and uniform NTs with sizes that varied systematically as a function of reaction time. Non-contact-mode imaging (using an AFM-CRM 200 microscope, WiTec GmbH) of the NTs was also conducted using a fresh cantilever. Since the tip interacted with the sample for only a short time, degradation of the tip or sample was unlikely. The non-contact-mode topographic and phase AFM images of NTs that were synthesized under optimized conditions are shown in Figure 1d,e. Most of the NTs observed had an edge length of 400–450 nm. There were small variations in the NTdimensions, even with synthesis under optimized conditions. Some areas, which appear as channels void of NTs in between two layers of NTs, are also observed (Fig. 1f). Such an image would not be likely if artifacts were indeed responsible for the results obtained. Other morphologies, such as spheres, are also observed. In addition, it is clear that a large number of lower-lying NTs are stacked and appear to be fused. This is further confirmed by the SEM images. If the tip was worn out or contaminated, the image would have shown separate NTs. However, in this case, the NTs are not well separated, but stacked on top of each other; some of the NTs even lie in different planes. The SEM images taken from different areas of the indium tin oxide (ITO) using a FEI QUANTA-200 SEMmicroscope show the presence of stacked NTs of the same dimensions observed in the AFM images (Fig. 2a,b). Because of the large edge-length/ thickness ratio, the NTs often appear fused and stacked. Corresponding energy dispersive analysis of X-rays (EDAX) data support the formation of Au NTs. The NTs were deformed by the electron beam, as is evident in Figure 2c. In the SEM images, underlying spherical nanoparticles can be clearly seen. The presence of such nanoparticles on different areas of the substrate may explain the increased ratio of the intensities of the (200) and the (111) peaks in the XRD spectra, since diffraction data were taken from very large areas compared to the areas used for the AFM scans. It was possible to increase the edge lengths of the NTs by slow reduction of Au ions on the surfaces of the growing NTs. The sizes of the NTs synthesized according to the reported procedure could be increased by treatment with excess Au3þ and ascorbic acid, allowing imaging of large NTs via optical microscopy (Fig. 2d; WiTec GmbH, CRM 200). Even though several equilateral NTs are observable in such images, their orientations are different from those of the parent NTs. In the UV-vis absorption spectra, the feature at 520 nm can be attributed to the transverse plasmon absorption, as is the case for other anisotropic structures. In addition, possible spherical particles below the surface may contribute to this feature. Only well-structured gold NTs can produce a UV-vis-near-IR absorption spectrum, as indicated in our original paper. Therefore, being able to obtain such a spectrum with characteristic features of gold NTs is in itself a clear indication that NTs are formed. For large numbers of truncated triangles, hexagons, and microplates, the spectra are different. The red-shift in the near-IR absorption spectra with respect to the spectra presented by Shankar et al. may be due to the coupling of the surface plasmon resonances of the triangles, which is caused by the uniform stacking of the individual NTs and their close proximities (as can be seen in the microscopy images). Synthesis of uniform NTs requires optimization and even small changes affect the results significantly. A 0.1mM cetyl trimethylammonium bromide (CTAB) solution of NTs appears turbid at 0 8C. However, upon warming to room temperature by keeping the solution for some time under ambient laboratory conditions, a clear solution was obtained. The sample was cleaned by washing repeatedly with water to remove

Method for the preparation of adsorption compositions including gold or silver nanoparticles

Abstract: This invention relates to novel adsorbent compositions for adsorbing pesticides like chlorpyrifos and malathion. This composition consists of nanoparticles of gold/silver supported on activated alumina or magnesia in powder or other forms. This invention includes a device and a method for decontaminating water contaminated with pesticides. This device consists of a housing provided with an inlet and an outlet. The housing is loaded with nanoparticles of gold/silver supported on activated magnesia. Contaminated water is allowed to pass through the housing while pesticides are adsorbed by the composition. Decontaminated water flows out through the outlet.

Industrial Utilization of Capacitive Deionization Technology for the Removal of Fluoride and Toxic Metal Ions (As3+/5+ and Pb2+)

Abstract: Capacitive deionization (CDI) is an emerging desalination technology, particularly useful for removing ionic and polarizable species from water. In this context, the desalination performance of fluoride and other toxic species (lead and arsenic) present in brackish water at an industrial scale of a few kilo liters using a CDI prototype built by InnoDI Private Limited is demonstrated. The prototype is highly efficient in removing ionic contaminants from water, including toxic and heavy metal ions. It can remove fluoride ions below the World Health Organization (WHO) limit (1.5 ppm) at an initial concentration of 7 ppm in the input feed water. The fluoride removal efficiency of the electrodes (at a feed concentration of 6 ppm) deteriorates by ≈4–6% in the presence of bicarbonate and phosphate ions at concentrations of 100 ppm each. The removal efficiency depends on flow rate, initial total dissolved solids, and other co‐ions present in the feed water. Interestingly, toxic species (As3+/5+ and Pb2+) are also removed efficiently (removal efficiency > 90%) by this technology. The electrodes are characterized extensively before and after adsorption to understand the mechanism of adsorption at the electrode.

Formation of Ethane Clathrate Hydrate in Ultrahigh Vacuum by Thermal Annealing

Abstract: : The existence of many molecules in the form of clathrate hydrates (CHs) in ultrahigh vacuum (UHV) and cryogenic conditions has not been explored adequately. In the present study, a detailed investigation by reflection absorption infrared spectroscopy confirmed that the three phases of ethane, i.e., amorphous, crystalline, and CH, coexist in a vapor-deposited ethane − water mixture at 60 K in UHV. Experiments were conducted with vapor-deposited ice films at 10 K, which were annealed to 60 K for tens of hours, and the IR spectral evolution was monitored systematically. Upon maintaining the system at 60 K, three phases of ethane were seen to coexist, but a gradual increase in the hydrate phase was noticed. The evolution of ethane CH from the amorphous ethane − water ice mixture was observed for the very first time in UHV under cryogenic conditions. The formation of the CH was further confirmed by temperature-programmed desorption (TPD) mass spectrometry. Quantum chemical calculation suggested the formation of 5 12 6 2 cage of structure I CH in the ice matrix. The formation of ethane CH in a thin ice film at such a low temperature under UHV suggests its existence in the cometary environment.

Thermal decomposition of C60Br24 and C60Br8: Absence of sequential elimination

Abstract: In-situ infrared spectroscopic investigations of the thermal decomposition of C60Br24 and C60Br8 reveal that elimination reactions leading to C60 occur in a single-step process. No partially brominated structures are observed, although theoretical predictions exist about derivatives such as C60Brn (12

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Gold nanoparticles in chemical and biological sensing.

Abstract: Detection of chemical and biological agents plays a fundamental role in biomedical, forensic and environmental sciences1–4 as well as in anti bioterrorism applications.5–7 The development of highly sensitive, cost effective, miniature sensors is therefore in high demand which requires advanced technology coupled with fundamental knowledge in chemistry, biology and material sciences.8–13 In general, sensors feature two functional components: a recognition element to provide selective/specific binding with the target analytes and a transducer component for signaling the binding event. An efficient sensor relies heavily on these two essential components for the recognition process in terms of response time, signal to noise (S/N) ratio, selectivity and limits of detection (LOD).14,15 Therefore, designing sensors with higher efficacy depends on the development of novel materials to improve both the recognition and transduction processes. Nanomaterials feature unique physicochemical properties that can be of great utility in creating new recognition and transduction processes for chemical and biological sensors15–27 as well as improving the S/N ratio by miniaturization of the sensor elements.28 Gold nanoparticles (AuNPs) possess distinct physical and chemical attributes that make them excellent scaffolds for the fabrication of novel chemical and biological sensors (Figure 1).29–36 First, AuNPs can be synthesized in a straightforward manner and can be made highly stable. Second, they possess unique optoelectronic properties. Third, they provide high surface-to-volume ratio with excellent biocompatibility using appropriate ligands.30 Fourth, these properties of AuNPs can be readily tuned varying their size, shape and the surrounding chemical environment. For example, the binding event between recognition element and the analyte can alter physicochemical properties of transducer AuNPs, such as plasmon resonance absorption, conductivity, redox behavior, etc. that in turn can generate a detectable response signal. Finally, AuNPs offer a suitable platform for multi-functionalization with a wide range of organic or biological ligands for the selective binding and detection of small molecules and biological targets.30–32,36 Each of these attributes of AuNPs has allowed researchers to develop novel sensing strategies with improved sensitivity, stability and selectivity. In the last decade of research, the advent of AuNP as a sensory element provided us a broad spectrum of innovative approaches for the detection of metal ions, small molecules, proteins, nucleic acids, malignant cells, etc. in a rapid and efficient manner.37 Figure 1 Physical properties of AuNPs and schematic illustration of an AuNP-based detection system. In this current review, we have highlighted the several synthetic routes and properties of AuNPs that make them excellent probes for different sensing strategies. Furthermore, we will discuss various sensing strategies and major advances in the last two decades of research utilizing AuNPs in the detection of variety of target analytes including metal ions, organic molecules, proteins, nucleic acids, and microorganisms.