58 research outputs found
Nondestructive detection of the freshness of fruits and vegetables using nano gold and silver mediated Graphene Enhanced Raman Spectroscopy
No full textRaman Spectroscopy is expanding its horizons into widespread applications as an analytical tool with immense potential. Raman has made distinct landmarks in the areas of pharmaceuticals, materials science, geosciences and gemology, forensics, nanotechnology, art and heritage, semiconductors technology and last but not the least in the surging field of biosciences too. The introduction of nanotechnology for surface enhanced Raman spectroscopy (SERS) application has led to a significant upgradation in the detection sensitivity of this tool. In the current work we demonstrate the use of a portable Raman system for assessing the freshness of fruits and vegetables. A dual nanoplatform has been used involving the use of nano gold/nanosilver seeded Graphene sheets as the SERS system for probing the freshness of fruits and vegetables. The use of nanogold versus nanosilver in combination with graphene was studied and the results showed that compared to nanosilver, nanogold seeded graphene nanosheet yielded better results. Also, a suitable method, named \ue2SERS microdrop method\ue2, whereby 10 \uc2\ub5L of the nanoparticle system was placed on the fruit surface, covered with a glass slip and then probed using the Raman probe has been reported. Fruits and vegetables like Wax apple, Lemon, Tomato, Red Pepper and Carrot were studied. Market fresh (bought from the fresh market) and refrigerated fruits and vegetables were probed at various time intervals ranging from 1 day to 2 weeks and the results presented in this paper. The results signify that the Raman signals increase with storage and certain peaks were found to appear with long term storage in the refrigerator. This study demonstrates that the quality of fruits and vegetables under even short term (1 week) storage even under cold storage conditions is impacted and should be avoided as much as possible. We discuss the changes effected on the fruits and vegetables under refrigeration and confirm the applicability of using nanogold enabled graphene enhanced Raman spectroscopy (GERS) as a successful platform for assessing the freshness of fruits and vegetables
Modal cost analysis of flexible structures: Modeling flexible structures for control design
No full textThe integration issues of structural modeling and control design for large flexible structures are very important for developing sound models in a closed loop environment. Consideration of these issues leads one to conclude that the modeling problem and control problem are not independent. The connection between these two problems must be understood to develop reliable control algorithms and reduce the cost of extensive laboratory and flight testing. For many large space structures, the primary consideration is the quality of the response at specific locations due to excitation at other locations. It is this input-output type phenomenon which must be reflected in our structural modeling. Classically, modal frequencies have been of primary concern. We will show that it is more important to obtain accurate modal costs in our structural models. The modal costs represent the contribution of a vibration mode in the system response for given input and output locations. This research provides a complete modal cost analysis for certain distributed parameter systems and shows that structural modeling and model reduction methods should be influenced by the specific control objectives. The analysis proceeds via the following steps: (1) Convergence properties of modal costs are discussed for vibration of various simple continua. Explicit formulas for the total cost of the system are derived. These formulas are useful for determining the modes that must be retained to provide a specified accuracy in the structural model with respect to the control objectives. (2) Open loop modal cost analysis is applied to finite element models of beam-like structures. These results are compared with exact modal costs in order to evaluate the accuracy of the modal costs determined using finite element methods. (3) Finite element models are used to develop Linear Quadratic Gaussian control laws while exact models are used to evaluate performance of the resulting closed loop systems. These control laws are necessarily suboptimal. The closed loop performance is then related to the open loop modal cost errors. This research presents a comprehensive modal cost analysis for simple continua and discusses its implications in subsequent control system design. (Abstract shortened with permission of author.
Biomedical Applications of Graphene and Their nanocomposites
No full text(1) Synthesis and antibacterial activities of graphene decorated with stannous dioxide
We report the synthesis and antibacterial activity of water dispersible stannous dioxide (SnO2) modified with graphene (G) nanosheets. Nanomaterials of G and SnO2@G were prepared and then characterized by transmission electron microscopy (TEM), ultraviolet (UV) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman and fluorescence spectroscopy. The antibacterial activities were investigated using Pseudomonas aeruginosa and Staphylococcus aureus as model strains of Gram negative and Gram positive bacteria, respectively. The antibacterial activities were evaluated using optical density (OD600) and plate counting methods. The results indicated that SnO2@G displayed a higher cytotoxicity than G by 1\ue23 fold. The G-based nanomaterials inhibited the growth of P. aeruginosa more effectively than for S. aureus. SnO2 increased the cytotoxicity of G against Gram negative bacteria by 3.6 times due to the synergic effect. The interactions between the prepared nanomaterials and bacteria cells were evaluated using TEM, fluorescence spectroscopy and matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The data revealed that there were many forces facilitating the SnO2@G nanosheets to adhere to bacteria cells, which block the cells from taking nutrients, and result in cell death. We expect that this novel G-based composite can be effectively applied in the future for environmental and clinical applications.
(2) Graphene nanosheet mediated MALDI-MS (GN-MALDI-MS) sensors for rapid, in situ and sensitive detection of incipient biofilm
Diagnosis is the first step to treatment, early detection of biofilm thus gains paramount importance. In the current study, a systematic study was conducted to trace the biofilm formation by Staphylococcus aureus and Vibrio alginolyticus on Aluminium, Titanium surfaces and surface modified counterparts with oxide films. The biofilm development on these four substrates has been studied from 1h- 2 month periods. Traditional MALDI-MS has been demonstrated as a potent tool for direct in situ detection of biofilms on material surfaces. In the subsequent part of the study the Graphene nanosheet mediated MALDI-MS (GN-MALDI-MS) approach using our inhouse synthesized Graphene nanosheets was combined with the traditional MALDI-MS study, to lower the LOD. Using this approach early detection of the biofilm was demonstrated to be 1h in case of titanium surfaces and 3h in case of Al surfaces. The results and discussion pertaining to these findings are presented in the following paper
A Survey of Experiments for Modeling Verification and Control of Flexible Robotic Manipulators
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Transient Dynamic Analysis of Rotating Beams Using Second-Order Theory: A Finite Difference Approach
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Solid phase microextraction combined with ambient ionization mass spectrometry for high-throughput pharmacokinetic analysis of human plasma
No full textThe content of this thesis mainly includes the development of solid phase microextraction combined with ambient mass spectrometry for high-throughput analysis of drug for pharmacokinetic studies. Traditionally, liquid or gas chromatography tandem mass spectrometry requires lengthy and laborious extraction and concentration process so that it is prone to misconducts and experimental errors. Therefore a simple and high-throughput analytical approach is deemed necessary. In this thesis, the solid phase microextraction technique combined thermal desorption electrospray ionization mass spectrometry (SPME-TD-ESI/MS) approach is used to rapidly determine the concentration of drugs in pharmacokinetics samples. Polar, relatively non-polar, and combine of both adsorption materials SPME fiber were explored for direct immersion solid phase microextraction thermal desorption electrospray ionization mass spectrometry approach. In addition, a new developed in-tip SPME device was firstly disclosed and proved to use 1 \uce\ubcL plasma sample for each analysis.
Experimental results shown that the average errors were less than 20% compared to LC-MS/MS method. Lower limit of quantification as low as 0.2 ng mL-1 and linear regression coefficient (r) values were above 0.995. The SPME extraction and instrument detection time was as short as 2.5 min. In overall, experimental results show that SPME-TD-ESI/MS approach is not only suitable for high-throughput analysis of pharmacokinetic samples. Polar and non-polar SPME fiber could also be flexibly combined for simultaneously extracting analytes of different polarity. The new design of in-tip SPME pushes down the sample volume to 1 \uce\ubcL plasma for each analysis greatly enhances its applicability in pharmacokinetics study especially in small animal models
Synthesis, characterization and study the role of nano particles in Biomedical & Environmental applications.
No full textThe prime interest of the thesis involves biomedical and environmental applications of
nanoparticles including sensors for bacteria and therapeutic agents present in the biological fluid and metal contaminants in environmental samples. This thesis was also focused on fabrication of anti-bacterial nanoparticles (calcium oxide nanoparticles) and fluorescent carbon dots using waste sea food as precursors.
The novel nanomaterials such as fluorescent carbon dots are investigated for their potential
application such as possible matrix in matrix assisted laser/desorption ionization mass
spectrometry (MALDI MS) for quantification of non-steroidal anti-inflammatory drug, and
mefenamic acid in serum. We found that the carbon dots can play an important role in the detection of low molecular weight compounds. In comparison with conventional matrix such as 2,5-dihydroxy benzoic acid, carbon dots were found to be an outstanding matrix to avoid background signals and fragmentation of the mefenamic acid signals. Furthermore, the developed methods were applied for the detection of mefenamic acid biological fluid such as serum.
The efficiency and function of the nanoparticles depend on their shape, size and surface modified
properties. To fine tune the nanoparticles, various synthetic methods were applied such as
hydrothermal pyrolysis, salvo-thermolytic including both top down and bottom up approaches. A novel method had been developed for the synthesis of calcium oxide nanoparticles from marine sea food waste by green synthesis method. Further, the antimicrobial effect of calcium oxide nanoparticles was also studied to against gram positive and gram-negative bacteria. We found that minimum inhibitory concentration of the calcium oxide nanoparticles was 10 \uce\ubcg /mL for micro-organisms by optical density, disk diffusion and MALDI-MS. Highly fluorescent carbon
dots were also synthesized as a byproduct of food waste recycling during the synthesis of calcium oxide nanoparticles.
We further explored these carbon dots as probes for a fluorescent Cu2+ ions sensing application.
This fluroscence sensing platform exhibited excellent selectivity and sensitivity toward Cu2+ ions with detection limit as low as 5 nM. The practical application of this sensing platform for the determination of Cu2+ ions in the seawater samples was also successfully demonstrated. This forms the fundamental basis of development of sustainable green technologies for exploiting organic and inorganic waste for nanoparticles synthesis. The method was tuned to enhance the yield of nanoparticles in order to make it to become the industrially powerful method.
A metal oxide nanoparticle such as zinc oxide was synthesized for separation of bacterial cells
from water samples using liquid phase micro-extraction. Zinc oxide nanoparticles were modified with polymethyl methacrylate to make the surface of zinc oxide completely hydrophobic to
clutch bacterial cells. The separated bacterial cells were identified using MALDI MS. The results
indicated that the above approach is a simple, rapid and efficient micro extraction technique for the analysis of pathogenic bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa.
The method was validated by the analysis of real samples, such as tap and drinking water
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