Plasmons in assembled metal nanostructures: radiative and nonradiative properties, near-field coupling and its universal scaling behavior

Noble metal nanostructures possess unique properties including large near-field enhancement and strong light scattering and absorption due to their plasmon resonance - the collective coherent oscillation of the metal free electrons in resonance with the electromagnetic field of light. The effect of nanostructure size, shape, composition, and environment on the plasmon resonance frequency and plasmonic enhancement is well known. In this thesis, we describe the effect of inter-particle coupling in assembled plasmonic nanostructures on their radiative and non-radiative properties. When metal nanoparticles assemble, plasmon oscillations of neighboring particles couple, resulting in a shift in the plasmon resonance frequency. Our investigation of plasmon coupling in gold nanorods shows that the coupling between the plasmons is "bonding" in nature when the plasmon oscillations are polarized along the inter-particle axis, whereas an "anti-bonding" interaction results when the polarization is perpendicular. We studied the distance-dependence of plasmon coupling using electrodynamic simulations and experimental plasmon resonances of lithographically fabricated gold nanoparticle pairs with systematically varying inter-particle separations. The strength of plasmon bonding, reflected by the fractional plasmon shift, decays near-exponentially with the inter-particle separation (in units of particle size) according to a universal trend independent of the nanoparticle size, shape, metal type, or medium. From the universal scaling model, we obtain a "plasmon ruler equation" which calculates (in good agreement with the experiments of Alivisatos and Liphardt) the inter-particle separation in a gold nanosphere pair from its plasmon resonance shift, making it applicable to the determination of inter-site distances in biological systems. Universal size-scaling is valid also in the metal nanoshell structure, a nanosphere trimer, and pairs of elongated nanoparticles, thus making it a generalized fundamental model, which is useful in optimizing plasmon coupling for achieving tunable plasmon resonances, enhanced plasmonic sensitivities, and large SERS cross-sections. Ultrafast laser pump-probe studies of non-radiative electronic relaxation in coupled metal nanospheres in aggregates and in gold nanospheres conjugated to thiol SAMs are also reported. We also show that the relative contribution of scattering (radiative) to absorption (non-radiative) part of the plasmon relaxation, respectively useful in optical and photothermal applications, can be increased by increasing the nanostructure size.Ph.D.Committee Chair: El-Sayed, Mostafa A.; Committee Member: Lyon, L. Andrew; Committee Member: Sherrill, C. David; Committee Member: Wang, Zhong Lin; Committee Member: Whetten, Robert L

Phase transition of copper (I) sulfide and its implication for purported superconductivity of LK-99

Lee, Kim, and coworkers have recently claimed ambient temperature and pressure superconductivity in a modified lead apatite material named LK-99. However, the polycrystalline material synthesized has a significant fraction of copper (I) sulfide. Copper (I) sulfide has a known phase transition at 104 degrees C from an ordered low-temperature phase to a high-temperature superionic phase. As a result of this phase transition, copper (I) sulfide exhibits sharp transitions in electrical resistivity and heat capacity, which are expected to coincide with the temperature-induced transitions reported for LK-99. This implies that LK-99 must be synthesized without any copper (I) sulfide to allow unambiguous validation of the superconducting properties of LK-99.Comment: 5 pages, 2 figure

In situ formation of catalytically active graphene in ethylene photo-epoxidation.

Ethylene epoxidation is used to produce 2 × 107 ton per year of ethylene oxide, a major feedstock for commodity chemicals and plastics. While high pressures and temperatures are required for the reaction, plasmonic photoexcitation of the Ag catalyst enables epoxidation at near-ambient conditions. Here, we use surface-enhanced Raman scattering to monitor the plasmon excitation-assisted reaction on individual sites of a Ag nanoparticle catalyst. We uncover an unconventional mechanism, wherein the primary step is the photosynthesis of graphene on the Ag surface. Epoxidation of ethylene is then promoted by this photogenerated graphene. Density functional theory simulations point to edge defects on the graphene as the sites for epoxidation. Guided by this insight, we synthesize a composite graphene/Ag/α-Al2O3 catalyst, which accomplishes ethylene photo-epoxidation under ambient conditions at which the conventional Ag/α-Al2O3 catalyst shows negligible activity. Our finding of in situ photogeneration of catalytically active graphene may apply to other photocatalytic hydrocarbon transformations

ANTICONVULSANT EFFECTS OF NIFEDIPINE ON MES INDUCED SEIZURES

Objective: To evaluate the anticonvulsant activity of Nifedipine against MES induced seizures.Methods: The study was induced by techno electroconvulsometer. The animals were treated with Nifedipine (100 μg/100 g i. p. and 200 μg/100 g i. p.) and MES was induced 2 h after the administration of the drug, and duration of various phases was noted. Duration of THLE was taken as an index for antiepileptic activity.Results: Nifedipine when administered in a dose of 100 μg/100 g ip, did not produce any changes in any phases of the MES induced seizure. But in a dose of 200 μg/100 g ip, it significantly reduced the duration of THLE.Conclusion: Nifedipine has a significant action against MES induced seizures suggesting an important role of CCBs as future, promising antiepileptic drug

Expanded Noise Margin 10T SRAM Cell using Finfet Device

Static random access memory (SRAM) cells are being improved in order to increase resistance to device level changes and satisfy the requirements of low-power applications. A unique 10-transistor FinFET-based SRAM cell with single-ended read and differential write functionality is presented in this study. This cutting-edge architecture is more power-efficient than ST (Schmitt trigger) 10T or traditional 6T SRAM cells, using only 1.87 and 1.6 units of power respectively during read operations. The efficiency is attributable to a lower read activity factor, which saves electricity. The read static noise margin (RSNM) and write static noise margin (WSNM) of the proposed 10T SRAM cell show notable improvements over the 6T SRAM cell, increasing by 1.67 and 1.86, respectively. Additionally, compared to the 6T SRAM cell, the read access time has been significantly reduced by 1.96 seconds. Utilising the Cadence Virtuoso tool and an 18nm Advanced Node Process Design Kit (PDK) technology file, the design's efficacy has been confirmed. For low-power electronic systems and next-generation memory applications, this exciting 10T SRAM cell has a lot of potential

Field Trials of Rapid-Setting Repair Materials

The primary objective of the present study was to identify the critical properties (based on the laboratory tests) that could be correlated to the field performance of the rapid setting repair materials. The first phase of the project involved laboratory evaluation of six commercial rapid-setting repair materials (RMs). When tested in the laboratory, all but two exhibited acceptable rates of strength gain and three RMs displayed relatively poor freeze-thaw resistance. All the RMs exhibited acceptable values for free-shrinkage, high resistance to cracking and good bond to substrate concrete. The resistance to chloride ion penetration of one of the RMs was very poor. The second phase of the project involved field installation and performance evaluation of the RMs. It was seen that while, in most cases, the controlled laboratory conditions yielded consistent mixes and acceptable performance, the properties of mixes produced on site were more variable. This variability was the result of somewhat uncontrolled changes in the amount of aggregate extension used, moisture content of the aggregates, amount water added and ambient temperature conditions. Follow-up inspection of the repair patches indicated that all the patches except one underwent premature failures (primarily cracking and edge de-bonding). The ambient temperature during the repairs was around 10°C and this led to an extended set-time for all the materials. The 12-hr compressive strengths values of the specimens from the field-mixes were in some cases lower than the 4-hr compressive strength values of laboratory mixes. Since the repairs were open to traffic after approximately 4 hours after placement, the low early age strengths could be a potential reason for premature failures of some of the patches. In general, several materials were found to be very sensitive to excess water added during mixing resulted in a significant impact on the durability properties – especially the freeze-thaw resistance. In the field, for most of the materials, the consistency of the mixes varied from batch to batch – this can be attributed to the variations in the aggregate extension adopted, mix-water added and also the moisture content of the aggregates used. Construction related issues (consolidation and finishing) also played an important role in the performance of the repair patches. Based upon laboratory and field results, modifications to the current INDOT performance specifications for rapid-setting repair materials have been suggested. Some recommendations for improvements in quality control measures of field-mixes and construction related issues have been suggested. Future research directions involving the evaluation of the robustness of the repair materials with respect to the uncertainties present on site have also been highlighted

A case of reading epilepsy in a patient having idiopathic generalized epilepsy

Reflex seizures are defined as epileptic events that are triggered only by specific stimuli which can be external or complex internalmental processes. Reading epilepsy is one such rare form of reflex epilepsy. In primary reading epilepsy, typical attacks are jaw jerks(clicking sensation or stammering), that may evolve into GTCS if reading continues. As reading epilepsy is task-specific, they aregenerally misdiagnosed as non-epileptic and thought to be due to stress related to studies. We report the case of a young male whohave jaw jerks along with blank staring spells while reading which was misdiagnosed as pseudoseizures. This rare case highlights thiseasily treatable benign reflex epilepsy syndrome