Anti-microbial Nanohybrids Based on Naturally Derived Citric Acid Intercalated Layered Double Hydroxides

Currently, there is an increased demand for advanced food packages, which can significantly increase the shelf life of food items. In the current context, it is envisaged that nanotechnology has the potential to address stability, toxicity, shelf-life, and low-cost issues of antimicrobials associated with the packaging industry. Antimicrobial nanocomposite systems are believed to be more efficient than their microscale counterparts due to the high surface area to volume ratio and quantum mechanical involvement in deciding their properties. As a result of high surface area, they are able to attach more copies of microbial molecules and cells, thus reducing the quantity of material required while significantly improving their activity. This study focuses on the development of slow-release antimicrobial material based on natural citrate (α-hydroxycitrate) intercalated layered double hydroxide (LDH) nanohybrid. Natural citrate ions available in Citrus aurantifolia (lime) were extracted by a simple chemical method and intercalated into Mg-Al-Layered Double Hydroxide following a one-step co-precipitation method. Successful intercalation of the citrate ion was confirmed by powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopic analysis. Release kinetics of resulted nanohybrid was studied and compared using different release kinetic models. Antimicrobial properties of this novel nanohybrid were confirmed against two common food pathogens, Colletotrichum gloeosporioides and Saccharomyces cerevisiae, and the results were compared against sodium benzoate, which is the commonly used commercial antimicrobial agent in the food industry. Successful intercalation of natural citrate ions into LDH and its activity against the tested microbes show the potential of using it as a slow-release nanohybrid material in many food-related applications. Keywords: Layered Double Hydroxide, α-Hydroxycitrate, Natural, Safe, Lime Extract, Slow Release, Antimicrobia

Engineering spasers: models,designs, and applications

The spaser nanolaser, which is the nanoplasmonic counterpart of the laser, enables the generation and amplification of coherent surface plasmons (SPs) by means of stimulated emission. Spaser opens up a new era of devices which overcome the speed barriers of electronics and miniaturizing barriers of optics. This research is mainly focused on engineering spaser devices, particulary the guidelines for design optimization, new designs with improved characteristics, and potential applications. First, a general quantum mechanical model is developed considering the degeneracy of localized SP modes supported by a resonator. Density matrix analysis of this system helps to derive an expression for SP generation rate and identify the tunable parameters for design optimization. The developed model is then applied to optimize a simple spaser design, in which a metal nanosphere is resonantly coupled to a quantum dot, by altering their material and geometrical parameters. Next, alternative spaser materials are considered. Although not commonly used in spaser designs, graphene possesses much better plasmonic properties compared to gold or silver and carbon nanotubes (CNTs) display excellent photoluminescence properties. Therefore, a new all-carbon spaser design is proposed where a square shaped graphene nanoflake (GNF) resonator powered by a CNT gain element offering the advantages of tunability, robustness, flexibility, and thermal stability. This design is also analyzed employing the general model to determine the different material and geometric parameters of GNF and CNT influencing the spaser operation. Based on these results, clear spaser design guidelines such as identifying the crucial tuning parameters, fabricating the resonator, choosing the appropriate gain medium and pumping mechanism, and relative placement of the components are also sought. Finally, some new applications of spaser nanolasers are proposed and a spaser powered cancer therapy is discussed in detail. In this setup, a large number of tiny nanolasers penetrate tumors to thermally ablate malignant cancer cells. Hence, this research as a whole contributes towards engineering the spaser and catalyzing the process of its practical use and commercialization

Engineering spasers: models,designs, and applications

The spaser nanolaser, which is the nanoplasmonic counterpart of the laser, enables the generation and amplification of coherent surface plasmons (SPs) by means of stimulated emission. Spaser opens up a new era of devices which overcome the speed barriers of electronics and miniaturizing barriers of optics. This research is mainly focused on engineering spaser devices, particulary the guidelines for design optimization, new designs with improved characteristics, and potential applications. First, a general quantum mechanical model is developed considering the degeneracy of localized SP modes supported by a resonator. Density matrix analysis of this system helps to derive an expression for SP generation rate and identify the tunable parameters for design optimization. The developed model is then applied to optimize a simple spaser design, in which a metal nanosphere is resonantly coupled to a quantum dot, by altering their material and geometrical parameters. Next, alternative spaser materials are considered. Although not commonly used in spaser designs, graphene possesses much better plasmonic properties compared to gold or silver and carbon nanotubes (CNTs) display excellent photoluminescence properties. Therefore, a new all-carbon spaser design is proposed where a square shaped graphene nanoflake (GNF) resonator powered by a CNT gain element offering the advantages of tunability, robustness, flexibility, and thermal stability. This design is also analyzed employing the general model to determine the different material and geometric parameters of GNF and CNT influencing the spaser operation. Based on these results, clear spaser design guidelines such as identifying the crucial tuning parameters, fabricating the resonator, choosing the appropriate gain medium and pumping mechanism, and relative placement of the components are also sought. Finally, some new applications of spaser nanolasers are proposed and a spaser powered cancer therapy is discussed in detail. In this setup, a large number of tiny nanolasers penetrate tumors to thermally ablate malignant cancer cells. Hence, this research as a whole contributes towards engineering the spaser and catalyzing the process of its practical use and commercialization

Spaser Made of Graphene and Carbon Nanotubes

Spaser is a nanoscale source of surface plasmons comprising a plasmonic resonator and gain medium to replenish energy losses. Here we propose a carbon-based spaser design in which a graphene nanoflake (GNF) resonator is coupled to a carbon nanotube (CNT) gain element. We theoretically demonstrate that the optically excited CNT can nonradiatively transfer its energy to the localized plasmon modes of the GNF because of the near-field interaction between the modes and the CNT excitons. By calculating the localized fields of the plasmon modes and the matrix elements of the plasmon–exciton interaction, we find the optimal geometric and material parameters of the spaser that yield the highest plasmon generation rate. The results obtained may prove useful in designing robust and ultracompact coherent sources of surface plasmons for plasmonic nanocircuits