Browsing by Author "Bigness, Alec"

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    The Design of Zinc Metal Organic Frameworks for Biomedical Drug Delivery
    (Florida Southern College, 2019-04) Bigness, Alec
    A vast library of zinc metal-organic frameworks (MOFs) have been prepared and evaluated for their use in pharmaceutical drug delivery. Their properties and structures have been modulated through the variation of reaction conditions like solvent, starting material ratios, and method of reaction. A novel metal-organic framework, AB MOF1, was successfully prepared and characterized by x-ray diffraction analysis. AB MOF1 was evaluated for its use in drug delivery by using the model pharmaceutical drug ibuprofen for uptake studies, and AB MOF1’s stability in common biological and medicinal solvents was evaluated through Powder X-ray Diffraction (PXRD). The evaporation of ibuprofen at 157 oC during Thermal Gravimetric Analysis (TGA) of AB MOF1 impregnated with ibuprofen along with the change in morphology of AB MOF1 using PXRD give a likely indication ibuprofen was absorbed into AB MOF1. The uptake of ibuprofen reached capacity after fourteen hours of stirring in an ibuprofen solution, and the uptake is comparable to previously published results. Computational DFT studies corroborate the fact that the interaction between ibuprofen and AB MOF1 is favorable. The energy of interaction, which is defined as [(energy of AB MOF1 with ibuprofen) - (energy of ibuprofen alone + energy of AB MOF1 alone)|], of the zinc paddlewheel motif and ibuprofen was calculated to be 1.030 kcal/mol, which substantiates that the interaction between ibuprofen and AB MOF1 is favorable. This work shows the promise of AB MOF1 as a novel drug delivery vessel, and further prove the efficacy of using metal-organic frameworks to uptake and release pharmaceutical drugs in biomedical applications.
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    The design and optimization of plasmonic crystals for surface enhanced Raman spectroscopy using the finite difference time domain method
    (MDPI AG, 2018) Bigness, Alec; Montgomery, Jason M.
    We present computational studies of quasi three-dimensional nanowell (NW) and nanopost (NP) plasmonic crystals for applications in surface enhanced Raman spectroscopy (SERS). The NW and NP plasmonic crystals are metal coated arrays of cylindrical voids or posts, respectively, in a dielectric substrate characterized by a well/post diameter (D), relief depth (R D), periodicity (P), and metal thickness (M T). Each plasmonic crystal is modeled using the three-dimensional finite-difference time-domain (FDTD) method with periodic boundary conditions in the x- and y-directions applied to a computational unit cell to simulate the effect of a periodic array. Relative SERS responses are calculated from time-averaged electric field intensity enhancements at λ exc and λ scat or at λ mid via G SERS 4 = g 2 ( λ exc ) × g 2 ( λ scat ) or G mid 4 = g 4 ( λ mid ) , respectively, where g 2 = | E | 2 / | E 0 | 2 . Comparisons of G SERS 4 and G mid 4 are made to previously reported experimental SERS measurements for NW and NP geometries. Optimized NW and NP configurations based on variations of D, P, R D, and M T using G SERS 4 are presented, with 6× and 2× predicted increases in SERS, respectively. A novel plasmonic crystal based on square NP geometries are considered with an additional 3× increase over the optimized cylindrical NP geometry. NW geometries with imbedded spherical gold nanoparticles are considered, with 10× to 10 3 × increases in SERS responses over the NW geometry alone. The results promote the use of FDTD as a viable in silico route to the design and optimization of SERS active devices.