Chemistry - Book Chapters
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Item Mesoporous materials as templates for semiconductor nanowires assembly(IOS Press, 2003) Holmes, Justin D.; Morris, Michael A.; Ryan, Kevin M.; European Commission; Intel Corporation; Intel Ireland Ltd.In this chapter is described a novel approach for synthesizing mesoporous silicas with tunable pore diameters, wall thickness and pore spacings that can be used as templates for the assembly of semiconductor nanowire arrays. Silicon and germanium nanowires, with size monodisperse diameters, can readily be formed within the mesoporous silica matrix using a supercritical fluid inclusion technique. These nano-composite materials display unique optical properties such as intense room temperature ultraviolet and visible photoluminescence. The implication of these mesoporous nanowire materials for future electronic and opto-electronic devices is discussed.Item Bioconjugated gold nanoparticles enhance siRNA delivery in prostate cancer cells(Springer, 2019-05-17) Rahme, Kamil; Guo, Jianfeng; Holmes, Justin D.; Dinesh Kumar, Lekha; Science Foundation Ireland; Irish Research Council; Department of Science and Technology of Jilin Province; National Council for Scientific ResearchHere we describe a simple way to create a gold nanoparticle (AuNP)-based non-viral delivery system to deliver siRNA into prostate cancer cells. Therefore, positively charged polyethylenimine (PEI)-capped AuNPs were synthesized in water and further conjugated with the targeting ligand (folic acid) for folate receptors (AuNPs-PEI-FA). The AuNPs-PEI-FA could effectively complex small interfering RNA (siRNA) through electrostatic interaction. Flow cytometry displayed that AuNPs-PEI-FA could specifically deliver siRNA into LNCaP cells, a prostate cancer cell line overexpressing prostate-specific membrane antigen (PSMA) that exhibits a hydrolase enzymatic activity with a folate substrate. In contrast, internalization of siRNA into PC-3 cells, a prostate cancer cell line not expressing PSMA or folate receptors, was not achieved using AuNPs-PEI-FA.siRNA. Following endolysosomal escape, the AuNPs-PEI-FA-.siRNA formulation resulted in significant endogenous gene silencing when compared to the nontargeted formulation, suggesting the potential of AuNPs-PEI-FA for targeted delivery of therapeutic siRNAs in the treatment of prostate cancer.Item Organometallic-metallic-cyclotriphosphazene mixtures: solid state method for metallic nanoparticle growth(Nova Science Publishers, 2013-04) Díaz, Carlos; Valenzuela, María Luisa; O'Dwyer, Colm; Roger Dong; Fondo Nacional de Desarrollo Científico, Tecnológico y de Innovación TecnológicaWe review a recent general solid state method to obtain metallic, metal oxide and phosphate nanoparticles and crystals by pyrolysis at 800°C using organometallic derivatives of cyclo and polyphosphazene precursors containing diverse organometallic fragments linked to polymeric or oligomeric phosphazenes. When the preparation of the molecular precursor is not possible or results in low yield, an alternative method using solid state mixtures of the type MLn/N3P3[O2C12H8]n, where MLn can be a single metallic salt, and a coordination compound or an organometallic, is possible. For AuCl(PPh3)/[NP(O2C12H8)]n mixtures, single crystal cubic Au nanoparticles form, whose morphology, crystal shape, size and distribution strongly depends on deposition quantity and the mixture molar ratio. Nanoparticles as small as 3.5 nm are observed if the mixture is prepared in a crucible and varied geometries of microcrystals found when the mixture was deposited on Si or SiO2 wafers, including single-crystal gold fullerene structures. Extension to Ag, Pd and Re-containing precursor mixtures such as Ag(PPh3)(CF3SO3)/ [NP(O2C12H8)]3, PdCl2/N3P3[O2C12H8]3, and KReO4/N3P3[O2C12H8]3 allows microcrystal formation during pyrolysis. A thermally induced phase demixing mechanism describes the evolution of the crystal growth, aided microphase separation of the polymer mixture. This microphase demixing is shown to be an overarching mechanism involved in the nano to micro scale growth of crystals. A probable mechanism of the atomic and molecular-level chemistry is also proposed based on decomposition of the macromolecular polymeric, trimer and oligomeric precursors for the initial stages.Item Gold nanoparticles: synthesis, characterization, and bioconjugation(CRC Press, Taylor & Francis, 2015-09) Rahme, Kamil; Holmes, Justin D.; Lyshevski, Sergey E.Gold nanoparticles (Au NPs) with diameters ranging between 4-150 nm have been synthesized in water. The strong reducing agent sodium borohydride (NaBH4) was used to produce small Au NPs with diameter about 4 +_1 nm. 15 and 30 nm Au NPs were obtained by a slightly modified Turkevich and Frens method using sodium citrate as both reducing and stabilizing agent at high temperature. The attempt to produce Au NPs with diameter larger than 30-40 nm by the Turkevich method resulted in an increase in the polydispersity and the shape diversity of the final Au NPs, indicating the importance of the trial of new reducing agents in the production of Au NPs especially for diameters above 40 nm. Therefore, hydroxylamine-o-sulfonic acid (NH2SO4H) (HOS) was used here for the first time as a new reducing agent for HAuCl4 at room temperature to produce Au NPs with diameter of about 60, 90 and 150 nm. This new method using HOS is an extension of the approaches described to produce Au NPs with diameter above 40 nm by direct reduction. The obtained nanoparticles were characterized using uv-visible spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Further biocojuguation on 15, 30 and 90 nm Au NPs were performed by grafting covalently Apolipoprotein E (ApoE) and Bovine Serum Albumin (BSA) through an ethylene glycol-N-hydroxysuccinimide linker (NHS-PEG-S-S-PEG-NHS) making them very attractive for drug delivery and cell targeting. Finally, functionalized polyethylene glycol-based thiol polymers were also used to stabilize the pre-synthesized Au NPs-PEG-Protein.