Multicomponent ligand interactions are involved in essentially all nanoparticle (NP) applications. However, the ligand conformation and ligand binding mechanisms on NPs are highly controversial. The research reported here is focused on deepening the fundamental understanding of multicomponent ligand interactions with gold and silver nanoparticles (AuNPs and AgNPs) in water. We demonstrated that AuNPs passivated by saturated layer of poly(ethylene glycol) (PEG-SH) have large fractions of AuNP surface area available for ligand adsorption and exchange. The fraction of AuNP surface area passivated by PEG-SH with molecular weights of 2000, 5000, and 30000 g/mol was calculated to be ~ 25%, ~20%, and ~9% using 2-mercaptobenzimidazole and adenine as model ligands. The effect of both reduced and oxidized protein cysteine residues on protein interactions with AgNPs was investigated. The model proteins included wild-type and mutated GB3 variants with 0, 1, or 2 reduced cysteine residues. Bovine serum albumin containing 34 oxidized (disulfide-linked) and 1 reduced cysteine residues was also included. Protein cysteine content that were found to have no detectable effect on kinetics of protein/AgNP binding. However, only proteins that contain reduced cysteine induced significant AgNP dissolution. We further demonstrated that organothiols can induce both AgNP disintegration and formation under ambient conditions by simply mixing organothiols with AgNPs or AgNO3, respectively. Surface plasmon- and fluorescence-active AgNPs formed by changing the concentration ratio between Ag+ and organothiol. Organothiols also induced AuNP formation by mixing HAuCl4 with organothiols, but no AuNP disintegration occured. Finally, we proposed that multicomponent ligand binding to AuNPs can be highly dependent on the sequence of ligand mixing with AuNPs. Quantitative studies revealed that competitive adenine and glutathione adsorption onto both as-synthesized and PEG-SH functionalized AuNPs is predominantly a kinetically controlled process. Besides providing new insights on multicomponent ligand interactions with colloidal AuNPs and AgNPs, this study opens a new avenue for fabrication of novel nanomaterials in biological/biomedical applications.

No description available.

The antimicrobial effects of silver nanoparticles were studied. Silver nanoparticles were synthesized through wet chemistry method, and were dispersed in aqueous suspension. With nanoscale silica particles served as heterogeneous nucleation sites, silver nanoparticles were formed anchoring on the silica surface. Suspensions were found to be stable at high silver concentrations as well as over a broad pH range. By varying the processing conditions, diameter of the silver nanoparticles could be controlled between ~2 nm to ~25 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to reveal the formation and the corresponding morphology of the silver-silica coupling nanoparticles. Ultra-violet visible (UV-vis) scanning spectrophotometer was used to detecting the distinct absorption spectrum of silver nanoparticles. The antimicrobial activities of these silver-silica coupling nanoparticles were investigated. E. coli and S aureus were used as representatives of Gram-negative and Gram-positive bacteria, respectively. Bacteriological tests showed either bacterial growth inhibition or cell death occurred, corresponding to different concentrations of silver nanoparticles and the type of bacteria that were testing on. Fluorescent microscopic images were also provided to confirm the bacterial viability after several hours' treatment with silver nanoparticles. / Master of Science

No description available.

The extensive use of nanoparticles (NPs) has started receiving increased attention because of the knowledge gaps regarding their fate in the environment and the possible impact on the environment and human health. The production of silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2-NPs) is increasing and it is expected that, due to their great number of applications, their concentration in waste streams will increase in the future. The presence of NPs in waste streams may affect the treatment process (e.g., composting) and, if they are not successfully removed from the waste streams, their presence in the treated waste (e.g., compost) may present an environmental risk. Composting of the biodegradable fractions of municipal solid waste (MSW) is a widely used waste management practice, mainly because it is a cost-effective treatment technology and the final product (i.e., compost) presents several benefits to the environment, particularly as a soil conditioner. The overall aim of this thesis is to assess the effect of Ag-TiO2NPs and AgNPs that may be present in the biodegradable fractions of municipal solid waste on composting and subsequent soil application of compost. For that purpose in-vessel composting of artificial municipal solid waste contaminated with commercial nanoparticles was investigated at laboratory scale, simulating a range of relevant concentration levels. Subsequently, the fate of NPs present in mature compost use as a top-layer soil conditioner was investigated using a column approach at laboratory scale. The toxicity effect of NPs present mature compost on plant growth was further investigated. The impact of NPs during composting was assessed by monitoring the temporal dynamics of organic matter (OM) using Excitation Emission Matrix (EEM) fluorescence spectroscopy. The fate of NPs following application of contaminated mature compost as a top-soil conditioner and potential release to groundwater was investigated using a column leaching experiment while the phytotoxicity of mature compost contaminated with NPs was assessed using a seed germination bioassay. Finally, to investigate further possible environmental impacts due to the application of mature compost contaminated with NPs to soils, a Life Cycle Assessment (LCA) was conducted. The impact of commercial Ag-TiO2 NPs and AgNPs on the in-vessel composting of biodegradable municipal solid waste was investigated over 21 days, using initial concentrations of 0, 5, 10, 20 and 50 mg Ag / kg of OM. Microbial activity was inhibited in the biodegradable waste reactors using 2% NaN3 to evaluate abiotic losses. Physicochemical parameters such as pH, ash content, weight loss, and the formation of humic substances (HS) were determined after 0, 4, 7, 14 and 21 days of composting and after a maturation phase. The results indicated that the presence of 2% NaN3 in biodegradable MSW inhibited effectively the microbial activity during the first week of composting. The microbial population was activated during the second week of composting but the decomposition rate was so low that did not result in the formation of humic substances (HS) following 21 days of composting when 2% NaN3 was used. Both treatments, using Ag-TiO2-NPs and AgNPs, did not show any inhibition of the decomposition process for all the tested concentrations and EEM peaks shifted towards the HS region during in-vessel composting. Higher inorganic carbon removal resulted from NP-contaminated compost with higher NP concentrations. This may indicate that the formation of humins was higher for non-contaminated compost and decreased as the NP concentration in waste increased. The shift of the peaks towards the HS region during composting for all the treatments suggested that NPs did not have an effect on humification and therefore on compost stability. The leaching properties of the NP-contaminated compost were investigated using a column leaching test. Five samples of leachate, of 50 mL each, were collected. The highest concentrations of HS were observed in the first two leaching samples. The leaching results suggested that only a low percentage of the total NPs (in weight) in compost, up to ca. 5% for Ag and up to ca. 15% for Ti, leached out from the columns, which was assumed the amount that potentially could leach to the environment. These results suggested that NPs will mainly accumulate in soils’ top layers following application of compost contaminated with NP. The phytotoxicity of NP-contaminated compost was assessed using a seed germination bioassay and the germination index was then calculated. The results indicated that the NP-contaminated compost did not present any toxic effects to cress germination. The possible environmental impacts due to the NP-contaminated compost application to soils were investigated by conducting a comparative LCA study. The LCA study indicated that the effects of NP-contaminated compost to human health and ecosystems endpoint categories increased due to the presence of NPs. The risks are associated with terrestrial ecotoxicity and human toxicity midpoint categories and are mainly attributed to the accumulation of Ag to soils.

Chiral molecules, which exist under enantiomers with non-mirror-symmetrical structures, have been the subject of intense research for their linear and nonlinear optical activities. Cysteine is such a chiral amino acid found as a building block of proteins throughout human bodies. Second harmonic generation (SHG) has been considered to investigate chiral molecules. SHG from metallic nanoparticles is promising for nanoplasmonics and photonic nanodevice applications. Therefore, it’s desirable to combine and study nonlinear properties due to both chirality and metallic nanoparticles, and help developing an alternatively optical diagnostic of chiral molecules. Our experiments are carried out with the FemtoFiber Scientific FFS laser system. SHG of silver nanoparticles (Ag NPs) modified by either L-Cysteine (L-C) or D-Cysteine (D-C) is observed, where L-Cysteine and D-Cysteine are a pair of enantiomers. Ag NPs are deposited through Vacuum Thermal Evaporation, controlled under different deposition thicknesses. UV-Vis/IR spectra and AFM are used to characterize Ag NPs under different conditions. Transmitted SHG measurements dependent on incidence are recorded with standard lock-in techniques. Deposition thickness of vacuum thermal evaporation plays an important role in forming diverse Ag NPs, which strongly imparts the intensity of SHG. Second harmonic intensity as a function of the incident angle presents similar results for Ag NPs with or without L-Cysteine or D-Cysteine modification, in the output of p- and s-polarization. However, we monitor reversed rotation difference in second harmonic intensities at linearly +45° and -45° polarization for L-C/Ag NPs and D-C/Ag NPs, while there’s no difference at linearly +45° and -45° polarization for Ag NPs alone. This optical rotation difference in SHG is termed as SHG-ORD. Also, for second harmonic light fixed at p-polarization, L-C/Ag NPs and D-C/Ag NPs exhibit a reversely net difference for SHG excited by right and left circular polarization, which is termed as SHG-CD. Experiments on SHG-ORD of chiral-modified Ag NPs by a mixture of L-Cysteine and D-Cysteine further help verifying the existence of chirality in chiral-modified Ag NPs. As a conclusion, SHG efficiently probed and distinguished L-Cysteine from D-Cysteine in chiral-modified Ag NPs. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-09-29 21:27:23.112

The handling of metallic nanoparticles often requires their dispersion into several polar and nonpolar solvents. Solid-phase stages or polymer-based ligands are commonly required to complete the transfer. The construction of a thiol ligand based in oleic acid, and its ability to efficiently assist in gold and silver nanoparticle aqueous-organic phase transfer is reported. After the transfer, the particles are completely dispersed in an organic solvent, preserving their diameter and morphology, as confirmed by ultraviolet-visible spectroscopy and scanning transmission electron micrographs.

A primeira parte do estudo consistiu em caracterizar as amostras de termoplástico elastomérico poliéster (TPE-E) modificadas via irradiação gama (γ) em presença de atmosfera de oxigênio e irradiadas com fonte de 60 Co nas doses de 5, 10, 20, 30, 50 e 100 kGy. Na segunda parte foram realizadas as caracterizações das dispersões coloidais de prata metálica adsorvida em sílica pirogênica (AgNPs_SiO2) e do óxido de zinco aditivado com prata metálica adsorvida em sílica pirogênica (AgNPs_ZnO). Na terceira e última parte, as concentrações de 250, 500, 1000 e 5000 ppm, em massa , de AgNPs_SiO2, idem para AgNPs_ZnO, foram misturados mecanicamente por 30 minutos com 1 % em massa de óleo ALKEST TW 80, 0.3 % em massa de anti-oxidante Irganox 1010 e grânulos de TPE-E, posteriormente processados, independentemente, via injeção plástica, extrusão monorosca e irradiação com prensagem a quente. As técnicas de caracterização utilizadas no trabalho foram: espectroscopia no infravermelho (FTIR), calorimetria exploratória diferencial (DSC), análise termogravimétrica (TGA), difração de raios X (DRX), espectrometria de fluorescência de raios X por dispersão de comprimento de onda (WD-XRF), microscopia eletrônica de varredura com espectroscopia por dispersão de energia de raios X (MEV-EDS), microscopia eletrônica de transmissão com espectroscopia por dispersão de energia de raios X (MET-EDS), índice de fluidez (MFR) e ensaios de tração. As amostras de TPE-E irradiadas apresentaram diminuição da temperatura de degradação (Tonset) e do índice de fluidez (IF) com o aumento da dose de irradiação. Foi possível observar nos resultados obtidos por espectrometria de fluorescência de raios X por dispersão de comprimento de onda a presença de prata nos compostos de sílica pirogênica e de óxido de zinco com sílica pirogênica. Todas as amostras de TPE-E contendo aditivos AgNPs_SiO2 e AgNPs_ZnO obtidas pelas diferentes técnicas apresentaram atividade bactericida para bactéria Gram-negativa Escherichia coli (E.Coli) e a bactéria Gram-positiva Staphylococcus aureus (S.Aureus), sendo os melhores resultados obtidos nos filmes de TPE-E irradiados e prensados com 0.5 % de AgNPs_ZnO com doses de 20 e 50 kGy e 0.5 % AgNPs_SiO2 com doses de 0 e 20 kGy. / The first part of the study consisted of characterizing samples of thermoplastic polyester elastomeric polyester (TPE-E) modified by gamma irradiation (γ) in the presence of oxygen atmosphere and irradiated with a 60 Co source at doses of 5, 10, 20, 30, 50 and 100 kGy. In the second part, the characterization of the colloidal dispersion of silver silicon adsorbed pyrogenic silica (AgNPs_SiO2) and the zinc oxide added with colloidal dispersion of metallic silver adsorbed on silica pyrogen (AgNPs_ZnO). In the third and final part, concentrations of 250, 500, 1000 and 5000 ppm, mass%, of AgNPs_SiO2, identical to AgNPs_ZnO, were mixed mechanically for 30 minutes with 1% by mass of ALKEST TW 80 oil, 0.3% by mass of Irganox 1010 anti-oxidant and TPE-E granules, further processed independently, via plastic injection, monosulfur extrusion and irradiation with hot pressing. The characterization techniques used in the work were: infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence spectrometry by wavelength dispersion WD-XRF), scanning electron microscopy with X-ray energy dispersion spectroscopy (SEM-EDS), transmission electron microscopy with X-ray energy dispersion spectroscopy (TEM-EDS), melt flow index (MFR) and traction tests. The irradiated TPE-E samples showed a decrease in degradation temperature (Tonset) and melt flow index (IF) with increasing irradiation dose. It was possible to observe in the results obtained by X-ray fluorescence spectrometry by wavelength dispersion the presence of silver in the silica pyrogenic compounds and of zinc oxide with pyrogenic silica. All the TPE-E samples containing additives AgNPs_SiO2 and AgNPs_ZnO obtained by the different techniques presented bactericidal activity for Gram-negative bacteria Escherichia coli (E.Coli) and Gram-positive bacteria Staphylococcus aureus (S.Aureus), being the best results obtained in the TPE-E films irradiated and pressed with 0.5% AgNPs_ZnO at doses of 0, 20 and 50 kGy and 0.5% AgNPs _SiO2 at doses of 0 and 20 kGy.

A primeira parte do estudo consistiu em caracterizar as amostras de termoplástico elastomérico poliéster (TPE-E) modificadas via irradiação gama (γ) em presença de atmosfera de oxigênio e irradiadas com fonte de 60 Co nas doses de 5, 10, 20, 30, 50 e 100 kGy. Na segunda parte foram realizadas as caracterizações das dispersões coloidais de prata metálica adsorvida em sílica pirogênica (AgNPs_SiO2) e do óxido de zinco aditivado com prata metálica adsorvida em sílica pirogênica (AgNPs_ZnO). Na terceira e última parte, as concentrações de 250, 500, 1000 e 5000 ppm, em massa , de AgNPs_SiO2, idem para AgNPs_ZnO, foram misturados mecanicamente por 30 minutos com 1 % em massa de óleo ALKEST TW 80, 0.3 % em massa de anti-oxidante Irganox 1010 e grânulos de TPE-E, posteriormente processados, independentemente, via injeção plástica, extrusão monorosca e irradiação com prensagem a quente. As técnicas de caracterização utilizadas no trabalho foram: espectroscopia no infravermelho (FTIR), calorimetria exploratória diferencial (DSC), análise termogravimétrica (TGA), difração de raios X (DRX), espectrometria de fluorescência de raios X por dispersão de comprimento de onda (WD-XRF), microscopia eletrônica de varredura com espectroscopia por dispersão de energia de raios X (MEV-EDS), microscopia eletrônica de transmissão com espectroscopia por dispersão de energia de raios X (MET-EDS), índice de fluidez (MFR) e ensaios de tração. As amostras de TPE-E irradiadas apresentaram diminuição da temperatura de degradação (Tonset) e do índice de fluidez (IF) com o aumento da dose de irradiação. Foi possível observar nos resultados obtidos por espectrometria de fluorescência de raios X por dispersão de comprimento de onda a presença de prata nos compostos de sílica pirogênica e de óxido de zinco com sílica pirogênica. Todas as amostras de TPE-E contendo aditivos AgNPs_SiO2 e AgNPs_ZnO obtidas pelas diferentes técnicas apresentaram atividade bactericida para bactéria Gram-negativa Escherichia coli (E.Coli) e a bactéria Gram-positiva Staphylococcus aureus (S.Aureus), sendo os melhores resultados obtidos nos filmes de TPE-E irradiados e prensados com 0.5 % de AgNPs_ZnO com doses de 20 e 50 kGy e 0.5 % AgNPs_SiO2 com doses de 0 e 20 kGy. / The first part of the study consisted of characterizing samples of thermoplastic polyester elastomeric polyester (TPE-E) modified by gamma irradiation (γ) in the presence of oxygen atmosphere and irradiated with a 60 Co source at doses of 5, 10, 20, 30, 50 and 100 kGy. In the second part, the characterization of the colloidal dispersion of silver silicon adsorbed pyrogenic silica (AgNPs_SiO2) and the zinc oxide added with colloidal dispersion of metallic silver adsorbed on silica pyrogen (AgNPs_ZnO). In the third and final part, concentrations of 250, 500, 1000 and 5000 ppm, mass%, of AgNPs_SiO2, identical to AgNPs_ZnO, were mixed mechanically for 30 minutes with 1% by mass of ALKEST TW 80 oil, 0.3% by mass of Irganox 1010 anti-oxidant and TPE-E granules, further processed independently, via plastic injection, monosulfur extrusion and irradiation with hot pressing. The characterization techniques used in the work were: infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence spectrometry by wavelength dispersion WD-XRF), scanning electron microscopy with X-ray energy dispersion spectroscopy (SEM-EDS), transmission electron microscopy with X-ray energy dispersion spectroscopy (TEM-EDS), melt flow index (MFR) and traction tests. The irradiated TPE-E samples showed a decrease in degradation temperature (Tonset) and melt flow index (IF) with increasing irradiation dose. It was possible to observe in the results obtained by X-ray fluorescence spectrometry by wavelength dispersion the presence of silver in the silica pyrogenic compounds and of zinc oxide with pyrogenic silica. All the TPE-E samples containing additives AgNPs_SiO2 and AgNPs_ZnO obtained by the different techniques presented bactericidal activity for Gram-negative bacteria Escherichia coli (E.Coli) and Gram-positive bacteria Staphylococcus aureus (S.Aureus), being the best results obtained in the TPE-E films irradiated and pressed with 0.5% AgNPs_ZnO at doses of 0, 20 and 50 kGy and 0.5% AgNPs _SiO2 at doses of 0 and 20 kGy.

Um dispositivo eletroquímico foi desenvolvido para a determinação simultânea de sulfametoxazol (SMX) e trimetoprim (TMP), utilizando voltametria de pulso diferencial e um eletrodo de carbono vítreo (GC) modificado com o compósito óxido de grafeno reduzido (rGO) e nanopartículas de prata (AgNPs), sintetizados por dois métodos: químico e o eletroquímico. A morfologia e o comportamento eletroquímico dos eletrodos GC modificados com os compósitos rGO/AgNPs (método químico) e rGO-AgNPs (método eletroquímico) foram caracterizados por microscopia eletrônica de varredura acoplada a um canhão de elétrons (FEG-SEM) e voltametria cíclica (CV). Essas técnicas demostraram que, nos dois métodos utilizados, o óxido de grafeno (GO) foi modificado com as AgNPs, e que o compósito sintetizado pelo método eletroquímico apresentou uma melhor dispersão das nanopartículas, resultando em um aumento da área superficial quando comparado ao compósito rGO/AgNPs. Assim, o eletrodo GC/rGO-AgNPs foi avaliado e otimizado na determinação simultânea de SMX e TMP e atingiu limites de detecção de 0,6 µmol L-1 para o SMX e 0,4 µmol L-1 para o TMP. O dispositivo eletroquímico proposto, GC/rGO-AgNPs, foi aplicado com sucesso na determinação simultânea de SMX e TMP em águas residuárias. / An electrochemical device was developed for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) using differential pulse voltammetry, and a glassy carbon electrode (GC) modified with the reduced graphene oxide composite (rGO) and silver nanoparticles (AgNPs), synthesized by two methods: chemical and electrochemical. The morphology and the electrochemical behavior of the GC electrode modified with composite rGO/AgNPs (chemical method) and rGO-AgNPs (electrochemical method) were characterized by scanning electron microscopy coupled to an electron gun (FEG-SEM) and cyclic voltammetry (CV). These techniques demonstrated that, in both methods, the graphene oxide (GO) was modified with AgNPs, and the composite synthesized by the electrochemical method showed a better dispersion of the nanoparticles, resulting in an increased surface area when compared to the composite rGO/ AgNPs. Thus, the GC/rGO-AgNPs electrode was evaluated and optimized for simultaneous determination of SMX and TMP and achieved detection limits of 0,6 µmol L-1 to SMX and 0,4 µmol L-1 for the TMP. The proposed electrochemical device, GC/rGO-AgNPS, was successfully applied for the simultaneous determination of SMX and TMP in wastewater.