Colon cancer (CC) ranks high in morbidity and mortality amongst the most frequent occurring cancers worldwide. Mortality rates are mostly caused by mis-diagnosis and the poor efficacy of treatment. The aim of this study was to enhance our insights of quantum dots, for early detection and targeted drug delivery, thereby reducing toxicity to normal cells and reducing side effects that are caused by previous colon cancer medicine. The synthesis, characterization and cytotoxicity studies of CdSe/ZnSe quantum dots (QDs), nanocrystals are reported. Toxicological properties of the Cd2+ core are reduced by capping quantum dots with ZnSe, varying chain length and functional group ligands. Fluorescence wavelength and their size is improved by varying Cd2+ source and varying nanocrystal synthesis growth temperature. CdSe/ZnSe quantum dots are characterized with FT-IR to elucidate their structure. High-resolution transmission electron microscopy (HRTEM), X-Ray Diffraction (EDX), Photoluminescence spectroscopy (PL) and Ultraviolet-visible spectroscopy (UV-Vis) are used to measure their size and composition. Ligand exchange reactions are conducted with the use of 3-Mercaptopropanoic acid (3-MPA) to facilitate bio-compatibility and stability of CdSe/ZnSe QDs. Temperature stability of various ligand capped and stabilized CdSe/ZnSe QDs are measured by using thermogravimetric analysis (TGA). Caco-2 cell line is cultured from colon cancer, and cytotoxic studies are conducted to test for cell viability of various capped 3-Mercaptopropanoic acid (3-MPA) CdSe/ZnSe quantum dots at various concentrations. Myristic acid capped CdSe/ZnSe quantum dots produce high fluorescing mono-disperse quantum dots. The capping material, synthesis temperature and Cd2+ source of CdSe/ZnSe QDs affect fluorescence wavelength and thermal stability of quantum dots. Fluorescence wavelength is improved by using CdCl2.7H2O source of Cd2+. Cytotoxicity was found to be dependent on the concentration and the capping material of quantum dots. CdSe/ZnSe quantum dots toxicity is adjusted and reduced by varying the length, size and type of the capping ligand on the surface of quantum dots.

This study shows a detailed report on the morphological, structural and optical properties of CdSe QDs synthesised by the hot injection method. Cadmium acetate dihydrate and Se powder were used as cadmium and selenide precursors, respectively. Various QD sizes were achieved by synthesizing in temperature range of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. The as synthesized QDs by the hot injection method were cross-examined for their morphological, structural and optical using HRTEM, FTIR, XRD, RS, and UV-Vis spectroscopy techniques respectively. FTIR analysis has revealed vibrations at 738, 738, 738, 738, 735, 735 and 733 cm-1 for the QDs synthesized at various temperatures of 150, 175, 200, 225, 250, 275, and 300℃, respectively. The presence of the above mentioned peaks confirms the presence of Cd-Se bond in our samples. XRD analysis of CdSe QDs revealed diffraction peaks at 2 angles of 16.66 , 25.20 , 34.77 , 40.9 , 45.39 and 49.1 for 150 17.4 , 25.22 , 34.85 , 41.7 , 44.45 and 47.5 for the QDs synthesized at various temperatures of 175 17.07 , 25.19 , 34.85 , 41.34 , 44.41 and 48.86 for 200 ; 16.34 , 25.20 , 34.76 , 40.6 , 44.74 and 49.48 for 225 ; 17.44 , 25.17 , 34.19 , 41.7 , 44.45 , 49.24 for 250 ; 16.70 , 25.16 , 34.85 , 40.32 , 45.1 and 49.1 7 for 275 ;and 17.35 , 25.18 , 35.13 , 41.63 , 45.7 , 49.48 for 300 . These XRD peaks relate to crystal planes of (100), (002), (102), (220), (103) and (112) which belong to hexagonal Wurtzite CdSe crystal structure. Additionally XRD analysis has revealed a general peak shift to higher 2 values was observed for CdSe QDs. HRTEM analysis showed that the synthesised CdSe QDs have a spherical shape and are monodispersed. Moreover, HRTEM analysis has revealed CdSe QDs modal crystallite size of 1.79 nm, 1.81 nm, 2.06 nm, 2.08 nm, 2.11 nm, 3.10 nm and 3.12 nm for the QDs synthesized at various temperatures of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. HRTEM results were in mutual agreement with XRD results. Additionally, the SAED images showed intense electron diffraction rings, which confirmed that the as-synthesised CdSe QDs have a Wurtzite crystal structure. RS analysis showed that CdSe QDs have LO and 2LO vibrational modes which are characteristic peaks for CdSe. The presence of these peaks in Raman spectra further supports our previous observation from XRD analysis and HRTEM analysis that the synthesized CdSe QDs have a Wurtzite crystal structure. The effect of synthesis temperature Raman peak shift, FHWH and peak intensity has been cross examined in this work, Moreover, the effect of increasing temperature on the peak shift, FWHM and peak intensity is discussed in detail below. UV-Vis analysis revealed an absorbance of CdSe QDs in higher wavelengths as temperature was increased. Furthermore, the Yu et al 2003 relation was used to calculate QD size and band gap energy of CdSe QDs. The results showed that QD size increases with increasing synthesis temperature, which is in agreement with HRTEM and XRD results.

The aim of this dissertation is to gain a better understanding of the unique electronic structure of lead salt quantum dots (QDs) and its influences on the nonlinear optical (NLO) properties as well as the time dynamics of the photogenerated charge carriers. A variety of optical techniques such as Z-scan, two-photon excited fluorescence and time-resolved pump probe spectroscopy are used to measure these properties. The one-photon as well as the degenerate and nondegenerate two-photon absorption (2PA) spectra are measured and the electronic wave functions from a four-band envelope function formalism are used to model the results. We observe local maxima in the 2PA spectra for QD samples of many different sizes at energies where only 1PA is predicted by the model. This is similar to the previously measured transitions in the 1PA spectra which are not predicted by the model but accrue at the energies of the two-photon allowed transitions. Most importantly we observe 2PA peaks for all samples at the energy of the first one-photon allowed transition. This result can only be understood in terms of symmetry breaking and therefore is strong evidence that other transitions, not predicted by the model if the selection rules are left intact, also have the origin in the lifted spatial symmetry of the wave functions. On the other hand, the uniquely symmetric eigenenergies of these quantum-confined energy states in the conduction and valance bands explain the observed trend toward larger two-photon cross-sections as the quantum confinement is increased in smaller QDs. Moreover, this unique feature is shown to reduce the possible relaxation channels for photoexcited carriers, which is confirmed experimentally by the reduced carrier relaxation rate as compared to CdSe QDs which lack this symmetry. Carrier multiplication (CM), a process in which several electrons are excited by the iv absorption of a single photon is studied in PbS QDs. We show that for PbS QDs with radius smaller than 2.5 nm the parameters of CM get very close to the theoretical optimum. Nextgeneration solar cells operating under these ideal conditions could potentially have conversion efficiency of up to 42%. This compares favorably to the 30% efficiency limit of a single junction silicon solar cell.

Orientador: Américo Sheitiro Tabata / Banca: Euzi Conceição Fernandes da Silva / Banca: Ligia de Oliveira Ruggiero / Banca: Sandro Martini / Banca: José Humberto Dias da Silva / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Neste trabalho investigamos pontos quânticos de InAs sobre um substrato de GaAs crescidos pela técnica de epitaxia por feixe molecular (MBE, Molecular Beam Epitaxy). Esses pontos quânticos emitem radiação no intervalo de 1,3 üm a 1,5 üm (0,95 eV a 0,83 eV), que corresponde à janela óptica onde ocorre a mínima atenuação do sinal em redes de transmissão por fibras ópticas. Realizamos dois tipos de estudo em dois conjuntos de amostras. No primeiro caso analisamos a influência de alguns parâmetros de crescimento nas propriedades ópticas desses pontos quânticos. No segundo caso, analisamos a influência de um tratamento térmico nas propriedades ópyicas. Resultados de fotoluminescência (PL - photoluminescence) para o primeiro estudo mostraram uma grande influência da velocidade de crescimento nos espectros de emissão que apresentaram múltiplos picos, muito provavelmente associados com o estado fundamental e seus respectivos estados excitados dos pontos quânticos. Para o segundo estudo os resultados de PL mostraram que a emissão óptica consistia de uma larga banda situada entre 1,3 a 1,5 üm. Entretanto, observou-se que, após tratamento térmico durante 3 horas a uma temperatura de 550 ºC, a intensidade da PL aumentou por um fator 3. Além disso, a larga banda observada tornou-se um conjunto de pelo menos 5 picos discretos. O efeito de tratamentos térmicos em poços quânticos é bem conhecido e foi bem explorado na literatura. Em pontos quânticos, os mesmos efeitos também existem, porém, outros de igual importância tembém se apresentam. Dentre os mais importantes podemos citar a redistribuição dos tamanhos dos pontos quânticos, que podem em alguns casos limites fazer com que o ponto quântico desapareça, e a redistribuição das tensões entre a interface ponto quântico/matriz. Neste trabalho... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study investigated InAs large quantum dot on GaAs substrate grown by the techique of molecular beam epitaxy (MBE). These quantum dots emit in the spectral range of 1.3 üm and 1.5 üm (0.95 eV to 0.83 eV), which corresponds to the window of minimal signal attenuation on transmission networks by optical fiber. We have performed two kinds of study into two different sets of samples. In the first case, we have analyzed the influence of some growth parameters on the optical properties of these quantum dots. In the second one, we have analyzed the influence of a thermal treatment on the optical properties. Results of photoluminescence (PL) on the first study showed a great influence of growth velocity in the PL spectra line shape. For the second study the results of PL on an as grown sample showed that the emission signal was a large optical band in the wave length range of 1.3 üm and 1.5 üm. However, it was observed that after the thermal treatment of 3 hours at a temperature of 550 ºC, the intensity of these PL emissions increased by a factor 3. Moreover, the observed large band has become a series of at least 5 discrete peaks. The effect of heat treatments in quantum wells is well known and has been well explored in literature. In quantum dot, the same effects are expected; however, other equally important effects are also present. The most important is the size redistribution of the quantum dots, which can in some limit cases, vanish these quantum dot. Our study identified the origin of these multiple peaks, and found emissions of PL at room temperature in the optical window between 1.3 and 1.5 üm. / Doutor

Orientador: José Antônio Brum / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T23:45:16Z (GMT). No. of bitstreams: 1 Andriolo_HelderFaria_M.pdf: 2066347 bytes, checksum: c0835c5528aa09df816a2dfb45249e5f (MD5) Previous issue date: 2015 / Resumo: Nesse trabalho estudamos um sistema de GaAs/In_{0.27}Ga_{0.73} As/Al_{0.3}Ga_{0.7}As, intencionalmente dopado com material do tipo-n, em que ocorre a transferência de elétrons, provenientes da dopagem, para o poço quântico de In_{0.27}Ga_{0.73}As, formando um gás de elétrons bidimensional no poço. A seguir o efeito da introdução de pontos quânticos auto-organizados de InAs na estrutura foi analisado. Nossos resultados mostram uma pequena mudança no perfil de potencial da estrutura. O que ocorre após a introdução dos pontos quânticos é, basicamente, uma redistribuição dos elétrons, que agora passam a ocupar o poço quântico e o ponto quântico. Estudamos também as propriedades ópticas, espectros de absorção e emissão, de pontos quânticos acoplados com gás de portadores. Para isso foi necessário estabelecer um método na qual discretizamos o contínuo de níveis energéticos do gás de portadores (elétrons), o método através da cadeia de Wilson foi o utilizado nos cálculos, embora outros dois métodos também tenham sido mostrados. Introduzimos, por fim, um íon de manganês no centro do ponto quântico e calculamos espectros de emissão desse sistema com os níveis do gás elétrons discretizados através da cadeia de Wilson / Abstract: In this work, we study a GaAs/In_{0.27}Ga_{0.73}As/Al_{0.3} Ga_{0.7}As system intentionally doped n-type material, which occurs a transfer of electrons from the doping into In_{0.27}Ga_{0.73}As quantum well, forming a two-dimensional electron gas in the well. Next, the effect of introducing self-assembled InAs quantum dots in the structure was analyzed. Our results show little change in potential profile of the structure. What happens after the introduction of quantum dots is basically a redistribution of electrons, that now occupy the quantum well and quantum dot. We also studied the optical properties, absorption and emission, of quantum dots coupled with carrier gas. This required establishing a method in which discretize the continuous energy levels of the carrier gas (electrons), the method by Wilson chain was used in the calculations, although other two methods also have been shown. Introduced, finally, a manganese ion in the center of the quantum dot, and we calculated emission spectra of this system, with the electron gas levels discretized by Wilson chain / Mestrado / Física / Mestre em Física / 131432/2013 / 2013/25371-1 / CNPQ / FAPESP

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-29Bitstream added on 2014-06-13T20:21:46Z : No. of bitstreams: 1 martins_mr_dr_bauru.pdf: 576235 bytes, checksum: cae5dc5f897a536d60d112303dafaf34 (MD5) / Secretaria de Educação do Estado de São Paulo / Neste trabalho investigamos pontos quânticos de InAs sobre um substrato de GaAs crescidos pela técnica de epitaxia por feixe molecular (MBE, Molecular Beam Epitaxy). Esses pontos quânticos emitem radiação no intervalo de 1,3 üm a 1,5 üm (0,95 eV a 0,83 eV), que corresponde à janela óptica onde ocorre a mínima atenuação do sinal em redes de transmissão por fibras ópticas. Realizamos dois tipos de estudo em dois conjuntos de amostras. No primeiro caso analisamos a influência de alguns parâmetros de crescimento nas propriedades ópticas desses pontos quânticos. No segundo caso, analisamos a influência de um tratamento térmico nas propriedades ópyicas. Resultados de fotoluminescência (PL - photoluminescence) para o primeiro estudo mostraram uma grande influência da velocidade de crescimento nos espectros de emissão que apresentaram múltiplos picos, muito provavelmente associados com o estado fundamental e seus respectivos estados excitados dos pontos quânticos. Para o segundo estudo os resultados de PL mostraram que a emissão óptica consistia de uma larga banda situada entre 1,3 a 1,5 üm. Entretanto, observou-se que, após tratamento térmico durante 3 horas a uma temperatura de 550 ºC, a intensidade da PL aumentou por um fator 3. Além disso, a larga banda observada tornou-se um conjunto de pelo menos 5 picos discretos. O efeito de tratamentos térmicos em poços quânticos é bem conhecido e foi bem explorado na literatura. Em pontos quânticos, os mesmos efeitos também existem, porém, outros de igual importância tembém se apresentam. Dentre os mais importantes podemos citar a redistribuição dos tamanhos dos pontos quânticos, que podem em alguns casos limites fazer com que o ponto quântico desapareça, e a redistribuição das tensões entre a interface ponto quântico/matriz. Neste trabalho... / This study investigated InAs large quantum dot on GaAs substrate grown by the techique of molecular beam epitaxy (MBE). These quantum dots emit in the spectral range of 1.3 üm and 1.5 üm (0.95 eV to 0.83 eV), which corresponds to the window of minimal signal attenuation on transmission networks by optical fiber. We have performed two kinds of study into two different sets of samples. In the first case, we have analyzed the influence of some growth parameters on the optical properties of these quantum dots. In the second one, we have analyzed the influence of a thermal treatment on the optical properties. Results of photoluminescence (PL) on the first study showed a great influence of growth velocity in the PL spectra line shape. For the second study the results of PL on an as grown sample showed that the emission signal was a large optical band in the wave length range of 1.3 üm and 1.5 üm. However, it was observed that after the thermal treatment of 3 hours at a temperature of 550 ºC, the intensity of these PL emissions increased by a factor 3. Moreover, the observed large band has become a series of at least 5 discrete peaks. The effect of heat treatments in quantum wells is well known and has been well explored in literature. In quantum dot, the same effects are expected; however, other equally important effects are also present. The most important is the size redistribution of the quantum dots, which can in some limit cases, vanish these quantum dot. Our study identified the origin of these multiple peaks, and found emissions of PL at room temperature in the optical window between 1.3 and 1.5 üm.