Le phototransistor est un nouveau type de photo-détecteur avec une structure MOSFET spéciale qui peut non seulement convertir la lumière absorbée en variation de courant, mais également auto-amplifier ce photo-courant. En particulier, avec des progrès continus dans la synthèse des points Quantum Dots (QDs), les caractères optiques et électriques uniques renforcent le coefficient d'absorption et la génération des trous d'électrons par des processus intégrés faciles. Dans cette thèse, on a synthétisé les PdS infrarouges PbS avec une large absorption infrarouge (IR) (600-1400 nm) et un rendement élevé pour être mélangés avec l'isolateur de porte SU8 des TFT à faible température de poly-silicium (LTPS). Grâce à l'utilisation de cet isolateur de porte photo-sensoriel hybride, ces LTPS TFT peuvent encore obtenir d'excellentes performances électriques telles qu'une mobilité suffisante (3.1 cm2 / Vs), des caractères TFT stables, un rapport marche / arrêt raisonnable (104 ~ 105) et une tension sous-seuil /Déc). De plus, en cas d'exposition à la lumière infrarouge incidente, la sensibilité élevée (1800 A/W) et la sensibilité non négligeable (13 A/W) se trouvent respectivement à 760 nm et 1300 nm. De plus, la photosensibilité atteint également jusqu'à 80 et le temps de réponse est d'environ 30 ms pendant un balayage du signal IR pulsé. Elle prend des mesures concrètes pour l'application générale du phototransistor IR. / Phototransistor is a novel type of photodetector with special MOSFET structure which can not only convert absorbed light into variation of current but also self-amplify this photocurrent. Especially, with continual advances in quantum dots' (QDs) synthesis, the unique optical-electrical characters reinforce absorption coefficient and electron-hole's generation by easy integrated processes. In this thesis, the infrared PbS QDs with wide infrared (IR) absorption (600-1400 nm) and high efficiency were synthesized to be blended with SU8 gate insulator of Low-Temperature-Poly-Silicon (LTPS) TFTs. Through using this hybrid photo-sensing gate insulator, this LTPS TFTs can still obtain excellent electrical performance such as enough mobility (3.1 cm2/Vs), stable TFT's characters, reasonable on/off ratio (104~105) and subthreshold voltage (3.2 V/Dec). Moreover, under incident IR light's exposure, the high responsivity (1800 A/W) and not negligible responsivity (13 A/W) can be found at 760 nm and 1300 nm respectively. In addition, the photosensitivity also reaches up to 80 and the response time is approximately 30 ms during a pulsed IR signal's scanning. It takes concrete steps forward for the broad application of IR phototransistor.

A size-selected series of water-soluble luminescent Ag–In–S (AIS) and core/shell AIS/ZnS QDs were produced by a precipitation technique. Up to 10–11 fractions of size-selected AIS (AIS/ZnS) QDs emitting in a broad color range from deep-red to bluish-green were isolated with the photoluminescence (PL) quantum yield reaching 47% for intermediate fractions. The size of the isolated AIS (AIS/ZnS) QDs varied from ~2 nm to ~3.5 nm at a roughly constant chemical compo- sition of the particles throughout the fractions as shown by the X-ray photoelectron spectroscopy. The decrease of the mean AIS QD size in consecutive fractions was accompanied by an increase of the structural QD imperfection/disorder as deduced from a notable Urbach absorption “tail” below the fundamental absorption edge. The Urbach increased from 90–100 meV for the largest QDs up to 350 meV for the smallest QDs, indicating a broadening of the distribution of sub-bandgap states. Both the Urbach energy and the PL bandwidth of the size-selected AIS QDs increased with QD size reduction from 3–4 nm to ~2 nm and a distinct correlation was observed between these parameters. A study of size-selected AIS and AIS/ZnS QDs by UV photoelectron spectroscopy on Au and FTO substrates revealed their valence band level EVB at ~6.6 eV (on Au) and ~7 eV (on FTO) and pinned to the Fermi level of conductive substrates resulting in a masking of any possible size- dependence of the valence band edge position.

A size-selected series of water-soluble luminescent Ag–In–S (AIS) and core/shell AIS/ZnS QDs were produced by a precipitation technique. Up to 10–11 fractions of size-selected AIS (AIS/ZnS) QDs emitting in a broad color range from deep-red to bluish-green were isolated with the photoluminescence (PL) quantum yield reaching 47% for intermediate fractions. The size of the isolated AIS (AIS/ZnS) QDs varied from ~2 nm to ~3.5 nm at a roughly constant chemical compo- sition of the particles throughout the fractions as shown by the X-ray photoelectron spectroscopy. The decrease of the mean AIS QD size in consecutive fractions was accompanied by an increase of the structural QD imperfection/disorder as deduced from a notable Urbach absorption “tail” below the fundamental absorption edge. The Urbach increased from 90–100 meV for the largest QDs up to 350 meV for the smallest QDs, indicating a broadening of the distribution of sub-bandgap states. Both the Urbach energy and the PL bandwidth of the size-selected AIS QDs increased with QD size reduction from 3–4 nm to ~2 nm and a distinct correlation was observed between these parameters. A study of size-selected AIS and AIS/ZnS QDs by UV photoelectron spectroscopy on Au and FTO substrates revealed their valence band level EVB at ~6.6 eV (on Au) and ~7 eV (on FTO) and pinned to the Fermi level of conductive substrates resulting in a masking of any possible size- dependence of the valence band edge position.

Submitted by NATHALIA CRISTINA RISSI null (nathaliarissi_farmacia@yahoo.com.br) on 2016-07-04T12:35:43Z No. of bitstreams: 1 Tese Nathalia Cristina Rissi 1.pdf: 3733548 bytes, checksum: bde3d4680fdf9def65256855510fa057 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-07-07T17:05:40Z (GMT) No. of bitstreams: 1 rissi_nc_dr_arafcf.pdf: 3733548 bytes, checksum: bde3d4680fdf9def65256855510fa057 (MD5) / Made available in DSpace on 2016-07-07T17:05:40Z (GMT). No. of bitstreams: 1 rissi_nc_dr_arafcf.pdf: 3733548 bytes, checksum: bde3d4680fdf9def65256855510fa057 (MD5) Previous issue date: 2016-06-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nos últimos anos, é possível observar um grande interesse no desenvolvimento de sistemas multifuncionais direcionados ao diagnóstico e tratamento do câncer. Estes sistemas também conhecidos como “teranósticos” têm se mostrado interessantes, pois ampliam a capacidade de liberação prolongada de fármacos anticancerígenos em células específicas, além de proporcionar um monitoramento ótico através da luminescência de pontos quânticos. Diante deste contexto, o presente estudo teve como objetivo estabilizar os pontos quânticos a base de óxido de zinco (ZnO) em meio aquoso através da modificação de superfície com o 3-(Glycidyloxypropyl)trimethoxysilane (GPTMS) e também em meio orgânico através da modificação com o Hexadecyltrimethoxysilane (HTMS), permitindo assim a veiculação do mesmo em micelas poliméricas A ligação entre os pontos quânticos e as moléculas dos modificadores ocorreu através das reações de hidrólise e condensação, utilizando como catalisador básico o hidróxido de lítio. Esta reação conduziu a formação de uma camada de siloxano ao redor das nanopartículas e resultou nas ligações covalentes do tipo ZnO-Si-O. Ainda com o objetivo de aumentar a estabilidade do ZnO em meio orgânico e consequentemente suas propriedades luminescentes, foi sintetizado uma bicamada formada entre o Ácido Oleico (AO) e o HTMS. As modificações na superfície do ZnO foram confirmadas pelas técnicas de espectroscopia vibracional na região do infravermelho e também pela espectroscopia de fotoelétrons induzidos por raios-X. O comportamento ótico foi feito através da espectroscopia de absorção na região do UV-Vis. Com está técnica, identificou-se o comprimento de onda limite associado ao pico excitônico do ZnO e através do monitoramento deste pico, observou-se estabilidade em água por um período de 15 dias para a grande maioria das amostras de ZnO modificado pelo GPTMS e também para o ZnO modificado pelo HTMS e pela bicamada de AO/HTMS em clorofórmio. O tamanho final dos pontos quânticos foi analisado pela microscopia de transmissão eletrônica, apresentando um tamanho médio entre 3,5- 4nm para as amostras de ZnO modificado pelo GPTMS e de 4,5 nm para as amostras de ZnO modificado pelo HTMS e pela bicamada de AO/HTMS. Com a técnica de difração de raios-X, identificou-se os picos de difração correspondentes a uma estrutura cristalina do tipo Wurtzita. As medidas de fotoluminescência permitiu a obtenção de informações sobre a intensidade luminescente, assim como as cores emitidas dos pontos quânticos e demostraram a importância das modificações de superfície em relação ao aumento da intensidade luminescente. A veiculação do ZnO estáveis no meio orgânico em micelas poliméricas formadas pelo Pluronic F127 e Pluronic F68, foi realizada com sucesso. Este fato foi observado por meio dos espectros de absorção no UV-vis e também pelas medidas de fotoluminescência. Com a técnica de espalhamento de luz dinâmico, avaliou-se parâmetros relacionados com o tamanho e o índice de polidispersidade das micelas. O teste de citotoxicidade in vitro foi feita através do MTT e apresentou uma boa viabilidade celular para as linhagens celulares de queratinócito humano (HaCat) e de hepatoma humano (HepG2). A quantificação das células em que houve a internalização das micelas contendo os pontos quânticos hidrofóbicos como marcador foi feita através da citometria de fluxo. Diante dos resultados obtidos, conclui-se a existência de um potencial a ser explorado em relação ao ZnO modificado pelo GPTMS em aturar futuramente como sondas biológicas. Já as propriedades hidrofóbicas concedidas ao ZnO modificado pelo HTMS e pela bicamada formada entre o AO/HTMS permitiu a incorporação dos mesmos em sistemas micelares e tem como objetivo auxiliar na aplicação futura desses pontos quânticos através do desenvolvimento de sistemas teranósticos. / In recent years, it is possible to observe a growing interest in the development of multifunctional systems used, that can be used in the diagnosis and treatment of cancer These systems also known as " theranostic " and have gained considerable attention due to their capacity of release anticancer drugs into specific cells, besides to optical monitoring through quantum dots. In this context, the present study was aimed to stabilize the quantum dots of of ZnO in water by modifying with 3-(Glycidyloxypropyl)trimethoxysilane (GPTMS) with and organic medium.by modifying with Hexadecyltrimethoxysilane (HTMS), thus allowing them to be incorporated into polymeric micelles The binding between the quantum dots with the modifiers occurred by hydrolysis and condensation reaction under basic catalysis by lithium hydroxide, thus leading to the formation of siloxane layer and resulted in ZnO-Si-O covalent bond. In order to improve the stability of ZnO-QDs and consequently their photoluminescence properties, was synthesized a coating bilayer by OA and HTMS. The ZnO surface modification was confirmed by infrared spectroscopy and also by X-ray photoelectron spectroscopy. The optical behavior was performed by absorption spectroscopy in the UV-Vis region. With this technique was possible to identify the wavelength limit associated with the excitonic peak and by monitoring of this peak was observed a great stability during 15 days for almost all samples of ZnO modified by GPTMS in water and ZnO modified by HTMS and bilayer AO / HTMS in chloroform. The finale size of quantum dots was analyzed by transmission electron microscopy that showed an average size about 3,5- 4nm for the samples of znO modified by GPTMS, and 4,5 nm by HTMS and AO/HTMS bilayer. By X-ray diffraction, it was possible to identify through the diffraction peak a wurtzite structure. The photoluminescence measurements allowed to obtain information about luminescence intensity, as well as the emitted colors by quantum dots and demonstrated the importance of surface modifications in relation to increase of luminescence intensity. The placement of hydrophobic ZnO into polymeric micelles formed by Pluronic F127 and Pluronic F68 was successful. This fact can be observed by absorption spectroscopy in UV-vis and by photoluminescence measurements. With the dynamic light scattering, it was possible to observe the hydrodynamic size distribution and polydispersity index of the micelles. In vitro cytotoxicity assay was performed by MTT and showed a great cellular viability for human keratinocytes cells (HaCat) and for hepatocellular carcinoma cells (HepG2). The cellular internalization was performed by flow cytometry. Based on these results, it was concluded a potential to be explored in to ZnO modified by GPTMS to acting in the future as biological probes. The hydrophobic properties of ZnO modified by HTMS and the AO / HTMS bilayer allowed the incorporation in micellar systems and aims to assist in the implementation of these quantum dots through the development of systems theranostics.

L'efficacité de la thérapie photodynamique (PDT) est confrontée à plusieurs verrous : les photosensibilisateurs (PSs) utilisés en clinique ne sont pas adaptés à la fenêtre thérapeutique, ils subissent un photoblanchiment lors du traitement, et leur nature organique pose des problèmes de solubilité en milieu biologique. Ils présentent également une faible sélectivité envers les tissus tumoraux à traiter. Dans le cadre de cette thèse, trois approches visant une amélioration de la PDT appliquée à la cancérologie ont été développées : la vectorisation, l'adressage, et l'optimisation de nouveaux PSs. La synthèse de structure PS/vecteur a permis d'élaborer des structures hydrophiles capables de vectoriser des PSs hydrophobes. Des porphyrines ont ainsi été greffées sur des dendrimères polyamidoamine (PAMAM) dissymétriques. La conservation des propriétés photophysiques des PSs après leur couplage au dendrimère a été mise en évidence. Des quantum dots (QDs), grâce à la modularité de leurs propriétés photophysiques et leur capacité à résister au photoblanchiment, ont été synthétisés et utilisés comme nouvelle classe d'agents photosensibilisants. Ces QDs ont été préparés afin d?être hydrophiles et utilisables dans la fenêtre thérapeutique de la PDT. Une étude in vitro des QDs couplés à l'acide folique a mis en évidence leur activité photodynamique. Des études réalisées par une approche de plans d'expérience a permis de hiérarchiser les facteurs expérimentaux en fonction de leurs impacts sur l'activité photodynamique. Nous avons en particulier montré une amélioration de la sélectivité des conjugués envers les cellules surexprimant le récepteur à l'acide folique. / Photodynamic therapy (PDT) efficiency is confronted to various barriers, such as photosensitizers (PSs) which are not optimized to the therapeutic window and endure photobleaching during treatment, moreover their organic nature can also lead to solubility problems for biological uses. Usual PSs show also a lack of selectivity toward tumor tissues to treat. In order to improve PDT treatment, three approaches were studied: delivery, targeting and use of a new class of photosensitizing agents.Synthesis of PS/delivery vehicle structure enabled to developed hydrophilic structure able to deliver hydrophobic PSs. Porphyrins were linked to dissymmetric polyamidoamine dendrimers. Conservation of the photophysical properties of PSs after linkage to the dendrimer was then highlighted.Due to the modularity of their photophysical properties and their capacity to resist to photobleaching, hydrodispersable Quantum dots (QDs) were synthesized to match the therapeutic window of PDT.In vitro studies of these QDs linked to folic acid showed their ability to induce a photodynamic activity. We used an experimental design approach to distinguish the impact of each experimental factor on the photodynamic activity of these QD-folic acid conjugates. We showed in particular an increase of the selectivity of the folic acid-linked QDs towards cell line overexpressing the folate receptor

Título de Ingeniería en Biotecnología Molecular / Los mecanismos involucrados en el control post-transcripcional del ciclo replicativo del Virus de la Inmunodeficiencia Humana (VIH), específicamente los eventos moleculares que permiten la interacción del ARN genómico (ARNg) viral con la maquinaria celular para su transporte, traducción o empaque dentro de la célula, aún no han sido completamente dilucidados. Actualmente existen diversas técnicas para el estudio de la localización sub-celular de ARNg, entre las que destaca RNA FISH (RNA Fluorescent in situ hybridization), método ampliamente utilizado para el estudio de la localización y cambios temporales de ARN y ribonucleoproteínas. Generalmente, en esta técnica se utilizan sondas acopladas a fluoróforos orgánicos que hibridan a regiones específicas para las que han sido diseñadas. No obstante, estas sondas presentan fotoblanqueamiento significativo, y un espectro de emisión amplio (50-100 nm), lo que limita su uso. Es por esto que surge la necesidad de recurrir a nuevas alternativas, tales como sondas acopladas a Quantum dots (QDs), los cuales en contraste con fluoróforos orgánicos poseen una vida fluorescente significativamente más larga, mayor fotoestabilidad y un amplio espectro de absorción. Considerando lo anterior, en el presente trabajo se propone la construcción de sondas específicas asociadas a QDs compuestos de Cadmio-Telurio recubiertos por Glutatión (QDs CdTe- GSH) que reconocen la región pBSK-GagPol como matriz para la transcripción in vitro, obteniendo así fragmentos de ARN, los cuales fueron desfosforilados en su extremo 5', para luego incorporarles en su lugar un fosfato γ unido a un grupo sulfhidrilo (SH). De esta forma, los transcritos de ARN fueron capaces de unirse a QDs CdTe-GSH a través de enlaces disulfuro. Generando así sondas de ARN xiii acoplada a QDs CdTe-GSH capaces de unirse al ARNg de VIH-1 en presencia y ausencia de la proteína Rev,la cual actúa como un regulador clave en el control post-transcripcional de la expresión génica viral, actuando principalmente en los procesos de exportación nuclear y traducción. De manera que en estas condiciones fue posible validar a través de experimentos de RNA FISH, el ingreso citoplasmático y nuclear de la sonda de ARN acoplada a QDs CdTe-GSH, además de una interacción específica con el ARN genómico de VIH-1. Este hecho representa la prueba de concepto de que es posible generar una sonda acoplada a QDs específica contra el ARN genómico de VIH-1, permitiendo el estudio de la expresión génica del virus, lo que también abre nuevas posibilidades para el estudio de VIH-2 u otros tipos de virus. / The mechanisms involved in the post-transcriptional control of the replicative cycle of the Human Immudeficiency Virus (HIV), specifically the molecular events allowing the interaction between the viral genomic RNA (gRNA) and the cellular machinery for the transport, translation or packaging, have not been elucidated yet. Currently, the study of localization and temporary changes of RNA and ribonucleoproteins relies mainly on RNA FISH (RNA Fluorescent in situ hybridization)-based strategies. RNA FISH uses specific hybridization probes coupled to organic fluorophores. However, these fluorescent molecules commonly present limiting characteristics such as significant photobleaching and a wide emission spectrum (50-100 nm). Therefore, a considerable demand arises for new alternatives, such as probed coupled to Quantum dots (QDs), which in contrast to organic fluorophores, exhibit longer fluorescence lifetime, higher photostability and broad absorption spectra. Considering previous facts, the aim of this work was to develop specific probes coupled to glutathione-capped cadmium-telluride quantum dots (QDs CdTe-GSH), able of recognizing and associate with the Gag-Pol region present on the HIV-1 genomic RNA (gRNA). Thus, in order to achieve this objective, the vector pBSK-GagPol was used as a template for in vitro transcription of Gag-Pol complementary RNA, which was fragmented and dephosphorylated at the 5' end, with the purpose to incorporate a γ phosphate coupled to a sulfhydryl group (SH) instead. Then, the SH-containing RNA fragments were attached to QDs CdTe-GSH by a disulfide bond. As a result, we generated single-stranded RNA probes coupled to QDs CdTe-GSH capable of hybridizing to HIV-1 gRNA in the presence and absence of the viral protein Rev, which acts as a key regulator of the post-transcriptional control of viral gene expression acting mainly during nuclear export and translation. Thereby, under these conditions, we validated the cytoplasmic and nuclear entrance of the probe coupled to Qds CdTe-GSH, and specific interaction between the probe and gRNA of HIV-1. This fact represents the proof of concept that it is possible to generate RNA probes coupled to QDs CdTe-GSH to study genetic expression of HIV-1, and also opens up new opportunities for the study of HIV-2 or other virus types.

Στην παρούσα Ειδική Ερευνητική Εργασία ερευνώνται οι οπτικές ιδιότητες των νανοκρυσταλλικών κβαντικών τελειών CuInS2/ZnS, γνωστές ως CIS/ZnS QDs, τόσο με τη χρήση φασματοσκοπίας σταθερής κατάστασης όσο και με τη χρήση φασματοσκοπίας χρονικής ανάλυσης με την τεχνική Time Correlated Single Photon Counting. Ειδικότερα, διερευνώνται οι μηχανισμοί που εμπλέκονται στη διαδικασία της εκπομπής φωτός, η επίδραση που έχει η πολικότητα του διαλύτη και η συγκέντρωση των κβαντικών τελειών, όταν είναι διαλυμένες εντός διαλύματος, καθώς και η αλληλεπίδραση μεταξύ των κβαντικών τελειών όταν είναι εναποτιθέμενες σε υμένια, είτε με την τεχνική drop-casting είτε με spin-coating. Τόσο η αύξηση της συγκέντρωσης των κβαντικών τελειών όσο και η αύξηση της πολικότητας του διαλύτη προκάλεσε τη μετατόπιση του εξιτονικού ώμου και του μήκους κύματος μέγιστης εκπομπής προς το ερυθρό, στα φάσματα σταθερής κατάστασης. Επίσης η μετατόπιση της φωτοφωταύγειας των CIS/ZnS QDs προς το ερυθρό ήταν μεγαλύτερη στα υμένια που είχαν παρασκευασθεί με την τεχνική drop-casting από τα υμένια με το ίδιο υπόστρωμα που είχαν παρασκευασθεί με την τεχνική spin-coating. Με χρήση φασματοσκοπίας χρονικής ανάλυσης, ανιχνεύθηκε η ύπαρξη τριών μηχανισμών στα διαλύματα με χρόνους ζωής 1-3, 20-40 και 200-300 ns, ενώ στα υμένια προστέθηκε ένας επιπλέον μηχανισμός με χρόνο ζωής από μερικές εκατοντάδες ps έως 4 ns. Ο χαρακτήρας της αποδιέγερσης των QDs στα υμένια κυμαίνεται μεταξύ διεκθετικού και τετραεκθετικού ανάλογα με το δείγμα και το μήκος κύματος ανίχνευσης. Το περίεργο χαρακτηριστικό του νέου μηχανισμού που ανιχνεύθηκε στα υμένια είναι ότι γίνεται πιο γρήγορος και πιο αποδοτικός καθώς το μήκος κύματος ανίχνευσης αυξάνει. Ένας παρόμοιος μηχανισμός δεν έχει αναφερθεί σε άλλες εργασίες με CIS/ZnS QDs, ενώ έχει αναφερθεί σε παλιότερες εργασίες με PbS QDs τόσο σε διαλύματα όσο και σε στερεά υμένια. Η μετατόπιση των πυκνών υμενίων προς το ερυθρό σε σχέση με τα αραιά αποτελεί ένδειξη της ύπαρξης μεταφοράς ενέργειας μεταξύ QDs διαφορετικών μεγεθών. / In this Master Thesis, the optical properties of CuInS2/ZnS nanocrystal quantum dots are investigated. For this purpose both steady state and time resolved spectroscopy, specifically the Time Correlated Single Photon Counting technique, were used. The photoluminescence properties of CuInS2/ZnS quantum dots, commonly known as CIS/ZnS QDs, either dissolved in solutions of different concentrations and solvent polarities or deposited on films made by spin-coating or drop-casting are studied. Either in the absorption and the photoluminescence steady state spectra, a red-shift both in the excitonic transition and the wavelength of the maximum intensity was observed as the concentration of the CIS/ZnS QDs or the polarity of the solvent increased. In films, a red-shifted photoluminescence spectrum is observed for films made by drop-casting compared to those prepared by spin-coating, having the same substrate material. By using time-resolved photoluminescence spectroscopy a three-exponential decay was observed in solutions, with time constants 1-3, 20-40 and 200-300 ns, while decays in films, apart from the three mechanisms also observed in solutions, also exhibit a fast decay component with a lifetime varying from some hundreds of ps until 4 ns. The attitude of the decay in films varies from two-exponential to four-exponential and it depends on the samples and the detection wavelength. The strange characteristic of the new mechanism which was detected in films is that its lifetime becomes shorter and its pre-exponential factor increases with the detection wavelength. To the best of our knowledge, such a faster decay as the emission wavelength increases has never been reported for CIS/ZnS QDs, but it has been reported for PbS QDs either diluted in solution or deposited in polymeric matrices. The time resolved photoluminescence spectra in the drop-casted films experience a larger transient red-shift than the spin-coated ones, indicative of a possible energy transfer among adjacent QDs with different diameters.

>Magister Scientiae - MSc / In this study PbSe quantum dots (QDs) were successfully synthesized via the organometallic and aqueous routes. Optical characterization was carried out using photoluminescence (PL) spectroscopy, structural and morphological characterization were carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDS) was used to determine the composition of the QDs. All the synthesized QDs were found to have emissions within the near-infrared region of the spectrum (≥1000 nm) with most of them being less than 5 nm in size. The aqueous synthesized QDs had a perfect Gaussian emission spectrum with a FWHM of ~23 nm indicating pure band gap emission and narrow size distribution respectively. The QDs were determined to have a cubic rock-salt crystal structure consistent with bulk PbSe. The aqueous synthesized QDs were however not stable in solution with the QDs precipitating after approximately 48 h. The organometallic synthesized QDs were transferred into the aqueous phase by exchanging the surface oleic acid ligands with 11-mercaptoundecanoic acid ligands. The ligand exchanged QDs were however stable in solution for over two weeks. The effects of reaction parameters on the optical and structural properties of the organometallic synthesized QDs were investigated by varying the reaction time, temperature, ligand purity, lead and selenium sources. It was observed that larger QDs were formed with longer reaction times, with reactions proceeding faster at higher reaction temperatures than at lower temperatures. Varying the ligand purity was found to have minimal effects on the properties of the synthesized QDs. The lead and selenium sources contributed largely to the properties of the QDs with lead oxide producing spherical QDs which were smaller compared to the cubic QDs produced from lead acetate. TBPSe was seen to produce smaller QDs as compared to TOPSe. The cytotoxity of the synthesized QDs was determined following the WST-1 cell viability assay with the QDs being found to be non-toxic at all the tested concentrations