Made available in DSpace on 2017-07-24T19:38:02Z (GMT). No. of bitstreams: 1 Karine Klider.pdf: 2018760 bytes, checksum: 075742018dbf1f087bc4c115d778a329 (MD5) Previous issue date: 2010-03-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The introduced work on this dissertation discussion presented in this master’s degree dissertation describes the development of a synthetic rote to obtain a compound that contains an aromatic ring and connected to it two dibromade methyl groups, a CN group and a dye. The dye used at this work was the Rhodamine B, and the final product consists on a monomer that when gets polymerized, by electrochemical route, produces a luminescent polymer to solar cell application. It was described the preparation and the characterization of a series of organic compounds. Some intermediary compounds were prepared after the realization of a lot of steps of synthesis to finally approach the best methodology. The compounds characterization were performed by means of infrared spectroscopic (FTIR) and nuclear magnetic resonance spectroscopic measurements (RMN H1). Another part of this work describes a soluble copolymer preparation by electrochemical rote and it characterization. The prepared copolymer consists on the soluble form of a mixture of poly(2-methoxy-5-bromo-p-phenylenevinylene) (MBPPV) and poly(2,5-dicyano-p-phenylenevinylene) DCN-PPV at different proportion. The copolymer DCN-PPV/MB-PPV and the polymer MB-PPV were synthesized by electrochemical rote and the charges transfer process were studied by cyclic voltammetry and chronoamperometry measurements. These copolymers were characterized by FTIR and UV-VISIBLE absorption spectroscopy and by measurements of fluorescence. / O trabalho apresentado nesta dissertação de mestrado descreve o desenvolvimento de uma rota sintética para a obtenção de um composto contendo um anel aromático e a ele ligados duas metilas dibromadas, um grupo CN, e um corante. O corante em questão é a Rodamina B, e o produto final é um monômero que, ao ser polimerizado por via eletroquímica, forma um polímero eletroluminescente com aplicação em células solares. Foram então descritas as preparações e as caracterizações de uma série de compostos orgânicos. Alguns compostos intermediários foram preparados após a realização de várias etapas de síntese até se obter a melhor metodologia. A caracterização destes compostos foi realizada por meio de medidas de espectroscopia de infravermelho (FTIR) e espectroscopia de ressonância magnética nuclear (RMN H1). Outra parte deste trabalho descreve a preparação via eletroquímica de um copolímero solúvel e a sua caracterização. O copolímero formado consiste na mistura do poli(2-metóxi-5-bromo-p-fenilenovinileno) (MB-PPV) com o poli(2,5- diciano-p-fenilenovinileno) (DCN-PPV) em diferentes proporções. O copolímero, assim como o polímero MB-PPV, foram sintetizados eletroquimicamente, sendo que o processo de transferência de carga que ocorre durante sua formação foi estudado por meio de medidas de voltametria cíclica e de cronoamperometria. As caracterizações foram realizadas por medidas de FTIR, de espectroscopia de absorção no UV-Visível e por medidas de emissão e excitação de fluorescência.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Complexos de bipiridinas de rutÃnio sÃo bastante estudados na literatura por apresentarem propriedades de interesse em diversas Ãreas como estudos fotoquÃmicos e fotofÃsicos, aplicaÃÃo em sistemas biolÃgicos e como fotosensibilizadores em cÃlulas solares. No presente trabalho, os complexos do tipo cis-[Ru(bpy)(dcbH2)(L)Cl], onde L = Azul do Nilo (NB), Azul de Toluidina (TBO), 9-Aminoacridina (9AA), Azure B (AB) e Violeta de Cresila (VC) foram sintetizados e caracterizados por tÃcnicas espectroscÃpicas e eletroquÃmica para aplicaÃÃo em cÃlulas solares sensibilizadas por corante (DSCs). AlÃm destes, o complexo cis-[Ru(dcbH2)(bpy)(TCNE)Cl] (Ru-TCNE) tambÃm foi testado como sensibilizador em DSC. Estes compostos apresentaram bandas de transferÃncia de carga do tipo MLCT na regiÃo do visÃvel e potenciais redox termodinamicamente favorÃveis para as reaÃÃes de transferÃncia de carga que ocorrem no dispositivo fotoeletroquÃmico. A adsorÃÃo quÃmica dos complexos sensibilizadores na superfÃcie do TiO2 foi evidenciada pelo deslocamento das bandas de MLCT para regiÃes de menor energia quando comparadas aos espectros em soluÃÃo. Os desempenhos fotovoltaicos dos complexos como sensibilizadores em DSC foram avaliados atravÃs das curvas corrente versus potencial, obtidas em condiÃÃes padrÃo AM 1,5. As DSCs contendo os sensibilizadores Ru-TBO e Ru-AB apresentaram os menores desempenhos fotovoltaicos com eficiÃncia global de 0,02 e 0,06%, respectivamente. JÃ as cÃlulas solares sensibilizadas pelos corantes Ru-NB e Ru-VC obtiveram um rendimento de 0,11% com baixos valores de eficiÃncia de incidÃncia de conversÃo de fÃtons a corrente, IPCE. Os melhores resultados foram para as cÃlulas contendo os corantes Ru-9AA e Ru-TCNE, as quais apresentaram rendimentos de 0,54 e 2,01%, respectivamente, com valores de IPCE iguais a 10% para Ru-9AA e 48% para Ru-TCNE. Todos os complexos apresentaram eficiÃncia global de conversÃo de energia solar em elÃtrica inferiores ao complexo padrÃo N3. / Bipyridines ruthenium complexes are widely studied in the literature for presenting interesting properties in various fields such as photochemical and photophysical studies, applications in biological systems and as photosensitizers in solar cells. In this work, the complexes of the type cis-[Ru(bpy)(dcbH2)(L)Cl], where L = Nile blue (NB), Toluidine blue (TBO), 9-aminoacridine (9AA), Azure B (AB) and Cresyl Violet (VC) were synthesized and characterized by spectroscopic and electrochemical techniques for application in dye-sensitized solar cells (DSC). In addition, the complex cis-[Ru(dcbH2)(bpy)(TCNE)Cl] (Ru-TCNE) was also tested as a sensitizer DSC. These compounds showed bands of charge transfer type MLCT in the visible region and thermodynamically favorable redox potentials for the charge transfer reactions which occur in the photoelectrochemical device. The adsorption of the chemical sensitizers complexes on the surface of TiO2 was evidenced by displacement of MLCT bands to lower-energy when compared to the spectra in solution. The photovoltaic performances of the complexes as sensitizers in DSC were evaluated through current versus potential curves obtained in standard AM 1.5 conditions. The DSC sensitizers containing Ru-TBO and Ru-AB had the lowest overall efficiency with photovoltaic performances of 0.02 and 0.06%, respectively. As for the dye-sensitized solar cells by Ru-NB and Ru-VC obtained a yield of 0.11% with low efficiency values of incident conversion of photon to current, IPCE. The best results were for cells containing the dyes Ru-9AA and Ru-TCNE, with energy conversion efficiency of 0.54 and 2.01%, respectively, with IPCE values equal to 10% for Ru-9AA and 48% for Ru-TCNE moieties. All complexes showed overall efficiency of converting solar energy into electricity below the N3 complex pattern.

Light yellow, air-sensitive single-crystals of the rhodium(III) orthoperiodato K₈[Rh(IO₆)₂]OH·3H₂O were synthesized starting from Rh₂O₃ and KIO₄. The reaction was carried out in a potassium hydroxide hydroflux with a molar water-base ratio of 1.8 at 200°C. Single-crystal X-ray diffraction revealed a triclinic crystal structure (space group P1). The most striking feature of the structure is the [Rh(IO₆)₂]⁷⁻ anion, a linear sequence of three face-sharing octahedra. It can be interpreted as a rhodium(III) cation coordinated by two orthoperiodato groups. A water molecule and a hydroxide ion form an associate (H₃O₂)⁻ .Together with other water molecules, they connect the [Rh-(IO₆)₂]⁷⁻ anions via hydrogen bridges to form layers. Upon heating, the compound first loses its crystal water, then the iodine is gradually reduced before evaporating during the final decomposition step, which results in K₀.₆₃RhO₂. In K₈[Rh-(IO₆)₂]OH·3H₂O, the unusually short Rh/III-I/VII distance of only 276.38(1) pm should allow direct charge transfer in the [Rh(IO6)₂]⁷⁻ anion. An electron-poor rhodium cation, accessible from the side, could be the active center in the rhodiumcatalyzed oxidation of unsaturated organic molecules by periodate.

En raison des problèmes d'instabilité à moyen termes des cellules solaires à colorant (DSSC), l'électrolyte liquide à base d'iodure a été remplacé par plusieurs types de matériaux solides transport de trous (HTM) pour obtenir des DSSCs à l'état solide (s-DSSCs). Parmi ces matériaux, l’utilisation des polymères conducteurs(PC) a attiré une attention considérable en raison de leur bonne stabilité, de leur haute conductivité et de la facilité de leur dépôt sur le semi-conducteur mésoporeux TiO2. Dans ce travail de thèse, plusieurs s-DSSCs basées sur des PC utilisés comme HTM ont été développés dans le but d'améliorer leurs performances photovoltaïques en tenant compte des deux objectifs suivants: (i) l'optimisation des processus de transfert inter facial de charge dans la cellule solaire, et (ii) l'optimisation du transport de charge dans le semi-conducteur d'oxyde de type n. Pour atteindre ces objectifs, chaque composant de la s-DSSC a été modifié afin d'étudier son effet sur les performances du dispositif final. En première tentative, une étude analytique est réalisée en faisant varier le sensibilisateur afin de déterminer les fragments de la structure du colorant, qui ont un effet important sur le processus de photopolymérization électrochimique in-situ (PEP) à la fois en milieu organique et en milieu aqueux mais aussi sur les performances des s-DSSCs. Sur la base de ces résultats, un nouveau concept a été développé et consiste en la suppression totale de l'interface entre le colorant et le HTM. Ceci est obtenu par la synthèse de nouveaux colorants liés de façon covalente à un monomère électroactif qui est co-polymérisé par la PEP in-situ. Le copolymère résultant, utilisé comme HTM, est lié de manière covalente au colorant. En outre, la nature de la liaison chimique, reliant le résidu triphénylamine TPA au monomère, est également étudiée comme un facteur clé dans les performances de s-DSSC. En outre, et pour optimiser les processus de transport de charges dans ce type de s-DSSC, de nouvelles s-DSSC basées sur ZnO ont été réalisées et étudiées. / Due to instability problems of dye sensitized solar cells (DSSCs) in longtime uses, the iodine based liquidelectrolyte has been replaced by several types of solid hole transporting materials (HTM) to perform solidstate DSSCs (s-DSSCs). Among them, the substitution by conducting polymers (CP) has attractedconsiderable attention because of their good stability, high hole-conductivity and simple deposition withinthe mesoporous TiO2 semiconductor. In this thesis work, several s-DSSCs based on CPs used as HTM havebeen developed in order to improve their photovoltaic performances taking into account the following twoobjectives: (i) the optimization of the interfacial charge transfer processes within the solar cell, and (ii) theoptimization of the charge transport within the n-type oxide semiconductor. To reach these goals, eachcomponent that constitutes the device was varied in order to investigate its effect on the device’sperformances. As first attempt, an analytical study is carried out by varying the sensitizer in order todetermine the fragments of the dyes structures, that have an important effect on the in-situ photoelectrochemical polymerization process (PEP) both in organic and in aqueous media and hence on theperformances of the s-DSSCs. Based on these results, a new concept of removing completely the interfacebetween the dye and the HTM is developed. This is achieved by the synthesis of new dyes covalently linkedto an electroactive monomer which is co-polymerized by in-situ PEP. The resulting co-polymer, used asHTM, is covalently linked to the dye. In addition, the nature of the chemical bond linking the triphenylamineresidue TPA to the monomer is also investigated as a key factor in the s-DSSCs performances. Besides, andto optimize the charge transport processes within this type of s-DSSC, the elaboration of novel ZnO baseds-DSSCs has been achieved and investigated.

Στην εργασία αυτή πραγματοποιήθηκε μια βιβλιογραφική ανασκόπηση σχετικά με τις ευαισθητοποιημένες ηλεκτροχημικές κυψελίδες, τις αρχές λειτουργίας τους, τα υλικά τους και τους τρόπους παρασκευής τους. Παρασκευάσαμε ηλεκτροχημικές κυψελίδες χρησιμοποιώντας διαφορετικές χρωστικές και ηλεκτρολύτες. Όλες οι κυψελίδες δοκιμάστηκαν κάτω από τις ίδιες συνθήκες για την εύρεση των παραγόντων που επηρεάζουν την απόδοσή τους. Παράγοντες όπως η συγκέντρωση της χρωστικής και ο χρόνος παραμονής του διαλύματος μέχρι την απόθεσή του στο υπόστρωμα, διαφορετικές χρωστικές και ηλεκτρολύτες κτλ δοκιμάστηκαν για την αύξηση της απόδοσης. Τέλος, εξετάστηκε η σταθερότητα των κυψελίδων αυτών με το χρόνο. / In this study we make a comprehensive literature review on dye-sensitized nanostructured solar cells, their operating principles, materials as well as their manufacturing methods. We have fabricated dye – sensitized electrochemical solar cells using different dyes and electrolytes. All solar cells were tested under the same conditions in order to find the factors limiting their efficiency. Factors like the concentration of the dye and the time of paste storage, different dyes and electrolytes etc were tested in order to improve efficiency. Finally, the stability of these solar cells were also evaluated for different time intervals.

Disertační práce se zabývá detailním studiem vlastností různých elektrických výbojů generovaných ve vodných roztocích. Tyto výboje se staly v posledním desetiletí velmi populárním tématem, a to zejména díky mnoha praktickým využitím jako například v biomedicíně, čištění odpadních vod, ekologii nebo nanoinženýrství. Studium je zaměřeno na generaci peroxidu vodíku, jakožto jednu z nejvýznamnějších částic generovaných právě elektrickými výboji v kapalinách. Pro první část této práce byla využita speciální výbojová komora zkonstruovaná na Fakultě chemické Vysokého Učení Technického v Brně. Komora byla rozdělena tenkou diafragmovou přepážkou na dvě poloviny, přičemž uvnitř přepážky se nacházela malá dírka. V každé části komory se nacházela jedna elektroda, a obě dvě části komory byly vyplněny kapalinou. Ze zdroje bylo do kapaliny aplikováno vysokofrekvenční napětí (1 a 2 kHz), které tak vlastně upravovalo roztok chloridu sodného (1.5 l). Bylo zjištěno, že tento druh napětí, v porovnání s DC, nezpůsobuje nežádoucí přehřívání roztoku (počáteční vodivost 100 - 800 S/cm) během jeho úpravy při zachování účinnosti produkce peroxidu. Experimentální aparatura pro druhou část práce byla sestavena na Gentské Univerzitě v Belgii. Stejnosměrný výboj byl generován v bublinách plynů (He, Ar, N2, vzduch) v prostředí vodných roztoků. Byla studována generace peroxidu vodíku a odbourávání organických barviv přítomných ve zkoumaném roztoku. Ke generaci peroxidu vodíku byl použit roztok NaH2PO4 . 2H2O (5 microS/cm, V= 750 ml), ke zkoumání rozkladu barviv byly použity roztoky organických barviv Direct Red 79 (20 mg/l) a Direct Blue 106 (20 mg/l, V= 750 ml). Minimální koncentrace peroxidu vodíku byla naměřena při aplikaci proudu 10 mA, zatímco maximální koncentrace peroxidu vodíku byla zaznamenána při použití proudu 30 mA. Rozklad organických barviv vykazoval stejné vlastnosti. Čím vyšší byla dodávaná energie, tím více barviva se odbouralo. Třetí část práce probíhala ve spolupráci s Queen's University of Belfast, Centrum for Plasma Physics, UK. K realizaci experimentů bylo využito vysokofrekvenčního plazmového skalpelu (Arthrocar). Bylo zjištěno, že hodnota koncentrace peroxidu vodíku dosahovala maxima v roztocích s nepatrným přídavkem alkoholu (0.25 %). Celkem byly studovány čtyři 0.15 M roztoky BaCl2, Na2CO3, KCl a NaCl (V= 20 ml), jejichž počáteční vodivost se pohybovala kolem 13 mS/cm. Z výsledků bylo patrné, že největší rozdíl hodnot pH byl zaznamenán u roztoků s přídavkem ethanolu. V optických emisních spektrech byly identifikovány především radikály OH, které jsou prekurzory peroxidu vodíku. Výsledky ukázaly, že plazma v takovémto roztoku je stále tvořeno, což může být považováno za první krok generace plazmatu v organických sloučeninách. Poslední část práce byla zaměřena na tzv. mikroplazmatický jet v přímém kontaktu s kapalnou fází. Tato experimentální práce byla realizována na pracovišti Nanotechnology & Integrated Bio-Engineering Centre (NIBEC), University of Ulster, UK během studijní stáže. Jako vodivé médium byl použit roztok trihydrátu kyseliny chlorozlatité s různou počáteční vodivostí. Zajímavým zjištěním je fakt, že při tomto druhu měření bylo generováno stabilní plazma i při velmi malém výbojovém proudu (0.05 a 0.2 mA), a tedy i peroxid vodíku vznikal při velmi malé vstupní energii, což může být považováno za velmi dobrý výsledek.

M.Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Several industries utilize species of synthetic dyes that are found in their wastewater, which is passed out in the environment. Methylene blue is one of the organic dyes that causes water pollution. It causes damage to the aquatic eco-system and health problems to human beings. It is non-biodegradable due to its chemical nature. Advanced oxidation processes (AOP’s) have been developed for the degradation of these dyes, however, some of these methods are limited due to their high cost and low efficiency. Among these methods, Fenton catalysis has been proven to be an effective method due to its low cost, high efficiency, and re-usability. Iron oxide nanoparticles have been mainly used in Fenton process however they are also limitated due to the forming of secondary pollutants, due to catalysts recovery difficulties, hence they require supporting materials. In this work, iron oxide-based catalyst supported on silica nanofibers were fabricated via electrospinning of silica sol incorporated with iron oxide, using three different routes, (a) Method 1 - wetness incipient impregnation, (b) Method 2 - direct addition of iron precursor to the silica sol and (c) Method 3 - incorporation of iron oxide nanoparticles into silica sol. The effect of iron oxide concentration loadings (1 wt%, 2 wt% and 5 wt %) was studied. Increase in iron content resulted in agglomeration of nanoparticles as embedded in the fibers as evident from their SEM images in method 3.1. The SEM results showed diameters from method 1, 2 and 3 ranging from the distribution ranges of 276 – 288 nm, 243 – 265 nm and 188 nm, respectively. EDS showed the presences of Si, P, Fe, O and P. XRD showed a crystalline phase of magnetite (9 nm) and goethite (32 nm) method 1 and 3, with vibrational modes at 3300 cm-1, 1100 cm-1, 950 cm-1 and 580 cm-1 ascribed to O-H, Si-O-Si, Si-O and Fe-O on the FTIR spectra, it showed both the presence of silica and iron oxide. The degradation of methylene blue was monitored by UV-Vis spectroscopy, the Fenton catalytic activity of the iron-oxide supported on silica nanofibers showed higher catalytic activity compared to the unsupported iron-oxide nanoparticles. The catalyst prepared by wetness incipient impregnation (method 1) had a degradation efficiency of 69.1%, the direct addition of iron precursor to the silica sol (method 2) had 75.2% and incorporation of iron oxide nanoparticles magnetite and goethite with the silica sol had 53.7% and 34.7%, respectively. The catalyst prepared by the direct addition of iron precursor in the sol (method 2) showed a high catalytic activity compared to the other catalyst prepared by other methods. Unsupported Iron oxide nanoparticles had a higher degree of leaching of 1.28 ppm magnetite, and 1.68 ppm goethite, compared to the supported iron oxide in method 1 and method 3. The catalyst incorporated with goethite showed a high degree of leaching, 3.95 ppm and 1.33 ppm. The catalyst with high catalytic activity showed a lower degree of leaching with 0.05 ppm.

The colourful past of the late 18th century marquetry furniture has seldom been highlighted. Through ageing and environmental influences, colourful marquetry furniture has lost their original expression. The current knowledge of how Swedish cabinet-makers in the late 18th century used dyes to colour their furniture is limited. Trace of colour has been observed and the use of dyes has been mentioned, but deeper research in this filed is missing. A visual examination and studies of archive documents and previous research have been performed to investigate the colourful past of Gottlieb Iwerssons masterpiece, a secretaire in Gustavian style made for the king Gustav III. The result shows that the secretaire has a colourful past in accordance with its original drawing. A hypothetical picture has been created to illustrate the colourful original appearance.

Exploring new technologies that can meet the world’s energy demands in an efficient and clean manner is critically important due to the depletion of natural resources and environmental concerns. Dye-sensitized solar cells (DSSCs) are low-cost and clean technology options that use solar energy efficiently and are being intensively studied. How to further reduce the cost of this technology while enhancing device performance is one of the demanding issues for large scale application and commercialization of DSSCs. In this research dissertation, four main contributions are made in this regard with the motivation to reduce further cost of DSSC technology. Firstly, ~10% efficiencies were achieved after developing understanding of key concepts and procedures involved in DSSCs fabrication. These efficiencies were achieved after step-by-step modifications in the DSSC design. Secondly, carbon nanotubes (CNTs) were successfully employed as an alternative to Pt in the counter electrodes of DSSCs. DSSCs fabricated with CNTs were ~86% as efficient as Pt-based cells. Non-aligned CNTs were successfully grown using four different CVD methods and finally, multi-walled vertically aligned CNTs (MW-VACNTs) were synthesized using water-assisted chemical vapor deposition (WA-CVD). Thirdly, carbon derived from pyrolysis of nanocrystalline cellulose (NCC) was successfully employed in counter electrodes of DSSCs instead of Pt. DSSCs with NCC were ~58% as efficient as Pt-based DSSCs. Fourthly, novel organic metal-free dyes were designed and employed instead of commonly used Ru-based dyes. DSSCs with these novel sensitizers were ~62% as efficient as those using the conventional Ru-based dyes. Characterization techniques including current-voltage measurements, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetery (CV), thermogravimetric analysis (TGA), small angle x-ray scattering (SAXS), atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) were used.

Luminescent materials find numerous applications in recent times and have enriched human lives in several different ways. From display and lighting technologies to security, sensing and biological investigations, luminescent organic compounds have become indispensible and often preferred over their inorganic counterparts. The versatility of organic materials arises from their comparative low costs, ease of fine-tuning, low toxicity and the possibility to develop flexible devices. Even until very recent times, the investigations and usage of organic luminescent materials were mostly limited to solution-state properties. However, with progress of available characterisation techniques and parallel development of their usage in solid-state devices and other applications (e.g. security, forensics, sensing etc.), significantly greater attention has been paid to the development and investigations of solid-state emissive organic materials. In solid-state applications, apart from the molecular properties of any given material, their cumulative i.e. bulk physical properties are of even greater importance. Thus, investigations of structure-property relationships in organic luminescent compounds to understand their molecular and bulk properties are of fundamental interest. In this thesis, NPI (1,8-naphthalimide) and BODIPY (boron-dipyrromethene) dyes were investigated to provide a broad overview of their structure-property correlations. Among commonly encountered organic luminescent materials, NPIs and BODIPYs have emerged as two broad classes of luminescent organic compounds, finding applications as functional luminescent materials in various fields. However, lack of understanding for controlling the cumulative emissive properties of these compounds has limited their usage as active solid-state emitters in various applications. This thesis presents several new insights into the molecular and bulk emissive properties of these two classes of luminescent dyes (NPIs and BODIPYs). The contents of the six chapters contained in this thesis are summarised below. Chapter 1 summarises the available understanding of the basic concepts of photoluminescence and the design strategies to develop solid-state luminescent and AIE (aggregation-induced emission) active materials. This chapter also emphasises in the basic nature of the NPI and BODIPY compounds, their substitution patterns and their inherent characteristics and touches upon the relatively unexplored properties of NPI and BODIPY based materials. The importance and scope of the work reported in the thesis is outlined at the end of the chapter. Chapter 2 describes a detailed investigation of a series of seven (4-oxoaryl substituted) NPI compounds (1-7) providing an insight into the molecular and cumulative photophysical behaviour of these compounds. The low ICT characteristics of the NPIs, coupled with the twisted geometry, facilitated solid-state luminescence in these materials. The solution and solid-state luminescent properties of these compounds can be directly correlated to their structural rigidity, nature of substituents and solid-state intermolecular interactions (e.g. π-π stacking, C-H•••O interactions etc.). The solid-state crystal structures of the NPI siblings are profoundly affected by the pendant substituents. All of the NPIs (1-7) show antiparallel dimeric π-π stacking interactions in the solid-state which can further extend in parallel, alternate, orthogonal or lateral fashion depending on the steric and electronic nature of the C-4′ substituents. Structural investigations including Hirsfeld surface analysis methods reveal that while strongly interacting systems show weak to moderate emission in their condensed states, weakly interacting systems show strong emission yields under the same conditions. The nature of packing and extended structures also affects the emission colors of the NPIs in the solid-state. DFT computational studies were utilized to understand the molecular and cumulative electronic behavior of the NPIs. Apart from the investigation of solid-state luminescence, other functional potentials of these NPIs were also explored. One of the compounds (i.e. 4) shows chemodosimetric response towards aqueous Hg(II) species with a ‘turn-on’ response. Also, depending on the molecular flexibility of the compounds, promising AIEE (aggregation-induced emission enhancement) features were observed in these NPIs. Later (in Chapter 3), we developed a systematic investigation in a series of purely organic NPIs, restricting various parameters, to attain a thorough understanding of such AIEE properties. Chapter 3 describes a detailed experimental and computational study in order gain an insight into the AIE (aggregation-induced emission) and AIEE mechanisms in NPI compounds. Systematic structural perturbation was used to fine tune the luminescence properties of three new 1,8-naphthalimides (8-10) in solution and as aggregates. The NPIs (8-10) show blue emission in solution state and the fluorescence quantum yields depend on their molecular rigidity. In concentrated solutions of the NPIs, intermolecular interactions were found to result in quenching of fluorescence. In contrast, upon aggregation (in THF:H2O mixtures), two of the NPIs show aggregation-induced-emission-enhancement (AIEE). The NPIs also show moderately high solid-state emission quantum yields (~10-12.7 %). The AIEE behaviors of the NPIs depend on their molecular rigidity and nature of intermolecular interactions. The NPIs (8-10) show different extents of intermolecular (π-π and C-H•••O) interactions in their solid-state structures depending on their substituents. Detailed photophysical, computational and structural investigations suggest that only an optimal balance of structural flexibility and intermolecular communication is the effective recipe for achieving AIEE characteristics in these NPIs. Chapter 4 presents the design, synthesis and detailed investigations and potential applications of a series of NPI-BODIPY dyads (11-13). The NPI and BODIPY moieties in these dyads are electronically separated by oxoaryl bridges and the compounds only differ structurally with respect to methyl substitutions on the BODIPY fluorophore. The NPI and BODIPY moieties retain their optical features in these molecular dyads (11- 13). Dyads 11-13 show dual emission in solution state originating from the two separate fluorescent units. The variations of the dual emission in these compounds are controlled by the structural flexibility of the systems. The dyads also show significant AIES (Aggregation-Induced-Emission Switching) features upon formation of nano-aggregates in THF-H2O mixtures with visual changes in emission from green to red color. Whereas the flexible and aggregation prone system (i.e. compound 11) shows aggregation-induced enhancement of emission, rigid systems with less favorable intermolecular interactions (i.e. compound 12-13) show aggregation-induced quenching of emission. The emission-intensity vs. the structural-flexibility correlations were found to be reverse in solution and aggregated states. Photophysical and structural investigations suggest that the intermolecular interactions (e.g. π-π stacking etc.) play major role in controlling emission of these compounds in aggregated states. Similar trends were also observed in the solid-state luminescence of these compounds. The applications of the luminescent dyads 11-13 as live-cell imaging dyes was also investigated. Chapter 5 describes investigations of photophysical properties of a series of six BODIPY dyes (14-19) in which there is a systematic alteration of a common -C6H4Si(CH3)3 substituent. Inrelated constitutional isomers, the systematic increment of steric congestion and lowering of molecular symmetry around the BODIPY core result in a steady increment of solution and solid- state fluorescence quantum yields. The increasing fluorescence quantum yields (solution, solid state) with increasing steric congestions show that the molecular free rotation and aggregation-induced fluorescence quenching of BODIPYs can be successfully suppressed by lowering the flexibility of the molecules. Photophysical and DFT investigations reveal that the electronic band gap in any set of these constitutional isomers remain almost similar. However, the crystal structures of the compounds reveal that the solid-state colour and quantum yields of the compounds in solid-state are also related to the nature of intermolecular interactions. Chapter 6 demonstrates the use of DFT computational methods to understand the effect of alkyl groups in governing the basic structural and electronic aspects of BODIPY dyes. As demonstrated in Chapter 4 and Chapter 5, apparently electronically inactive alkyl groups can be of immense importance to control the overall photophysics of BODIPYs. In this context, a systematic strategy su was utilized considering all possible outcomes of constitutionally-isomeric molecules to understand the effects of alkyl groups on the BODIPY molecules. Four different computational methods were employed to ascertain the unanimity of the observed trends associated with the molecular properties. In line with experimental observations, it was found that alkyl substituents in BODIPY dyes situated at 3/5-positions effectively participate in stabilization as well as planarization of such molecules. Screening of all the possible isomeric molecular systems was used to understand the individual properties and overall effects of the typical alkyl substituents in controlling several basic properties of such BODIPY molecules.