Dissertations / Theses on the topic 'Solid-state luminescence'

碩士
國立高雄應用科技大學
光電與通訊研究所
94
ZnS is a wide-gap (3.66 eV) II-VI compound semiconductor material and is commercially used as phosphor for electroluminescence devices. ZnS has good luminescence property, it is a candidate material for phosphors that emit visible light. The major and important applications of phosphor are in light sources, display devices, and high energy radiation detector. Two subjects on this thesis have been discussed. The first one is the synthesis of the traditional ZnS-based phosphors. The effect of preparation parameters, such as synthesis temperature, sintering time, dopants and doping concentration, on the luminescence characteristics of phosphor was studied. X-ray diffractometer (XRD), photoluminescence (PL), cathodeluminescence (CL) and scanning electron microscopy (SEM) were used to analyze the characterizations of crystalline structure, luminescence and microstructure of phosphor. From the XRD pattern, transformation temperature of the ZnS phosphor was determined. It was also found that the luminescence property of host lattice changed along with the amount of hexagonal phase. The higher the firing temperature, the higher the amount of hexagonal phase could be found. From photoluminescence and cathodeluminescence spectra, luminescence intensity related to the sintering temperature, doping concentration and sintering time were evaluated. When ZnS doped with Mn and Ce ion, a yellow-orange emission wavelength around 568 nm is observed. Increasing the doping concentration, the concentration quenching effect was observed. When the co-doping concentration is 0.9 mol%, sintering temperature is 1200℃ and sintering time is 1 hour, the optima emission efficiency of phosphor was achieved. The phosphor which was synthesized in the first subject was applied to the second subject subsequently. The ZnS-based phosphor used as the phosphor layer for electroluminescence device, which was prepared by screen-printing method. After the electrode was fabricated, a yellow-orange EL device was obtained.

碩士
國立臺南大學
材料科學系碩士班
99
After being replaced by various positive ions, the properties of SrTiO3 are different due to the changes in temperature and in ratio of compositions. SrTiO3 is an excellent candidate system in lead-free piezoelectric materials because of its a wide range of applications in integrated microelectronics. Nevertheless, the luminescence properties of SrTiO3 on are also studied. In the study, novel phosphors based on Sr1-1.5xErxTiO3（x=0~ 0.18）have been synthesized by solid-state method. Effects of contents of Er3+ on crystal structure and photoluminescence properties by 514.5 nm Ar+ laser excitation were also discussed. The regions of emission are 516~537 nm（2H11/2→4I15/2）、537~570 nm（4S3/2→4I15/2）、640~690 nm（4F9/2→4I15/2）and 830~870 nm（4S3/2→4I13/2）. The results revealed that the emission intensity enlarges when the growth temperature（1100 °C、1200 °C、1300 °C and 1400 °C）rises. The results show the strongest emission intensity occurs when doping 11 mol% at 1300 °C and 11 mol% at 1400 °C , respectively. While changing the ratio of lattice, Sr0.9Ba0.1TiO3：Er3+ possesses the most preferred emission intensity. So we have found that luminescence emission changes as the structure of lattice varies.

碩士
國立成功大學
材料科學及工程學系碩博士班
100
The aim of this study was to develop some new phosphor whose host material contained no rare-earth (RE) element. We chose CaWO4, BaWO4 and CaNb2O6 as the RE-free host and studied the spectroscopic properties of Dy3+ in these hosts. Na+ was co-doped with Dy3+ in order to maintain the overall charge neutrality. The experiment results showed that after sintering at 900 C for 20 hours Ca0.96Dy0.02Na0.02WO4 and Ba0.96Dy0.02Na0.02WO4 crystallized in the monoclinic Scheelite structure, while the sintering temperature for Ca0.96Dy0.02Na0.02Nb2O6 to form the monoclinic tungsten-bronze (MTB) was 1100 C. The later showed a low temperature phase transition and after annealing at 650 C for 10 hours, the sample transformed to the tungsten-bronze (TTB) structure. Photoluminescence spectroscopy showed that under the 350 nm excitation Ca0.96Dy0.02Na0.02WO4, Ba0.96Dy0.02Na0.02WO4, and Ca0.96Dy0.02Na0.02Nb2O6 gave out two dominant emissions at 487 nm (4F9/2→6H15/2, blue) and 574 nm (4F9/2→6H13/2, yellow), respectively. The yellow lights were stronger than the blue lights in all three phosphors. The CIE color coordinates for Ca0.96Dy0.02Na0.02WO4 and Ba0.96Dy0.02Na0.02WO4 were calculated to be (0.34, 0.33) and (0.32, 0.29) respectively, which were all located in the white region. The yellow emission of the MTB-structured Ca0.96Dy0.02Na0.02Nb2O6 was far too stronger and the mixture of the two emissions was not in the white region. However, in the TTB-structured Ca0.96Dy0.02Na0.02Nb2O6 the yellow emission was reduced, presumably arising from the higher symmetry of the structure. The CIE color coordinate of the TTB-structured Ca0.96Dy0.02Na0.02Nb2O6 was (0.32, 0.30), which was also in the white region. Key words:phosphor,Scheelite,rare earth

The emphasis of this work has been in two areas of optical materials - the crystal-chemical development of new optical frequency converters and the synthesis and study of new hosts for Cr����� luminescence and lasing. A simple method has been developed to identify promising frequency-doubling materials containing triangular oxoanions by estimation of nonlinear susceptibilities. Implementation of this method and its results have generated predictive capabilities in determining the relationships among crystal structure, nonlinear properties, and threshold powers. The new noncentrosymmetric borate SrLiB���O������ is discussed; its structure is built from a 3-dimensional condensation of B���0��� units with channels alternately filled with Sr and Li atoms. From these studies, a prescription for new pyroborate frequency converters has been developed. The material CdC������C���H7NO���, has been synthesized and structurally characterized by single-ciystal X-ray diffraction. Three new alkaline-earth beryllium borates, built from unique 2- and 3- dimensional networks and frameworks, have been identified. The structure of SrBe���(B0���)��� consists of layers of composition [Be���(BO���)���] interleaved by Sr atoms. CaBeB���O��� is constructed from a Ca0��� polyhedral network and a beryllium borate network. In BaBe���(B0���)��� the structure is composed of a beryllium borate framework intermingled with a Ba-centered dodecahedral framework. Several materials with potential as hosts for Cr����� lasing have been analyzed. The structural study of the laser host LiSrAIF6 revealed the distortions at the Al site that contribute to the unique optical properties of the Cr����� -doped crystals. The family of solid state oxide A���MM'(B0���)��� is one of the largest families of oxide reported to date. Metal site preferences, disorder, solid solubility, and the interrelationship between this structure and the layered structure type of Ba���Sc(B0���)��� are detailed. An optimal synthetic procedure has been developed for these materials to provide pure, highly crystalline phases. Also, the structural and optical features of (Cr�����:) Sr���In(B0���)��� with A= Sr and M=M'= In have been studied. The material Sr���LilnB���O������, was discovered while searching for a suitable lithium borate flux for crystal growth of the compound Sr���In(B0���)���.
Graduation date: 1993

In this study, triphenylpyridine derivatives were synthetized and fully characterized, including their photophysical properties. The triphenylpyridine core presented fluorescence in solution with quantum yields that surpass anthracene’s, with compound [4-(2-(2-methoxyphenyl)-6-phenylpyridin-4-yl)-N,N-dimethylaniline] being the brightest. This study allowed to identify the importance of 2-(pyridin-2-yl)phenol moiety for achieving fluorescence in solid state and not in solution. Complexation of boron was attempted for 2-(pyridin-2-yl)phenol derivatives with boron trifluoride, however the complex was not stable in solution. Five derivatives were analysed by single crystal x-ray diffraction and their structural features were indicative of the possibility of solid-state emission with very weak intermolecular and intramolecular interactions. All derivatives presented solid-state fluorescence with three compounds showing potential for further solid-state luminescence studies.
Neste estudo foram sintetizados e caracterizados derivados de trifenilpiridinas. Os derivados de trifenilpiridina apresentaram fluorescência, com alguns derivados a apresentarem rendimentos quânticos de fluorescência acima do composto de referência (antraceno). O composto [4-(2-(2-metoxifenil)-6-fenilpiridin-4-il)-N,N-dimetilanilina] apresenta ser o derivado com valores superiores de rendimento quântico de fluorescência. Os estudos realizados permitiram identificar a importância do grupo 2- (piridin-2-il)fenol para obter fluorescência em estado sólido e não em solução. Foi tentada a complexação de boro com os derivados de 2-(piridin-2-il)fenol com eterato de trifluoreto de boro no entanto os complexos obtidos não mostraram ser estáveis em solução. Cinco dos derivados foram analisados por cristalografia de raio-x: -os resultados permitiram avaliar as interações intramoleculares e intermoleculares em estado sólido. Todos os derivados apresentaram fluorescência em estado sólido demonstrando o potencial de fluoróforos baseados em trifenilpiridina para futuros estudos de luminescência em estado sólido.
Mestrado em Química

We are living in an age where the demand for energy is growing rapidly. This means that supplies to easily accessible oil and natural gas is unlikely to keep up with the demand as times goes on. The world will have to use energy more efficiently and increase its use of other sources of energy. This study is aiming at developing materials that will improve the power conversion efficiency of photovoltaic cells by using up and down-converting phosphor materials. ZnTiO3-Zn2TiO4 composite and ZnTiO3 phosphors doped with Er3+,Yb3+, Eu3+ and Al3+, which display up and down-converted luminescence were synthesized by a simple high temperature conventional solid state reaction method. The structure, particle morphology, absorption, photoluminescent properties and elemental distribution were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis-NIR absorption spectrometer, photoluminescence (PL) spectroscopy and time of flight secondary ion mass spectroscopy (TOF-SIMS), respectively. ZnTiO3-Zn2TiO4 composite doped with different concentration of Er3+ ions was synthesized via solid state chemical reaction method at 1100 ℃. The X-ray diffraction (XRD) confirmed the crystallization of both the hexagonal ZnTiO3 and cubic spinel Zn2TiO4 phases of the composite. The SEM images of ZnTiO3-Zn2TiO4:Er3+ composite showed that the particle morphology was made up of faceted hexagons. Furthermore, the ZnTiO3-Zn2TiO4:Er3+ phosphors were excited in the near-infrared (NIR) region using a laser diode with a wavelength of 980 nm and displayed both green and red up-conversion emission bands in the visible range at 543, 553, 650 – 670 nm. These emission bands correspond to 2H11/2, 4S1/2→ 4 I15/2 and 4F9/2→ 4 I15/2 transitions of Er3+ ions. However, the interaction mechanisms involved in the upconversion process of ZnTiO3-Zn2TiO4:Er3+ phosphor is discussed with the help of an energylevel schematic diagram and the number of the photons involved in the up-conversion luminescence process were of a double photon mechanism. The decay lifetimes were studied by fitting the luminescence decay curve with a single-component exponential decay. Er3+ and Yb3+ incorporated zinc titanate (ZnTiO3) phosphor powders were synthesized using conventional solid-state reaction method at 800 ℃. A ZnTiO3:Er3+,Yb3+ phosphor that resembled an ecandrewsite single phase with space group R-3 (148) was obtained, as proven by X-ray diffraction (XRD). The SEM image showed a surface morphology composed of agglomerated irregular shaped particles. The energy band gap of ZnTiO3 was engineered by incorporating different concentration of the dopant ions. After irradiating ZnTiO3:Er3+with a 980 nm laser beam, the phosphor up-converted the photon energy to display green and red emissions in the visible range that were positioned at 527, 545 and 665 nm. Enhancement of the luminescence intensity of ZnTiO3:Er3+ phosphor was achieved by variation of Er3+ concentration. Co-doping with Yb3+ ions proved to be effective in enhancing the luminescence intensity of the optimized Er3+ ion emission and new emission bands at 410 and 480 nm, through an energy transfer mechanism were observed. The enhancement of the lifetime of the up-conversion luminescence was also achieved by co-doping ZnTiO3:Er3+ phosphor with Yb3+ ion. The energy transfer mechanisms involved in Er3+ - Yb3+ co-doped ZnTiO3 phosphor was illustrated and discussed in detail. The ZnTiO3:Er3+, Yb3+ thin films were successfully deposited by pulsed laser deposition (PLD) by varying the silicon (100) substrate temperature. The distribution of the ions in the films was investigated and the TOF-SIMS showed that the ions were homogeneously distributed throughout the ZnTiO3 host lattice which indicated a successful incorporation of the Er3+ and Yb3+ ions. The optical response of the phosphors revealed that the reflectance percentages of the ZnTiO3:Er3+, Yb3+ vary with the silicon substrate temperature due to the differences in the thickness and morphological roughness of the thin films. The ZnTiO3:Er3+, Yb3+ thin films also exhibited up-conversion emission from Er3+ electronic transitions, with violet, blue, green and red emission lines at 410, 480, 525, 545 and 660 nm from 2H9/2 → 4 I15/2, 4F7/2 → 4 I15/2, 2H11/2 → 4 I15/2, 4S3/2 → 4 I15/2 and 4F9/2 → 4 I15/2 transitions, respectively. These up-conversion emissions were enhanced by increasing the silicon substrate temperature during the deposition. ZnTiO3 host co-doped with Eu3+ and Al3+ was synthesized by solid state reaction to convert the UV photons to visible photons. Charge compensation effects of Al3+ incorporated ZnTiO3:Eu3+ as a co-dopant ion was reported in detail. The structural and morphological characterization show that the addition of Eu3+ and Al3+ does not affect the phase formation and the surface morphology of the host. The visible emission intensity of Eu3+ ions for an optimal concentration of 2 mol% under 395 nm excitation, was enhanced by incorporating Al3+. The energy level diagram showing the charge compensation mechanism was proposed for the co-doped system.
College of Engineering, Science and Technology

碩士
中原大學
奈米科技碩士學位學程
106
A luminescent solar concentrator (LSC) is consisted of the luminophores and a waveguide that can be used to spatially concentrate both direct and diffused sunlight without the need of complex and expensive solar-tracking and cooling systems. Recently, colloidal quantum dots (CQDs) with some unique photophysical properties have attracted much attention as the luminophores in LSCs. However, most of mature CQDs contain heavy metals and need to be synthesized in the hazardous organic solvent. In addition, they also suffered from concentration-induced quenching (CIQ), thus the loading concentration of luminophores doped in LSCs is restricted. Unfortunately, this would reduce the light-absorbing efficiency, leading to large transmission losses. To address all the issues mentioned previously, organosilane-functionalized carbon nanodots (Si-CNDs) were synthesized based on cost-effective, earth-abundant precursors using a simple hydrothermal method. Such Si-CNDs exhibit some unique photophysical properties, including large absorption coefficient, high PL quantum yields (PL-QYs) and resistance to CIQ effect. Due to good film-forming properties, greener LSCs with different loading concentrations can be simply fabricated by directly cross-linking Si-CNDs on the glass waveguide. The LSCs are highly transparent even under high loading concentration up to 75 wt%, indicating high uniformity of Si-CND distribution. The LSCs with 25 wt% loading contents still possess high solid-state PL-QYs up to ~41% upon the calibration of reabsorption losses and high internal quantum efficiency of ~23% due to low scattering losses. We expect our demonstration can pave a way to further design efficient greener LSCs after further reducing the reabsorption losses.

The thesis entitled “Local structure-property relationship in some selected Solid State Materials” mainly focuses on two fundamental topics: (a) evaluation of some standard global structural concepts in terms of local structure to provide a unique description of the crystal structure, and (b) the role of the crystal structure at different length-scales in controlling the properties in some selected materials.

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.

The present thesis provides a systematic investigation of coordination polymers of 3d, rare-earth (4f) and main group element (Bi) using both rigid aromatic, flexible aliphatic linkers. Luminescent sensing behavior towards nitro aromatics, metal ions and ferroelectric behavior have been investigated using some of the prepared compounds. The possible usefulness of lone pair on the structure has been investigated using bismuth based coordination polymers. The thermal and optical behavior of lanthanide coordination polymers (Ce, Pr and Nd) have also been studied. Chapter 1 An Overview of Coordination Polymer (CP) Compounds This chapter presents a brief introduction to coordination polymer (CP) compounds. Starting from the brief historical background on coordination compounds, this chapter shed light on some earlier developments in this family of compounds by Yaghi, Robson and others. The usefulness of carboxylate and imidazolates in construction of some important coordination polymer compounds like MOF-5, HKUST-1, ZIFs, MIL-53, UiO-66, CD-MOF-1 etc has been described in detail along with its properties. The coordination polymers exhibit many important properties and some of the properties like sorption, separation, ionic conductivity, catalysis and ferroelectricity have been discussed briefly and summerized. Chapter 1 also provides the general synthetic and characterization approaches that have been employed during the present studies. Chapter 2 Part A: Adenine Based Coordination Polymers with Cyclohexane dicarboxylic acids This chapter presents the synthesis, structure and properties of four new coordination polymers [Zn4(C8H10O4)2.5(C5H4N5)3.2H2O].7H2O.2DMA (I), [Cd3(C8H10O4)2(C5H4N5)2.H2O] (II), [Cd(C8H11O4)2(C5H5N5)2.2H2O] (III), [Cd(C8H10O4)(C7H8N5O).H2O]. 4H2O (IV), (CHDA = cyclohexane dicarboxylic acid, ad = adenine, DMA = dimethylacetamide, 9-HEA = 9-hydroxyethyl adenine). The compound I and II forms three-dimensional structure having distinct arrangements of 1,4-CHDA and adenine units with Zn and Cd metals respectively. The molecular complex unit is observed in compound III with 1,2-CHDA and adenine. Compound IV forms two-dimensional structure with 9-HEA and 1,2-CHDA. The observation of base-pairing interactions in the above compounds is noteworthy. In compounds I, II and IV amino groups are appears to be free and utilized for the detection of nitro aromatic explosives through fluorescence quenching. The results revealed that the emission behavior of the present compounds is greatly influenced by the hydroxyl nitroaromatic analyses like indophenol, dinitrophenyl and trinitrophenols with very low detection limits. The compound I also exhibits considerable sensitivity towards metal ion detection, especially Fe2+/Fe3+, Cr3+, Ag+ and Hg2+ ions in solution. The presence of free nitrogen sites in compound II has been explored for the base catalyzed Knoevenagel condensation reaction, the quantitative yields are observed with various aldehyde substrates. Part B: Adenine Based Coordination Polymer with Oxydiacetic acid: [Cd2(C4H4O5)2(C5H5N5)].H2O.DMA The synthesis, structure and properties of a Cd based coordination polymer with oxydiacetic acid and adenine, [Cd2(C4H4O5)2(C5H5N5)].H2O. DMA is described. The compound has a two-dimensional structure formed by the connectivity involving Cd and oxydiacetic acid. The adenine ligand binds with the Cd metal center through the pyrimidine nitrogen and hangs in the inter layer spaces. The layers are stacked in a ABAB.... fashion and the inter layer spaces occupied by the dimethyl amine and water molecules. The water molecules are very labile and its removal can be accomplished by heating the sample at 100°C, which is also confirmed by the single crystal XRD, PXRD and IR studies. The availability of free amino groups of adenine molecule has been utilized for the detection of nitroaromatics, especially nitrophenols with good sensitivity. The amino group was also found to be useful in catalyzing Knoevenagel condensation reactions. Chapter 3: Rare-Earth Metal Carboxylates: Ln2(µ3-OH)(C4H4O5)2(C4H2O4)].2H2O [Ln=Ce, Pr and Nd] This chapter describes synthesis, structure and properties of series of rare-earth based compounds, [Ln2(µ3-OH)(C4H4O5)2(C4H2O4)].2H2O (Ln = Ce, Pr and Nd). The malic acid and fumaric acid form part of the structure. The lanthanide centers are connected by the malate units to form a two dimensional layers, which are pillared by fumarate units forming the three-dimensional structure. Overall, structure can be described as I2O1 type inorganic in two-dimension (Ln-O-Ln layers) and organic in one dimension. The extra framework water molecules form a dimer and occupy the channels. The robustness of the framework was reflected in terms of facile removal and reinsertion of the water molecules, which is also confirmed by single crystal XRD, variable temperature IR and cyclic TGA study. The presence of water dimers and weakly interacting water chain suggested the possibility of proton migration in these compounds. Proton conductivity studies reveal the conductivity values of ~2.85 x 10-6 Ω-1cm-1 at 98% relative humidity. The optical studies revealed an up-conversion behavior involving more than one photon for the neodymium compound. Chapter 4: Bismuth Carboxylates with Brucite and Fluorite Related Structures The synthesis, structure and properties of three new bismuth based coordination polymers have been described in this chapter. The compounds [C4N2H10][Bi(C7H4NO4)(C7H3NO4)].H2O (I), [Bi(C5H3N2O4) (C5H2N2O4)] (II) and [Bi(µ2-OH)(C7H3NO4)] (III) were isolated employing hydrothermal condition with three different heterocyclicdicarboxylic acids, 3,6-pyridinedicarboxylic acid, 4,5-imidazoledicarboxylic acid and 3,4-pyridinedicarboxylic acid respectively. The structures of all the compounds have linkages between Bi2O2 and the corresponding dicarboxylate forming a simple molecular unit in I, a bilayer arrangement in II and a three-dimensional extended structure in III. The topological arrangement of the nodal building units in the structures resembles brucite related layers in II and fluorite related arrangement in compound III. By utilizing the secondary interactions, the structure of III can be correlated to a Kagome related net. The observation of such classical inorganic related structures in the bismuth carboxylates is noteworthy. Heterogeneous catalytic studies indicate Lewis acidic nature in the bismuth center in all three compounds. Chapter 5: Solvent dependent Delamination, Restacking and Ferroelectric studies in a Two-Dimensional Compound [NH4][Ag3(C9H5NO4S)2(C13H14N2)2].8H2O This chapter describes synthesis, structure, water dependent delamination/restacking and ferroelectric behavior in a layered coordination polymer compound, [NH4][Ag3(C9H5NO4S)2(C13H14N2)2].8H2O. The compound has a two-dimensional structure with the water molecules occupying the inter-lamellar spaces. The lattice water molecules can be fully removed and reinserted, which accompany the crystalline-amorphous-crystalline transformation. This transformation resembles the collapse/delamination and re-stacking of the layers. This transformation has also been investigated by in-situ IR and PXRD studies. The presence of a natural dipole (anionic framework and cationic ammonium ions) along with the non-centrosymmetric space group gives rise to a room-temperature ferroelectric behavior to the compound with saturation polarization (Ps) of 1.95 μC/cm2 and remnant polarization of 0.63 μC/cm2. The temperature dependent dielectric measurements indicate that the ferroelectric-paraelectric transformation occurs at 320 K. The ferroelectric-paraelectric transformation also follows the crystalline-amorphous-crystalline transitions.

The metal-organic framework (MOF) compounds have witnessed rapid growth in the past decade and currently emerged as a highly unique area in the field of chemistry, materials science, and multiple branches of engineering. It presents applications in diverse fields such as gas sorption, catalysis, ionic conductivity, sensing etc. These compounds are built by the inorganic metal ions which are bridged by organic linkers to form extended structures. These compounds are mainly synthesized by either one-pot synthesis or in a sequential manner. In the former case, the inorganic metal ions and the respective organic linker are reacted together in a particular solvent or solvent mixture, whereas in the later case, a metalloligand is prepared by using the organic linker and the primary metal ion, which react with the secondary metal ion forming the desired structure. In this thesis, the synthesis of metal-organic framework compounds by one-pot synthesis as well as the sequential synthesis is presented. The structures of all the synthesized compounds have been determined by single crystal X-ray diffraction technique. The prepared compounds were employed in the study of sensing of nitroaromatic compounds, toxic metal ions and highly oxidizing anions. In addition, detailed studies of heterogeneous catalysis employing the prepared MOFs were investigated along with catalysis by metal nanoparticle incorporated within MOFs. In select cases, the labile nature of the lattice water molecules was established by performing in-situ single crystal to single crystal (SCSC) structural transformation studies. In addition, the proton conductivity and the magnetic behavior have also been studied. Chapter 1 of the thesis presents a brief overview on metal-organic framework compounds and summarizes its various important properties. In chapter 2, the synthesis, structure, and characterization of heterometallic metal-organic framework compounds using 2-mercaptonicotinic (H2mna) and Cu(I) / Ag(I) based two metalloligands, [Cu6(Hmna)6] and [Ag6(Hmna)2(mna)4](NH4)4 are presented. In chapter 3, we present the synthesis, structure and nitroaromatic sensing behavior of [Ag6(mna)6](NH4)6 metalloligand based heterometallic metal-organic framework compounds. In chapter 4, the synthesis, structure and Lewis acid catalytic behavior of 6-mercaptonicotinic acid based heterometallic metal-organic framework compounds are presented. In chapter 5, the stabilization of the palladium nanoparticles in the newly synthesized 1,10-phenanthroline based metal-organic framework compounds and their catalytic behavior is presented. In chapter 6, we present the synthesis, structure and the sensing behavior of hazardous chemicals such as toxic metal ions and highly oxidizing anions. In addition, the adsorption and desorption of synthetic dye molecules by the metal-organic framework compounds are also presented.