Study On The Preparation, Optical And Electronic Properties Of Inorganic-organic Nanohybrids Optical Chemosensor

Anion plays a fundamental role in a wide range of biological, medical, chemical and environmental processes. So the development of artificial anion receptors has attracted increasing interest in the field of supramolecular chemistry. And up to the present, numerous efforts have been devoted to the development of abiotic receptors for anionic species. However, because of the properties of anions, it is more difficult to design suitable receptors for anion than for cation. Bacause the strong hydrogen-bond donor capaility and lessened dependence on pH values, thiourea groups have been used as binding units for design and synthesis of neutral anion receptors. Most of artificial receptors includ hydrogen bonding donor units and signal subunits(chromophores, fluorophores, and electropotential unit), which are covalently linked. In our research, Some anion receptors containing thiourea groups were synthesized and assembled on to the surface of gold gold nanoparticles (GNPs) by the formation of Au-S bond to obtain a complex receptor for anions. The inorganic-organic nanohybrids optical sensing systems, especially GNPs-based optical sensing, which have thiourea subunits acting as anion binding sites, can selectively recognize anions.Chapter 1:IntroductionAnions play a fundamental role in a wide range of chemical, biological, industrial, and environmental biological processes, numerous efforts have been devoted to the development of a biotic receptor for anionic species. Especially, given the important role of dicarboxylates in biology, such as their critical roles in numerous metabolic processes, the need for their selective recognition by synthetic sensors utilizing weak hydrogen bonding interactions is of great importance in molecular recognition research. Researches of anion recognition systems have been reported. Therefore the content of this chapter includes:(i) The interaction of anions and receptors, measure of anion recognition. (ii) The design of anion receptors, the development of thiourea based anion receptors which have tweezer structure.Chapter 2:Synthesis and characteristic of gold nanoparticles (GNPs) of about 13 nm and 3 nm.In recent years, surface functionalizations of gold nanoparticles (GNPs) has attracted growing attention due to the singular physical properties of gold nanoparticles, the possibility of cooperativity between receptor sites at the surfaces and the practicality of device fabrication. The optical properties of gold nanoparticles are dominated by the changes in the surface plasmon resonance (SPR) which is dependent on the aggregation state, surface morphology and so on. The surface plasmon band is highly sensitive to changes in the environment near to the nanoparticles surface, such as the composition of the self-assembled monolayer (SAM) on the nanoparticles and the solution around the nanoparticles. As gold nanoparticles have tremendously high molar absorptive in the visible region, and may be encrusted with biomolecule, they must have considerable potential for optical detection of small anions and molecules such as dicarboxylate. In this chapter, gold nanoparticles (AuNPs) of 13 nm and 3.2 nm have been prepared by the method of chemical reduction of gold salts in aqueous and the two phase liquid-liquid.Chapter 3:Organic-inorganic nanohybrided receptor functionalized with mono-thioureaTwo types of anion receptors containing mono-thiourea groups was synthesized and assembled on to the surface of gold nanoshells by the formation of Au-S bond to obtain a complex receptor for anions. The recognition behavior of receptors towards anions was investigated by measuring the UV-vis absorption spectra upon the addition of several anions as their tetrabutylammonium salt. But upon addition of anions such as F-, Br-, I-, AcO-and dicarboxylate anions, a slight change (enhancement) was observed. Thus, it indicated that receptors was weakly binding or not interacting significantly with anions in this solvent medium (DMSO). Chapter 4:Organic-inorganic nanohybrided receptor functionalized with bis-thiourea armsA novel organic-inorganic nanohybrided receptor functionalized with bis-thiourea arms and then assembled on gold nanoparticles was synthesized by a simple method. The bis-thiourea receptor showed a selective binding ability to dicarboxylates, which is unsurprising given that the hydrogen bonding alignment for dicarboxylates and bis-thiourea are complementary. It is because receptor has two thiourea motieties that can form hydrogen bonding complexes with bis-anions. And it showed that the two thiourea motieties gives rise to the selective binding of dicarboxylates anions compared with the free receptor. Job plots showed that receptor formed 1:2 complexes with simple anions, such as acetate and dihydrogen phosphate (F-, Cl-, Br-, H2PO4-, CH3COO-) and 1:1 complexes with dicarboxylate anions. Receptor can bind dicarboxylate anions in the order of malonate> adipate> glutarate > adipate> pimelate> sebacate.