Preparation And Study On Logic Functions Of Optical Chemosensors For Anions

The miniaturization of components for the construction of silicon-based electroniccomputers is currently pursued by using the top-down approach. With the decreaseof the components size, there are more and more intrinsic limitations, such as costissues, current leakage, and heat dissipation. For the development of the informationtechnology, the new approaches for further miniaturization are pursued, and thechemical molecules with small size but easy to operate have attracted growingattention. Molecular-scale devices based on chemical molecules with intelligentresponses by bottom-up approach have promising applications. In the field ofmolecular recognition, optical chemical sensors, which translate the molecularinformation into optical signals, make it possible to dialogue between human beingsand molecules, and construct the bridge between the macrocosm and the microcosm.This kind of molecular device has attracted much attention because of its excellentadvantages, such as trace detection, high sensitivity, good selectivity, fast response,and so on. Molecular-scale logic gates derived by optical chemical sensors haveclose association with functional simulation of silicon-based microprocessor. Basedon molecular recognition, molecular logic function can be available with chemicaland/or optical stimulus as the input and optical signal as the output by settingsuitable logical threshold. Theoretical basis and molecular-scale devices formolecular computer in future can be provided by exploring such molecular logicgates. The purpose of this thesis is to design and synthesize novel suitable acceptors as well as research their recognition performance for ions and molecular logicalfuntions in solution or solid substrate. The major achievement obtained is as follow:（1） A novel fluorescent chemosensing hybrid material was designed andprepared through the functionalization of silica nanoparticles covalentlygrafted with a rhodamine derivative. As a fluorescence-quenching-basedchemosensor, the obtained material （Rh6G-SiO₂） shows a good linearitybetween the fluorescence intensity of Rh6G-SiO₂and the concentrationof nitrite ion and demonstrates a good selectivity and a high sensitivitywith detection limit of1.2μM. Besides, the successful covalent-graftingof the rhodamine derivative to the surface of silica nanoparticles caneffectively prevent the organic dye leakage. More importantly, thesensing detection for nitrite ion is reversible and then Rh6G-SiO₂showsgood regenerative ability. These results indicate that this nanocompositesensing material could be developed as a promising fluorescencechemosensor for detecting nitrite ions in water.（2） A novel Eu（III） complex of [Eu（DBM）3DPPZ] was design andsynthesized and the photophysical properties were discussed. Theeuropium complex sensor shows good selectivity, high sensitivity withdetection limit of1μM, which is applicable to naked-eye detection forAcO. Moreover, the Eu³⁺emission is also found to be sensitive tomolecular oxygen through a back-energy transfer mechanism. Based onthis, this “off-on”-type luminescence sensor could successful mimic amolecular level IMP （IMPLICATION） gate with AcO and oxygen astwo inputs where the output, a sharp characteristic Eu³⁺emission, is readas “0” only in the absence AcO under oxygen atmosphere. As far as weknown, this is the first example of a europium complex logic gatecorresponding to a two-input IMP function.（3） A simple organic molecular of2-naphthol-1-aldehyde-conjugatedthiourea was designed and synthesized, depending on the choice of2-naphthol as the chromophore and fluorophore core. Absorption and fluorescence spectra response profiles of receptor1with different ionicinputs vary significantly in a DMSO-H₂O solution （V/V=9:1）. Inparticular, the changes of the dual-modal spectra when anions, such as F,AcO or H2PO4, are introduced in such an aqueous solution indicate thatreceptor1could be tolerant to H₂O at least to some extent in recognizinganions. On the basis of the above results, monitoring changes ofabsorption and fluorescence as outputs, this molecule can operate asbinary logic gates （a NOR gate and two OR gates） when Zn²⁺and F^-areused as inputs. With the introduction of Cu²⁺as the third input, themolecular device can achieved a combinational logic circuit with a NORgate, an OR gate and an INHIBIT gate. We believe that the presentsystem will provide useful information on the range of optical devicesthat can operate at molecular level.