| Tungsten disulfide（WS2） is a kind of compound consisted of W atom and S atom, which is similar with compounds such as molybdenum disulfide（Mo S2）, molybdenum diselenide（Mo Se2） and tungsten diselenide（WSe2） in both aspects of structure and properties. All the materials above could be exfoliated to form the structures of nanosheets, making the analogues of graphene, which is a kind of two-dimensional material. WS2 nanosheets have the layered “sandwich S-W-S” structure, where Van der Waals force acts as the combination of each layer, in which case, it is easy for WS2 to become WS2 nanosheets of several hundred nanometers in the horizontal dimension and several nanometers in the lateral length. The nanosheets mentioned above possess the remarkable merits which graphene possess, especially in the areas like biologic adsorption and hydrogen evolution reaction（HER）, to follow these merits, it is highly recommended for WS2 nanosheets to be applied in the fields such as the optical detection of small biological molecules and the substitutes for Platinum for the catalysis of HER.The biological detection and energy science weigh much in the fields like research, normal life and development nowadays, in this paper, the fabrication of WS2 nanosheets, especially those which are the water-dispersed were studied and the water-dispersed WS2 nanosheets were applied in the biological detection（the detection of triphosadenine（ATP）） and in the energy science（HER）, which, in any case, could be the exploitation and contribution to the developments of our country and the whole mankind futuremore. Here is the specific word in this paper:Part 1 The fabrication and characterization of the materialIn the sections for fabrication and characterization of this material, raw WS2 powder was reckoned to be the starting material to harvest the WS2 nanosheets dispersed in dimethyl sulfoxide（DMSO）, dimethylformamide（DMF）, n-butyl alcohol, propyl alcohol, isopropyl alcohol and alcohol- water cosolvent through sonication method, moreover, the same sonication method was used either to harvest water-dispersed WS2 nanosheets modified by polyethylene glycol（PEG）, polyacrylic acid（PAA） and Sodium Cholate respectively. For the characterization, scanning electron microscope（SEM）, transmission electron microscopy（TEM）, atomic force microscopy（AFM）, X-ray photoelectron spectroscopy（XPS）, X-ray diffraction spectrum（XRD） and UV-vis spectrum were used to confirm the integrated structural and expected functional WS2 nanosheets. This paper also provides the comparison between the as-mentioned water-dispersed WS2 nanosheets and the traditional WS2 nanosheets which was dispersed in the organic solvents with big surface energy, indicating the better utility and practicability of the as- mentioned water-dispersed WS2 nanosheets than the traditional WS2 nanosheets with the similar structure and function. Specially, in the biological detection, the toxic organic solvents were not allowed to be induced in the environment while at the same time, organic solvents also could influence the HER procedure as a consequence of the transmission of electrons, so the water-dispersed WS2 nanosheets were induced to prevent these interferences.Part 2 Establishing water-dispersed WS2 nanosheets as a platform for the detection of ATPPlenty of small biology molecules（such as single-strain DNA（ss DNA）, RNA） could be adsorbed by WS2 nanosheets by Van der Waals force causing by the relatively big specific surface area while as a result that negative charges were aggregated at the surface of WS2 nanosheets, the negative-charged small biological molecules（such as double strain DNA（ds-DNA）, ATP-aptamer complex） would be repulsed to be far away from the surface of WS2 nanosheets, rejecting the adsorption（considering the repulsion is stronger than the Van der Waals force）. The adsorption with such selectivity could contribute to the detection procedure: the as- mentioned WS2 nanosheets adsorbed the FAM or FERT modified ss DNA which is designed to be the aptamer of ATP to cause the fluorescence- resonance energy transfer（FRET）, quenching the fluorophore, decreasing the fluorescence signal, while the ATP-aptamer complex could not be adsorbed by the WS2 nanosheets because of the repulsion between the negative charges, so the differences in the fluorescence signal between these two situations could be managed to manifest the exist of ATP or not, fulfilling the detection of ATP.In this paper, for the reason that the as- mentioned WS2 nanosheets could disperse in the water and hardly aggregate, besides, the nanosheets are nontoxic for the biological detection, the as- mentioned WS2 nanosheets were applied for the platform of detecting ATP in the process like: the fluorophore was modified at the 3-terminal of the ss DNA, which is the aptamer of ATP, and the ss DNA was reacted with ATP under suitable conditions to achieve the ATP-aptamer complex, then with the addition of WS2 nanosheets, the fluorescence signal would not change as a consequence of no adsorption between them, while in the contrast process, without ATP, the ATP-aptamer complex could not be formed and the ss-DNA could be adsorbed by WS2 nanosheets to cause the FRET, resulting in the decrease of fluorescence signal. Moreover, exonuclease III（EXO III） was induced in the paper to build a cycle amplification biosensor for the promotion of sensitivity and selectivity.Part 3 Establishing wate r-dispe rsed WS2 nanosheets as the catalysis for the hydrogen evolution reactionAs a benefit from the S-W-S “sandwich” structure of WS2, the W metal edge would be exposed to the environment in a way, which, in fact, possessed a sort of catalysis of HER, when WS2 nanosheets was used as the catalysis of HER, as a result of its nano-sized structure, the metal edge wo uld expose more and besides, the S atom would disperse the electron cloud of W atom, enhancing the conductivity of electrons, which could push in the process of forming hydrogen at the edge of the WS2 nanosheets, indicating the decreasing of the overpotential which inhibits the evolution of hydrogen.In this paper, as- mentioned WS2 nanosheets were applied for the catalysis of HER（As the electrolyte of the experiment is sulfuric acid solution and the working electrode used is glassy carbon electrode（GC E）, the use of organic solvent would affect the process or even cause the damage to GCE, so, our water-dispersed WS2 nanosheets are so suitable for the HER that will have no harm or negative influence to the process.）. And the three-electrode system is used for the study: the working electrode is GCE modified with as- mentioned WS2 nanosheets and Perfluorinated sulfonic acid solution（nafion solution） for the protection, the reference electrode is saturated calomel electrode（SC E）, the counter electrode is a platinum wire, using this system to fulfill the detection of polarization curve, tafel curve and electrochemical impedance spectrum（EIS） and comparing the outcomes with the contrast experiments, where the working electrode is a platinum wire to conclude the ability of as-mentioned WS2 nanosheets to be the catalysis of HER. |
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