Carbon Nanotubes/semiconductor Nanoparticles Preparation Of Hybrid Materials And Their Nonlinear Optical Properties

Carbon nanotubes （CNTs） have shown strong application potentialin many fields since they were discovered because of their uniquestructure and properties, including high surface area, unusual opticaland electronic properties, high mechanical strength, and excellentchemical and thermal stability. To improve the performance of CNTs forpotential applications, there has been widespread interest infabricating the novel one-dimensional CNT/nanoparticles （NPs） hybridmaterials by loading NPs on CNTs. Up to now, various organic andinorganic NPs have been assembled on CNTs via different techniques.Semiconductor NPs have also attracted much attention due to theirunique size-tunable chemical and physical properties. The attachmentof semiconductor NPs on CNTs can produce novel hybrids thatcombine the excellent properties of these two functional nanoscalematerials. Several semiconductor NPs such as SnO₂, TiO₂, CdSe, ZnO,and CdS have been bound to the surfaces of CNTs. However, there arefew papers in the literature concerning the in situ loading of ternarychalcogenide semiconductor NPs on CNTs. As an important categoryof I-IV（Ⅲ）-VI ternary chalcogenides, the Cu-Sn（In）-S system has showngreat potential to be used as nonlinear optical （NLO） materials andsmall or mid-band-gap semiconductors due to their outstanding optical,thermal and mechanical properties. In this thesis, ternary chalcogenideCu-Sn（In）-S NPs have been in situ grown on carbon nanotubes bysolvothermal methods, and then the composition, morphology,nonlinear optical properties and optical limiting performance of theresulting hubrdis were studied. There are four chapters in this thesis.In chapter1, the unique properties of CNTs, the way to modifycarbon nanotubes with semiconductor nanoparticles or other materialsand their applications in optical limiting have been summarized. Meanwhile, the theories of nonlinear optical property, optical limiting,and z-scan technique are also reviewed. The research envisagement ofthis thesis is proposed in the end. In chapter2, we are concerned aboutthe in situ simultaneously growth of Cu₃SnS₄（or Cu₂SnS₃） NPs and twoimportant semiconductor NPs, viz., Cu₂S and SnO₂, on the sidewall ofmultiwalled carbon nanotubes （MWCNTs）. Cu₂S is a p-typesemiconductor, while SnO₂is an n-type semiconductor. On account oftheir unique properties, these two materials have been widelyinvestigated for various potential applications. The solvothermalpathway has been proved to be a helpful technique to preparenanocrystalline materials under mild conditions without organometallicor toxic procurers. Herein, by the solvothermal treatment of a mixture ofpoly（sodium4-styrenesulfonate）（PSS） wrapped MWCNTs, metal （Cu₂+and Sn2+）chloride, and thiourea, a series of MWCNT/PSS/NPs hybridswith two （Cu₂S and Cu₃SnS₄, or Cu₂SnS₃and SnO₂） or three types（Cu₃SnS₄, Cu₂S and SnO₂） of semiconductor NPs loaded on CNTs weresynthesized. By tuning the charge ratio of Cu₂+to Sn2+, thecomposition of NPs can be controlled. Under charge ratios of3:1and2:1, MWCNTs can be simultaneously attached with Cu₂S and Cu₃SnS₄NPs. When the charge ratio is reduced to1:1, Cu₃SnS₄, Cu₂S and SnO₂NPs would be formed at the same time. Further decreasing the chargeratio would result in the formation of Cu₂SnS₃and SnO₂instead ofCu₃SnS₄and Cu₂S. Open-aperture z-scan measurements have beencarried out on three typical MWCNT/PSS/NPs samples to study theiroptical limiting （OL） properties. The addition of semiconductor NPs canimprove the OL performance of MWCNTs, and importantly, thecomposition of the NPs has a significant effect on the OL behaviors ofthe hybrids. These MWCNT/PSS/NPs obtained by loading different typesof semiconductor nanoparticles on carbon nanotubes may havebroad application prospects in the area of laser safety.In chapter3, the complexes of In（DEDC）₃and Cu（DEDC）₂were synthesized and thenused as precursors to prepare MWCNTs/CuInS₂hybrids. By thesolvothermal treatment of a mixture of In（DEDC）₃, Cu（DEDC）₂,oleylamine, oleic acid, and octadecene, the MWCNTs/CuInS₂hybridswere obtained. This method is highly efficient, because the CuInS₂NPscan be uniformly loaded on the surface of MWCNTs without intensiveoxidation treatment by concentrated acid or surface modification bypolyelectrolytes. We also compared the composition and morphologyof the obtained materials, which were prepared under the conditions ofdifferent solvent, reaction time, reaction temperature, and the reactantfeeding amount. The results showed that, only using CuCl2and InCl3but not In（DEDC）₃and Cu（DEDC）₂as precursors, the CuInS₂NPs cannot be uniformly modified on MWCNTs to produce MWCNT/CuInS₂hybrid materials. The resulting MWCNT/CuInS₂hybrids prepared byusing In（DEDC）₃and Cu（DEDC）₂as precursors were then wellcharacterized by a variety of microscopy and spectroscopictechniques. And finally, the optical limiting （OL） properties of theprepared MWCNT/CuInS₂hybrids were studied by the Z-scan technique.The measurements revealed that, after the loading of CuInS₂NPs, theoptical limiting performance of MWCNTs was significantly improved. Inchapter4, the important conclusions obtained in this work aresummarized, and the application prospects of the prepared materialsin the laser protection fields are also mentioned.