Studies On The Preparation And Properties Of Poly(Vinyl Alcohol)-Sulfur Quantum Dots Fluorescent Nanocomposites

As a promising luminescent material,quantum dots(QDs)materials have attracted wide attention because of their excellent optical properties.Common metal-based quantum dots,carbon quantum dots and perovskite quantum dots have been widely used in optoelectronic devices,fluorescent probes,battery sensitization,biological cell imaging and other fields.Since the direct preparation of fluorescent sulfur quantum dots(SQDs)from elemental sulfur was published,SQDs have attracted more and more attention because of its unique composition,good optical properties,low toxicity,easy preparation and so on,and have also been widely studied in many application fields.At present,there are many methods for the synthesis of SQDs,most of which use the affinity between the hydroxyl groups of poly(ethylene glycol)(PEG)and the surface of quantum dots to stabilize SQDs.However,PEG ligands cannot give enough stability to SQDs nanoparticles(SQDs NPs),and the prepared SQDs solutions usually show poor optical stability,which limits their practical applicability.In this case,this paper attempts to use poly(vinyl alcohol)(PVA)containing large numbers of lateral hydroxyl groups to stabilize SQDs NPs,and to prepare PVA-based fluorescent composites with good optical properties,in order to make full use of the fluorescence properties of SQDs.The main research contents are as follows:(1)SQDs NPs coated with PVA molecules were prepared by using elemental sulfur as raw material and PVA macromolecule as stabilizer.The prepared SQDs NPs have good water dispersibility and stability,bright fluorescence,good optical stability and low cytotoxicity.It is also verified that SQDs have sensitive selective fluorescence quenching to Fe³⁺and responsiveness to temperature,which can be used for intracellular sensing detection.In addition,numbers of hydroxyl groups on the surface of PVA also provide better modification ability for SQDs.(2)The composite films were prepared by blending SQDs with PVA solution with high fluorescence efficiency.SQDs NPs are uniformly dispersed in the polymer matrix with stable structure and good sunlight transmittance.The UV stability of SQDs NPs in PVA matrix is greatly enhanced,and the addition of SQDs NPs can also improve the tensile strength and thermal stability of polymers,which can not only give PVA films excellent fluorescence properties,but also make the films have a certain UV shielding effect and expand the application of materials.(3)The fluorescent composite fiber films with uniform size were prepared by electrospinning SQDs NPs and PVA.The addition of glutaraldehyde to the fiber membrane formed by PVA molecules can keep the morphology of the fiber smooth and complete,and the fiber membrane will not be dissolved in the aqueous phase because of the cross-linked structure formed.By adding SQDs NPs to the spinning fiber,the composite fiber membrane can not only have good fluorescence properties,but also show a good selective fluorescence detection of Fe³⁺,so it can be used as a convenient test paper.