Fabrication And Properties Of Biomass-based Copper Sulfide Nanocrystals For Composite Functional Materials

Copper sulfide is an important transition metal sulfides amd belongsto p-type semiconductors.Copper sulfide nanocrystals?CuS-NCs?possess excellent photoelectric,photothermal,catalytic,conductivity,and capacitance properties,which have been widely used in optical,electrical,sensing,catalysis and biomedical fields.The traditional synthesis methods of CuS-NCs always require synthetic surfactants to prevent the agglomeration of nanocrystals,resulting in complicated preparation,high cost,difficult purification,and environmental pollution,which has so far limited the applications of CuS-NCs.Biomass is the most abundant source of organic compounds on earth.The renewable,biodegradable,and non-toxic make biomass one of the ideal resources to replace petrochemical resources.Polyhydroxyl biopolymers can form supramolecules by intermolecular hydrogen bonds,which can be used as a template for guiding the growth of CuS-NCs and stabilize it,avoiding the use of synthetic surfactants.In addition,biopolymers possess good biodegradability and biocompatibility,and are capable of forming chemical bonds with many guest molecules.More importantly,there is no need to separate biopolymers form CuS-NCs,which contributes to solving the application problem of CuS-NCs.In this dissertation,CuS-NCs were synthesized conveniently with biopolymers as green template and stabilizer.Novel biomass-based CuS-NCs functional materials were developed,including antibacterial paper,conductive/photocatalytic paper,electrodematerial for supercapacitor,and antitumor material.The main contents of this work are listed as below:?1?CuS nanoparticles?CuS NPs?were synthesized with xylan as green template and stabilizer at room-temperature.After characterization of morphology and structure of the xylan/CuS NPs complex?CuS@Xylan NPs?,we found that the spherical CuS@Xylan NPs were evenly distributed with average particle size of 10.1 nm.And the peeling reaction of reducing end group of xlyan occurred in the xylan/NaOH aqueous medium.Except this,the chemical structure of xylan before and after the synthesis of CuS@Xylan NPs was the same,indicating that xylan mainly acted as the template and stabilizer in the synthesis of CuS@Xylan NPs.The synthesized CuS@Xylan NPs were added into the cellulose nanofibers?CNF?network to prepare the composite paper.The results showed that CuS@Xylan NPs/CNF composite paper showed strong photothermal property.With NIR laser irradiation,composite paper exhibited excellent antimicrobial effect on Escherichia coli,Bacillus subtilis,and Staphylococcus aureus.Moreover,composite could effectively kill Aspergillus niger which was difficult to inhibit by traditional bacteriostatic agents.In addition,the tensile strength,tear strength,and burst strength of the composite paper were improved by 50%.?2?In this study,with the help of biomass as a stabilizer and adhesive,the CuS-NCs were uniformly distributed on the surface of CNF by insitu deposition to prepare conductive/photocatalytic composite paper.Here we choose lignin,xylan,or starch as stabilizer and adhesive,and the differenteffect of biopolymers on CuS-NCs distribution was compared.We found that the ability to improve the uniformity of CuS-NCson CNF from weak to strong was lignin<xylan<starch.Biomass improved the conductivity and the photocatalytic activity of composite paper by improving the distribution uniformity of CuS-NCs on CNF.With starch as stabilizer and adhesive,the CuS-NCsshowed the highest loading and the most uniform distribution on CNF.The conductivity of CuS-NCs/starch/CNF composite paper was as high as 10 Scm^-1,and the reaction rate constant on photocatalytic degradationof rhodamine B was as high as 0.317 min^-1,which was higher than most CuS-NCs-based photocatalytic materials.In addition,the composite papers showed good stability in photocatalytic cycle.?3?In order to increase the loading and deposition stability of CuS-NCs in composite paper,Quaternized chitosan?QCS?was used as stabilizer and adhesive to anchor CuS-NCs on CNF by hydrogen bonding and electrostatic attraction in this study.The composite paper was used as a working electrode for supercapacitor.The results showed that the bondability between CuS-NCs and CNF was improved with the introduction of QCS,resulting in a 50%increase in the wet strength of composite paper over the CNF paper.Moreover,the introduction of QCS contributed to increasing the dispersion uniformity of CuS-NCs on CNF.The conductivity of CuS-NCs/QCS/CNF composite paper was up to 110.56 Scm^-1.Supercapacitor showed good capacitive property and electrochemical stability with CuS-NCs/QCS/CNF composite paper as electrode material:the specific capacitance of CuS-NCs/QCS/CNF paper was as high as 314.3 F/g at a current density of 1 A/g.A high rate capacitance of 252.6 F/g was achieved even at a high current density of 10A/g,which corresponded to 80.4%capacitance retention.The capacitance retention rate still retained as high as 88.8%after 5000 cycles.?4?QCS was used as green template and stabilizer to synthesize CuS NPs for NIR laser-induced tumor therapy in this study.The results showed that the spherical CuS@Xylan NPs were evenly distributed with average particle size of 5.6 nm.There was no difference in the chemical structure of QCS before and after the synthesis of CuS@QCS NPs,indicating that QCS mainly acted as the template and stabilizer in the synthesis of CuS@QCS NPs.CuS@QCS NPs showed satisfactory photothermal conversion efficiency.The antitumor experiments in vitro and in vivo showed that 4T1 mammary tumor cells were killed⁹0%by CuS@QCS NPs?20?g/mL?irradiated with NIR laser?808 nm,1.5W/cm²?,resulting in the significant inhibition of 4T1 mammary tumor in mice.And there was no obvious lethal toxicity to liver function,kidney function,and vital organs.?5?In order to improve the antitumor efficiency of CuS NPs,CuS@SA NPs?CuS NPs synthesized with sodium alginate as green template and stabilizer?and glucose oxidase?GOD?were co-loaded on mesoporous silicone to forma composite for tumor therapy in this study.The photothermal,photodynamic,and photocatalytic effects of CuS NPs were applied jointly for more efficient cancer treatment.The results showed that the average particle size of spherical CuS@SA NPs was 5.6 nm.There was no difference in the chemical structure of SA before and after the synthesis of CuS@SA NPs,indicating that SA mainly acted as the template and stabilizer in the synthesis of CuS@SA NPs.CuS@SA NPs and GOD could be loaded on the mesoporous structures of silicone nanoparticles.The antitumor experiments in vitro showed that MCF-7 mammary tumor cells were killed effectively by mesoporous silicone/CuS@SA NPs/GOD complex?6.25?g/mL was enough?irradiated with NIR laser?808 nm,1.5W/cm²?.