Study On Laccase-like Activity And Application Of Copper Nanoparticles Loaded On Porous Silicon Particles

Nanozymes are defined as nanomaterials with enzyme-like activities,which have attracted extensive research interest due to their multi-function,low cost and high stability.Compared with natural enzymes,nano-enzymes show better stability and durability due to the inherent properties of nano-materials.Laccase is a member of multiple copper oxidases(MCOs),which catalyze the one-electron oxidation of a variety of organic substrates,such as polyamines,aromatic diamines,catechol,hydroquinone and polyphenols,and then oxidize molecules for water.Therefore,laccase can be used as a green catalyst for wastewater treatment.However,the stability of laccase in a complex environment is poor,and the cost is high,and it is difficult to recycle,which seriously hinders the practical application of laccase.In order to obtain highly stable biocatalysts,it is a promising strategy to construct a nanozyme that mimics natural enzymes.Due to the large pore volume and large surface area of porous silicon,the synthesized nanozyme has many catalytic sites and good catalytic activity.We choose porous silicon particles as the carrier,isopropanol as the reaction solvent,reduce copper sulfate pentahydrate with hydrazine hydrate,and use polyvinylpyrrolidone(PVP)a s the copper coating agent to reduce the copper nanoparticles to the porous silicon particles.In the hole,a porous silicon-supported copper nanoparticle with laccase-like activity(hereinafter referred to as Si@Cu NPs)was synthesized.Studies have shown that the porous silicon particles protect the copper nanoparticles distributed in the pores to improve stability,and the distribution of active particles in the pores increases the collision probability of the reactants and thus improves the catalytic activity.Phenolic compounds(such as chlorophenols)and dyes in the textile industry have become common toxic pollutants due to their wide application in wood preservatives,pesticides,disinfectants,and printing and dyeing processes.These toxic compounds are considered to pose a threat to human health through carcinogenicity,reproductive toxicity,neurotoxicity and endocrine interference,and are also widely detected in underground soil and water bodies.Therefore,it is urgent to remove these toxic substances.The Si@Cu NPs synthesized by us have laccase-like activity,so they can be used to degrade chlorophenols and dyes.The specific research content is as follows:(1)Synthesis and preparation of Si@Cu NPs and their laccase-like activity:Synthesize copper nanoparticles into the pores of porous silicon particles to make them possess laccase-like activity.At the same time,the synthesized materials were characterized by scanning of ultraviolet absorption spectrum,transmission electron microscopy(TEM),scanning transmission electron microscopy(STEM),X-ray energy spectrum analysis(EDS)and X-ray photoelectron spectroscopy(XPS).At the same mass concentration,Si@Cu NPs have a K_m(Michaelis constant)similar to laccase and a higher K_cat and k_cat/K_m,excellent catalytic activity and substrate versatility,and at pH=7,temperature at 80? ,the laccase-like activity is highest.Moreover,Si@Cu NPs show strong stability under various conditions such as high temperature and long-term storage.(2)Application of Si@Cu NPs in the degradation of chlorophenols and dyes:In the application of degradation of chlorophenols,The degradation rate of the three kinds of chlorophenols by natural laccase is below 40%.Si@Cu NPs laccase has a higher degradation efficiency for chlorophenols.The degradation rate of 2-DP by Si@Cu NPs laccase can reach71.48%,the degradation rate of 2,4-DP is 63.46%,and the degradation rate of 2,6-DP is54.02%,and the degradation rate increases with time.With the increase of chlorophenol concentration,Si@Cu NPs laccase did not increase or decrease its degradation rate.In other words,Si@Cu NPs laccases can degrade chlorophenols within a certain concentration range.In terms of degrading dyes,Si@Cu NPs laccases are more efficient in degrading dyes.Si@Cu NPs laccases are more effective for crystal violet and methyl blue(triphenylmethane),chrome black T(Azos),Indigo carmine(indigo)has a good degradation effect.The degradation rate of crystal violet is 84.73%,the degradation rate of methyl blue is 90.3%,the degradation rate of indigo carmine is as high as 99.19%,and the degradation rate of chrome black T is 72.64%,and with the extension of time,the degradation rate has increased.The results indicate that indigo carmine,crystal violet,methyl blue and chrome black T may be suitable substrates for Si@Cu NPs laccases,especially indigo carmine,crystal violet and methyl blue.However,Si@Cu NPs laccase has a poor degradation effect on ramolizole brilliant blue R(RBBR)(Anthraquinones),with a degradation rate of only 8.6%,which shows that ramolizole brilliant blue R is not a more suitable substrate of Si@Cu NPs laccase.With the increase of dye concentration,Si@Cu NPs laccase did not increase nor reduce its degradation rate.In other words,Si@Cu NPs laccase can degrade dyes within a certain concentration range well.