| Silk protein(silk fibroin,sericin) and silk peptide(the hydrolysis product of silk fibroin) are widely used in biomedical material,food,cosmetic,pharmacy and textile industries because of their excellent biocompatibility,anti-oxidation and enough amino acids contains.Also,dyes used in textiles can be applied in other domain such as electrochemistry.In this paper,silk and some dyes are investigated with electrochemical methods.Two kinds of biocompatible functional interface are set up and their properties are investigated.The determination of silk fibroin in raw liquid silk samples and sericin in degumming waste water are performed with SWV method,respectively.The dye-uptakes of 4 kinds of dyes dyeing fiber are carried out using SWV,respectively. These studies are significant to opening the biocompatible functional interface, broadening the application range of electrochemistry and building the link between electrochemistry and textiles.The paper consists of four chapters.The main contributions are summarized and presented as follows:1."P-SP" is obtained by electrochemical polymerization of silk peptide on carbon paste electrode surface in 0.04 mol·L-1 phosphate buffer(pH7.4).Compared with the few particles of the self-assembled SP on the surface of carbon paste electrode(S-SP-CPE), "P-SP" is formed with a large number of particle clusters.The P-SP-CPE is characterized by cyclic voltammetry and shows a pair of well-defined redox peaks in 0.1 mol·L-1 H2SO4 solution(pH 1.1),which is ascribed to the redox reaction of proton combined with "P-SP",while S-SP-CPE has no voltammetric response.2.Electrochemical switch formed by positive-charged dye malachite green(MG) and negative-charged anionic surfactant sodium dodecyl benzene sulfonate(SDBS) on the interface of "P-SP" is studied in 0.1 mol·L-1 H2SO4 solution(pH1.1) using cyclic voltammetry.The protonated degree of "P-SP" is reduced by the interaction of MG, which induce the concentration of proton decrease and then the peak current of proton redox peaks become low.After 80 min,no response is nearly observed,suggested that "MG" shuts off the redox of proton on P-SP interface.This interface is named P-SP-MG-CPE.The redox response of proton is found again with the interacting time increase of P-SP-MG-CPE with SDBS solution,indicating that "SDBS" opens the redox of proton.Therefore,MG,SDBS and P-SP form a simple "electrochemical switch".In addition,the interaction between MG and P-SP obeys the 1st order rate equation:In CH+,0/CH+,t=1.19 + 9.67×10-2 t;interaction rate constant = 9.67×10-2 min-1,t1/2= 7.17 min.3.The inclusion and recognition ofβ-CD with "P-SP" is investigated in 0.1 mol·L-1 H2SO4 solution(pH 1.1) with cyclic voltammetry.The oxidative peak currents decrease with the peak potential shifting negatively as a result ofβ-CD inclusion "P-SP".The inclusion reaction obeys the 1st order rate rate equation:In CH+,0/ CH+,t= 0.952 +2.88×10-2 t,inclusion rate constant = 2.88×10-2 min-1,t1/2 = 24.1 min.Based on the "Linear method",the inclusion constant and ratio are calculated as 2.9×105 L·mol-1, 1:1,respectively.The△G10 of inclusion reaction is -31.136 kJ·mol-1.4."P-SE" is prepared by electrochemical polymerization of sericin in 0.02 mol·L-1 phosphate buffer(pH 7.0) on nanometer TiO2 modified carbon paste electrode surface. The net structure is formed on this interface.A pair of stable redox peaks has been found in pH 1.81B-R buffer for P-SE-TCPE.This redox reaction can be hindered by cationic surfactants while enhanced by anionic surfactants.Also,the electrode reaction rate constant of potassium ferrocyanide in 0.02 mol·L-1 PBS(pH 7.0) on P-SE-TCPE is 0.26 s-1,which is higher than that of 0.03s-1 on TCPE.5.The electrochemical behavior of protein material silk fibroin is studied in pH 2.0 of hydrochloric acid solution with cyclic voltammetry and square wave voltammetry at a CPE.Silk fibroin has a clearly irreversible oxidation peak(Pa,1) and a pair of weak-defined reversible peak(Pa,2 and Pc).The peak currents of peak Pa,1 are proportional to the concentration of silk fibroin in the range of 5.8×10-8 to 1.1×10-6 mol·L-1.Sericin,amino acids and inorganic ions do not interfere with silk fibroin determination.This method is applied to the determination of SF in raw silk liquid samples without any pre-separation and pre-purification.The average recoveries are 97.0-103.0%.6.The interaction between carmine and sericin is investigated with electrochemical methods and the UV-Vis spectrophotometry.In the absence of sericin,carmine has a pair of well-defined redox peaks in a pH 1.81 B-R buffer solution.Although no new redox peaks appear upon the addition of sericin into a carmine solution,the peak currents of the old peaks reduce while the peak potentials shift positively.This observation is attributed to the decrease in the diffusion coefficient and electrode reaction rate constant of carmine in the presence of sericin.The main binding mode between carmine and sericin is electrostatic attraction.The binding constant and binding ratio are calculated as 2.32×106 L·mol-1 and 1:1,respectively.Furthermore,the decrease in the peak currents is found proportional to the sericin concentration in the range of 32.0-800.0μg·mL-1.The method is further applied to the determination of sericin in a degumming wastewater with satisfied average recoveries from 96.7 to 103.3%.The results are in good agreement with those obtained by the conventional Coomassie brilliant blue G-250 spectrophotometric method.7.The electrochemical behaviors of malachite green(MG),brilliant acid scarlet red 3R,C.I. Acid Blue 120(WAGR) and reactive yellow K-4G are studied with cyclic voltammetry and square wave voltammetry at a CPE.Based on the linear correlation between peak currents and dye concentrations,SWV methods are set up to the determination of dye-uptakes of these four dyes dyeing different fibers(MG dyeing acrylic fiber,brilliant acid scarlet red 3R dyeing silk and wool,C.I.ACID BLUE 120 dyeing silk and reactive yellow K-4G dyeing silk).The results are in accordance with the traditional spectrophotometric method. |
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