Елелектрохімічне одержання та властивості гібридних наноструктур на основі поруватого кремнію і поліаніліну

Abstract

Вивчено закономірності електрохімічного одержання гібридних наноструктур на основі тонких шарів поліаніліну на поверхні поруватого кремнію в умовах електрохімічної полімеризації аніліну з циклічною розгорткою потенціалу. Методом атомносилової мікроскопії досліджено топологію поверхні отриманих структур. Виявлено, що наявність тонкого поліанілінового шару спричиняє незначний зсув максимуму і деяке послаблення фотолюмінесценції поруватого кремнію, а також окисновідновну та сенсорну активність одержаних наноструктур. Ключові слова: поруватий кремній, електрополімеризація, поліанілін, наноструктура, фотолюмінесценція..

Belong the semiconductor materials a special place is occupied by the heterogeneous systems based on nanoporous silicon (PS), having a wide application in optoelectronic and sensor devices. Of great interest are the heterostructures created on the PS and surface organic layers, among which the conjugated conducting polymers now intensively studied. In the present work the possibility of electrochemical obtaining of the hybrid nanostructures based on thin polyaniline (PANI) layers on the surface of porous silicon in the conditions of electrochemical polymerization has been investigated. The porous silicon layers were formed by etching of the silicon wafers (100) with n-type of conductivity in a 40% HF ethyl alcohol solution at a current density of 10 mA. cm-2 during 20 minutes. For creation of PS-PANI hybrid layer a method of electrochemical polymerization with cyclic potential sweeping in 0.1M solutions of purified aniline in 0.5 M H2SO4 was used. A wafer of PS of the area of 1 cm2 was as an operating electrode, a platinum wire was used as a counter electrode and saturated Ag/AgCl electrode was employed as a reference. The potentiostat PI-50 was a power source. After film coating the samples were rinsed with deionized water and dried under vacuum at 353 – 373 K. Linear dependence of the peak current on the potential sweep number in the interval of N = 4…16 give the possibility to control the process of electroactive film formation on the surface of the porous silicon. The surface topology of the prepared structures was investigated by the method of atom force microscopy. It found that PANI films obtained on the surface of PS by electropolymerization method in general repeat the relief of the surface forming a continuous polymer layer. However, the morphology of the films is difficult interpret due to the irregularity of PS surface. As has been shown by the profile analysis of PS-polymer heterostructure a thickness of PS-polymer layer achieves 40–45 nm. Obtained nanostructures were examined on the ability to photoluminescence (PL) and electrochemical activity. Higher electrochemical activity of PS-PANI nanostructure in comparison with PS probably connected with particularities of the polyaniline structure, obtained in the condition of electropolymerization with cyclic potential sweeping where polymer synthesis proceeds both on the surface and inside the silicon pores. It has been found that presence of the thin polyaniline layer causes an insignificant displacement of the maximum and some weakness of PL in comparison with PL of clean porous silicon. Because electrical and optical properties of PANI is significantly depend on the level of oxidation or reduction, this polymer is very sensitive to the action of chemical substances (value of рН, adsorption of polar gases), therefore coating of PS by PANI film may improving the properties of sensor devices based on PS. A sensor activity of the obtained heterostructures in gas medium has been study. It found that increasing the ammonia pressure leads to growing the PL intensity, which may be explained by the processes of PANI film reduction with formation of colorless form of polymer - leucoemeraldine, in result of this increases an optical transparence of the film and, correspondently, yield of emission. Key words: porous silicon, electropolymerization, polyaniline, nanostructure, photoluminescence

Изучены закономерности электрохимического получения гибридных наноструктур на основе тонких слоев полианилина на поверхности пористого кремния в условиях электрохимической полимеризации анилина с циклической разверткой потенциала. Методом атомно-силовой микроскопии исследовано топологияю поверхности полученных структур. Установлено, что наличие тонкого полианилинового слоя вызывает незначительный сдвиг максимума и некоторое ослабление фотолюминесценции пористого кремния, а также окислительно - восстановительную и сенсорную активность полученных гетероструктур. Ключевые слова: пористый кремний, электрополимеризация, полианилин, наноструктура, фотолюминесценция.