Nanophotochromism

Abstract

Abstract:The review presents the state-of-the-art analysis of investigations in the field of a new line of research of photochromism -nanophotochromism. The design, properties, and possible applications of photochromic nanoparticles prepared by different methods with the use of photochromic substances (aggregates, host-guest, and polymer systems, solid nanoparticles) as well as core-shell photochromic nanostructures based on polymers, silica, quantum dots, doped upconversion nanocrystals, and Ag, Au, etc. nanoparticles have been reviewed. Keywords: photochromism; photochromic nanoparticles; core-shell photochromic nanoparticles design; photoswitching; aggregates; polymer systems, host-guest systems IntroductionPhotochromism is a very important phenomenon for different applications in photonics. The applications are based on reversible phototransformations of photochromic compounds between two states and changes of their properties that accompany these transformations At present, systems and materials containing photochromic nanopatricles have become highly significant. Among these are nanodimensional particles of photochromic substances, including aggregates, and coreshell systems. As a core, inorganic nanoparticles of gold, silver, metal oxides, quantum dots (QD), and also polymeric nanoparticles are used. The shell consists of photochromic molecules or their aggregates connected to a core surface either chemically or physically. Photochromic nanoparticles with photocontrolled fluorescence arouse a special interest because the fluorescence technique is becoming a leading strategy in biological diagnosis, imaging, and detection applications. This paper is a state-of-the-art review which presents results of studying photochromic nanoparticles including author's own data. The results of earlier research are also surveyed in some other reviews [1][2][3][4][5][6][7][8][9][10][11][12][13]. Photochromic nanoparticles:properties and applications Nanoparticles based on photochromic substances AggregatesThe most known photochromic nanoparticles are aggregates of photochromic organic compounds [14]. These compounds experience reversible photoinduced transformations between two states, Sch. 1A and Sch. 1B. Scheme 1The photoinduced colored merocyanine form B absorbing visible irradiation is formed from a colorless form A as a result of photodissociation of the -C-O-bond of the pyran heterocycle under UV radiation, and this is followed by spontaneous isomerization of the cis-form to the trans one. The colored form B can be converted back to the initial colorless form A upon absorption of visible light or spontaneously during the dark relaxation, which is accelerated by heating.The J-aggregates of nitro-substituted indoline spiropyrans Sch. 2 with long alkyl substituents are of special interest [15].The narrow absorption bands of J-aggregates of these photochromic compounds (Fig. 1) made it possible prepare a specimen of the multilayered optical disk providing freUnauthenticated Download

Фотоуправляемые Обратимые Изменения Электронных И Колебательных Спектров Фотохромного Диарилэтена В Различных Наноструктурированных Системах

“…Особый интерес представляют наноструктурированные фотохромные гибридные (композитные) системы [7], включающие молекулы фотохромных органических соединений, в частности из класса ДАЭ, и наночастицы благородных металлов, а именно золота [8][9][10][11][12][13][14] и серебра [9,15,6], а также неорганических полупроводников [17].…”

Polymer nanospheres containing CdSe/ZnS quantum dots and photochromic diaryletenes with photoswitchable luminescence

“…In development of previous studies [20][21][22][23][24][25][26][27][28][29], this article is devoted to the first comparative spectral-kinetic study of the properties of nanospheres based on CdSe/ZnS QDs with radiation wavelengths of 525, 550, 635 nm and photochromic DAEs of various structures in order to create the scientific basis for development of photochromic radiation nanoswitches.…”

Фотохромные Органо-Силикатные Наночастицы

“…В последние годы значительный практический интерес привлекают фотохромные наночастицы, которые испытывают обратимое фотоиндуцированное изменение своих свойств [1,2]. Одним из направлений их разработки является создание фото-хромных наночастиц на основе наночастиц диоксида кремния (ДК).…”