Upconversion Nanocomposite Materials With Designed Thermal Response for Optoelectronic Devices


Upconversion is a non-linear optical phenomenon by which low energy photons stimulate the emission of higher energy ones. Applications of upconversion materials are wide and cover diverse areas such as bio-imaging, solar cells, optical thermometry, displays, and anti-counterfeiting technologies, among others. When these materials are synthesized in the form of nanoparticles, the effect of temperature on the optical emissions depends critically on their size, creating new opportunities for innovation. However, it remains a challenge to achieve upconversion materials that can be easily processed for their direct application or for the manufacture of optoelectronic devices. In this work, we developed nanocomposite materials based on upconversion nanoparticles (UCNPs) dispersed in a polymer matrix of either polylactic acid or poly(methyl methacrylate). These materials can be processed from solution to form thin film multilayers, which can be patterned by applying soft-lithography techniques to produce the desired features in the micro-scale, and luminescent tracks when used as nanocomposite inks. The high homogeneity of the films, the uniform distribution of the UCNPs and the easygoing deposition process are the distinctive features of such an approach. Furthermore, the size-dependent thermal properties of UCNPs can be exploited by a proper formulation of the nanocomposites in order to develop materials with high thermal sensitivity and a thermochromic response. Here, we thus present different strategies for designing optical devices through patterning techniques, ink dispensing and multilayer stacking. By applying upconverting nanocomposites with unique thermal responses, local heating effects in designed nanostructures were observed.



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Martinez, ED; Brites, CDS; Carlos, LD; Urbano, RR; Rettori, C

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This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brasil (CAPES) -Finance Code 001, and by Fundacilo de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) through Grants #2011/19924-2, #2012/04870-7, #2012/05903-6, #2015/21290-2, and #2015/21289-4. Work was partially developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. PCT UID/CTM/50011/2013), financed by Portuguese funds through the Eundayao para a Ciencia e a Tecnologia/Ministerio da Educacao e Ciencia (PCT/MEC) and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. The financial support of PCT (PTDC/CTNI-NAN/4647/2014 and POCI-01-0145-FEDER-016687) is also acknowledged. EM acknowledges, respectively, the post-doctoral FAPESP fellowship #2015/23882-4 and BEPE #2018/12489-8. CB acknowledges the grant financed by the SusPhotoSolu Lions project CENTRO-01-0145-FEDER-000005.

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