Electrochromic Switch Devices Mixing Small- and Large-Sized Upconverting Nanocrystals


The hasty progress in smart, portable, flexible, and transparent integrated electronics and optoelectronics is currently one of the driving forces in nanoscience and nanotechnology. A promising approach is the combination of transparent conducting electrode materials (e.g., silver nanowires, AgNWs) and upconverting nanoparticles (UCNPs). Here, electrochromic devices based on transparent nanocomposite films of poly(methyl methacrylate) and AgNWs covered by UCNPs of different sizes and compositions are developed. By combining the electrical control of the heat dissipation in AgNW networks with size-dependent thermal properties of UCNPs, tunable electrochromic transparent devices covering a broad range of the chromatic diagrams are fabricated. As illustrative examples, devices mixing large-sized (>70 nm) beta-NaYF4:Yb,Ln and small-sized (<15 nm) NaGdF4:Yb,Ln@NaYF4 core@shell UCNPs (Ln = Tm, Er, Ce/Ho) are presented, permitting to monitor the temperature-dependent emission of the particles by the intensity ratio of the Er3+ 2H11/2 and S-4(3/2) -> I-4(15/2) emission lines, while externally controlling the current flow in the AgNW network. Moreover, by defining a new thermometric parameter involving the intensity ratio of transitions of large- and small-sized UCNPs, a relative thermal sensitivity of 5.88% K-1 (at 339 K) is obtained, a sixfold improvement over the values reported so far.



subject category

Chemistry; Science & Technology - Other Topics; Materials Science; Physics


Martinez, ED; Brites, CDS; Carlos, LD; Garcia-Flores, AF; Urbano, RR; Rettori, C

our authors


Authors are grateful to Prof. G. J. A. A. Soler-Illia for his help in establishing this international collaboration and to Prof. Daniel Jaque for helpful discussions. This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brazil (CAPES)-Finance Code 001 and FundacAo de Amparo a Pesquisa do Estado de SAo Paulo (FAPESP) under Grant Nos. 2011/19924-2, 2012/04870-7, 2012/05903-6, 2015/21290-2, and 2015/21289-4. This work was partially developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by Portuguese funds through the FundacAo para a Ciencia e a Tecnologia/Ministerio da EducacAo e Ciencia (FCT/MEC) and when applicable cofinanced by FEDER under the PT2020 Partnership Agreement. The financial support from FCT (PTDC/CTM-NAN/4647/2014 and POCI-01-0145-FEDER-016687) is also acknowledged and the project has received funding from the European Union's Horizon 2020 FET Open programme under Grant No. 801305. E.D.M. acknowledges the postdoctoral FAPESP fellowship 2015/23882-4 and BEPE 2018/12489-8. C.D.S.B. acknowledges the grant financed by the SusPhotoSolutions project CENTRO-01-0145-FEDER-000005. The SEM, TEM, and AFM data were acquired at LNNano, Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) in Campinas, SP, Brazil.

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