Thermal enhancement of upconversion emission in nanocrystals: a comprehensive summary

Luminescence thermal stability is a major figure of merit of lanthanide-doped nanoparticles playing an essential role in determining their potential applications in advanced optics. Unfortunately, considering the intensification of multiple electron-vibration interactions as temperature increases, luminescence thermal quenching of lanthanide-doped materials is generally considered to be inevitable. Recently, the emergence of thermally enhanced upconversion luminescence in lanthanide-doped nanoparticles seemed to challenge this stereotype, and the research on this topic rapidly aroused wide attention. While considerable efforts have been made to explore the origin of this phenomenon, the key mechanism of luminescence enhancement is still under debate. Here, to sort out the context of this intriguing finding, the reported results on this exciting topic are reviewed, and the corresponding enhancement mechanisms as proposed by different researchers are summarized. Detailed analyses are provided to evaluate the contribution of the most believed ‘‘surface-attached moisture desorption’’ process on the overall luminescence enhancement of lanthanide-doped nanoparticles at elevated temperatures. The impacts of other surface-related processes and shell passivation on the luminescence behaviour of the lanthanide-doped materials are also elaborated. Lack of standardization in the reported data and the absence of important experimental information, which greatly hinders the cross-checking and reanalysis of the results, is emphasized as well. On the foundation of these discussions, it is realized that the thermal-induced luminescence enhancement is a form of recovery process against the strong luminescence quenching in the system, and the enhancement degree is closely associated with the extent of luminescence loss induced by various quenching effects beforehand.publishe

Usando a Luz para Medir Temperatura

As exigências tecnológicas atuais em micro e nanoeletrónica, fotónica, micro e nanofluídica e biomedicina, entre outras áreas, atingiram um ponto em que a utilização de termómetros convencionais de contacto é incapaz de efetuar medições com resolução espacial na escala submicrométrica. O desenvolvimento de novas sondas térmicas de monitorização remota é, então, inevitável, o que tem contribuindo para a época expansionista da termometria de luminescência que estamos a atravessar. Em particular, a termometria de luminescência baseada em iões lantanídeos (trivalentes) tornou -se muito popular desde 2010 devido às características intrínsecas destes iões, onde se destacam a versatilidade e estabilidade da sua emissão de luz cobrindo todo o espectro eletromagnético com rendimentos quânticos relativamente elevados. Neste artigo, apresentamos uma visão geral do campo desde os seus primórdios na década de 1950 até aos desenvolvimentos mais recentes. O movimento atual para a utilização da técnica como ferramenta para a imagem térmica, deteção precoce de tumores e como ferramenta para desvendar propriedades dos próprios termómetros ou do seu ambiente local é, também, resumidamente discutido.info:eu-repo/semantics/publishedVersio

Upconverting nanoparticles as primary thermometers and power sensors

Luminescence thermometry is a spectroscopic technique for remote temperature detection based on the thermal dependence of the luminescence of phosphors, presenting numerous applications ranging from biosciences to engineering. In this work, we use the Er3+ emission of the NaGdF4/NaGdF4:Yb3+,Er3+/NaGdF4 upconverting nanoparticles upon 980 nm laser excitation to determine simultaneously the absolute temperature and the excitation power density. The Er3+ 2H11/2→4 I15/2 and 4 S3/2→4 I15/2 emission bands, which are commonly used for thermometric purposes, overlap with the 2 H9/2 →4 I13/2 emission band, which can lead to erroneous temperature readout. Applying the concept of luminescent primary thermometry to resolve the overlapping Er3+ transitions, a dual nanosensor synchronously measuring the temperature and the delivered laser pump power is successfully realized holding promising applications in laser-supported thermal therapies.publishe

Designing Ln3+-doped BiF3 particles for luminescent primary thermometry and molecular logic

The design of molecular materials suitable for disparate fields could lead to new advances in engineering applications. In this work, a series of Ln3+-doped BiF3 sub-microparticles were synthesized through microwave-assisted synthesis. The effects of doping are evaluated from the structural and morphological viewpoint. In general, increasing the Ln3+ concentration the octahedral habitus is distorted to a spheric one, and some aggregates are visible without any differences in the crystalline phase. The optical response of the samples confirms that the BiF3 materials are suitable hosts for the luminescence of the tested trivalent lanthanide (Ln3+) ions (Ln = Eu, Tb, Tm, Ho, Er, Yb). A Yb3+/ Er3+ co-doped sample is presented as an illustrative example of all-photonic molecular logic operations and primary luminescent thermometry.publishe

A luminescent molecular thermometer for long-term absolute temperature measurements at the nanoscale

El pdf del artículo es la versión post-print.A unique Eu3+/Tb3+ luminescent self-referencing nanothermometer allowing absolute measurements in the 10–350 K temperature range and sub-micrometer spatial resolution is reported (see Figure). It has up to 4.9%·K−1 temperature sensitivity and high photostability for long-term use. The combination of molecular thermometry, superparamagnetism and luminescence in a nanometric host matrix provides multifunctionality opening the way for new exciting applications.We acknowledge Fundação para a Ciência e a Tecnologia (FCT, Portugal), COMPETE and FEDER programs (PTDC/CTM/101324/2008) and Integrated Spanish-Portuguese Action PT2009–0131 for fi nancial support. The work in Zaragoza has been supported by the grants MAT2007–61621 and CONSOLIDER CSD2007–00010 from the Ministry of Education. CDSB (SFRH/BD/38472/2007) and PPL (SFRH/BPD/34365/2006) thank FCT for grants.Peer Reviewe

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

Self-Calibrated Double Luminescent Thermometers Through Upconverting Nanoparticles

Luminescent nanothermometry uses the light emission from nanostructures for temperature measuring. Non-contact temperature readout opens new possibilities of tracking thermal flows at the sub-micrometer spatial scale, that are altering our understanding of heat-transfer phenomena occurring at living cells, micro electromagnetic machines or integrated electronic circuits, bringing also challenges of calibrating the luminescent nanoparticles for covering diverse temperature ranges. In this work, we report self-calibrated double luminescent thermometers, embedding in a poly(methyl methacrylate) film Er3+- and Tm3+-doped upconverting nanoparticles. The Er3+-based primary thermometer uses the ratio between the integrated intensities of the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions (that follows the Boltzmann equation) to determine the temperature. It is used to calibrate the Tm3+/Er3+ secondary thermometer, which is based on the ratio between the integrated intensities of the 1G4→3H6 (Tm3+) and the 4S3/2→4I15/2 (Er3+) transitions, displaying a maximum relative sensitivity of 2.96% K−1 and a minimum temperature uncertainty of 0.07 K. As the Tm3+/Er3+ ratio is calibrated trough the primary thermometer it avoids recurrent calibration procedures whenever the system operates in new experimental conditions

Sustainable smart tags with two‐step verification for anticounterfeiting triggered by the photothermal response of upconverting nanoparticles

No abstract available.This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020) and Shape of Water (PTDC/NAN-PRO/3881/2020) financed by Portuguese funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. F.E.M. acknowledges the funding received from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 823941. The support of the European Union’s Horizon 2020 FET Open program under grant agreement no. 801305 (NanoTBTech) is also acknowledged. R.R.S. acknowledges the financial support from the Brazilian agency FAPESP (process no. 16/06612-6).publishe

Organic-Inorganic Eu3+/Tb3+ codoped hybrid films for temperature mapping in integrated circuits

The continuous decrease on the geometric size of electronic devices and integrated circuits generates higher local power densities and localized heating problems that cannot be characterized by conventional thermographic techniques. Here, a self-referencing intensity-based molecular thermometer involving a di-ureasil organic-inorganic hybrid thin film co-doped with Eu3+ and Tb3+ tris (3-diketonate) chelates is used to obtain the temperature map of a FR4 printed wiring board with spatio-temporal resolutions of 0.42 mu m/4.8 ms

Lanthanide luminescence to mimic molecular logic and computing through physical inputs

The remarkable advances in molecular logic reported in the last decadedemonstrate the potential of luminescent molecules for logical operations, aparadigm-changing concerning silicon-based electronics. Trivalent lanthanide(Ln3+) ions, with their characteristic narrow line emissions, long-lived excitedstates, and photostability under illumination, may improve the state-ofthe-art molecular logical devices. Here, the use of monolithic silicon-basedstructures incorporating Ln3+ complexes for performing logical functions isreported. Elementary logic gates (AND, INH, and DEMUX), sequential logic(KEYPAD LOCK), and arithmetic operations (HALF ADDER and HALF SUBTRACTOR)exhibiting a switching ratio >60% are demonstrated for the firsttime using nonwet conditions. Additionally, this is the first report showingsequential logic and arithmetic operations combining molecular Ln3+ complexesand physical inputs. Contrary to chemical inputs, physical inputs mayenable the future concatenation of distinct logical functions and reuse of thelogical devices, a clear step forward toward input–output homogeneity that isprecluding the integration of nowadays molecular logic devices.</p