Optical Printing of Single Au Nanostars.

Obtaining arrays of single nanoparticles with three-dimensional complex shapes is still an open challenge. Current nanolithography methods do not allow for the preparation of nanoparticles with complex features like nanostars. In this work, we investigate the optical printing of gold nanostars of different sizes as a function of laser wavelength and power. We found that tuning the laser to the main resonances of the nanostars in the near-infrared makes it possible to avoid nanoparticles reshaping due to plasmonic heating, enabling their deposition at the single particle level and in ordered arrays.

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.

Testing the efficacy of INtegral Cognitive REMediation (INCREM) in major depressive disorder: study protocol for a randomized clinical trial.

BACKGROUND: Given the limitation of pharmacological treatments to treat cognitive symptoms in patients with Major Depressive Disorder (MDD), cognitive remediation programs has been proposed as a possible procognitive intervention but findings are not conclusive. This study investigates the efficacy of an INtegral Cognitive REMediation (INCREM) that includes a combination of a Functional Remediation (FR) strategy plus a Computerized Cognitive Training (CCT) in order to improve not only cognitive performance but also the psychosocial functioning and the quality of life. METHODS: A single blind randomized controlled clinical trial in 81 patients with a diagnosis of MDD in clinical remission or in partial remission. Participants will be randomized to one of three conditions: INCREM (FR + CCT), Psychoeducation plus online games and Treatment As Usual (TAU). Intervention will consist in 12 group sessions, of approximately 110 min once a week. The primary outcome measure will be % of change in psychosocial functioning after treatment measured by the Functional Assessment Short Test (FAST); additionally, number of sick leaves and daily activities will also be recorded as pragmatic outcomes. DISCUSSION: To our knowledge, this is the first randomized controlled clinical trial using a combination of two different approaches (FR + CCT) to treat the present cognitive deficits and to promote their improvements into a better psychosocial functioning. TRIAL REGISTRATION: Clinical Trials NCT03624621 . Date registered 10th of August 2018 and last updated 24th August 2018.

Tethering Luminescent Thermometry and Plasmonics: Light Manipulation to Assess Real-Time Thermal Flow in Nanoarchitectures.

The past decade has seen significant progresses in the ability to fabricate new mesoporous thin films with highly controlled pore systems and emerging applications in sensing, electrical and thermal isolation, microfluidics, solar cells engineering, energy storage, and catalysis. Heat management at the micro- and nanoscale is a key issue in most of these applications, requiring a complete thermal characterization of the films that is commonly performed using electrical methods. Here, plasmonic-induced heating (through Au NPs) is combined with Tb3+/Eu3+ luminescence thermometry to measure the thermal conductivity of silica and titania mesoporous nanolayers. This innovative method yields values in accord with those measured by the evasive and destructive conventional 3ω-electrical method, simultaneously overcoming their main limitations, for example, a mandatory deposition of additional isolating and metal layers over the films and the previous knowledge of the thermal contact resistance between the heating and the mesoporous layers.

Randomized clinical trial of integral cognitive remediation program for major depression (INCREM).

BACKGROUND: Despite achieving clinical remission, patients with depression encounter difficulties to return to their premorbid psychosocial functioning. Cognitive dysfunction has been proposed to be a primary mediator of functional impairment. Therefore, the new non-pharmacological procognitive strategy INtegral Cognitive REMediation for Depression (INCREM) has been developed with the aim of targeting cognitive and psychosocial functioning. METHODS: This is a single-blind randomized controlled clinical trial with three treatment arms. Fifty-two depressed patients in clinical remission, with psychosocial difficulties and cognitive impairment, were randomly assigned to receive INCREM intervention, Psychoeducation programme, or treatment as usual. Patients were assessed before and after the study period, and six months after. The primary outcome was the change from baseline of patients' psychosocial functioning. Changes in cognitive functioning and other variables were considered secondary outcomes. RESULTS: The analysis showed a significant improvement in psychosocial functioning in the INCREM group, especially six months after the intervention, compared to patients who received the psychoeducation programme. An improvement in cognitive performance was also observed in the INCREM group. LIMITATIONS: This study includes a small sample size due to the anticipated end of the clinical trial because of the COVID-19 pandemic. DISCUSSION: These results provide preliminary evidence on the feasibility and potential efficacy of the INCREM program to improve not only cognitive performance but also psychosocial functioning in clinically remitted depressed patients, and such improvement is maintained six months after. It can be speculated that the maintenance is mediated by the cognitive enhancement achieved with INCREM.

Controlling the thermal switching in upconverting nanoparticles through surface chemistry.

Photon upconversion taking place in small rare-earth-doped nanoparticles has been recently observed to be thermally modulated in an anomalous manner, showing thermal enhancement of the emission intensity. This effect was proved to be linked to the role of adsorbed water molecules as surface quenchers. The surface capping of the particles has a direct influence on the thermal dynamics of water adsorption and desorption, and therefore on the optical properties. Here, we show that the upconversion intensity of small-size (<25 nm) nanoparticles co-doped with Yb3+ and Er3+ ions, and functionalized with different capping molecules, presents clear irreversibility patterns upon thermal cycling that strongly depend on the chemical nature of the nanoparticle surface. By performing temperature-controlled luminescence measurements we observed the formation of a thermal hysteresis loop, resembling an optical switching phenomenon, whose shape and trajectory depend on the hydrophilicity of the surface. Additionally, an intensity overshoot takes place immediately after turning off the heating source, affecting each radiative transition differently. We performed numerical modelling to understand this effect considering non-radiative energy transfer from the surface defect states to the Er3+ ions. These findings are relevant for the comprehension of nanoparticle-based luminescence and the interplay between the surface and volume effects, and more generally, for applications involving UCNPs such as nanothermometry and bioimaging, and the development of optical encoding systems.

Electrical conductivity in patterned silver-mesoporous titania nanocomposite thin films: towards robust 3D nano-electrodes.

The space-resolved electrical conductivity of patterned silver nanoparticle (NP) arrays embedded in mesoporous TiO(2) thin films was locally evaluated using a conductive-tip AFM. A remarkable conductivity dependence on the film mesostructure and metal NP loading was observed, confirming a three-dimensional current flow throughout the nanocomposite.

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 2 H 11 / 2 → 4 I15/2 and 4 S 3 / 2 → 4 I15/2 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 1 G 4 → 3 H6 (Tm3+) and the 4 S 3 / 2 → 4 I15/2 (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.

Thermoplasmonic enhancement of upconversion in small-size doped NaGd(Y)F4 nanoparticles coupled to gold nanostars.

Plasmon enhancement of luminescence is a common strategy to boost the efficiency of both fluorescence and upconversion via the augmented local electromagnetic field. However, the local heating produced when exciting the plasmon resonance of metallic nanoparticles is often overlooked. As higher temperatures are usually detrimental for radiative processes, only the electromagnetic contribution is exploited for enhancement. We show here that for small size (<20 nm) rare-earth doped ß-NaGd(Y)F4 upconversion nanoparticles (UCNPs), the photothermal properties of gold nanostars (AuNSs) can be used to enhance the total emission intensity. On the contrary, for UCNPs of larger size, the thermoplasmonic effect is adverse for the emissivity. Therefore, we developed a novel strategy to enhance the emission intensity by combining the thermoplasmonic effect on AuNSs with the size-dependent thermal properties of UCNPs. Furthermore, by following the integrated intensity ratio between the emission lines of Er3+, 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2, a direct correlation between the local temperature and the emission intensity could be established. Optical thermometry measurements show that the thermoplasmonic effect in AuNSs, with a plasmon absorption band close to the excitation wavelength, can produce an increment of the local temperature of more than 100 °C when exposed to 976 nm continuous-wave laser light at 50 W cm-2 of power density. The results provided here are relevant for the design and implementation of plasmon-enhanced luminescent devices, upconversion solar-cells, bioprobes and also for hyperthermia.

Magnetic Gold Confined in Ordered Mesoporous Titania Thin Films: A Noble Approach for Magnetic Devices.

In the past decade, the surprising magnetic behavior of gold nanoparticles has been reported. This unexpected property is mainly attributed both to size and surface effects. Mesoporous thin films are ideal matrices for metallic nanoparticles inclusion, because of their highly accessible and tailorable pore systems that lead to completely tunable chemical environments. Exploiting these features, we synthesized Au nanoparticles within mesoporous titania thin films (film thickness of ∼150 nm and pore diameter of ∼5 nm), and we studied their magnetic properties under confinement. Here, we present the results of the magnetization as a function of temperature and magnetic field for this system, which are consistent with the previously reported for free (unconfined) thiol-capped gold nanoparticles. The successful inclusion of stable magnetic Au nanoparticles within transparent mesoporous thin films opens the gates for the application of these nanocomposites in two-dimensional (2D) microdevices technology and magneto-optical devices.

Silver nanoparticle-mesoporous oxide nanocomposite thin films: a platform for spatially homogeneous SERS-active substrates with enhanced stability.

We introduce a nanoparticle-mesoporous oxide thin film composite (NP-MOTF) as low-cost and straightforward sensing platforms for surface-enhanced Raman Spectroscopy (SERS). Titania, zirconia, and silica mesoporous matrices templated with Pluronics F-127 were synthesized via evaporation-induced self-assembly and loaded with homogeneously dispersed Ag nanoparticles by soft reduction or photoreduction. Both methods give rise to uniform and reproducible Raman signals using 4-mercaptopyridine as a probe molecule. Details on stability and reproducibility of the Raman enhancement are discussed. Extensions in the design of these composite structures were explored including detection of nonthiolated molecules, such as rhodamine 6-G or salicylic acid, patterning techniques for locating the enhancement regions and bilayered mesoporous structures to provide additional control on the environment, and potential size-selective filtration. These inorganic oxide-metal composites stand as extremely simple, reproducible, and versatile platforms for Raman spectroscopy analysis.

Patterned production of silver-mesoporous titania nanocomposite thin films using lithography-assisted metal reduction.

A simple method that allows selective positioning of nanoparticles into mesoporous monolayer or multilayer thin films is presented. This technique applies UV lithography in order to bring about in situ light-induced reduction of silver in templated cavities of TiO2. The nanoparticle lithography presented here provides a novel approach to hierarchical lithography patterning for multifunctional devices.