Synthesis and optical characterization of Er-doped bismuth titanate nanoparticles grown by sol-gel hydrothermal method

The Er-doped bismuth titanate (BiTiO, BIT) nanoparticles were synthesized by a combined sol-gel and hydrothermal method under a partial oxygen pressure of 30 bar. The composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman scattering. They showed pure and homogeneous spherical BIT nanoparticles with a size below the 30 nm. The incorporation of Er ions showed a strong decrease in the lattice parameters, as well as averaged particle size. The photoluminescence up-conversion (excitation wavelength =1480 nm) showed an enhancement of the infrared emission (980 nm) as Er concentration increased, achieving a maximum for 6% mol, while photoluminescence spectra (excitation wavelength =473 nm) showed a strong green emission (529 and 553 nm) with a maximum at 4% mol

Regular oscillations and random motion of glass microspheres levitated by a single optical beam in air

We experimentally report on optical binding of many glass particles in air that levitate in a single optical beam. A diversity of particle sizes and shapes interact at long range in a single Gaussian beam. Our system dynamics span from oscillatory to random and dimensionality ranges from 1 to 3D. The low loss for the center of mass motion of the beads could allow this system to serve as a standard many body testbed, similar to what is done today with atoms, but at the mesoscopic scale

Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study

: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI

Clustering of aerosols in a single potential-well trap

We experimentally demonstrate clustering of spherical and non-spherical aerosols in a smooth optical-tweezers. Our empty trap has only a single local-minimum with additional minima being born by the aerosols that join the trap

Synthesis and optical characterization of Er-doped bismuth titanate nanoparticles grown by sol-gel hydrothermal method

The Er-doped bismuth titanate (BiTiO, BIT) nanoparticles were synthesized by a combined sol-gel and hydrothermal method under a partial oxygen pressure of 30 bar. The composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman scattering. They showed pure and homogeneous spherical BIT nanoparticles with a size below the 30 nm. The incorporation of Er ions showed a strong decrease in the lattice parameters, as well as averaged particle size. The photoluminescence up-conversion (excitation wavelength =1480 nm) showed an enhancement of the infrared emission (980 nm) as Er concentration increased, achieving a maximum for 6% mol, while photoluminescence spectra (excitation wavelength =473 nm) showed a strong green emission (529 and 553 nm) with a maximum at 4% mol

GdVO4:Er3+/Yb3+ nanocrystalline powder as fluorescence temperature sensor. Application to monitor the temperature of an electrical component

The temperature sensing properties of an Er3+/Yb3+ co-doped GdVO4 nanocrystalline powder were studied. The down-conversion emission spectrum of the sample was observed under excitation at 457 nm. Two methods were used to calibrate the temperature of the sample: one based on the Fluorescence Intensity Ratio (FIR) technique and the other using the fluorescence lifetime of the thermally-coupled energy levels of Er3+. The relative sensitivities for each method were calculated and it was found out that the FIR-based temperature sensor has higher sensitivity (1.17% K−1) than the lifetime-based sensor (0.24% K−1). Furthermore, a temperature uncertainty of 0.37 K was obtained for the FIR-based sensor. The GdVO4 nanoparticles were also used to study the change in temperature of an electrical component when it is operating and not. © 2019 Elsevier B.V

Optical gain in dye-doped polymer waveguides using oxidized porous silicon cladding

We report on a novel organic/inorganic hybrid waveguide approach, which is composed of a cladding of extremely low refractive index oxidized porous silicon formed on a bulk silicon substrate and of it, a polymeric (polymethylmethacrylate) core doped with a visible laser dye (Nile-Blue) was deposited by spin coating. The waveguiding properties of the structures have been characterized by means of the m-line technique, demonstrating that the use of oxidized porous silicon as a cladding can considerably improve the mode confinement factor of single-mode waveguides. The low refractive index achievable in the cladding (n=1.16) allows forming waveguides with a low index polymer cores. Variable stripe length (VSL) measurements have been also performed in order to characterize the amplification properties of the waveguides. We demonstrate a clear transition from losses to gain at 694nm with a pump threshold of 28mJ/cm2. Values of net optical gain up to 104dB/cm have been measured at this wavelength

Europium(III)-Doped Gadolinium(III) Complex for High-Sensitivity Temperature Sensing in the Physiological Range

A new Eu3+-doped Gd3+ complex of formula [Eu0.0135Gd0.9865(pta)3me-phen] was synthesized and structurally characterized (Hpta = benzoyltrifluoroacetone, me-phen = 5-methyl-1,10-phenanthroline). The photoluminescence study revealed that when the compound was excited at RT, under a 457 nm continuous laser, the material exhibited high luminescence due to the antenna effect of the ligands, as well as a good balance between the phosphorescence from the spin-forbidden triplet (from the organic ligands), and the characteristic lanthanide f-f transitions. The ratio between the previous emissions drastically changed when the sample was heated up to 62 °C inside a tubular furnace. This ratio was investigated using the luminescence intensity ratio method, to analyze the capabilities of the sample as a temperature sensor. The relative sensitivity reached a maximum of 11.4 °C−1 %, maintaining a detection limit below 0.15 °C for the whole temperature range

Experimental and Numerical Validation of Whispering Gallery Resonators as Optical Temperature Sensors

This study experimentally and numerically validates the commonly employed technique of laser-induced heating of a material in optical temperature sensing studies. Furthermore, the Er3+-doped glass microspheres studied in this work can be employed as remote optical temperature sensors. Laser-induced self-heating is a useful technique commonly employed in optical temperature sensing research when two temperature-dependent parameters can be correlated, such as in fluorescence intensity ratio vs. interferometric calibration, allowing straightforward sensor characterization. A frequent assumption in such experiments is that thermal homogeneity within the sensor volume, that is, a sound hypothesis when dealing with small volume to surface area ratio devices such as microresonators, but has never been validated. In order to address this issue, we performed a series of experiments and simulations on a microsphere supporting whispering gallery mode resonances, laser heating it at ambient pressure and medium vacuum while tracking the resonance wavelength shift and comparing it to the shift rate observed in a thermal bath. The simulations were done starting only from the material properties of the bulk glass to simulate the physical phenomena of laser heating and resonance of the microsphere glass. Despite the simplicity of the model, both measurements and simulations are in good agreement with a highly homogeneous temperature within the resonator, thus validating the laser heating technique