In principle, a population inversion in semiconductor quantum\ud dots can be achieved through electrical, chemical or optical\ud pumping. To date however, it has only been successfully\ud demonstrated with optical pumping in the 1-photon absorption\ud range (i.e., above the semiconductor bandgap). Under\ud these conditions amplified stimulated emission (ASE) in 1-D\ud waveguides and lasing within microsphere cavities and distributed\ud feedback structures has been observed. In these studies,\ud it was demonstrated that for the archetypal CdSe system,\ud a given nanocrystal must encompass more than one electronhole\ud (e–h) pair for a population inversion to be achieved. This\ud value reflects the twofold degeneracy of the lowest electronic\ud state in the wurtzite crystal structure

The development of a solution-deposited up-converted distributed feedback laser prototype is presented. It employs a sol-gel silica/germania soft-lithographed microcavity and CdSe-CdZnS-ZnS quantum dot/sol-gel zirconia composites as optical gain material. Characterization of the linear and nonlinear optical properties of quantum dots establishes their high absorption cross-sections in the one-and two-photon absorption regimes to be 1 × 10 −14 cm 2 and 5 × 10 4 GM, respectively. In addition, ultrafast transient absorption dynamics measurements of the graded seal quantum dots reveal that the Auger recombination lifetime is 220 ps, a value two times higher than that of the corresponding CdSe core. These factors enable the use of such quantum dots as optically pumped gain media, operating in the one-and two-photon absorption regime. The incorporation of CdSe-CdZnSZnS quantum dots within a zirconia host matrix affords a quantum-dot ink that can be directly deposited on our soft-lithographed distributed feedback grating to form an all-solution-processed microcavity laser.

Background: Since the beginning of SARS-CoV-2 outbreak, a large number of infections have been reported among healthcare workers (HCWs). The aim of this study was to investigate the occurrence of SARS-CoV-2 infection among HCWs involved in the first management of infected patients and to describe the measures adopted to prevent the transmission in the hospital. Methods: This prospective observational study was conducted between February 21 and April 16, 2020, in the Padua University Hospital (north-east Italy). The infection control policy adopted consisted of the following: the creation of the “Advanced Triage” area for the evaluation of SARS-CoV-2 cases, and the implementation of an integrated infection control surveillance system directed to all the healthcare personnel involved in the Advance Triage area. HCWs were regularly tested with nasopharyngeal swabs for SARS-CoV-2; body temperature and suggestive symptoms were evaluated at each duty. Demographic and clinical data of both patients and HCWs were collected and analyzed; HCWs’ personal protective equipment (PPE) consumption was also recorded. The efficiency of the control strategy among HCWs was evaluated identifying symptomatic infection (primary endpoint) and asymptomatic infection (secondary endpoint) with confirmed detection of SARS-CoV-2. Results: 7595 patients were evaluated in the Advanced Triage area: 5.2% resulted positive and 72.4% was symptomatic. The HCW team was composed of 60 members. A total of 361 nasopharyngeal swabs were performed on HCWs. All the swabs resulted negative and none of the HCWs reached the primary or the secondary endpoint. Conclusions: An integrated hospital infection control strategy, consisting of dedicated areas for infected patients, strict measures for PPE use and mass surveillance, is successful to prevent infection among HCWs.

We report a facile production of an up-converted surface-emitting DFB laser, performed by exploiting the versatility of sol-gel chemistry, the intriguing properties of well designed graded CdSe-CdS-Cd(0.5)Zn(0.5)S-ZnS colloidal quantum dots, and the scalability of nanoimprinting. Our laser prototype operates in the visible region following efficient optical pumping by either direct one-photon excitation or through the up-conversion of near infrared (NIR) light. By achieving cavity mode Q-factors in excess of 650 and retaining high lasing stabilities in air, this work highlights the feasibility of creating integrated lasing devices through solution based methods.

Dielectric elastomers (DE's) offer promising applications as soft and light-weight electromechanical actuators. It is known that beside the dielectric material, the electrode properties are of particular importance regarding the DE performance. Therefore, in recent years various studies have focused on the optimization of the electrode in terms of conductivity, stretchability and reliability. However, less attention was given to efficient electrode processing and deposition methods. In the present study, digital inkjet printing was used to deposit highly conductive and stretchable electrodes on silicone. Inkjet printing is a versatile and cost effective deposition method, which allows depositing complex-shaped electrode patterns with high precision. The electrodes were printed using an ink based on industrial low-cost MWCNT. Experiments have shown that the strain-conductivity properties of the printed electrode are strongly depended on the deposition parameters like drop-spacing and substrate temperature. After the optimization of the printing parameters, thin film electrodes could be deposited showing conductivities of up to 30 S cm −1 without the need of any post-treatment. In addition, electromechanical tests with fabricated DE actuators have revealed that the inkjet printed MWCNT electrodes are capable to self-clear in case of a dielectric breakdown.