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The polyvinyl alcohol (PVA)-capped ZnS:Mn nanoparticles with Mn content of 8 mol% and different PVA mass (denoted as ZnS:Mn/PVA) are synthesized by co-precipitation method, in which PVA solution is mixed from the beginning with the initial solutions used to synthesize ZnS:Mn nanoparticles. The microstructures, morphology and average crystalline size of ZnS:Mn/PVA nanoparticles were investigated by X-ray diffraction patterns, high resolution transmission electron microscopy, thermal gravimetric analysis (TGA) and differential thermal gravimetric analysis and Fourier transform infrared absorption spectra. The role of PVA to the photoluminescence (PL) of Mn 2? ions in these nanoparticles at 300 K were studied by the PL and photoluminescence excitation (PLE) spectra. The investigated results show that the PVA covering for ZnS:Mn nanoparticles almost is not change the microstructure, morphology, the crystal field and the peak positions in their PL and PLE spectra, but the maximum intensity of peaks increased with PVA mass from 0.2 to 1.0 g. The clear peak positions in PLE spectra show that the energy levels of Mn 2? ions were splitted into multiple levels in the ZnS:Mn crystal field, that its strength D q was caculated. Furthermore, the effect of PVA on the PL enhancement of Mn 2? ions in ZnS:Mn/PVA nanoparticles also was explained.

With remarkable advances in IoT, big data, and AI, the fourth industrial revolution is upon us. Low power design methodologies and techniques have been greatly contributing to these advancements by addressing the critical issue of how to increase the device service life under a fixed and limited energy source. In particular, ultra-low power (ULP) technology, which exploits ultra-low voltage (ULV) operating circuit, has recently emerged as a cutting-edge technology for realizing ULP devices. Although a number of studies on ULV circuits have been made so far, and the results have been very successful, research on DC–DC converters optimized for the ULV operation must be carried out in order to use them ultimately in ULP devices. In this paper, a DC–DC converter with low power, small area, and high-resolution digital pulse width modulator (DPWM) for ultra-low voltage (ULV) operating IoT platforms is presented. The proposed DPWM design uses a much smaller number of D flip-flops than conventional ones, achieving significant power saving and area reduction while showing excellent resolution of power conversion. In addition, by utilizing the proposed DPWM, the DC–DC converters can take full advantage of the dynamic switch width modulation technology without overhead, greatly improving the power conversion efficiency under ultra light load conditions. A prototype DC–DC converter with the proposed DPWM is fabricated in Samsung 65nm technology, and the experimental work with this converter and a target ULV operating platform demonstrates that this converter is best suited for the target platform.

The upconversion luminescence (UCL) of Gd 2 O 3 : Er 3+ monodisperse nanospheres, synthesized by multistep chemical method, and nanoparticles, produced by combustion synthesis, are presented for comparison. The UCL of nanospheres Gd 2 O 3 : Er 3+ and Gd 2 O 3 : Er 3+ @Silica have shown strong red or green emission under excitation at 976 nm or 980 nm by a diode laser with a remarkable increase of the bright red color in the nanospheres. In the core/shell structured nanospheres Gd 2 O 3 : Er 3+ @Silica, we find a higher intensity of upcoversion emission, increased stability and better dispersion capability in solvents and water. The UCL intensities of green and red color while 976 nm or 980 nm excitation were dependent on the diode laser power. The slope values of Er 3+ ion's transitions 2 H 11/2 4 I 15/2 , 4 S 3/2 4 I 15/2 and 4 F 9/2 4 I 15/2 in the silica-coated nanospheres are 1.99, 1.62 and 1.66 respectively, which properly indicate the two-photon mechanism of upconversion emission. The synthesized Gd 2 O 3 nanospheres codoped with Yb and Er show strong UCL intensity than those of Gd 2 O 3 : Er 3+ . The obtained Gd 2 O 3 : Er 3+ nanospheres and nanoparticles, as well as Gd 2 O 3 : Yb 3+ , Er 3+ and its silica-coated versions, are promising materials to develop with potential application in high technology and biomedicine.

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