We report preparation and characterization of Si1-xGex alloys with varied composition x of a large range from 0-1. The materials have been obtained by co-sputtering, followed by a heat treatment process at 600, 800, and 1000 °C for 30 min in a nitrogen gas atmosphere. X-ray diffraction data have revealed the formation of single-phase nanoparticles in the face-centered cubic (FCC) structure of Si1-xGex alloys. We found that lattice constant a of the Si1-xGex alloys increased linearly with the composition parameter x. Average diameters of the single-phase nanoparticles were estimated to be between 3-10 nm. Further evidence of FCC single-phase [Formula: see text] nanoparticles has been obtained by high resolution transmission electron microscopy. From absorption spectra, the gradual shift of the direct phononless transition identified for the E1 point in the Brillouin zone of bulk Ge is observed in single-phase Si1-xGex nanoparticles as a function of the composition parameter x.

We report high-efficiency and long-lifetime inverted green cadmium-free (InP-based) quantum dot light-emitting diodes (QLEDs) using a stable ZnO/ZnS cascaded electron transport layer (ETL). We have successfully developed a strategy to spin-coat stable ZnS ETLs with a relatively higher conduction band minimum (CBM) and lower electron mobility than that of ZnO, which leads to balanced carrier injection and an improved device lifetime. Analysis shows that by using the ZnO/ZnS cascaded ETL, electron injection is reduced, resulting in an improved charge balance in the QD layer and suppressed exciton quenching, which preserves the emission properties of QDs. Optimized devices with ZnO/ZnS cascaded ETLs show a maximum external quantum efficiency of 10.8% and a maximum current efficiency of 37.5 cd/A; these efficiency values are an almost 2.2-fold improvement compared to those of reference devices without ZnS. The QLED devices also showed a remarkably long lifetime (LT 70 ) of 265 h at an initial luminance of 1000 cd/m 2 . The predicted half-lifetime (LT 50 ) at 100 cd/m 2 is 60,255 h, which, to our knowledge, is currently the longest lifetime yet reported for InP-based green QLEDs.

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Here we report a synthesis approach that is simple, surfactant free, and green, and which is additionally cost effective in terms of its material requirements. The approach entails the use of an inkjet microreactor for the deposition of silver nanoparticles on the surface of office paper decorated with chitosan nano-wrinkles for the preparation of a reproducible and sensitive paper-based surface-enhanced Raman scattering (SERS) substrate. Silver nanoparticles were synthesized directly in the head nozzles of the inkjet printer via the reduction of silver nitrate (AgNO 3) by ascorbic acid. Pre-modification of the paper with chitosan allowed the formation of randomly oriented nano-wrinkles on the surface, thus enabling the formation of silver nanoparticles with good hotspots. The novel paper-based SERS substrate showed outstanding sensitivity and spot-to-spot reproducibility for on-site detection using a portable Raman spectrometer with a limit of detection (LOD) of 10.7 pM. Moreover, our paper-based SERS substrate has an excellent enhancement factor (EF) of 7.4 × 10 8 , which is difficult to achieve on a paper substrate because of the microporous nature of paper. Finally, the batch-to-batch reproducibility and long-term stability of the SERS substrate under ambient conditions make this substrate a good candidate for point-of-care test applications. K E Y W O R D S chitosan, flexible, nano-wrinkles, plasmonic paper, SERS, silver nanoparticles 1 INTRODUCTION Over the last decades, platforms based on nanomaterials and optical measurement techniques, including fluorescence, surface plasmon resonance (SPR), and colorimetry, This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.