Enhanced Air Stability of Perovskite Quantum Dots by Manganese Passivation

Organic-inorganic perovskite quantum dots (PeQDs) have attracted attention due to their excellent optical properties, e.g., high photoluminescence quantum yields (PLQYs; >70%), a narrow full width at half maximum (FWHM; 25 nm or less), and color tunability adjusted by the halide components in an entire tunability (from 450 nm to 730 nm). On the other hand, PeQD stability against air, humidity, and thermal conditions has still not been enough, which disturbs their application. To overcome these issues, with just a focus on the air stability, Mn2+ ion passivated perovskite quantum dots (Mn/MAPbBr3 QDs) were prepared. Mn2+ could be expected to contract the passivating layer against the air condition because the Mn2+ ion was changed to the oxidized Mn on PeQDs under the air conditions. In this research, Mn/MAPbBr3 QDs were successfully prepared by ligand-assisted reprecipitation (LARP) methods. Surprisingly, Mn/MAPbBr3 QD films showed more than double PLQY stability over 4 months compared with pure MAPbBr3 ones against the air, which suggested that oxidized Mn worked as a passivating layer. Improving the PeQD stability is significantly critical for their application.

Silicon Ribbon-Based Dual-Beam Optical Phased Array with Low Crosstalk and Large FoV

In this paper, a silicon ribbon (SR)-based microstructure is developed and added to a 32-channel optical phased array (OPA) to reduce the crosstalk between the antennas of grating waveguides. The spacing between the chirped grating antennas can be as close as 600 nm to effectively improve the field of view (FoV) of the OPA in the horizontal direction to 95 degrees. This SR-based approach substantially reduces the side lobe by 10 dB, effectively suppressing the noise and increasing the main lobe by 6 dB and considerably expanding the grating length with linear energy decay. The full width at the half maximum of the light spot reaches about 0.24 degrees. The antenna sites can simultaneously be scanned vertically by bi-directional inputs, effectively increasing the FoV to 30 degrees in the vertical direction.

THE INFLUENCE OF CATHODE MATERIAL ON THE CHARACTERISTICS OF PULSED NEGATIVE CORONA IN OXYGEN

Change in time for the shape of the discharge current pulses of the pulsed negative corona in oxygen with cop-per and stainless steel cathodes has been studied for two discharge modes. The change lies in the decrease of the pulse amplitude and duration at half maximum. It is shown that for stainless steel cathodes, the amount of electric charge transferred in one pulse of the discharge current is 15% greater than for copper cathodes. It is also shown that under the maximum load mode, the amount of charge transferred in one pulse of the discharge current is de-creased with time by 10% for both types of cathodes. It is shown that ozone synthesis in the electrode system with copper cathodes is 25% more efficient.

AT 2018lqh and the Nature of the Emerging Population of Day-scale Duration Optical Transients

We report on the discovery of AT 2018lqh (ZTF 18abfzgpl)—a rapidly evolving extragalactic transient in a star-forming host at 242 Mpc. The transient g-band light curve’s duration above a half-maximum light is about 2.1 days, where 0.4/1.7 days are spent on the rise/decay, respectively. The estimated bolometric light curve of this object peaked at about 7 × 1042erg s−1—roughly 7 times brighter than the neutron star (NS)–NS merger event AT 2017gfo. We show that this event can be explained by an explosion with a fast (v ∼ 0.08 c) low-mass (≈0.07 M ⊙) ejecta, composed mostly of radioactive elements. For example, ejecta dominated by 56Ni with a timescale of t 0 ≅ 1.6 days for the ejecta to become optically thin for γ-rays fits the data well. Such a scenario requires burning at densities that are typically found in the envelopes of neutron stars or the cores of white dwarfs. A combination of circumstellar material (CSM) interaction power at early times and shock cooling at late times is consistent with the photometric observations, but the observed spectrum of the event may pose some challenges for this scenario. We argue that the observations are not consistent with a shock breakout from a stellar envelope, while a model involving a low-mass ejecta ramming into low-mass CSM cannot explain both the early- and late-time observations.

MEASUREMENT OF PARAMETERS OF BROADBAND EMISSION USING MINI-SPECTROMETERS

On the basis of mini-spectrometers, a reference lamp of the SIRSH type with a known color temperature, and line spectrum sources, an inexpensive hardware complex has been created for measuring the emission parameters of heterodiodes and interference filters. Examples of recording the emission of heterodiodes (full width at half maximum is 17–30 nm) with a maximum of emission in the region of 659 and 764 nm and measurement of an interference filter (FWHM of the bandwidth is 12 nm) with a maximum transmission of 727 nm are given. The emission parameters of the SIRSH standard lamp are introduced into the program for measuring and processing data, due to which it is possible to significantly refine the value of the wavelength of the maximum emission and transmission.

Fabrication and electroluminescence properties of alloyed CdSxSe1-x quantum dots-based LEDs

We report the facile synthesis of alloyed CdSxSe1-x QDs via one-pot method using simultaneous injection of Se and S source into a solution of the Cd precursor dissolved in a coordinating mixture of hexadecylamine and trioctylphosphine, during which the formation of CdSxSe1-x nanocrystals was controlled by growth time at a certain temperature of 260 oC. In particular, emission peak and full width at half maximum of photoluminescence (PL) of alloyed CdSxSe1-x QDs were tunable in a range of 588 - 604 nm and 36 - 38 nm, respectively, with a PL quantum yield up to 55 % by a reaction time of 60 min. Importantly, the structural advantage of alloyed CdSxSe1-x QDs based LEDs have been fabricated and their electroluminescence properties were characterized. A good performance device with a maximum luminance and luminous efficiency of 761 cd/m2 and 0.82 cd/A was obtained, respectively.

Pengaruh lama maturasi pada sintesis biokeramik komposit CaO-TiO2 terhadap ukuran kristal, mikrostruktur dan kekerasan

Perkembangan Ilmu Pengetahuan dan Teknologi (IPTEK) akhir-akhir ini mendorong banyaknya inovasi dalam dunia medis terutama penggunaan biomaterial sebagai implan pengganti tulang dan gigi, salah satunya bahan tersebut adalah biokeramik komposit CaO-TiO2. Bahan biokeramik komposit CaO-TiO2 dapat digunakan untuk memperbaiki bagian tubuh yang rusak terutama sebagai implan gigi, penyambung tulang, struktur penahan katup jantung, dan pengganti tulang tengkorak. Paduan antara CaO-TiO2 memiliki beberapa keuntungan diantaranya memiliki biokompatibilitas yang baik, dapat tumbuh serta berkembang bersama-sama dengan tulang asli serta memiliki ketahanan mekanik yang baik. Berdasarkan paparan di atas, tujuan dari penelitian ini adalah mengetahui pengaruh lama maturasi pada biokeramik komposit CaO-TiO2 dengan metode kopresipitasi terhadap kristalinitas, mikrostruktur, dan kekerasan. Pada penelitian ini bahan dasar yang digunakan adalah CaO yang berasal dari batuan kapur alam yang diambil dari pantai Balekambang Kabupaten Malang dan TiO2 dengan kemurnian 99 persen. Sampel dilarutkan dalam aquades dan distirer selama 15 jam pada suhu 70 derajat celcius. Lama maturasi divariasi mulai dari 12, 24, 36, 48, dan 60 jam, dianneling pada suhu 100 derajat celcius selama 24 jam dan disintering selama 4 jam pada suhu 1100 derajat celcius. Sampel dikarakterisasi ukuran kristal, mikrostruktur, dan kekerasan, dengan menggunakan XRD, SEM, dan Micro Vickers Hardness. Hasil analisis CaO-TiO2 menunjukkan kecocokan dan keberhasilan sintesis dengan model pembanding CaO-TiO2 dari Inorganic Crystal Structure Database (ICSD) dengan nilai score diatas 50. Berdasarkan perhitungan teoritik yang dilakukan dengan menentukan nilai FWHM (Full Widht at Half Maximum) dari pola difraksi sampel yang kemudian digunakan pada formula scherrer, diperoleh hasil peningkatan ukuran kristal yang bervariasi terhadap lama maturasi komposit CaO-TiO2 dengan besar antara 45,06 nm-70,85 nm. Dengan meningkatnya ukuran kristal terhadap lama maturasi maka akan disertai oleh peningkatan ukuran butir, sehingga semakin sedikit jumlah pori-pori yang terbentuk pada bahan yang ditunjukan oleh menurunnya nilai luas fraksi pori sebesar 4,97 persen pada lama maturasi 12 jam menjadi 4,79 persen pada lama maturasi 60 jam. Dengan semakin kecilnya nilai fraksi total pori maka semakin besar kekerasan dari bahan tersebut, hal ini ditunjukan dengan nilai kekerasan tertinggi diperoleh pada lama maturasi 60 jam sebesar 497,2 MPa.

Electro-optic Q-switched Cr:LiSAF laser

We demonstrate electro-optic Q-switched solid state laser with Cr:LiSAF active medium. A single 50 ns pulse with 14 mJ of output energy is demonstrated. Simultaneous generation of several peaks with a step of 1.4 nm within the spectrum envelope with a full width at half maximum of 10.3 nm is demonstrated. For an electro-optic Q-switched mode a Pockels cell is used. Demonstrated laser can be used in differential absorption lidar systems.