Improvement on Electrical Properties and Magnetoresistance Induced by Pd or Ag Addition in Lao.67（Ca0.65Ba0.35）0.33MnO3 Manganites

Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.

Highly efficient synthesis and application of aryl diazonium salts via femtosecond laser-tailored 3D flow microfluidic chips

The first example of the microfluidic chips(MFCs) consisting of centimeter-level 3D channels with highdensity and large-volume fabricated by femtosecond laser micromachining were utilized to develop a time-saving, economical and hazardless flow synthesis process, and its advantages have been proved by in situ formation of aryldiazonium salts and subsequent borylation with bis(pinacolato)diboron. There are several important advantages in our 3D MFC-based flow synthesis technology, including the following:(1) the reaction temperature was altered from ice bath to room temperature;(2) the residence time was reduced by 10 times;(3) the yield was greatly improved, that is, several arylboronates were successfully obtained with higher yield compared to traditional batch process. Therefore, it can be envisioned that a novel, simplified flow synthetic protocol will be developed toward green organic synthesis via MFCs.

Highly Emissive Luminogens in Both Solution and Aggregate States

Organic light-emitting materials have attracted considerable attention because of their promising applications in diverse areas.Most fluorophores emit brightly in either dilute solutions or aggregate states;the former generally suffer from aggregation-caused quenching problem,and the latter encounter intensity loss at low concentrations.Herein,we propose a new strategy to overcome these dilemmas by balancing the planar and distorted structures of terphenyl-based luminogens and obtain three luminogens,2PB-AC,2Me2PB-AC,and 2T2PB-AC,with bright emission in both solution and aggregate states.Among them,2PB-AC shows absolute photoluminescence quantum yields(ФPL)higher than 90%in both tetrahydrofuran solution(90.2%)and aggregate states(92.7%for powder and 95.3%for crystal).Thus,2PB-AC could be an efficient probe to realize dual-channel explosive detection in both solution and aggregate states.Moreover,it could be used to image live-cell lipid droplets at a wide range of concentrations.In addition,benefiting from its thermodynamically favorable intersystem crossing process,2Me2PB-AC could be doped in polymethyl methacrylate matrix to provide efficient room-temperature phosphorescence.Thus,this work provides a feasible strategy for the design of luminogens with highly efficient emission in both solution and aggregate states,greatly facilitating and broadening their practical applications.

Ultralong Room-Temperature Phosphorescence of Silicon-Based Pure Organic Crystal for Oxygen Sensing

Quantitative oxygen detection is of great importance in biological fields,complex environments,and chemical process engineering.Due to the high sensitivity and rapid response of long-lived phosphorescence to oxygen,pure organic room-temperature phosphorescence(RTP)for oxygen detection has recently attracted considerable interest.However,to simultaneously achieve ultralong phosphorescence at room temperature and quantitative oxygen detection from pure organic crystals is difficult.Tight packing to restrict nonradiative decay is not apt to allow oxygen diffusion for sensing.Reported herein is an exceptional example,that is,a crystal of simple carbazole molecules that bridges with an ethoxysilane(DCzC2OSi)and is capable of oxygen sensing with remarkable sensitivity.Photophysical studies and single-crystal structure analysis reveal that DCzC2OSi crystals display ultralong RTP and suitable oxygen diffusion channels from its butterfly-like tetrahedron geometry.Further comparisons with the crystals of CzC2OH and DCzSi verify the important roles of silicon and ethoxy groups of DCzC2OSi for both enhanced phosphorescence lifetime and oxygen sensitivity.When the crystals of DCzC2OSi were doped into polymer,the lifetime-based oxygen sensor exhibited high KSV(5.308 kPa^(−1))with full reversibility,which is attractive for the development of practical oxygen sensors from pure organic crystals.

SnO/SnO_(2) heterojunction:an alternative candidate for sensing NO_(2) with fast response at room temperature

The SnO_(2)-based family is a traditional but important gas-sensitive material.However,the requirement for high working temperature limits its practical application.Much work has been done to explore ways to improve its gas-sensing performance at room temperature(RT).For this report,SnO_(2),SnO,and SnO/SnO_(2) heterojunction was successfully synthesized by a facile hydrothermal combined with subsequent calcination.Pure SnO_(2) requires a high operating temperature(145℃),while SnO/SnO_(2) heterojunction exhibits an excellent performance for sensing NO_(2) at RT.Moreover,SnO/SnO_(2) exhibits a fast response,of 32 s,to 50 ppm NO_(2) at RT(27℃),which is much faster than that of SnO(139 s).The superior sensing properties of SnO/SnO_(2) heterojunction are attributed to the unique hierarchical structures,large number of adsorption sites,and enhanced electron transport.Our results show that SnO/SnO_(2) heterojunction can be used as a promising high-performance NO_(2) sensitive material at RT.