光学魔术——斑斓的微结构色

自然界中的一些颜色是由非常精细的微米级结构或者纳米级结构而形成的结构色。这种结构色是生物体亚显微结构形成,通常具有光泽,颜色会随视角发生变化,例如蝴蝶翅色、一些鸟类羽毛、甲虫体壁表面等。结构色具有不褪色和环保等优点,通过对自然界中结构色的研究可以促进防伪、装饰等领域的发展。本实验采用了一种绿色简单的方法,将廉价易得的正硅酸乙酯与氨水简单混合即可得到均匀的二氧化硅纳米颗粒。通过改变正硅酸乙酯和氨水的加入量可以调节二氧化硅纳米颗粒的粒径,从而获得不同结构色的悬浮性墨水,可直接用于书写或绘制结构色图案,有望用于低成本制备彩色颜料。

Revealing the promising near-room-temperature thermoelectric performance in Ag_(2)Se single crystals

With high carrier mobility and intrinsic low lattice thermal conductivity,Ag_(2)Se compounds have attracted increasing attention for thermoelectric application near room temperature.Due to its phase transition at~406 K and resulting thermal volume expansion,the growth and thermoelectric properties of large-sized Ag_(2)Se single crystals have seldom been reported so far.In this work,the vertical Bridgeman method was used for growing bulk Ag_(2)Se single crystal,with an orientation preference along lowsymmetric(201)plane.The Hall mobility as high as 2000 cm^(2)/(V·s)and weak electron-phonon coupling contributes to a high electronic quality BE of~7.0 in near-room-temperature b-Ag_(2)Se single crystals,which is superior to the high-temperature phase a-Ag_(2)Se.The observed low lattice thermal conductivity of 0.8 W/(m·K)at 300 K is due to the low group speeds and strong anharmonicity.A promising peak zT of 0.66 at 375 K and an average zT of 0.65 at 300-375 K were realized in b-Ag_(2)Se crystals.The low Vickers hardness and good ductile properties were confirmed by experiment and theoretical analysis.This work not only synthesized large-sized and highly-orientated Ag_(2)Se crystals,but also revealed its great potential of thermoelectric performance and mechanical properties for various applications near room temperature.

Manipulation of Band Degeneracy and Lattice Strain for Extraordinary PbTe Thermoelectrics

Maximizing band degeneracy and minimizing phonon relaxation time are proven to be successful for advancing thermoelectrics.Alloying with monotellurides has been known to be an effective approach for converging the valence bands of PbTe for electronic improvements,while the lattice thermal conductivity of the materials remains available room for being further reduced.It is recently revealed that the broadening of phonon dispersion measures the strength of phonon scattering,and lattice dislocations are particularly effective sources for such broadening through lattice strain fluctuations.In this work,a fine control of MnTe and EuTe alloying enables a significant increase in density of electron states near the valence band edge of PbTe due to involvement of multiple transporting bands,while the creation of dense in-grain dislocations leads to an effective broadening in phonon dispersion for reduced phonon lifetime due to the large strain fluctuations of dislocations as confirmed by synchrotron X-ray diffraction.The synergy of both electronic and thermal improvements successfully leads the average thermoelectric figure of merit to be higher than that ever reported for p-type PbTe at working temperatures.

Solute manipulation enabled band and defect engineering for thermoelectric enhancements of SnTe

With years of development, SnTe as a homologue of PbTe has shown great potentialfor thermoelectric applications in p-type conduction, and the most successfulstrategy is typified by alloying for maximizing the valence band degeneracy.Among the known alloy agents, MnTe has been found to be one of the most effectiveenabling a band convergence for an enhancement in electronic performance ofSnTe, yet its solubility of only ~15 at% unfortunately prevents a full optimizationin the valence band structure. This work reveals that additional PbTe alloying notonly promotes the MnTe solubility to locate the optimal valence band structure butalso increases the overall substitutional defects in the material for a substantialreduction in lattice thermal conductivity. In addition, PbTe alloying simultaneouslyoptimizes the carrier concentration due to the cation size effect. These features allenabled by such a solute manipulation synergistically lead to a very high thermoelectricfigure of merit, zT of ~1.5 in SnTe with a 20 at% MnTe and a 30 at% PbTealloying (Sn0.5Mn0.2Pb0.3Te), demonstrating the effectiveness of solute manipulationfor advancing SnTe and similar thermoelectrics.

Thermoelectric Transport Properties of TmAg_(x)Cu_(1-x)Te_(2) solid solutions

Intrinsic partial occupation of Cu induces strong phonon scattering for an extremely low lattice thermal conductivity in TmCuTe_(2),which leads this material to be a promising candidate for thermoelectric applications.This work focus on the electronic and phononic transport properties of TmCuTe_(2) with Agalloying on the Cu site.Such a Ag/Cu substitution is found to enable a decrease in Hall carrier concentration from 141019 to 81019 cm^(3) for an evaluation of the charge transport based on a single parabolic band(SPB)model with acoustic scattering.In addition,Ag-substitution simultaneously introduces Cu/Ag point defects for extra phonon scattering,leading the lattice thermal conductivity to be as low as~0.25 W/m-K in a broad temperature.The optimization in carrier concentration and the reduction in lattice thermal conductivity contribute to a~40%improvement in average thermoelectric figure of merit(zT).The determination of band parameters enables a guidance for further advancements in this promising thermoelectric material.

Biosafety materials for tuberculosis treatment

Tuberculosis(TB)is among the deadliest infectious diseases worldwide.Although the existing antituberculosis(anti-TB)drugs remain to be effective,the administration of these complex anti-TB drug combinations with obvious toxicity often leads to patients’nonadherence.This may contribute toward the emergence of drug-resistant strains as well as lead to treatment failure and relapse.Therefore,in the past half century,the main focus of anti-TB drug research was to reduce the frequency of administration and toxicity and improve patients’compliance and drug sensitivity.Following these principles,the development of engineered biosafety materials is one of the most effective and promising methods in resolving these challenges.Compared with traditional drugs,biosafety materials provide a viable platform for treating TB,which are beneficial in reducing the frequency of drug administration and systemic toxicity,improving patients’compliance and drug sensitivity,and enhancing drug targeting.In this review,we summarized the application of biosafety materials in treatment of TB in recent years and discussed the challenges faced when developing a safe,more effective,and economical pharmacotherapy against TB.

MnTe_(2) as a novel promising thermoelectric material

Semiconducting manganese ditelluride(MnTe_(2))crystalizes in a high symmetry cubic structure with sufficient band gap and consists of nontoxic elements only,therefore is focused on in this work for its potential thermoelectric applications.This material intrinsically comes with a very low hole concentration of 10^(19)cm^(-3),which can be successfully increased to 4×10^(20)cm^(-3)through Ag-doping at Mn site.Such a broad carrier concentration enables an effective optimization on thermoelectric power factor,and the doping process effectively reduces the lattice thermal conductivity down to~0.5 W/m-K due to the phonons scattered by additional point defects.As a result,a peak zT of~0.7 is obtained in p-type conduction.Moreover,the SPB model with acoustic scattering estimates the electronic properties well,which also enables insight into the underlying physical parameters related to the thermoelectric performance.Importantly,band structure calculation suggests a potentially higher thermoelectric performance for n-type conduction due to both higher band degeneracy and lower band effective mass.This work reveals MnTe_(2)is a novel promising thermoelectric material.