Thermal-mechanical response of microscale functional film for infrared window

Infrared window in hypersonic missile usually suffers complex aerodynamic force/heat during high-speed flight.A finite element method was adopted to simulate the thermal and stress response of microscale functional film for infrared window under different aerodynamic heats/forces conditions.Temperature and stress distribution were obtained with different heat fluxes.There is almost constant stress distribution along the film thickness except a sudden decrease near the substrate.The maximum stresses are located at the points which are 0.3 mm away from the edges.Different film materials result in different stress values.The temperature and stress in ZrN are larger than those in Y2O3.Besides the numerical simulation,an oxygen propane flame jet impingement test was performed to investigate thermal shock failure of the infrared window.Some place of the window surface has spots damage and some place has line crack damage after thermal shock.

New insight into pyrrolic-N site effect towards the first NIR window absorption of pyrrolic-N-rich carbon dots

Controlled C-N configurations,i.e.,pyrrolic-N,pyridinic-N,and graphitic-N,are promising strategies to tailor the carbon dots’(CDs)optical properties into the first near infrared(NIR)window(650-900 nm),a responsive range for biomedical application.However,a deep understanding of the role of the C-N configuration in the CDs’properties is still challenging and thoughtprovoking owing to their complex structure.Here,an underlying pyrrolic-N concentration and position effect on the pyrrolic-N-rich CDs’absorption was comprehensively elucidated based on the integrated experimental and computational studies.The assynthesized pyrrolic-N-rich CDs exhibit a first NIR window absorption centered at 650 nm with high photothermal conversion.Pyrrolic-N concentrations from 1.4%to 11.3%and positions(edge and mid-site)were systematically investigated.A mid-site pyrrolic-N was subsequently generated after the pyrrolic-N concentration more than 10%.Edge-site pyrrolic-N induces a frontier orbital hybridization,reducing bandgap energy,while mid-site pyrrolic-N plays a critical role in inducing a first NIR window absorption owing to their high charge transfer.Also,pyrrolic-N-rich CDs inherit a bowl-like topological feature,elevating the CDs’layer thickness as much as 0.71 nm.This study shed light on the design and optimization of pyrrolic-N on CDs for the first NIR window responsive materials in any biomedical application.

Recent progress in NIR-Ⅱ emitting lanthanide-based nanoparticles and their biological applications

The second near-infrared(NIR-Ⅱ,1000-1700 nm)window provides a superior optical platform with high resolution,deep penetration and high signal-to-noise ratios(SNRs),which results from the intrinsic low scattering and auto fluorescence in biological tissues.As one of the promising NIR-Ⅱemitting probes,lanthanide based nanoparticles(LnNPs)exhibit high photo stability and chemostability,long photoluminescence lifetimes,low long-term cytotoxicity and narrow emission bandwidths.All these merits have spurred the evolution of related bio-optics and a variety of biomedical applications of LnNPs.This mini-review discusses the most recent advances in both the design-the composition and surface modifications-and the applications of NIR-Ⅱemitting LnNPs in bioimaging,disease diagnosis and therapy.We also summarize the current limits and challenges facing the applications of LnNPs as well as discuss the directions of future development.

Numerical simulation of aerodynamic heating and stresses of chemical vapor deposition ZnS for hypersonic vehicles

Hypersonic vehicles subjected to strong aerodynamic forces and serious aerodynamic heating require more stringent design for an infrared window. In this paper, a finite element analysis is used to present the distributions of thermal and stress fields in the infrared window for hypersonic vehicles based on flowfield studies. A theoretical guidance is provided to evaluate the influence of aerodynamic heating and forces on infrared window materials. The aerodynamic heat flux from Mach 3 to Mach 6 flight at an altitude of 15 km in a standard atmosphere is obtained through flowfield analysis. The thermal and stress responses are then investigated under constant heat transfer coefficient boundary conditions for different Mach numbers. The numerical results show that the maximum stress is higher than the material strength at Mach 6, which means a failure of the material may occur. The maximum stress and temperatures are lower than the material strength and melting point under other conditions, so the material is safe.

Mesoporous radiosensitized nanoprobe for enhanced NIR-Ⅱ photoacoustic imaging-guided accurate radio-chemotherapy

Oxygen deficiency is a major obstacle to hypoxic-related cancer theranostics,and developing the oxygen production nanoplatforms received the widespread attention.However,it is remaining a challenge to structure a nanoplatform with hypoxia alleviation effect and imaging-guided cancer radiotherapy.Herein,we present a novel theranostics nanoplatform(Au NPs/UCNPs/WO_(3)@C)comprising of tungsten trioxide(WO3)that loaded gold nanoparticles(Au NPs)and up-conversion nanoparticles(UCNPs)for improved photoacoustic(PA)imaging performance in the second near infrared window(NIR-Ⅱ,900-1,700 nm).Au NPs/UCNPs/WO_(3)@C exhibited superior oxygen-generation effect and doxorubicin loading capacity,thus serving as an efficient radiosensitizer for radio-chemo anti-cancer therapy.Importantly,the accumulated Au NPs/UCNPs/WO_(3)@C in the tumor region led to the increased NIR-Ⅱ PA imaging signal and the blood oxygen saturation signal,which could enhance radiation sensitivity and accurately guiding cancer radiotherapy to reduce side effects on normal tissues.This study with proof-of-concept confirmed the multifaceted characteristics and encouraging potential of biomimetic Au NPs/UCNPs/WO_(3)@C for NIR-Ⅱ PA imaging-guided tumor therapeutics.