π-Conjugated Unit-Dependent Optical Properties of Linear Conjugated Oligomers

The optical properties of three linear conjugated oligomers （F-P, F-P-F, and P-F-P-F-P）, where phenothiazine （P） and fluorene （F） groups arrange alternately, are investigated. With the enhancement of the π-conjugated system, their absorption and emission bands both gradually red shift, and their two-photon properties are also improved. Meanwhile, their fluorescence dynamic traces are analyzed with continuous rate distribution model, exhibiting that their decay rates gradually accelerate and the rate distribution width become narrower. The quantum chemical calculation offers their molecular structures and transition mechanism, showing that the enhancement of π-conjugated system should be responsible for tile improvement of two-photon properties.

基于碳点功能化的二氧化硅封装螺吡喃的光响应材料用于动态信息加密

开发刺激响应荧光材料对于解决信息安全的新兴需求至关重要.本文中,我们提出了一种刺激响应双发射荧光材料SP@SiO_(2)-CDs(SP:螺吡喃),该材料是通过将螺吡喃化合物封装到碳点功能化的二氧化硅中得到的.这种复合材料显示碳点在470 nm处发射蓝色光,螺吡喃在620 nm处发射红色光.在连续紫外光(365 nm)照射下,螺吡喃分子经历从闭环到开环的过程,SiO_(2)-CDs和异构部花青之间可以实现显著的荧光能量共振转移.SP@SiO_(2)-CDs复合物粉末不仅可以在紫外光刺激下光致变色从黄色到粉色,而且可以实现从淡蓝色到橙红色的双发射荧光转换.当暴露在白光下时,这种动态荧光行为可以完全恢复到初始状态.基于荧光的时间依赖性,本文成功开发了动态防伪图案和多重编码.此外,通过掺杂聚二甲基硅氧烷,获得了具有高柔韧性和机械强度的薄膜,并展示了其在高级信息加密中的应用.该工作为提高离线便携式信息加密的安全性提供了一种新方法.

Dynamically Securing the Data by^(1)O_(2)Sensitization of Fluorescent Composites with a High Latency and Uncrackable Features

Dynamic fluorescent materials play a crucial role in secure inks for data encryption;however,they are still plagued by issues such as photodegradation,poor latency,and susceptibility to unauthorized access.Herein,we propose a photochemically modulated dynamic fluorescent encryption system based on^(1)O_(2)sensitization of fluorescent composites,comprising a^(1)O_(2)-sensitive fluorophore(F2)and non-emissive polymers.After UV irradiation,in-situ generated^(1)O_(2)from the polymer effectively binds with F2 to form endoperoxides(F2EPO),resulting in a significant redshift in emission,up to 150 nm.The^(1)O_(2)concentration is closely related to the irradiation time,rendering different fluorescent colors in a time-gated fashion.Moreover,the emission of F2EPO can be regulated by polymer chemical structure,molecular weight,and crosslinking density.Relying on these merits,we develop a dynamic data encryption method with various non-emissive polymers as the data storage media,UV light irradiation as the data encoder,and F2 as the data decoder.UV light irradiation of diverse polymer solutions generates^(1)O_(2)at different concentrations,effectively encoding the data,which remains invisible under both UV and natural lights.The addition of F2 to these irradiated polymer solutions produces different redshifted fluorescence,enabling secure data decryption.Attributing to the non-emissive nature of the polymers,time-gated readout fashion,excellent latency of^(1)O_(2),and subtle interactions between^(1)O_(2)and F2,this data encryption is nearly undecipherable.This work offers an advantage data encryption approach beyond the reach of conventional fluorophores.

High-throughput phenotyping by applying digital morphometrics and fluorescence induction curves in seeds to identifying variations:A case study of Annona(Annonaceae)species

Differences in physical and structural characteristics of seeds may indicate variability within and between plant populations.In the present study,we performed a close characterization of dimension,shape,and tegument delayed chlorophyll fluorescence in seeds obtained from three species of the genus Annona(Annonaceae),i.e.,Annona coriacea,A.montana,A.squamosa.Results showed that studied seeds may be sorted as scalene ellipsoids expressing low values for the seed sphericity.The morphological estimates suggested differences in seed shape for all species.A high correlation was observed between surface area and volume(r^2>99%)for all the three species suggesting that in addition to structural shape.In addition,we also observed very high positive correlations(Rho=1.000,p<0.001)between surface area and arithmetic mean diameterof the seeds for all species.The first principal component(PCA1)of elliptical Fourier descriptors explained most of the variations in morphological structure of the seeds in the three species.Additionally,a less intense tegument delayed chlorophyll fluorescence was observed for A.montana while the highest intensity was recorded for A.squamosa,revealing the potential use of fluorescence spectroscopy in discrimination at the species level by analyzing the frequency domain by means of Fourier Transform spectra as well as the relationship time-frequency of chlorophyll fluorescence.

Positioning a fluorescent probe at the core of a glassy star polymer for detection of local dynamics

Accessing local dynamics within a single macromolecule is the key to understand the physical origin of the viscoelasticity and especially the glass transition. In order to extract specific information on the dynamics of the branch point of a star polymer around its glass transition temperature, four-arm star poly （n-butyl methacrylate） with a fluorescent core was synthesized using perylene diimide as initiator and polymerization conducted via atom transfer radical polymerization. The process is found to be effective in positioning the fluorophore at the branch point with the fluorophore intact, which allows the successful application of single molecule fluorescence defocus imaging in examining the local site- sensitive dynamics. The power spectra of rotation trajectories, the population of rotating fluorophores as well as the distribution of angular displacement were used to revel the difference in local dynamics between branch point and the arm＇s end. It is discovered that the local dynamics at the core of the star polymer is much less activated than that at the arm＇s end. The results demonstrate the strong effect dues to the topological constrain at the branch point and the more free space at the arm＇s end.

Excitation-wavelength-dependent fluorescent organohydrogel for dynamic information anti-counterfeiting

Anti-counterfeiting labels with various fluorescent colors are of great importance in information encryption-decryption,but are still limited to static information display.Therefore,it is urgent to develop new materials and encryption-decryption logic for improving the security level of secret information.In this study,an organohydrogel made up of poly(N,N-dimethylacrylamide)(pDMA)hydrogel network and polyoctadecyl methacrylate(pSMA)organogel network that copolymerized with two fluorophores,6-acrylamidopicolinic acid moieties(6APA,fluorescent ligand)and spiropyran units(SPMA,photochromic monomer),was prepared by a two-step interpenetrating method.As UV light of 365nm and 254nm can both cleave C_(spiro)-O bonds of SPMA,and the green fluorescence of 6APA-Tb^(3+) can only be excited by 254nm light,the organohydrogel displays yellow and red under the irradiation of 254nm and 365 nm,respectively.In addition to wavelength selectivity,these two fluorophores are thermal-responsive,leading to the fluorescence variation of the organohydrogel during heating process.As a result,secret information loaded on the organohydrogel can be decrypted by the irradiation of UV light,and the authenticity of the information can be further identified by thermal stimulation.Our fluorescent organohydrogel can act as an effective anti-counterfeiting label to improve the information security and protect the information from being cracked.

uorescence microendoscopy imaging based on GRIN lenses with one- and two-photon excitation modes

With the rapid development of life sciences, there is an increasing demand for intravital fluorescence imaging of small animals. However, large dimensions and limited working distances of objective lenses in traditional fluorescence microscopes have limited their imaging applications mostly to superficial tissues. To overcome these disadvantages, researchers have developed the graded-index （GRIN） probes with small diameters for imaging internal organs of small animals in a minimally invasive fashion. However, dynamic imaging based on GRIN lens has not been studied extensively. Here, this paper presented a fluorescence endoscopic imaging system based on GRiN lenses using one-photon and two-photon excitation. GRIN lenses with 1.15 mm diameter and 7.65 mm length were used in the system. The images were acquired by a compact laser scanning imaging system with a resonant galvo-mirror system to scan the laser beam and a photomultiplier tube （PMT） to detect fluorescence signals. Experimental results showed that this system using two-photon excitation could implement dynamic fluorescence microendoscopic imaging and monitor the movement of blood flow beneath the skin in anesthetized mice while producing images with higher contrast and signal to noise ratio （SNR） than those using one photon excitation. It would be a useful tool for studying biological processes of small animals or plants in vivo.