Energy Transfer and Photoluminescence Enhancement in WS_(2)/hBN/MoS_(2) Heterostructures

Two-dimensional(2D)transition metal dichalcogenides(TMDs)and their heterostructures(HSs)exhibit unique optical properties and show great promise for developing next-generation optoelectronics.However,the photo-luminescence(PL)quantum yield of monolayer(1L)TMDs is still quite low at room temperature,which severely lim-its their practical applications.Here we report a PL enhancement effect of 1L WS_(2) at room temperature when con-structing it into 1L-WS_(2)/hBN/1L-MoS_(2) vertical HSs.The PL enhancement factors(EFs)can be up to 4.2.By using transient absorption(TA)spectroscopy,we demonstrate that the PL enhancement effect is due to energy transfer from 1L MoS_(2) to 1L WS_(2).The energy transfer process occurs on a picosecond timescale and lasts more than one hundred picoseconds which indicates a prominent contribution from exciton-exciton annihilation.Furthermore,the PL en-hancement effect of 1L WS_(2) can be observed in 2L-MoS_(2)/hBN/1L-WS_(2) and 3L-MoS_(2)/hBN/1L-WS_(2) HSs.Our study provides a comprehensive understanding of the energy transfer process in the PL enhancement of 2D TMDs and a fea-sible way to optimize the performance of TMD-based optoelectronic devices.

Lifetime-tunable circularly polarized luminescent system based on triplet-to-singlet Förster resonance energy transfer

Circularly polarized luminescence(CPL)materials have received widespread attention due to their remarkable performance and broad applications.However,current CPL material research primarily focuses on tunable color,intensity,and reversibility.Constructing CPL with adjustable lifetime remains a significant challenge.Herein,a series of CPL polymeric materials with tunable lifetime were obtained by employing phosphorescent terephthalic acid and chiral organic small molecule R/S-BNAF(a luminescent binaphthol derivative)to copolymerize with acrylamide in different ratios.It was verified that this performance results from the different energy transfer efficiency between luminophores with varying ratios of the monomers for copolymerization.This strategy to realize CPL with tunable lifetime by modulating the energy transfer efficiency will provide a new perspective to broaden the applications of CPL materials.

Ultralong organic room-temperature phosphorescence of electrondonating and commercially available host and guest molecules through efficient Förster resonance energy transfer

Ultralong organic room-temperature phosphorescence(RTP)materials have attracted tremendous attention recently due to their diverse applications.Several ultralong organic RTP materials mimicking the host-guest architecture of inorganic systems have been exploited successfully.However,complicated synthesis and high expenditure are still inevitable in these studies.Herein,we develop a series of novel host-guest organic phosphorescence systems,in which all luminophores are electron-rich,commercially available and halogen-atom-free.The maximum phosphorescence efficiency and the longest lifetime could reach 23.6%and 362 ms,respectively.Experimental results and theoretical calculation indicate that the host molecules not only play a vital role in providing a rigid environment to suppress non-radiative decay of the guest,but also show a synergistic effect to the guest through Förster resonance energy transfer(FRET).The commercial availability,facile preparation and unique properties also make these new host-guest materials an excellent candidate for the anti-counterfeiting application.This work will inspire researchers to develop new RTP systems with different wavelengths from commercially available luminophores.

Ambient White-Light Afterglow Emission Based on Triplet-to-Singlet Förster Resonance Energy Transfer

Compared with fluorescent materials,metal-free organic environmental afterglow materials,with larger Stokes shifts,longer lifetimes,higher S/N ratios,and sensitivities,present potential in new applications.However,achieving air stability and long lifetime organic afterglow systems with tunable emission color still remains a challenge.Herein,we have designed and synthesized luminescent copolymers exhibiting afterglow emission with tunability including white-light afterglow with considerable quantum yield[Commission Internationale de l’Eclairage(CIE)coordinates(0.32,0.33),ΦP=11%]in the amorphous state through the rarely reported triplet-to-singlet Förster resonance energy transfer(TS-FET).Also,they can emit different colors under UV light,including white-light[CIE coordinates(0.31,0.33),ΦPl=27%].This strategy was achieved by copolymerizing two simple-structured single-benzene-based compounds with acrylamide(AM)in different ratios.In addition,these materials can also be employed as a safety ink for paper paving the way for long lifetime luminescent material applications.

Flexible Förster resonance energy transfer-assisted optical waveguide based on elastic mixed molecular crystals

Flexible molecular crystal waveguides based on elastic molecular crystals(EMCs)are essential inflexible and compact optical materials.An increased loss coeffi-cientαdue to self-absorption is often a problem in optical waveguides(OWGs)offluorescent chemical materials waveguiding photons in active mode.Herein,the development of anthracene-based elastic mixed molecular crystals(EMMCs)is reported for Förster Resonance Energy Transfer(FRET)-assisted OWG.To yield a FRET crystal system based on elastic molecular crystals,1%–5%accep-tor doping forfluorescent molecular crystals of 9,10-dibromoanthracene 1 was successful by selecting the same regioisomer having electron-withdrawing group,9,10-diformylanthracene 2,as a dopant.In addition to conversion to the mixed system,there is a difference in the elastic modulus and hardness in EMC C1 and EMMC C2@1.However,the elastic behaviour was also shown in a few percent doping of the acceptor.Theαvalue of this EMMC,composed of 1 including 1%of 2(0.0077 dB/μm),is much lower than that of EMC composed of 1(0.1258 dB/μm)because of reducing self-absorption in the FRET system.An efficient andflexible OWG was successfully developed by selecting an appropriate acceptor molecule and its low doping rate for mixed crystal construction.This method is a practical approach in various functional andflexible crystal systems.

Tuning of Förster Resonance Energy Transfer in Metal–Organic Frameworks: Toward Amplified Fluorescence Sensing

The assembly of Förster resonance energy transfer(FRET)donor and acceptor for amplified fluorescence sensing has been considered a big challenge.Herein,by using the multivariate approach,we report the design and synthesis of a series of FRET-based metal–organic frameworks(MOFs)with variable donor fluorophore-to-the-acceptor ratios.

Utilizing dual-pathway energy transfer in upconversion nanoconjugates for reinforced photodynamic therapy

Enhancing the therapeutic effect of existing treatments or developing new non-invasive treatments are important measures to achieve high-efficiency treatment of malignant tumors.Photodynamic therapy(PDT)is an emerging treatment modality,and the key for achieving high-efficiency PDT is to select light with strong tissue penetration depth and enhance the generation of reactive oxygen species(ROS).Although the upconversion nanoparticles(UCNPs)modified with the photosensitizers could achieve PDT with strong penetration depth under near-infrared light irradiation,the ROS generated by traditional single-pathway PDT is still insufficient.Herein,we developed a novel nanoconjugate(UCNP-Ce6/AIEgen)for dual-pathway reinforced PDT,in which the UCNPs were co-modified with chlorin e6(Ce6)and luminogen with aggregation-induced emission(AIEgen).Due to the presence of AIEgen,UCNP-Ce6/AIEgen could avoid aggregation-caused luminescence quenching in biological water environments and convert upconversion luminescence(UCL)of UCNPs to Ce6-activatable fluorescence.Therefore,under the irradiation of 808 nm laser,UCNP-Ce6/AIEgen can not only undergo direct lanthanide-triplet energy transfer to activate Ce6,but also convert the UCL of UCNPs to the light that can activate Ce6 through Fӧrster resonance energy transfer to generate more ROS,thus promoting tumor cell apoptosis.This work broadens the applications of nanoconjugates of lanthanide-based inorganic materials and organic dyes,and provides a conception for reinforced PDT of tumors.

A carbon nanoparticle-peptide fluorescent sensor custom-made for simple and sensitive detection of trypsin

Herein,we report a novel sensor to detect trypsin using a purpose-designed fluorescein-labelled peptide with negatively charged carbon nanoparticles(CNPs)modified by acid oxidation.The fluorescence of the fluorescein-labelled peptide was quenched by CNPs.The sensor reacted with trypsin to cleave the peptide,resulting in the release of the dye moiety and a substantial increase in fluorescence intensity,which was dose-and time-dependent,and trypsin could be quantified accordingly.Correspondingly,the biosensor has led to the development of a convenient and efficient fluorescent method to measure trypsin activity,with a detection limit of 0.7 mg/mL.The method allows rapid determination of trypsin activity in the normal and acute pancreatitis range,suitable for point-of-care testing.Furthermore,the applicability of the method has been demonstrated by detecting trypsin in spiked urine samples.

FLIM as a Promising Tool for Cancer Diagnosis and Treatment Monitoring

Fluorescence lifetime imaging microscopy(FLIM)has been rapidly developed over the past 30 years and widely applied in biomedical engineering.Recent progress in fluorophore-dyed probe design has widened the application prospects of fluorescence.Because fluorescence lifetime is sensitive to microenvironments and molecule alterations,FLIM is promising for the detection of pathological conditions.Current cancer-related FLIM applications can be divided into three main categories:(i)FLIM with autofluorescence molecules in or out of a cell,especially with reduced form of nicotinamide adenine dinucleotide,and flavin adenine dinucleotide for cellular metabolism research;(ii)FLIM with Förster resonance energy transfer for monitoring protein interactions;and(iii)FLIM with fluorophore-dyed probes for specific aberration detection.Advancements in nanomaterial production and efficient calculation systems,as well as novel cancer biomarker discoveries,have promoted FLIM optimization,offering more opportunities for medical research and applications to cancer diagnosis and treatment monitoring.This review summarizes cutting-edge researches from 2015 to 2020 on cancer-related FLIM applications and the potential of FLIM for future cancer diagnosis methods and anti-cancer therapy development.We also highlight current challenges and provide perspectives for further investigation.

High-fidelity SIM reconstruction-based super-resolution quantitative FRET imaging

Structured illumination-based super-resolution Förster resonance energy transfer microscopy(SIM-FRET)provides an approach to resolving molecular behavior localized in intricate biological structures in living cells.However,SIM reconstruction artifacts will decrease the quantitative analysis fidelity of SIMFRET signals.To address these issues,we have developed a method called HiFi spectrum optimization SIM-FRET(HiFi-SO-SIM-FRET),which uses optimized Wiener parameters in the two-step spectrum optimization to suppress sidelobe artifacts and achieve super-resolution quantitative SIM-FRET.We validated our method by demonstrating its ability to reduce reconstruction artifacts while maintaining the accuracy of FRET signals in both simulated FRET models and live-cell FRET-standard construct samples.In summary,HiFi-SO-SIM-FRET provides a promising solution for achieving high spatial resolution and reducing SIM reconstruction artifacts in quantitative FRET imaging.

Can DyeCycling break the photobleaching limit in single-molecule FRET?

Biomolecular systems,such as proteins,crucially rely on dynamic processes at the nanoscale.Detecting biomolecular nanodynamics is therefore key to obtaining a mechanistic understanding of the energies and molecular driving forces that controlbiomolecular systems.Single-molecule fluorescence resonance energy transfer(smFRET)is a powerful technique to observe inreal-time how a single biomolecule proceeds through its functional cycle involving a sequence of distinct structural states.Currently,this technique is fundamentally limited by irreversible photobleaching,causing the untimely end of the experiment andthus,a narrow temporal bandwidth of≤3 orders of magnitude.Here,we introduce“DyeCycling”,a measurement scheme withwhich we aim to break the photobleaching limit in smFRET.We introduce the concept of spontaneous dye replacement bysimulations,and as an experimental proof-of-concept,we demonstrate the intermittent observation of a single biomolecule forone hour with a time resolution of milliseconds.Theoretically,DyeCycling can provide>100-fold more information per singlemolecule than conventional smFRET.We discuss the experimental implementation of DyeCycling,its current and fundamentallimitations,and specific biological use cases.Given its general simplicity and versatility,DyeCycling has the potential torevolutionize the field of time-resolved smFRET,where it may serve to unravel a wealth of biomolecular dynamics by bridgingfrom milliseconds to the hour range.

Efficient energy transfer in organic light-emitting transistor with tunable wavelength

Key challenges in the development of organic light-emitting transistors(OLETs)are blocking both scientific research and practical applications of these devices,e.g.,the absence of high-mobility emissive organic semiconductor materials,low device efficiency,and color tunability.Here,we report a novel device configuration called the energy transfer organic light-emitting transistor(ET-OLET)that is intended to overcome these challenges.An organic fluorescent dye-doped polymethyl methacrylate(PMMA)layer is inserted below the conventional high-mobility organic semiconductor layer in a single-component OLET to separate the functions of the charge transport and light-emitting layers,thus making the challenge to essentially integrate the high mobility and emissive functions within a single organic semiconductor in a conventional OLET or multilayer OLET unnecessary.In this architecture,there is little change in mobility,but the external quantum efficiency(EQE)of the ET-OLET is more than six times that of the conventional OLET because of the efficient Förster resonance energy transfer,which avoids exciton-charge annihilation.In addition,the emission color can be tuned from blue to white to green-yellow using the sourcedrain and gate voltages.The proposed structure is promising for use with electrically pumped organic lasers.

Single-molecule FRET studies on interactions between elongation factor 4 (LepA) and ribosomes

Elongation factor 4（EF4） is one of the highly conserved translational GTPases, whose functions are largely unknown. Structures of EF4 bound ribosomal PRE-translocation and POST-translocation complexes have both been visualized. On top of cellular, structural, and biochemical studies, several controversial models have been raised to rationalize functions of EF4. However, how EF4 modulates elongation through its interactions with ribosomes has not been revealed. Here, using single-molecule fluorescence resonance energy transfer assays, we directly captured short-lived EF4·GTP bound ribosomal PRE and POST translocation complexes, which may adopt slightly different conformations from structures prepared using GDP, GDPNP, or GDPCP. Furthermore, we revealed that EF4·GTP severely impairs delivery of aminoacyl-tRNA into the A-site of the ribosome and moderately accelerates translocation. We proposed that functions of EF4 are to slow overall elongation and to stall majority of ribosomes in POST states under stress conditions.

有机混合薄膜中的Frster能量转移

通过掺杂不同的染料有机电致发光器件可以得到不同颜色的光发射。掺杂小分子有机材料苝酸四甲酯perylene- 3,4,9,10 -tetracarboxylicacid(TMEP)到蓝色发光聚合物poly(N -vinyl carbazole)聚乙烯基咔唑(PVK),得到了很好的绿光发射。TEMP掺杂质量分数为0.01时,295. 5nm激发波长的荧光光谱可以明显观察到在420 nm处PVK和530 nm处TEMP的发射峰值;当TMEP掺杂质量分数达到0.050.10之间,器件的电致发光光谱和荧光光谱发射峰几乎完全被TEMP的绿光所占据。光谱的转移归因于从聚合物PVK到小分子有机材料TMEP的F -rster能量转移。荧光光谱中随着TMEP掺杂浓度的的增大发射峰值有明显的红移,这种现象被归因于在TMEP高浓度掺杂情况下激基缔合物的形成。激基缔合物的形成从TMEP在薄膜状态下与溶液状态下的荧光光谱的比较中得到证实。

Development of NIR Responsive Upconversion Nanosensor for Turn-on Detection of 4-Nonylphenol

4-Nonylphenol(NP)is a kind of estrogen belonging to the endocrine disrupter,widely used in various agricultural and industrial goods.However,extensive use of NP with direct release to environment poses high risks to both human health and ecosystems.Herein,for the first time,we developed near-infrared(NIR)responsive upconversion luminescence nanosensor for NP detection.The Förster resonance energy transfer based upconversion nanoparticles(UCNPs)-graphene oxide sensor offers highly selective and sensitive detection of NP in linear ranges of 5−200 ng/mL and 200−1000 ng/mL under 980 nm and 808 nm excitation,respectively,with LOD at 4.2 ng/mL.The sensors were successfully tested for NP detection in real liquid milk samples with excellent recovery results.The rare-earth fluoride based upconversion luminescence nanosensor with NIR excitation wavelength,holds promise for sensing food,environmental,and biological samples due to their high sensitivity,specific recognition,low LOD,negligible autofluorescence,along with the deep penetration of NIR excitation sources.

盐离子作用下组蛋白变体H2A.Z增强核小体结构的稳定性

真核生物染色质的基本结构组成单元是核小体,基因组DNA被压缩在染色质中,核小体的存在通常会抑制转录、复制、修复和重组等发生在DNA模板上的生物学过程。组蛋白变体H2A.Z可以调控染色质结构进而影响基因的转录过程,但其详细的调控机制仍未研究清楚。为了比较含有组蛋白变体H2A.Z的核小体和常规核小体在盐离子作用下的稳定性差异,本文采用F rster共振能量转移的方法检测氯化钠、氯化钾、氯化锰、氯化钙、氯化镁等离子对核小体的解聚影响。实验对Widom 601 DNA序列进行双荧光Cy3和Cy5标记,通过荧光信号值的变化来反映核小体的解聚变化。F rster共振能量转移检测结果显示:在氯化钠、氯化钾、氯化锰、氯化钙和氯化镁作用下,含有组蛋白变体H2A.Z的核小体解聚速度相比于常规核小体要慢,且氯化钙、氯化锰和氯化镁的影响更明显。电泳分析结果表明,在75℃条件下含有组蛋白变体H2A.Z的核小体的解聚速率明显低于常规核小体。采用荧光热漂移检测(fluorescence thermal shift analysis,FTS)进一步分析含有组蛋白变体H2A.Z核小体的稳定性,发现两类核小体的荧光信号均呈现2个明显的增长期,含有组蛋白变体H2A.Z核小体的第1个荧光信号增速期所对应的温度明显高于常规核小体,表明核小体中H2A.Z/H2B二聚体的解聚变性温度要高于常规的H2A/H2B二聚体,含有组蛋白变体H2A.Z核小体的热稳定性高。研究结果均表明,含有组蛋白变体H2A.Z的核小体的结构比常规核小体的结构稳定。

几种纳米荧光能量受体的比较

本文以荧光素(FAM)为荧光供体,通过与6种不同的纳米材料(还原型氧化石墨烯、氧化石墨烯、纳米Au、纳米Pd、纳米WS2和纳米MoS2)组成能量供-受体对,以DNA为作用媒介,从理论上和实验上比较6种纳米材料对FAM的荧光猝灭效果,希望从中确定最佳的荧光能量受体及其荧光共振能量转移(FRET)相关性质,为荧光传感器提供基础研究数据。研究表明,6种纳米材料中,还原型氧化石墨烯的猝灭效果最好,且还原型氧化石墨烯和纳米Au表现出了长距离FRET的性质。

Assembly of highly efficient aqueous light-harvesting system from sequence-defined peptoids for cytosolic microRNA detection

Precisely controlled spatial distributions of artificial light-harvesting systems in aqueous media are of significant importance for mimicking natural light-harvesting systems;however,they are often restrained by the solubility and the aggregation-caused quenching effect of the hydrophobic chromophores.Herein,we report one highly efficient artificial light-harvesting system based on peptoid nanotubes that mimic the hierarchical cylindrical structure of natural systems.The high crystallinity of these nanotubes enabled the organization of arrays of donor chromophores with precisely controlled spatial distributions,favoring an efficient Förster resonance energy transfer(FRET)process in aqueous media.This FRET system exhibits an extremely high efficiency of 98.6%with a fluorescence quantum yield of 40%and an antenna effect of 29.9.We further demonstrated the use of this artificial light-harvesting system for quantifying miR-210 within cancer cells.The fluorescence intensity ratio of donor to acceptor is linearly related to the concentration of intercellular miR-210 in the range of 3.3–156 copies/cell.Such high sensitivity in intracellular detection of miR-210 using this artificial light-harvesting system offers a great opportunity and pathways for biological imaging and detection,and for the further creation of microRNA(miRNA)toolbox for quantitative epigenetics and personalized medicine.

Copper-Free Click Chemistry-Mediated Assembly of Single Quantum Dot Nanosensor for Accurately Monitoring Locus-Specific m^(6)A in Cancer Cells

N6-methyladenosine(m^(6)A)plays an important role in embryogenesis,nuclear export,transcription splicing,and protein translation control.Herein,we demonstrate a copper-free click chemistry-mediated assembly of single quantum dot(QD)nanosensor for accurately monitoring locus-specific m^(6)A in cancer cells.The m^(6)A-sensitive endoribonuclease MazF can digest the unmethylated A-RNA,and the intact m^(6)A-RNA then hybridizes with DNA probes a and b to produce a sandwich hybrid,initiating the click chemistry to generate probe a–b ligation product via first tandem ligation detection reaction(LDR)cycle.Subsequently,DNA probes c and d can hybridize with the probe a–b ligation product to generate the probe c–d ligation product via second LDR cycle.Both LDR cycles can be repeated through denaturation and annealing reaction to generate abundant biotin-/fluorophore-modified probe c–d ligation products that can easily assemble on the QD surface to induce distinct fluorescence resonance energy transfer(FRET)between QD and Cy5.This assay can be homogenously performed without the involvement of copper catalyst,m^(6)A-specific antibody,radioactive labeling,ligase enzyme,enzymatic reverse transcription,and next-generation sequencing.Moreover,it can discriminate even 0.01% m^(6)A level in complex samples and accurately measure cellular m^(6)A-RNA expression,providing a promising avenue for clinical diagnostics and biomedical research.

A strategy for accurate detection of glucose in human serum and whole blood based on an upconversion nanoparticles-polydopamine nanosystem

The accurate detection of blood glucose is of critical importance in the diagnosis and management of diabetes and its complications. Herein, we report a novel strategy based on an upconversion nanoparticles-polydopamine （UCNPs-PDA） nanosystem for the accurate detection of glucose in human serum and whole blood through a simple blending of test samples with ligand-free UCNPs, dopamine, and glucose oxidase （GOx）. Owing to the high affinity of lanthanide ions exposed on the surface of ligand-free UCNPs, dopamine monomers could spontaneously attach to the UCNPs and further polymerize to form a PDA shell resulting in a remarkable upconversion luminescence （UCL） quenching （97.4%） of UCNPs under 980-nm excitation. Such UCL quenching can be effectively inhibited by H2O2 produced from the GOx/glucose enzymatic reaction, thus enabling the detection of H2O2 or glucose based on the UCL quenching/inhibition bioassay. Owing to the highly sensitive UCL response and background-free interference of the UCNPs-PDA nanosystem, we achieved a sensitive, selective, and high-throughput bioassay for glucose in human serum and whole blood, thereby revealing the great potential of the UCNPs-PDA nanosystem for the accurate detection of blood glucose or other HRO2-generated biomolecules in clinical bioassays.