Comparison of point detection and area detection for point-scanning structured illumination microscopy

Structured illumination microscopy(SIM)is suitable for biological samples because of its relatively low-peak illumination intensity requirement and high imaging speed.The system resolution is affected by two typical detection modes:Point detection and area detection.However,a systematic analysis of the imaging performance of the different detection modes of the system has rarely been conducted.In this study,we compared laser point scanning point detection(PS-PD)and point scanning area detection(PS-AD)imaging in nonconfocal microscopy through theoretical analysis and simulated imaging.The results revealed that the imaging resolutions of PSPD and PS-AD depend on excitation and emission point spread functions(PSFs),respectively.Especially,we combined the second harmonic generation(SHG)of point detection(P-SHG)and area detection(A-SHG)with SIM to realize a nonlinear SIM-imaging technique that improves the imaging resolution.Moreover,we analytically and experimentally compared the nonlinear SIM performance of P-SHG with that of A-SHG.

Quantitative heterogeneity and subgroup classification based on motility of breast cancer cells

Cancer cell motility and its heterogeneity play an important role in metastasis, which is responsible for death of 90% of cancer patients. Here, in combination with a microfluidic technique, single-cell tracking, and systematic motility analysis,we present a rapid and quantitative approach to judge the motility heterogeneity of breast cancer cells MDA-MB-231 and MCF-7 in a well-defined three-dimensional(3D) microenvironment with controllable conditions. Following this approach,identification of highly mobile active cells in a medium with epithelial growth factor will provide a practical tool for cell invasion and metastasis investigation of multiple cancer cell types, including primary cells. Further, this approach could potentially become a speedy(~ hours) and efficient tool for basic and clinical diagnosis.

Preparation of chitosan-Epigallocatechin-3-O-gallate nanoparticles and their inhibitory effect on the growth of breast cancer cells

In this paper,we prepared the nanoparticle drug carrier system between nanoparticles chitosan and Epigallocatechin-3 O-gallate(EGCG)for breast cancer cell inhibiting application.For this drug carrier system,chitosan acts as a carrier and EGOG as a drug.Which were systematically characterized and thoroughly evaluated in terms of their inhibition rate and biocompatibility.We also did a cell scratch test and the result indicated that the chitosan EGCG nanoparticles have inhibitory effect on the growth of breast cancer cells.The inhibition rate could reach up to 21.91%.This work revealed that the modification of nanopartidles paved a way for specific biomedical applications.

Dependence Study of Optoelectronics Performance on Carefully Differed LiF Thickness in Alq₃Based OLEDs

The effect of LiF thickness on the electrical and luminescent characteristics in OLEDs has been studied by carefully varying thickness value range from 0 nm to 1.2 nm. It’s interesting to find that the device with 0.2 nm LiF layer performs the largest current and comparative lower luminescent efficiency, while the one with 0.6 nm LiF performs another current peak (lower than that of device with 0.2 nm LiF layer) but the highest luminescent efficiency in all devices. Here the much enhanced electron injection and destructive efficiency for 0.2 nm LiF device are understood by the chemical interaction model at cathode interface, while the fairly increased electron injection and much improved efficiency for 0.6 nm LiF device would be interpreted by other mechanisms, and LiF plays a protective part in preventing the deposition-induce photoluminescence from quenching by Al cathode.

Improvement in Resolution of Multiphoton Scanning Structured Illumination Microscopy via Harmonics

We describe a multiphoton(mP)-structured illumination microscopy(SIM)technique,which demonstrates substantial improvement in image resolution compared with linear SIM due to the nonlinear response of fluorescence.This nonlinear response is caused by the effect of nonsinusoidal structured illumination created by scanning a sinusoidally modulated illumination to excite an mP fluorescence signal.The harmonics of the structured fluorescence illumination are utilised to improve resolution.We present an mP-SIM theory for reconstructing the super-resolution image of the system.Theoretically,the resolution of our m P-SIM is unlimited if all the high-order harmonics of the nonlinear response of fluorescence are considered.Experimentally,we demonstrate an 86 nm lateral resolution for two-photon(2P)-SIM and a 72 nm lateral resolution for second-harmonic-generation(SHG)-SIM.We further demonstrate their application by imaging cells stained with F-actin and collagen fibres in mouse-tail tendon.Our method can be directly used in commercial mP microscopes and requires no specific fluorophores or high-intensity laser.

Applications,of fluorescence lifetime imaging in clinical medicine

Fluorescence lifetime is not only associated with the molecular structure f fuorophores,but alsostrongly depends on the environment around them,which llows fuorescence lifetime imagingmicroscopy(FLIM)to be used as a tool for precise measurement of the cell or tisue microenvironment,This review introduces the basic principle of fuorescence lifetime imagingtechnology and its application in clinical medicine,including research and diagnosis of diseases inskin,brain,eyes,mouth,bone,blood vessels and cavity organs,and drug evaluation.As anoninvasive,nontoxic and nonionizing radiation technique,FLIM demonstrates excellent per-formance with high sensitivity and specificity,which allows to determine precise position of thelesion and,thus,has good potential for application in biomedical research and clinical diagnosis.

Observations of intracellular second-harmonic generation imaging in black phosphorus nanosheets

Functionalized black phosphorus(BP)nanosheets have been considered as promising nanoagents in cancer therapy due to their excellent photothermal conversion efficiency.However,it is still difficult to visually monitor the dynamic localization of BP nanoagents in cancer cells.In this paper,we systematically studied the second-harmonic generation(SHG)signals originating from exfoliated BP nanosheets.Interestingly,under the excitation of a high frequency pulsed laser at 950 nm,the SHG signals of BP nanosheets in vitro are almost undetectable because of their poor stability.However,the intracellular SHG signals from BP nanosheets could be measured by in vivo optical imaging due to the efficient enrichment of living HeLa cells.Moreover,the SHG signal intensity from BP nanosheets increases with the prolonged incubation time.It can be expected that the BP nanosheets could be a promising intracellular SHG nanoprobe employed for visually in vivo biomedical imaging in practical cancer photothermal therapy(PIT).

The influence of an Si_xN_y interlayer on a GaN film grown on an Si(111) substrate

A method to drastically reduce dislocation density in a GaN film grown on an Si（111） substrate is newly developed. In this method, the SixNy interlayer which is deposited on an A1N buffer layer in situ is introduced to grow the GaN film laterally. The crack-free GaN film with thickness over 1.7 micron is successfully grown on an Si（lll） substrate. A synthesized GaN epilayer is characterized by X-ray diffraction （XRD）, atomic force microscope （AFM）, and Raman spectrum. The test results show that the GaN crystal reveals a wurtzite structure with the （0001） crystal orientation and the full width at half maximum of the X-ray diffraction curve in the （0002） plane is as low as 403 arcsec for the GaN film grown on the Si substrate with an SixNy interlayer. In addition, Raman scattering is used to study the stress in the sample. The results indicate that the SizNy interlayer can more effectively accommodate the strain energy. So the dislocation density can be reduced drastically, and the crystal quality of GaN film can be greatly improved by introducing an SixNy interlayer.

LiF Thickness dependence of Electron Injection Models for Alqa/LiF/A1 Cathode Structure

We present the experimental evidences showing that three different electron injection models play roles in Alq3 based organic light-emitting diodes in sequence when the thickness of LiF interlayer is changed. It is found that the device with a 0.2nm LiF layer displays the largest current with declined luminescence. However, the one with a 0.6 nm LiF layer displays the second largest current and the highest luminescence of all. Combining with the photoluminescent test results, three models, namely chemical reaction at ternary interface, dipole effect at binary interface and tunneling enhancement effect, are expected to play roles in sequence when the LiF thickness is increased from 0 nm to 4 nm.

Synthesis of two-dimensional transition metal dichalcogenides for electronics and optoelectronics

Tremendous efforts have been devoted to preparing the ultrathin two-dimensional(2D)transition-metal dichalcogenides(TMDCs)and TMDCS-based heterojunctions owing to their unique properties and great potential applications in next generation electronics and optoelectronics over the past decade.However,to fulfill the demands for practical applications,the batch production of 2D TMDCs with high quality and large area at the mild condi-tions is still a challenge.This feature article reviews the state-of-the art research progresses that focus on the preparation and the applications in elec-tronics and optoelectronics of 2D TMDCs and their van der Waals hetero-junctions.First,the preparation methods including chemical and physical vapor deposition growth are comprehensively outlined.Then,recent progress on the application of fabricated 2D TMDCs based materials is revealed with particular attention to electronic(eg,field effect transistors and logic circuits)and optoelectronic(eg,photodetectors,photovoltaics,and light emitting diodes)devices.Finally,the challenges and future prospects are considered based on the current advance of 2D TMDCs and related heterojunctions.

In vitro three-dimensional cancer metastasis modeling:Past,present,and future

Metastasis is the leading cause of most cancer deaths, as opposed to dysregulated cell growth of the primary tumor. Molecular mechanisms of metastasis have been studied for decades and the findings have evolved our understanding of the progression of malignancy. However, most of the molecular mechanisms fail to address the causes of cancer and its evolutionary origin, demonstrating an inability to find a solution for complete cure of cancer. After being a neglected area of tumor biology for quite some time, recently several studies have focused on the impact of the tumor microenvironment on cancer growth. The importance of the tumor microenvironment is gradually gaining attention, particularly from the per- spective of biophysics. In vitro three-dimensional （3-D） metastatic models are an indispensable platform for investigating the tumor microenvironment, as they mimic the in vivo tumor tissue. In 3-D metastatic in vitro models, static factors such as the mechanical properties, biochemical factors, as well as dynamic factors such as cell-cell, cell-ECM interactions, and fluid shear stress can be studied quantitatively. With increasing focus on basic cancer research and drug development, the in vitro 3-D models offer unique advantages in fundamental and clinical biomedical studies.

Broadband Pulsed Fiber Laser Generation with Topological Insulator: Towards the Mid-Infrared Regime

In recent years, topological insulators have aroused the attention of a great number of scientists due to their unique electronic structures and peculiar physical properties. Triggered by the similar electronic structures as graphene, the broadband nonlinear absorption properties of topological insulator were investigated. Moreover, the mode-locked or Q-switched fiber lasers based on topological insulator were realized for broadband operating wavelength. Here, we present an overview of the preparation, transferring, linear and nonlinear optical properties and their applications of topological insulators in pulsed fiber lasers. The pulsed fiber lasers towards mid- infrared regimes have been proposed.

Broadband ultrafast nonlinear optical response of few-layers graphene: toward the mid-infrared regime

Gapless linear energy dispersion of graphene endows it with unique nonlinear optical properties, including broadband nonlinear absorption and giant nonlinear refractive index. Herein, we experimentally observed that fewlayers graphene has obvious nonlinear absorption and large nonlinear refraction, as investigated by the Z-scan technique in the mid-infrared（mid-IR） regime. Our study may not only, for the first time to our knowledge, verify the giant nonlinear refractive index of graphene(～10-7cm2∕W) at the mid-IR, which is 7 orders of magnitude larger than other conventional bulk materials, but also provide some new insights for graphene-based mid-IR photonics,potentially leading to the emergence of several new conceptual mid-IR optoelectronics devices.

Promoting near-infrared photocatalytic activity of carbon-doped carbon nitride via solid alkali activation

Ultrabroad spectral absorption is required for semiconductor photocatalysts utilized for solar-to-chemical energy conversion.The light response range can be extended by element doping,but the photocatalytic performance is generally not enhanced correspondingly.Here we present a solid alkali activation strategy to synthesize near-infrared(NIR)light-activated carbon-doped polymeric carbon nitride(A-cPCN)by combining the copolymerization of melamine and 1,3,5-trimesic acid.The prepared A-cPCN is highly crystalline with a narrowed bandgap and enhanced efficiency in the separation of photogenerated electrons and holes.Under irradiation with NIR light(780 nm≥λ≥700 nm),A-cPCN shows an excellent photocatalytic activity for H_(2)generation from water with rate of 165µmol g^(−1)h^(−1),and the photo-redox activity for H_(2)O_(2)production(109µmol g^(−1)h^(−1))from H_(2)O and O_(2),whereas no observed photocatalytic activity over pure PCN.The NIR photocatalytic activity is due to carbon doping,which leads to the formation of an interband level,and the alkali activation that achieved shrinking the transfer distance of photocarriers.The current synergistic strategy may open insights to fabricate other carbon-nitrogen-based photocatalysts for enhanced solar energy capture and conversion.

Ultrafast fiber lasers mode-locked by two-dimensional materials:review and prospect

The year 2019 marks the 10th anniversary of the first report of ultrafast fiber laser mode-locked by graphene.This result has had an important impact on ultrafast laser optics and continues to offer new horizons.Herein,we mainly review the linear and nonlinear photonic properties of two-dimensional(2D)materials,as well as their nonlinear applications in efficient passive mode-locking devices and ultrafast fiber lasers.Initial works and significant progress in this field,as well as new insights and challenges of 2D materials for ultrafast fiber lasers,are reviewed and analyzed.

In vivo mice brain microcirculation monitoring based on contrast-enhanced SD-OCT

In this paper,we proposed a contrast-enhanced homemade spectral domain optical coherence tomography(SD-OCT)method for monitoring of brain microcirculation.We used the polyethylene glycol(PEG)-ylated gold nanorods(GNRs)as a contrast-enhanced agent,obtained clearly 2D and 3D OCT images of blood vessels and dynamic changes of probes in mouse blood vessels.Owing to high scattering of the PEG-GNRs,more tiny blood vessels can be imaged and the OCT signal can be enhanced by 5.87 dB after injection of PEG-GNRs for 20 min,the enhancement then declined gradually for 60 min.Our results demonstrate an effective technique for the enhanced imaging of blood vessels in vivo,especially for studies of the brain microcirculation,which could be serviced for disease mechanism research and therapeutic drug monitoring.

Nonlinear scanning structured illumination microscopy based on nonsinusoidal modulation

Structured illumination microscopy(SIM)is an essential super-resolution microscopy technique that enhances resolution.Several images are required to reconstruct a super-resolution image.However,linear SIM resolution enhancement can only increase the spatial resolution of micros-copy by a factor of two at most because the frequency of the structured illumination pattern is limited by the cutoff frequency of the excitation point spread function.The frequency of the pattern generated by the nonlinear response in samples is not limited;therefore,nonlinear SIM(NL-SIM),in theory,has no inherent limit to the resolution.In the present study,we describe a two-photon nonlinear SIM(2P-SIM)technique using a multiple harmonics scanning pattern that employs a composite structured illumination pattern,which can produce a higher order harmonic pattern based on the fluorescence nonlinear response in a 2P process.The theoretical models of super-resolution imaging were established through our simulation,which describes the working mechanism of the multi-frequency structure of the nonsinusoidal function to improve the reso-lution.The simulation results predict that a 5-fold improvement in resolution in the 2P-SIM is possible.

Graphene/phosphorene nano-heterojunction:facile synthesis, nonlinear optics, and ultrafast photonics applications with enhanced performance

Owing to its thickness-modulated direct energy band gap, relatively strong light–matter interaction, and unique nonlinear optical response at a long wavelength, few-layer black phosphorus, or phosphorene, becomes very attractive in ultrafast photonics applications. Herein, we synthesized a graphene/phosphorene nano-heterojunction using a liquid phase-stripping method. Tiny lattice distortions in graphene and phosphorene suggest the formation of a nano-heterojunction between graphene and phosphorene nanosheets. In addition, we systematically investigate their nonlinear optical responses at different wavelength regimes. Our experiments indicate that the combined advantages of ultrafast relaxation, broadband response in graphene, and the strong light–matter interaction in phosphorene can be combined together by nano-heterojunction. We have further fabricated two-dimensional(2D) nano-heterojunction based optical saturable absorbers and integrated them into an erbium-doped fiber laser to demonstrate the generation of a stable ultrashort pulse down to 148 fs. Our results indicate that a graphene/phosphorene nano-heterojunction can operate as a promising saturable absorber for ultrafast laser systems with ultrahigh pulse energy and ultranarrow pulse duration. We believe this work opens up a new approach to designing 2D heterointerfaces for applications in ultrafast photonics and other research.The fabrication of a 2D nano-heterojunction assembled from stacking different 2D materials, via this facile and scalable growth approach, paves the way for the formation and tuning of new 2D materials with desirable photonic properties and applications.

Two-dimensional selenium and its composites for device applications

Two-dimensional(2D)selenium was synthesized successfully in 2017.Its advanced properties,including size-dependent bandgap,excellent environmental robustness,strong photoluminescence effect,anisotropic thermal conductivity,and high photoconductivity,render it and selenium-based composites a promising candidate for various device applications.These include batteries,modulators,photodetectors,and photothermal effects in medical applications.However,compared to other commonly used 2D materials,such as graphene,transition metal dichalcogenides,and black phosphorus,2D Se is much less known.Motivated by the need to overcome this lack of knowledge,this article focuses on recent progress and elucidates the crystal structure,synthesis methods,physical properties,applications,challenges,and prospects of 2D Se nanoflakes.

Scanless multitarget-matching multiphoton excitation fluorescence microscopy

Using the combination of a refective blazed grating and a reflective phase-only difractive spatiallight modulator(SLM),scanless multitarget-matching multiphoton excitation fuorescence mi.croscopy(SMTM-MP M)was achieved.The SLM shaped an incoming mode-locked,near-infraredTi:sapphire laser beam into an excitation pattern with addressable shapes and sizes that matchedthe samples of interest in the field of view.Temporal and spatial focusing were simultaneouslyrealized by combining an objective lens and a blazed grating.The fluorescence signal fromilluminated areas was recorded by a two-dimensional sCMOS camera.Compared with a conventional temporal focusing multiphoton microscope,our microscope achieved effective use of thelaser power and decreased photodamage with higher axial resolution.