A SIMULTANEOUS MULTI-PROBE DETECTION LABEL-FREE OPTICAL-RESOLUTION PHOTOACOUSTIC MICROSCOPY TECHNIQUE BASED ON MICROCAVITY TRANSDUCER

We demonstrate the feasibility of simultancous multi-probe detection for an optcal-resolution photoacoustic microscopy(OR-PAM)system.OR-P AM has elicited the attention of biomedical imaging researchers because of its optical absorption contrast and high spatial resolution with great imaging depth.OR-PAM allows label-free and noninvasive imaging by maximizing the optical absorption of endogenous biomolecules.However,given the inadequate absoption of some biomolcules,detection sensitivity at the same incident intensity requires improvement.In this study,a modulated continuous wave with power density less than 3mW/cm^(2)(1/4 of the ANSI safety limit)excited the weak photoacoustic(PA)signals of biological cells.A microcavity traneducer is developed based on the bulk modulus of gas five orders of magnitude lower than that of solid;air pressure variation is inversely proportional to cavity volume at the same temperature increase.Considering that a PA wave expands in various directions,detecting PA signals from different positions and adding them together can increase detection sensitivity and signal-to-noise ratio.Therefore,we employ four detectors to acquire tiny PA signals simul-taneously.Experimental results show that the developed OR-PAM system allows the label-free imaging of cells with weak optical absorption.

In vivo monitoring of microneedle-based transdermal drug delivery of insulin

Soluble microneedles(MNs)have recently become an eficient and minimally invasive tool in transdermal drug delivery because of their excellent biocompatibility and rapid dissohution.However,direct monitoring of structural and functional changes of MNs in vivo to estimate the efficieancy of insulin delivery is difficult.We monitored the dissolution of MNs to obtain structural imaging of MNs'changes by using optical coherence tomography(OCT).We also observed the effect of MNs on microvascular conditions with laser speckle contrast imaging(LSCIT)and measured the blood perfusion of skin to obtain functional imaging of MNs.We determined the performance of two soluble MN arrays made from polyvinyi alcohol(PVA)and polyvinyl alco-hol/polyvinylpyrolidone(PVA/PVP)by calculating the cross sectional areas of the micro-channels in mouse skin as a function of time.Moreover,the change in blood glucose before and after using MNs loaded with insulin was evaluated as an auxiliary means to demonstrate the ability of the soluble MNs to deliver insulin.Results showed that the structural imaging of these MNs could be observed in vivo via OCT in real time and the fumctional imaging of MNs could be showed using LSCI OCT and LSCI are potential tools in monitoring MNs structural and functional changes.

Towards growth of pure AB-stacked bilayer graphene single crystals

Given its intriguing band structure and unique tunable bandgap,AB-stacked bilayer graphene has great potentials in the applications of high-end electronics,optoelectronics and semiconductors.The epitaxial growth of AB-stacked single-crystal bilayer graphene films requires a strict AB-stacked lattice,identical orientations and seamless stitching of bilayer graphene islands.However,the particles inevitably present on the metal surface that produced during high temperature growth would induce random orientations,twisted stacking islands,and uncontrollable multilayers,which is a great challenge to overcome.Here,we propose a heat-resisting-box assisted strategy to produce nearly pure AB-stacked bilayer graphene single-crystal films on Cu/Ni(111)foils.With our technique,the particles on the Cu/Ni(111)surface are effectively eliminated,which greatly minimizes the occurrence of randomly twisted islands and uncontrollable multilayers.The as-grown AB-stacked bilayer graphene films show>99%alignment and>99%AB stacking order.Our work provides a promising method towards the growth of pure AB-stacked bilayer graphene single crystals and would accelerate its device applications.

Towards intrinsically pure graphene grown on copper

The state-of-the-art semiconductor industry is built on the successful production of silicon ingot with extreme purity as high as 99.999999999%,or the so-called"eleven nines".The coming high-end applications of graphene in electronics and optoelectronics will inevitably need defect-free pure graphene as well.Due to its two-dimensional(2D)characteristics,graphene restricts all the defects on its surface and has the opportunity to eliminate all kinds of defects,i.e.,line defects at grain boundaries and point or dot defects in grains,and produce intrinsically pure graphene.In the past decade,epitaxy growth has been adopted to grow graphene by seamlessly stitching of aligned grains and the line defects at grain boundaries were eliminated finally.However,as for the equally common dot and point defects in graphene grain,there are rare ways to detect or reduce them with high throughput and efficiency.Here,we report a methodology to realize the production of ultrapure graphene grown on copper by eliminating both the dot and point defects in graphene grains.The dot defects,proved to be caused by the silica particles shedding from quartz tube during the high-temperature growth,were excluded by a designed heat-resisting box to prevent the deposition of particles on the copper surface.The point defects were optically visualized by a mild-oxidation-assisted method and further reduced by etching-regrowth process to an ultralow level of less than 1/1,000 μm^(2).Our work points out an avenue for the production of intrinsically pure graphene and thus lays the foundation for the large-scale graphene applications at the integrated-circuit level.

Redox responsive nanoparticle encapsulating black phosphorus quantum dots for cancer theranostics

Effective cancer treatment puts high demands for cancer theranostics.For cancer diagnostics,optical coherence tomography(OCT)technology(including photothermal optical coherence tomography(PT-OCT))has been widely investigated since it induces changes in optical phase transitions in tissue through environmental changes(such as temperature change for PT-OCT).In this report,redox responsive nanoparticle encapsulating black phosphorus quantum dots was developed as a robust PT-OCT agent.Briefly,black phosphorus quantum dots(BPQDs)are incorporated into cysteine-based poly-(disulfide amide)(Cys-PDSA)to form stable and biodegradable nanoagent.The excellent photothermal feature allows BPQD/Cys-PDSA nanoparticles(NPs)as a novel contrast agent for high-resolution PT-OCT bioimaging.The Cys-PDSA can rapidly respond to glutathione and effectively release BPQDs and drugs in vitro and in vivo.And the obtained NPs exhibit excellent near-infrared(NIR)photothermal transduction efficiency and drug delivery capacity that can serve as novel therapeutic platform,with very low chemo drug dosage and side effects.Both of the polymer and BPQD are degradable,indicating this platform is a rare PT-OCT agent that is completely biodegradable.Overall,our research highlights a biodegradable and biocompatible black phosphorus-based nanoagent for both cancer diagnosis and therapy.