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In situ laser reflectivity to monitor and control the nucleation and growth of atomically-thin 2D materials
摘要： The growth of atomically-thin two-dimensional (2D) layered and other quantum materials is typically performed without in situ monitoring or control. Here, a simple laser reflectivity approach is demonstrated to provide in situ control over sub-monolayer thickness and growth kinetics during pulsed laser deposition (PLD) of MoSe2 layers. First, the general technique is presented with emphasis on designing the maximum sensitivity of the optical contrast through consideration of Fresnel’s equations with proper choice of layer thickness, substrate, and laser monitoring wavelength, incidence angle, and laser polarization. Then the 633 nm optical reflectivity of MoSe2 layers on SiO2/Si substrates was predicted and compared with in situ monitoring of MoSe2 growth by PLD under actual growth conditions using a probe HeNe laser beam. The measurements showed high sensitivity and excellent agreement with MoSe2 surface coverages calculated from atomic resolution STEM analysis of 2D layers deposited in arrested growth experiments. Growth kinetics revealed by these measurements showed sigmoidal nucleation and growth stages in the formation of the 2D MoSe2 layers that are described by a simple model, indicating the promise of the laser reflectivity technique for in situ monitoring and control of 2D materials deposition.
关键词： pulsed laser deposition (PLD),MoSe2,kinetic modeling,in situ reflectivity,2D materials
更新于2025-09-16 10:30:52
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pH-Controlled Intracellular in Situ Reversible Assembly of Photothermal Agent for Smart Chemo-Photothermal Synergetic Therapy and ATP Imaging
摘要： To advance anti-tumor efficiency and lessen adverse effect caused by nanodrug residues in body, a smart nanoagent system is developed and successfully used in intracellular ATP-imaging and in vivo chemo-photothermal synergetic therapy. The nanoagent system is facilely prepared using DNA complex to modify gold nanoparticles (AuNPs). The DNA complex is formed by three oligonucleotides (ATP aptamer, rC-DNA and rG-DNA). CG-rich structure in ternary DNA complex could be exploited for payload of chemotherapeutic medicine doxorubicin (DOX), thus making efficient DOX transport into tumor site possible. In tumor cells, especially in acidic organelles (e.g. endosome and lysosome), DOX could be rapidly released via the dual stimuli of over-expressed ATP and pH. What’s more, the specific recognition of fluorescent-labelled aptamer strand to ATP can achieve the intracellular ATP imaging. pH-controlled reversible folding and unfolding of intermolecular i-motif formed by C-rich strands can lead to intracellular in situ assembly of AuNP aggregates with high photothermal conversion efficiency, and promote relatively facile renal clearance of AuNPs through the disassociation of the aggregates in extracellular environments. Experiments in vivo and vitro present feasibility for synergetic chemo-photothermal therapy. Such an in situ reversible assembly strategy of chemo-photothermal agent also presents a new paradigm for smart and highly efficient disease treatment with reduced side effects.
关键词： chemo-photothermal therapy,doxorubicin,ATP-imaging,AuNP aggregate,intracellular in situ reversible assembly
更新于2025-09-16 10:30:52
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Au-nanorod-clusters patterned optical fiber SERS probes fabricated by laser-induced evaporation self-assembly method
摘要： Optical ?ber surface-enhanced Raman scattering (SERS) probes provide a novel platform for liquid-phase in situ and remote SERS detections. However, it is still a challenge to fabricate noble metal nanostructures with large SERS enhancement factor (EF) onto optical ?ber surfaces. In this article, we successfully prepare Au-nanorod cluster structures on optical ?ber facets by a laboratory-developed laser-induced evaporation self-assembly method. It is demonstrated that the optimized optical ?ber SERS probes show high detection sensitivity (10?10 M for rhodamine 6G solution, and 10?8 M for malachite green or crystal violet solution) and excellent reproducibility (relative standard deviation less than 6%). As the laser-induced evaporation self-assembly method is a simple and low-cost method capable of achieving automatic and reproducible preparations of cluster patterned optical ?ber SERS probes, this work may ?nd important application prospects in various liquid-phase SERS detection areas.
关键词： Au-nanorod clusters,liquid-phase in situ detection,laser-induced evaporation self-assembly,SERS,optical fiber
更新于2025-09-16 10:30:52
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<p>Intraocular Pressure Calculation in Myopic Patients After Laser-Assisted In Situ Keratomileusis</p>
摘要： Background: Corneal refractive surgery is widely used worldwide. Myopia is the most common reason for laser-assisted corneal refractive surgery (LASIK) and one of the risk factors for glaucoma. Intraocular pressure (IOP) measurement becomes variable postoperatively as the results are affected by the decrease in corneal thickness and biomechanics. This prospective clinical case study attempted to establish a simple correction formula for the calculation of IOP in post-LASIK myopic patients. Methods: This study included 300 eyes of 150 patients with myopia and myopic astigmatism as a refractive error who underwent LASIK. IOP was measured preoperatively and 6 months postoperatively. Preoperative and postoperative corneal thickness as well as ablation depth were measured. Statistical analysis was performed to detect the relationship between ablation depth and change in IOP. An attempt was made to construct a correction formula for the calculation of post-LASIK IOP. Results: The age of the patients ranged between 18 and 50 (mean ± SD 34.78±8.8) years. The spherical equivalent of refractive error ranged between ?1.5 and ?10 diopters. The mean IOP decreased signi?cantly from 15.72±2.37 mmHg preoperatively to 11.71±2.24 mmHg postoperatively, with a mean difference of 4±1.75 mmHg (p?0.001). A positive correlation was detected between corneal thickness and IOP difference among patients both preoperatively and postoperatively (p?0.001). A positive correlation was identi?ed between ablation depth and IOP change (p?0.001). The correction formula for IOP was established: Real IOP=4+0.7(preoperative IOP)?0.3(ablation depth). Conclusion: IOP measurements change after corneal refractive surgery with LASIK. A corrected formula may be a good option for the proper calculation of post-LASIK IOP.
关键词： intraocular pressure calculation,Goldmann applanation tonometry,laser in situ keratomileusis,glaucoma,post-LASIK glaucoma
更新于2025-09-16 10:30:52
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Facile synthesis of durable perovskite quantum dots film with near unity photoluminescence quantum yield for efficient perovskite light emitting diode
摘要： In this work, a bright uniform PSK QDs film is synthesized in-situ using an amorphous polymer and optimizing the stoichiometry. The in-situ formed QDs film grown in the presence of poly(vinylpyrrolidone) chains shows a photoluminescence quantum yield (PLQY) as high as 98% even under low light intensities (0.01mW/cm2) with a long shelf lifetime of up to 2 years under ambient light (nanocrystals retain 100% of the initial PLQY). The near unity PLQY is due to the passivation of the surface defects of the PSK QDs by the Lewis base pyrrolidone groups of the polymer chain. Further, the QDs film shows higher thermal stability that increases by a factor of more than 5 compared to the bulk film. High efficient green perovskite light-emitting diodes (PLEDs) are fabricated without electron transporting layer using the high luminescent in situ synthesized low roughness QDs film with a current efficiency of 48.18 cd/A and power efficiency of 6.88 lm/W. Such devices start emitting green light at 2.5V and reach a maximum luminance of 124727 cd m?2 at 7V with external quantum efficiency of 10.5%. Further, the flexible PLED based on PSK QDs yields a maximum luminance of 43990 cd m-2 at 7V.
关键词： Perovskite quantum dots,perovskite light emitting diode,in situ synthesis
更新于2025-09-16 10:30:52
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An Approach for In Situ Rapid Detection of Deep-Sea Aromatic Amino Acids Using Laser-Induced Fluorescence
摘要： Amino acids are the material basis of almost all life activities. An improved understanding of the source, state, and cycle of amino acids is essential for determining the energy flow and material circulation of marine ecosystems. In the present study, an in situ rapid detection method of ultraviolet (UV; 266 nm) laser-induced fluorescence (LIF) technology was used to detect three natural, aromatic amino acids in the seawater. The laser-induced fluorescence peaks of aromatic amino acids tryptophan, tyrosine, and phenylalanine were located at 350 nm, 300 nm, and 280 nm, respectively. High, linear correlations between the concentrations of the aromatic amino acids and the fluorescence peak heights were observed, and the lowest detectable concentrations of tryptophan, tyrosine, and phenylalanine were 4.70 × 10?9 mol/L, 2.76 × 10?8 mol/L, and 6.05 × 10?7 mol/L, respectively, which allowed us to quantify their concentrations by using laser-induced fluorescence. This paper not only provides a practical method for the detection of aromatic amino acids in seawater, but a new means to further understand the biogeochemical processes of carbon cycles in the deep sea.
关键词： in situ detection,soluble aromatic amino acid,laser-induced fluorescence
更新于2025-09-16 10:30:52
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Non-contact, bi-directional tool tip vibration measurement in CNC milling machines with a single optical sensor
摘要： Vibration measurements of tools are significant for machine modelling, error prone state identification and machine operation optimization. In the milling process, forced vibrations are the main factor resulting in shape deviations as well surface roughness of machined work pieces and depend on the spindle speed and tool properties. Numerical models for predicting the dynamic behavior of machine systems can help to reduce vibrations. For an optimization, the model parameters need to be evaluated by simultaneously measuring the vibration of the tool tip in force direction and its vertical direction under different rotational speeds with high spatio-temporal resolution. In this work, a non-contact, single-sensor system and a signal processing algorithm are presented for measuring the vibrational behavior inside of a CNC milling machine with a known force. It enables in situ, simultaneous bi-directional vibration measurements directly at the tool tip with measurement rates up to 50 kHz, a circumferential resolution below 230 lm and a displacement uncertainty down to 40 nm, at rotational speeds up to 300 Hz. The dynamic behavior parameters of the tool are evaluated depending on the measured vibration (cid:1)2, enabling model optimizations. The measurements show a decrease of the natural frequency with increasing spindle speed. While the laser-based measurement principle does not bias the vibrational behavior it inherently guarantees orthogonality of the sensing axes, as well.
关键词： Interferometry,Bi-directional measurement,Dynamic behavior,Tip vibration,High-speed,In-situ
更新于2025-09-16 10:30:52
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Phase transformation at controlled locations in nanowires by in situ electron irradiation
摘要： Solid state phase transformations have drawn great attention because they can be effectively exploited to control the microstructure and property of materials. Understanding the physics of such phase transformation processes is critical to designing materials with controlled structure and with desired properties. However, in traditional ex situ experiments, it is hard to achieve position controlled phase transformations or obtain desirable crystal phase on nanometer scale. Meanwhile the underlying mechanisms of the reaction processes are not fully understood due to the lack of direct and real-time observation. In this paper, we observe phase transformation from body-centered tetragonal PX-PbTiO3 to monoclinic TiO2(B) on the atomic scale by in situ electron irradiation during heat treatment in transmission electron microscope, at pre-defined locations on the sample. We demonstrate that by controlling the location of the incident electron beam, a porous TiO2(B) crystal structure can be formed at the desired area on the nanowire, which is difficult to achieve by traditional synthesis methods. Upon in situ heating, the Pb atoms in the crystal migrate out of the pristine nanowire through inelastic scattering under incident electrons while high temperature(> 400 °C) provides energy for the crystallization of TiO2(B) and the volatilization of a substantial number of Pb atoms, which makes the resultingTiO2(B) nanowires to be porous. In contrast, at temperatures < 400 °C, the segregated Pb atoms form Pb particles and the TiOx nanowires remain in the amorphous state. This work not only provides in situ visualization of the phase transition from the PX-PbTiO3 to monoclinic TiO2(B), but also suggests a crystallography engineering strategy to obtain the desired crystal phase at controlled locations on the nanometer scale.
关键词： controlled locations,phase transformation,in situ,transmission electron microscopy
更新于2025-09-16 10:30:52
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Higha??Efficiency Lowa??Temperaturea??Processed Mesoscopic Perovskite Solar Cells from SnO <sub/>2</sub> Nanorod Selfa??Assembled Microspheres
摘要： Mesoporous scaffolds in perovskite solar cells (PSCs) can accelerate the formation of heterogeneous nucleation sites, leading to enhanced quality of perovskite films and uniform perovskite coverage over large areas. Nevertheless, the mesoporous electron transport layers (ETLs) can effectively compensate for the drawback of shorter electron diffusion lengths than their hole counterparts. Therefore, most mesoscopic PSCs usually show superior photovoltaic performance to their planar counterparts. However, mesoporous ETLs, particularly those prepared with metal oxide nanocrystals, often require a high-temperature sintering process for the removal of residual organics and the improved crystallization of metal oxides. Here, a novel emulsion-based bottom-up self-assembly strategy is used to prepare sizable SnO2 microspheres from oleic acid capped SnO2 nanorods. Combined with an in-situ ligand-stripping strategy, the low-temperature solution-processed mesoscopic PSCs can achieve efficiency as high as 21.35% with slight hysteresis and good reproducibility. In particular, the emulsion-based bottom-up self-assembly strategy is a general way for preparing microspheres from several kinds of semiconductor nanocrystals, so it will greatly expand the material selection range for preparing efficient mesoscopic PSCs and even inverted mesoscopic devices.
关键词： mesoscopic perovskite solar cells,in situ ligand stripping,low-temperature process,SnO2 nanorod self-assembled microspheres
更新于2025-09-16 10:30:52
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Enhanced wear resistance and new insight into microstructure evolution of in-situ (Ti,Nb)C reinforced 316??L stainless steel matrix prepared via laser cladding
摘要： An MC (M: Ti,Nb) carbide-reinforced 316 L coating was synthesized in-situ via laser cladding. A strong relationship between the (Ti,Nb)C content and the microstructure and tribological properties of the resulting components was established. This relationship helped explain the in?uence of the (Ti,Nb)C content on the phase evolution, microstructure characteristics, and exothermic reaction behavior. It was found that the size and morphology of in-situ generated (Ti,Nb)C particles changed as the carbide content increased. When the MC carbide content increased from 2.5 wt% to 10 wt%, the morphology of in-situ generated (Ti,Nb)C evolved from irregular geometry particles, to spherical particles, and ?nally into near-regular geometry. When the carbide content reached 15 wt%, the (Ti,Nb)C particles displayed an equilibrium octahedral structure. The calculated formation enthalpy of MC carbides showed that the reaction enthalpy increased with the MC carbide content, which a?ected the dynamic temperature of the molten pool and eventually led to carbides with di?erent crystal morphologies and sizes. Room-temperature dry sliding friction and wear tests showed that the submicron (Ti,Nb)C carbide reinforced (carbide content: 5 wt%) coating and 1.5 ??m regular octahedral particle-reinforced coating (carbide content: 20 wt%) exhibited a lower friction coe?cient and wear volume loss. Understanding the morphological evolution mechanism of (Ti,Nb)C and its corresponding tribological behavior will enable the development of guidelines to obtain (Ti,Nb)C/316 L metal matrix composite coatings produced by laser cladding.
关键词： (Ti,Nb)C,Laser cladding,Tribological behavior,Microstructure,In-situ
更新于2025-09-16 10:30:52