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- 2019
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- Photodynamic inactivation
- Gold nanoparticles
- Low-power density laser
- Surface plasmon resonance
- upconversion luminescence
- mesoporous silica
- core–shell nanoparticles
- bismuth silicate
- Bi2SiO5
- nitrogen vacancy centers
- Optoelectronic Information Science and Engineering
- Polymer Materials and Engineering
- Chemistry
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- Biomedical Engineering
- Physics
- Applied Physics
- Korea Advanced Institute of Science and Technology (KAIST)
- Ca’ Foscari University of Venice
- Institute for Basic Science (IBS)
- Université de Haute-Alsace
- Peking University
- Daegu Gyeongbuk Institute of Science and Technology (DGIST)
- Babol Noshirvani University of Technology
- Florida International University
- Université Paris-Saclay
- Hebrew University of Jerusalem
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Temperature-dependent photo-response in multiferroic BiFeO 3 revealed by transmission measurements
摘要： We studied the light-induced effects in BiFeO3 single crystals as a function of temperature by means of optical spectroscopy. Here, we report the observation of several light-induced absorption features, which are discussed in terms of the photostriction effect and are interpreted in terms of excitons. The temperature dependence of their energy position suggests a possible coupling between the excitons and the lattice vibrations. Moreover, there are hints for anomalies in the temperature evolution of the excitonic features, which might be related to the temperature-induced magnetic phase transitions in BiFeO3. Our findings suggest a coupling between light-induced excitons and the lattice and spin degrees of freedom, which might be relevant for the observed ultrafast photostriction effect in multiferroic BiFeO3.
关键词： multiferroic,excitons,optical spectroscopy,BiFeO3,photostriction
更新于2025-11-25 10:30:42
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Hydrogen peroxide detection with a silver nanoparticle grating chip fabricated by plasmonic plating
摘要： An optical detection of hydrogen peroxide (H2O2) is proposed, using grating structures of silver nanoparticles (AgNPs). Periodic line structures of AgNPs are deposited on a gold nanoparticle (AuNP)-decorated glass plate using an interference exposure with a green laser beam, based on the plasmonic plating method. This AgNP grating chip diffracts incident light, and the diffraction efficiency is dependent on the amount of AgNPs. By applying a drop of H2O2 solution onto the chip, the diffraction intensity declines due to the autocatalytic decomposition of AgNPs. A portable measurement system of the diffraction intensity change is constructed, and the H2O2 detection in the concentration range 6.7 – 668 μmol/L is performed in 2 min simply by dropping the H2O2 solution onto the substrate.
关键词： silver nanoparticles,plasmonic plating,optical sensor,hydrogen peroxide detection,diffraction grating
更新于2025-11-25 10:30:42
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Graphene-Coated Glass Substrate for Continuous Wave Laser Desorption and Atmospheric Pressure Mass Spectrometric Imaging of Live Hippocampal Tissue
摘要： Atmospheric pressure mass spectrometric (AP-MS) imaging technology combined with an inverted optical microscopic system is a powerful tool for determining the presence and spatial distributions of specific biomolecules of interest in live tissues. Efficient desorption and ionization are essential to acquire mass spectrometric (MS) information in an ambient environment. In this study, we demonstrate a new and efficient desorption process using a graphene-coated glass substrate and a continuous wave (CW) laser for high-resolution AP-MS imaging of live hippocampal tissue. We found that desorption of biomolecules in a live tissue slice was possible with the aid of a graphene-coated glass substrate and indirect application of a 532 nm CW-laser on the graphene substrate. Interestingly, the desorption efficiency of live tissue on the graphene-coated substrate was strongly dependent on the number of graphene layers. Single-layer graphene was found to be the most sensitive substrate for efficient desorption and reproducible high-resolution hippocampal tissue imaging applications. The subsequent ionization process using nonthermal plasma generated sufficient amounts of molecular ions to obtain high-resolution 2-dimensional MS images of the cornu ammonis (CA) and the dentate gyrus (DG) regions of the hippocampus. Therefore, graphene-coated substrates could be a promising platform to induce an efficient desorption process essential for highly reproducible ambient MS imaging.
关键词： Hippocampal tissue,Mass spectrometry imaging,Laser desorption,Graphene-coated substrate,Ambient mass spectrometry
更新于2025-11-25 10:30:42
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Utility of fluorescent heme analogue ZnPPIX to monitor conformational heterogeneity in vertebrate hexa-coordinate globins
摘要： Here we report preparation and photo-physical characterization of hexa-coordinate vertebrate globins, human neuroglobin (hNgb) and cytoglobin (Cygb), with the native iron protoporphyrin IX (FePPIX) cofactor replaced by a fluorescent isostructural analogue zinc protoporphyrin IX (ZnPPIX). To facilitate insertion of ZnPPIX into hexa-coordinate globins, apoproteins prepared by a butanone extraction were unfolded by addition of GuHCl and subsequently slowly refolded in the presence of ZnPPIX. The absorption/emission spectra of ZnPPIX reconstituted hCygb are similar to those observed for ZnPPIX reconstituted myoglobin whereas absorption and emission spectra of ZnPPIX reconstituted hNgb are blue shifted by ~ 2 nm. Different steady state absorption and emission properties of ZnPPIX incorporated in hCygb and hNgb are consistent with distinct hydrogen bonding interactions between ZnPPIX and the globin matrix. The fluorescence lifetime of ZnPPIX in hexa-coordinate globins is bimodal pointing towards increased heterogeneity of the heme binding cavity in hCygb and hNgb. ZnPPIX reconstituted Ngb binds to cytochrome c with the same affinity as reported for the native protein, suggesting that fluorescent analogues of Cygb and Ngb can be readily employed to monitor interactions between vertebrate hexa-coordinate globins and other proteins.
更新于2025-11-25 10:30:42
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Enhancement of optical resolution in three-dimensional refractive-index tomograms of biological samples by employing micromirror-embedded coverslips
摘要： Optical diffraction tomography (ODT) enables the reconstruction of the three-dimensional (3D) refractive-index (RI) distribution of a biological cell, which provides invaluable information for cellular and subcellular structures in a non-invasive manner. However, ODT suffers from an inferior axial resolution, due to the limited accessible angles imposed by the numerical aperture of the objective lens. In this study, we propose and experimentally demonstrate an approach to enhance the 3D reconstruction performance in ODT. By employing trapezoidal micromirrors, side scattered signals from the sample are measured for various side-plane-wave-illumination angles. By combining the side scattered fields with the forward scattered fields, the axial resolution and 3D image quality of ODT are improved, without changing optical instruments. The feasibility and applicability of the proposed method are demonstrated by reconstructing the 3D RI distribution of a red blood cell and HeLa cells in hydrogel. We also present systematic analyses of the improved 3D imaging performance using numerical simulations and experimental measurements for the 3D transfer function, a point object, and a microsphere. The analyses demonstrate an improved axial resolution of 0.31 μm, 4.8 times smaller than that of the conventional method. The proposed method enables the non-invasive and accurate 3D imaging of 3D cultured cells, which is crucial for cell biology studies.
更新于2025-11-25 10:30:42
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Surface plasmon resonance of naked gold nanoparticles for photodynamic inactivation of Escherichia coli
摘要： Although antimicrobial photothermal inactivation of naked gold nanostructures using powerful pulsed lasers has been previously studied, there are little reports about their photodynamic antimicrobial properties under the irradiation of low-power density continuous wave lasers. Therefore, this paper attempts to fill this gap. In this paper, we studied the effects of a 40-mW/cm2 continuous Nd:Yag laser at 532 nm and naked gold nanoparticles on inactivation of Escherichia coli ATCC25922. According to our results, 60 min illumination using the Nd:Yag laser caused a 0.15log reduction of the bacterial viability. Also, the employed gold nanoparticles with an average size of 15 nm were toxic to E. coli ATCC 25922 in the concentrations above 0.5 μg/ml. In addition, synergistic effects of 0.5 μg/ml gold nanoparticles and the light illumination led to a 2.43log reduction of the viability after a 60-min exposure and did not show any considerable temperature change on the media. The obtained results were justified based on the possible interaction mechanisms of low-power density laser lights and naked gold nanoparticles. The paper is proposed as a prelude for future research about localized inactivation of resistant pathogens with minimum side effects on neighbor tissues.
关键词： Photodynamic inactivation,Gold nanoparticles,Low-power density laser,Surface plasmon resonance
更新于2025-11-25 10:30:42
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Tailoring the collagen film structural properties via direct laser crosslinking of star-shaped polylactide for robust scaffold formation
摘要： Application of restructured collagen-based biomaterials is generally restricted by their poor mechanical properties, which ideally must be close to those of a tissue being repaired. Here, we present an approach to the formation of a robust biomaterial using laser-induced curing of a photosensitive star-shaped polylactide. The created collagen-based structures demonstrated an increase in the Young’s modulus by more than an order of magnitude with introduction of reinforcing patterns (from 0.15±0.02 MPa for the untreated collagen to 51.2±5.6 MPa for the reinforced collagen). It was shown that the geometrical configuration of the created reinforcing pattern affected the scaffold’s mechanical properties only in the case of a relatively high laser radiation power density, when the effect of accumulated thermomechanical stresses in the photocured regions was significant. Photo-crosslinking of polylactide did not compromise the scaffold’s cytotoxicity and provided fluorescent regions in the collagen matrix, that create a potential for noninvasive monitoring of such materials’ biodegradation kinetics in vivo.
关键词： mechanical properties,collagen,reinforcements,photopolymerization,biocompatible polymers,riboflavin
更新于2025-11-21 11:24:58
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Negative charge enhancement of near-surface nitrogen vacancy centers by multicolor excitation
摘要： Nitrogen vacancy (NV) centers in diamond have been identified over the past few years as promising systems for a variety of applications, ranging from quantum information science to magnetic sensing. This relies on the unique optical and spin properties of the negatively charged NV. Many of these applications require shallow NV centers, i.e., NVs that are close (a few nm) to the diamond surface. In recent years there has been increasing interest in understanding the spin and charge dynamics of NV centers under various illumination conditions, specifically under infrared (IR) excitation, which has been demonstrated to have significant impact on the NV centers’ emission and charge state. Nevertheless, a full understanding of all experimental data is still lacking, with further complications arising from potential differences between the photodynamics of bulk and shallow NVs. Here we suggest a generalized quantitative model for NV center spin- and charge-state dynamics under both green and IR excitation. We experimentally extract the relevant transition rates, providing a comprehensive model which reconciles all existing experimental results in the literature, except for highly nonlinear regimes. Moreover, we identify key differences between the photodynamics of bulk and shallow NVs, and use them to significantly enhance the initialization fidelity of shallow NVs to the useful negatively charged state.
关键词： nitrogen vacancy centers,recombination,shallow NVs,bulk NVs,photodynamics,green excitation,ionization,charge state,IR excitation,diamond
更新于2025-09-23 15:23:52
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Noninvasive optical activation of Flp recombinase for genetic manipulation in deep mouse brain regions
摘要： Spatiotemporal control of gene expression or labeling is a valuable strategy for identifying functions of genes within complex neural circuits. Here, we develop a highly light-sensitive and efficient photoactivatable Flp recombinase (PA-Flp) that is suitable for genetic manipulation in vivo. The highly light-sensitive property of PA-Flp is ideal for activation in deep mouse brain regions by illumination with a noninvasive light-emitting diode. In addition, PA-Flp can be extended to the Cre-lox system through a viral vector as Flp-dependent Cre expression platform, thereby activating both Flp and Cre. Finally, we demonstrate that PA-Flp–dependent, Cre-mediated Cav3.1 silencing in the medial septum increases object-exploration behavior in mice. Thus, PA-Flp is a noninvasive, highly efficient, and easy-to-use optogenetic module that offers a side-effect-free and expandable genetic manipulation tool for neuroscience research.
更新于2025-09-23 15:22:29
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Bi <sub/>2</sub> SiO <sub/>5</sub> @g-SiO <sub/>2</sub> upconverting nanoparticles: a bismuth-driven core–shell self-assembly mechanism
摘要： Core–shell systems have attracted increasing interest among the research community in recent years due to their unique properties and structural features, and the development of new synthetic strategies is still a challenge. In this work, we have investigated lanthanide-doped Bi2SiO5 nanocrystal formation inside mesoporous silica nanoparticles (MSNs). The role of both synthesis temperature and concentration of the bismuth precursor impregnated into the MSNs is discussed, showing an unprecedented strategy for the simultaneous stabilization of a crystalline core and a glassy shell. Temperature dependent synchrotron radiation X-ray powder diffraction (SR-XRPD) and high resolution transmission electron microscopy (HR-TEM) analyses allow one to follow the crystalline core growth. A mechanism for the formation of a Bi2SiO5@g-SiO2 core–shell nanosystem is proposed. In addition, the easy tunability of the color output of the upconverting system is demonstrated by means of suitable doping lanthanide ions with potential applications in several fields.
关键词： upconversion luminescence,mesoporous silica,core–shell nanoparticles,bismuth silicate,Bi2SiO5
更新于2025-09-19 17:15:36