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Preparation and Two-Photon Photoluminescence Properties of Organic Inorganic Hybrid Perovskites (C6H5CH2NH3)2PbBr4 and (C6H5CH2NH3)2PbI4
摘要： Organic inorganic hybrid perovskites have potential applications in solar cells, electroluminescent devices and radiation detection because of their unique optoelectronic properties. In this paper, the perovskites (C6H5CH2NH3)2PbBr4 and (C6H5CH2NH3)2PbI4 were synthesized by solvent evaporation. The crystal structure, morphology, absorption spectrum, laser power dependence of the photoluminescence (PL) intensity and lifetime were studied. The results showed that the perovskites (C6H5CH2NH3)2PbBr4 and (C6H5CH2NH3)2PbI4 display a layered stacking structure of organic and inorganic components. The absorption peaks are located at 392 nm (3.16 eV) and 516 nm (2.40 eV), respectively. It was observed that the PL intensity and photoluminescence quantum yield (PLQY) increases with increasing laser power, and that the PL lifetime decreases with increasing laser power, which is mainly due to the non-geminate recombination.
关键词： perovskites,photoluminescence lifetime,two-photon excitation,photoluminescence spectrum
更新于2025-09-09 09:28:46
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A Mixed-Ligand Metal-Organic Framework for Two-Photon Responsive Photocatalytic C-N and C-C Coupling Reactions
摘要： Multiple-photon photochemical process breaks the existing energy limitation of visible-light photocatalysis. Through careful incorporation of both bis(3,5-dicarboxyphenyl)-pyridine and bis(3,5-dicarboxyphenyl)methylpyridinium ligands into a single metal?organic framework, we reported herein photocatalytic C?N and C?C oxidative coupling reactions that evidenced the direct two-photon response process. Time-dependent luminescence decays studies demonstrated that the framework reached the same excited state by a two-photon absorption process as that reached via a single-photon absorption process, and the excited state could activate substrates even under NIR light irradiation. Under a 660 nm LEDs irradiation, both the photooxidative C?N coupling reaction of benzylamine to form benzylidene-1-phenylmethanamine, and the C?C coupling reaction between nitromethane and N-phenyl-trtrahydroisoquinoline were accelerated directly in a heterogeneous manner. Control experiments suggested that the minimal by-products were formed under the NIR light irradiation comparing to those of the UV light catalytic reactions. Importantly, photon intensity-dependent studies exhibited a nonlinear correlation between catalytic efficiency of MTV-MOFs and photon power intensity, verifying the two-photon responsive nature, which indicated that metal?organic framework with high-density and ordered photoactive motifs could enhance the two-photon absorption ability, thereby improve photocatalytic efficiency even under LEDs irradiation.
关键词： coupling reactions,two-photon photocatalysis,metal?organic framework,nonlinear optics,visible-light
更新于2025-09-09 09:28:46
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Nonlinear emission from silver-coated 3D hollow nanopillars
摘要： High aspect ratio metal nanostructures have been the subject of a number of studies in the past, due to their pronounced resonances in the infrared that can be exploited to enhance vibrational spectroscopies. In this work, we investigate the nonlinear optical response of both individual and closely-packed assemblies of vertical hollow Ag nanopillars upon excitation with ultrafast laser pulses. In particular, the analysis of their nonlinear emission spectra evidences an intense two photon photoluminescence (TPPL) emission and a neat signature of second harmonic generation (SHG). Given the relatively low background, this pronounced nonlinear emission could be employed as a local probe for analytes trapped at the surface of the nanopillar or flowing through it. For this reason, these nanostructures may become appealing building blocks in multi-purpose devices for nonlinear photonics and sensing.
关键词： Two Photon Photoluminescence,Ag Nanopillars,Localized Surface Plasmons,3D nanofabrications,Second Harmonic Generation
更新于2025-09-09 09:28:46
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Isomerism and coordination mode effects on two-photon absorption of tris(picolyl)amine-based fluorescent probes for zinc ions
摘要： One-photon absorption and two-photon absorption (TPA) properties of three tris(picolyl)amine-based zinc ion sensors are investigated by employing the density functional response theory in combination with the polarizable continuum model. The different isomer and coordination geometry of each probe are taken into account. Special emphasis is placed on the effects of isomerism and the coordination mode on the optical properties. The intra-molecular charge transfer (ICT) properties are specified by natural bond orbital charge analysis. It is shown that the isomerism has non-negligible effects on TPA properties of free ligands. It is found that both the TPA wavelength and the cross section are highly dependent on the coordination mode. When the zinc ion connects with the picolyl unit in the middle of a ligand, the zinc complex has a large TPA intensity in a long wavelength range due to the increased ICT mechanism.
关键词： isomerism,zinc ion,coordination mode,two-photon absorption
更新于2025-09-09 09:28:46
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surface alloy
摘要： We have investigated the atomic and electronic structure of the (√3×√3)R30? SnAu2/Au(111) surface alloy. Low-energy electron diffraction and scanning tunneling microscopy measurements show that the native herringbone reconstruction of bare Au(111) surface remains intact after formation of a long-range ordered (√3×√3)R30? SnAu2/Au(111) surface alloy. Angle-resolved photoemission and two-photon photoemission spectroscopy techniques reveal Rashba-type spin-split bands in the occupied valence band with comparable momentum space splitting as observed for the Au(111) surface state, but with a hole-like parabolic dispersion. Our experimental findings are compared with density functional theory (DFT) calculation that fully support our experimental findings. Taking advantage of the good agreement between our DFT calculations and the experimental results, we are able to extract that the occupied Sn-Au hybrid band is of (s, d )-orbital character, while the unoccupied Sn-Au hybrid bands are of (p, d )-orbital character. Hence we can conclude that the Rashba-type spin splitting of the hole-like Sn-Au hybrid surface state is caused by the significant mixing of Au d with Sn s states in conjunction with the strong atomic spin-orbit coupling of Au, i.e., of the substrate.
关键词： angle-resolved photoemission spectroscopy,density functional theory,SnAu2/Au(111) surface alloy,Rashba-type spin splitting,two-photon photoemission spectroscopy
更新于2025-09-09 09:28:46
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Two-photon decay of P-wave positronium: a tutorial
摘要： A detailed exposition of two-photon decays of P-wave positronium is given to fill an existing gap in the pedagogical literature. Annihilation decay rates of P-wave positronium are negligible compared to the rates of radiative electric dipole transitions to the lower energy S-states. This circumstance makes such decays experimentally inaccessible. However the situation is different for quarkonium and the experimental and theoretical research of two-photon and two-gluon decays of P-wave quarkonia is a still flourishing field.
关键词： two-photon decays,quarkonium,P-wave positronium,annihilation decay rates,pedagogical literature
更新于2025-09-09 09:28:46
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Endogenous Fluorophores Enable Two-Photon Imaging of the Primate Eye
摘要： Noninvasive two-photon imaging of a living mammalian eye can reveal details of molecular processes in the retina and RPE. Retinyl esters and all-trans-retinal condensation products are two types of retinoid fluorophores present in these tissues. We measured the content of these two types of retinoids in monkey and human eyes to validate the potential of two-photon imaging for monitoring retinoid changes in human eyes.
关键词： primate retina,retinoid cycle,two-photon microscopy,rod photoreceptors,cone photoreceptors
更新于2025-09-09 09:28:46
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[Polymers and Polymeric Composites: A Reference Series] Functional Polymers || Photo-polymerization
摘要： The synthesis of functional polymers by photopolymerization thrives on the rich tradition of industrial photochemistry. Photo-induced polymerization can be broadly divided based on the initiation mechanism as radical, cationic, and anionic photopolymerization. A wide variety of initiators, photosensitizers, and polymerizable materials have been studied for various applications. This chapter is intended to be a primer to major concepts of photopolymerization. In the beginning of the chapter, physical aspects of light matter interactions are presented followed by photochemical pathways leading to reactions. In the subsequent sections radical polymerization is discussed by introducing different types of initiating systems and polymerizable materials. Within the section on radical polymerization, visible light polymerization and thio-ene photochemistry are also discussed. The section on thiol-ene looks at the fundamentals of thiol-ene reactions, their initiation, reactivity, and advantages over other radical driven polymerizations. Cationic polymerization is covered based on the material science of ionic and nonionic photoacid generators (PAGs). This section also discusses spectral broadening of reactivity in PAGs to visible wavelengths through electron transfer sensitization and free radical promoted cationic polymerization (FRPCP). Unlike radical and cationic polymerization there are little or no reports of commercial application of anionic polymerization. However, due to typical monomers employed in anionic polymerization and the control over the extent of polymerization afforded by this techniques makes it very attractive for functional applications. The section on anionic polymerization summarizes recent developments in this field. Finally in the section about two-photon initiated polymerization, we discuss the scope of nonlinear optical phenomena in photopolymerization.
关键词： anionic polymerization,radical polymerization,two-photon absorption,photopolymerization,photoinitiators,photosensitizers,cationic polymerization
更新于2025-09-09 09:28:46
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A series of two-photon absorption organotin (IV) cyano carboxylate derivatives for targeting nuclear and visualization of anticancer activities
摘要： Compared to organotin (IV) compounds with biochemical activity, two-photon absorption (2PA) organotin (IV) complexes for targeting nuclear with anticancer activities are rarely reported. Here, two novel 2PA organotin (IV) cyano carboxylate complexes (C1Sn-1, C1Sn-2) are synthesized and characterized. The two-photon absorption cross section values (δ) in the near-infrared region are significantly enhanced for C1Sn-2 compared to C1Sn-1, thus developing for targeting nuclear by two-photon fluorescence microscopy (2PFM). C1Sn-2 could specifically target nuclear DNA in vitro. The mechanism demonstrated that there are abundant hydrogen bond interactions between hydroxy group of C1Sn-2 and DNA. The animal mode studies are first proposed that C1Sn-2 displayed a certain anti-cancer efficiency with non-significant toxicity.
关键词： anticancer,organotin,two-photon absorption
更新于2025-09-09 09:28:46
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Fully Convolutional DenseNets for Segmentation of Microvessels in Two-photon Microscopy*
摘要： Segmentation of microvessels measured using two-photon microscopy has been studied in the literature with limited success due to uneven intensities associated with optical imaging and shadowing effects. In this work, we address this problem using a customized version of a recently developed fully convolutional neural network, namely, FC-DensNets. To train and validate the network, manual annotations of 8 angiograms from two-photon microscopy was used. Segmentation results are then compared with that of a state-of-the-art scheme that was developed for the same purpose and also based on deep learning. Experimental results show improved performance of used FC-DenseNet in providing accurate and yet end-to-end segmentation of microvessels in two-photon microscopy.
关键词： deep learning,two-photon microscopy,FC-DenseNets,microvessels,Segmentation
更新于2025-09-09 09:28:46