Numerical Simulation of Photothermal Lens Spectrometry Models Relevant for Analytical Chemistry

Three numerical models (radial symmetry two-dimensional and three-dimensional with cw and pulsed excitation) that correspond to the samples and schematics of dual-beam thermal lens measurements in solution most commonly used in chemical analysis are implemented by finite element analysis using COMSOL Multiphysics and geometry simulations using MATLAB. The comparison of the results obtained using the implemented models with the existing infinite two-dimensional model by Shen and Snook (J Appl Phys 73(10):5286, 1993.  https://doi.org/10.1063/1.353761) under the same conditions showed their good agreement. The models were used to study the influence of the basic geometric and physical parameters of the sample. Conditions are found under which the boundary conditions for heat transfer and the geometrical parameters of the cell have the strongest and weakest effects on the signal.     

Super‐Resolution Nonlinear Photothermal Microscopy

Super‐resolution fluorescence microscopy enables imaging of fluorescent structures beyond the diffraction limit. However, this technique cannot be applied to weakly fluorescent cellular components or labels. As an alternative, photothermal microscopy based on nonradiative transformation of absorbed energy into heat has demonstrated imaging of nonfluorescent structures including single molecules and ~1‐nm gold nanoparticles. However, previously photothermal imaging has been performed with a diffraction‐limited resolution only. Herein, super‐resolution, far‐field photothermal microscopy based on nonlinear signal dependence on the laser energy is introduced. Among various nonlinear phenomena, including absorption saturation, multiphoton absorption, and signal temperature dependence, signal amplification by laser‐induced nanobubbles around overheated nano‐objects is explored. A Gaussian laser beam profile is used to demonstrate the image spatial sharpening for calibrated 260‐nm metal strips, resolving of a plasmonic nanoassembly, visualization of 10‐nm gold nanoparticles in graphene, and hemoglobin nanoclusters in live erythrocytes with resolution down to 50 nm. These nonlinear phenomena can be used for 3D imaging with improved lateral and axial resolution in most photothermal methods, including photoacoustic microscopy.     

直接吸收式太阳能集热纳米流体光热特性研究

采用两步法配制了Co-H2O纳米流体,针对不同粒径、不同质量分数、不同pH值的纳米流体,与去离子水一起同步测试了其光热转换特性。实验结果表明:纳米流体的温升速率及集热量明显优于去离子水的。纳米流体质量分数有一最佳值,实验中质量分数为0.1%时效果最好,其最高温度要比纯水高出30.3%。30 nm Co-H2O纳米流体的光吸收能力要强于50 nm Co-H2O纳米流体的。pH值对光热特性有较大影响,实验中p H=8效果最佳。Co-H2O纳米流体优异的光吸收性能表明其有望运用在直接吸收式太阳能系统中。     

Photothermal Ring Integrated Intraocular Lens for High‐Efficient Eye Disease Treatment

Posterior capsule opacification (PCO) is the most common complication after cataract surgery. So far, the only method for PCO treatment is the precisely focused laser surgery. However, it causes severe complications such as physical damages and neuron impairments. Here, a nanostructured photothermal ring integrated intraocular lens ( Nano‐IOLs ) is reported, in which the rim of commercially available IOLs ( C‐IOLs ) is decorated with silica coated Au nanorods (Au@SiO₂), for high‐efficient prevention of PCO after cataract surgery. The Nano‐IOLs is capable of eliminating the residual lens epithelial cells (LECs) around Nano‐IOLs under mild laser treatment and block the formation of disordered LECs fibrosis, which eventually leads to the loss of vision. The Nano‐IOLs shows good biocompatibility as well as extraordinary region‐confined photothermal effect. In vivo studies reveal that PCO occurrence in rabbit models is about 30%–40% by using Nano‐IOLs , which is significantly lower than the control group that treated with C‐IOLs (100% PCO occurrence) 30 d postsurgery. To the best of our knowledge, it is the first example to integrate nanotechnology with intraocular implants aiming to clinically relevant PCO. Our findings indicate that spatial controllability of photothermal effect from nanomaterials may provide a unique way to intervene the PCO‐induced loss of vision.     

气溶胶光热干涉测量系统激发参数研究

气溶胶吸收直接影响光在大气中的传播造成光的衰减。本文采用折返式Jamin偏振干涉结构建立了气溶胶光热干涉实验系统,提出并实验研究了在激光照射(加热)和降温两个阶段分别测量吸收系数的方法,确定了两种方法测量气溶胶吸收系数的激发激光功率,为进一步开展气溶胶吸收系数的实验研究提供了参数支持。     

Characterization of an Optimized Nonlinear Joint Transform Correlator

Abstract

The performance of a nonlinear joint transform correlator which employs a GEC-Marconi optically addressed spatial light modulator in the Fourier plane is investigated in terms of the device operating conditions and other system parameters. We discuss the optimum performance characteristics of the correlator and the sensitivity to changes in the rotation, scale and separation of the objects in the input plane.     

Separation of Optical Thin Film and Substrate Absorption by Obliquely-crossed Photothermal Deflection: Theory

Abstract

An explicit three-dimensional calculation of c.w. modulated photothermal deflection (PTD) with obliquely crossed geometry, including optical thin film and substrate absorption, has been presented. Theoretical results show that the obliquely crossed PTD technique is feasible to separate the thin film and substrate absorption, and to measure low thin film absorption under high substrate absorption by appropriately adjusting the cross-point position of the excitation and probe beams. Measurement of the thin film absorption is not affected by the thermal properties of the substrate. The obliquely crossed PTD also provides a method for real-time monitoring of thin film generation.     

Determination of the Exciton Binding Energy Using Photothermal and Photoluminescence Spectroscopy

In this paper, experimental photoluminescence (PL) and piezoelectric photothermal (PPT) spectra of selected II–VI binary crystals are presented and analyzed. The quantitative analysis of the photothermal spectra was performed using a modified and extended Jackson–Amer model. The values of the bandgap energies of investigated semiconductors were computed from the PT amplitude and phase spectra. From the temperature dependence of the exciton emission so-called “excitonic energy gaps” have been determined. It follows from the theory that the exciton binding energy is the difference of these two values of energy gaps derived from PPT and PL spectroscopy.     

Copper Chloride Nonlinear Optical Absorption under Quantum Confinement

Abstract

With the aid of two independently tunable lasers the influence has been studied of optical excitation on light absorption in the Z₃-band of CuCl crystals with size 25–75 Å in a glass matrix. It has been found that resonance pumping leads to a significant blue shift of the band caused by the interaction of excitations under quantum confinement. Interband excitation with intensity up to 0·3 GW cm^?2 does not affect the exciton absorption.     

Absorption spectrum (340-640 nm) of pure water. I. Photothermal measurements

We measured the absorption spectrum (340-640 nm) of the purest available water with photothermal deflection spectroscopy. Our spectrum exhibits an absorption minimum in the blue region of the spectrum that is deeper than in most previously documented pure-water absorption studies. We attribute this to exceptional sample purity and our technique's inherent freedom from scattering effects. Because the absorption minimum is significantly lower, our spectrum displays high-order molecular resonance structure not observed in any previous absorption studies to our knowledge. We find the minimum in the absorption spectrum of pure water is 0.0062 ? 0.0006 m(-1) at 420 nm and 25 degrees C.     

Thermal Lens Spectrometric Determination of Colloidal and Ionic Silver in Water

Collinear dual beam thermal lens spectrometric (TLS) detection, combined with flow injection analysis (FIA), was developed and applied to determine simultaneously concentrations of ionic and colloidal silver in the Russian drinking water supplies of the International Space Station (ISS). The newly developed method is based on on-line generation of silver colloids by sodium borohydride (NaBH₄). The generated silver nanoparticles exhibit an absorption maximum close to 400 nm, which enables their excitation with a 407 nm line of a Kr laser offering a very sensitive TLS detection scheme with impressive limits of detection (LOD) of 1.5μg · L⁻¹. Ionic and colloidal silver present initially in the sample can be discriminated by performing the measurements with and without NaBH₄.     

Free Boundary Determination in Nonlinear Diffusion

Free boundary problems with nonlinear diffusion occur in various applications, such as solidification over a mould with dissimilar nonlinear thermal properties and saturated or unsaturated absorption in the soil beneath a pond. In this article, we consider a novel inverse problem where a free boundary is determined from the mass/energy specification in a well-posed one-dimensional nonlinear diffusion problem, and a stability estimate is established. The problem is recast as a nonlinear least-squares minimisation problem, which is solved numerically using the lsqnonlin routine from the MATLAB toolbox. Accurate and stable numerical solutions are achieved. For noisy data, instability is manifest in the derivative of the moving free surface, but not in the free surface itself nor in the concentration or temperature.     

Determination of Thin-film Absorption Coefficients from Photoacoustic Data

Abstract

A photoacoustic measurement technique is described to obtain absorption coefficients of PbF₂ layers. Different deposition conditions have been investigated and the evaporation parameters producing the least absorption are given.     

Photothermal Beam Deflection Spectroscopy for the Determination of Thermal Diffusivity of Soils and Soil Aggregates

Photothermal beam deflection spectroscopy (BDS) with a red He–Ne laser (632.8 nm, 35 mW) as an excitation beam source and a green He–Ne laser (543.1 nm, 2 mW) as a probe was used for estimating thermal diffusivity of several types of soil samples and individual soil aggregates with small surfaces (2?×?2 mm). It is shown that BDS can be used on demand for studies of changes in properties of soil entities of different hierarchical levels under the action of agrogenesis. It is presented that BDS clearly distinguishes between thermal diffusivities of different soil types: Sod-podzolic [Umbric Albeluvisols, Abruptic], 29?±?3; Chernozem typical [Voronic Chernozems, Pachic], 9.9?±?0.9; and Light Chestnut [Haplic Kastanozems, Chromic], 9.7?±?0.9 cm²·h^?1. Aggregates of chernozem soil show a significantly higher thermal diffusivity compared to the bulk soil. Thermal diffusivities of aggregates of Chernozem for virgin and bare fallow samples differ, 53?±?4 cm²·h^?1 and 45?±?4 cm²·h^?1, respectively. Micromonoliths of different Sod-podzolic soil horizons within the same profile (topsoil, depth 10–14 cm, and a parent rock with Fe illuviation, depth 180–185 cm) also show a significant difference, thermal diffusivities are 9.5?±?0.8 cm²·h^?1 and 27?±?2 cm²·h^?1, respectively. For soil micromonoliths, BDS is capable to distinguish the difference in thermal diffusivity resulting from the changes in the structure of aggregates.     

均匀设计法优化聚乙烯醇/甲基纤维素薄膜吸湿性的研究

为优化薄膜的制备工艺,采用均匀设计法,对聚乙烯醇(PVA)/甲基纤维素(MC)薄膜吸湿性进行了研究。试验以PVA/MC的体积比、甘油含量、pH、戊二醛浓度为考察因素,以吸湿率为考察指标,建立了4因素7水平均匀设计试验,应用SPSS软件对数据进行了多元一次回归分析。结果表明:影响薄膜吸湿性的因素主次顺序为戊二醛浓度甘油含量体积比pH;当PVA与MC体积比为2:1,甘油含量为0.11mL/(100mL),pH为3.06,交联剂浓度为2.26×10-4 mol/L时,制得的薄膜吸湿率为2.68,抗张强度为42.17MPa,伸长率为48.2%,性能较优。     

Two-photon Absorption and Nonlinear Optical Properties of A New Organic Dye DEASPI

A new organic dye trans-4- [p-(N,N-diethylamino) styryl]-N-methylpyridinium iodide (abbreviated' as DEASPI thereafter) with large two-photon absorption (TPA) cross section and excellent upconverted lasing properties was synthesized. The melting point and decompound point were measured to be 230 degreesC and 264.7 degreesC respectively. The molecular TPA cross section was measured to be sigma (2)=6.9x10(-48) cm(4).s/photon at 1064 nm by using an open aperture Z-scan system. The linear and nonlinear optical properties of this dye were systematically studied. The highest net upconversion efficiency from the absorbed pump energy to the output upconverted lasing energy is as high as 18.6% at the pump energy of 2.17 mJ from a mode-locked Nd:YAG ps laser. The nonlinear transmittance at the wavelengths from 720 to 1100 nm was measured. The dye solution also shows a clear optical power limiting effect.     

The Determination of the Absorption Coefficient of Luminescent Microcrystals

The absorption and luminescence emission of single Zn-type microcrystals was investigated. A photoelectric microscope photometer was built which consists of a Zeiss microscope and a 931 A multiplier phototube. Evaluating the results of absorption measurements, neither a plane-parallel, nor a spherical crystal model furnished reliable results for the absorption coefficient. The application of an empirical model, based on the non-absorbed radiation (5 770 Å) made possible the determination of the ultraviolet absorption coefficient by comparing the transmission of single microcrystals for different wavelengths. The method was experimentally checked on K₂Cr₂O₇ crystals. The ultraviolet absorption coefficient of luminescent microcrystals may also be determined from the dependence of the light emission on the particle size. On étudie ici l'absorption et l'émission luminescente d'un microcristal simple de Zn-type. Un microphotomètre photoélectrique a été construit dans ce but, à partir d'un microscope Zeiss et d'une cellule photomultiplicatrice 931 A. L'interprétation des mesures d'absorption n'a donné de résultats valables ni pour un cristal plan parallèle ni pour un cristal sphérique. L'utilisation d'un modèle empirique, basé sur la radiation non absorbée (5 770 Å) a rendu possible la détermination de coefficient d'absorption de l'ultraviolet, par comparaison avec la transmission de quelques microcristaux pour différentes longueurs d'onde. La méthode a été appliquée expérimentalement pour des cristaux de K₂Cr₂O₇. Le coefficient d'absorption de l'ultraviolet de micro-cristaux luminescents peut aussi être déterminé en relation avec l'émission lumineuse de la particule. Die Absorption und Lumineszenzstrahlung eines einzelnen Mikrokristalls vom Zn-Typ wurde untersucht. Hierzu wurde ein elektrisches Mikrophotometer aus einem Zeiss-Mikroskop und einem Multiplier 931 A zusammengestellt. Bei der Auswertung der Absorptionsmessungen ergeben sich aber weder für eine planparallele Platte noch für einen sphärischen Modellkristall zuverlässige Werte des Absorptionskoeffizienten. Erst die Verwendung eines empirischen Modelles, das von der nicht absorbierten Strahlung (5 770 Å) ausgeht, machte es möglich, den Absorptionskoeffizienten im Ultraviolett zu bestimmen, indem man die Durchlässigkeit einzelner Mikrokristalle für verschiedene Wellenlängen vergleicht. Die Methode wurde experimentell an K₂Cr₂O₇-Kristallen erprobt. Der Absorptionskoeffizient im Ultraviolett kann bei einem lumineszierenden Mikrokristall auch aus der Abhängigkeit der Lichtemission von der Teilchengrösse ermittelt werden.     

氢化物发生-原子吸收光谱法测定金银花中的痕量铅

目的:研究了氢化物发生-原子吸收光谱法测定金银花中的铅的反应体系;方法:使用氢化物发生-原子吸收光谱法;结果:相对标准偏差小于(RSD,n=7)小于1.723%,回收率为95.38%~108.67%,检出限为6.1×10-10;结论:方法具有快速、准确、灵敏度高、经济实用等优点,用于金银花中铅的测定,结果令人满意。