Photothermal Probe Research Articles

The Development of a Photothermal Immunochromatographic Lateral Flow Strip for Rapid and Sensitive Detection of Bisphenol A in Food Samples

A novel quantitative photothermal-sensing immunochromatographic assay (PT-ICA) with high sensitivity was developed for the detection of bisphenol A (BPA). Gold acid chloride trihydrate (HAuCl4·3H2O) was first reduced by citric acid trisodium salt (C6H5Na3O7) to form Au nanoparticles and adsorbed on the surface of black phosphorus nanosheets to form a black phosphorus-Au (BP-Au) complex. The antibody against BPA was then coupled to the BP-Au complex to form the black phosphorus-Au-antibody (BP-Au-Ab) photothermal probe for capturing BPA in samples. During the detection, the precoated antigen BPA-bovine serum albumin (BPA-BSA) on the T line and free BPA molecules in the sample would competitively bind to the limited BP-Au-Ab photothermal probes. After that, the exothermic process under an 808-nm laser was recorded using an infrared thermal imager, which represented the concentration of BPA in the samples. The PT-ICA demonstrated high sensitivity with a limit detection of 0.24 ng/mL, which was 6.25 times lower than that of the visual-ICA. In addition, the assays were highly specific, only minor cross-sensitivity occurred between BPA and 4-cumylphenol. The optimized assay was applied in the detection of BPA in different food samples with recoveries ranging from 75.91 to 119.59%. Finally, the PT-ICA was verified using a commercial enzyme-linked immunosorbent assay (ELISA) kit. The results of the developed assay showed good agreement with that of the ELISA kit. The optimized PT-ICA required a shorter detection time (approximately 30 min) than the ELISA kit (approximately 2 h), which has potential applications in the detection field.

A bio-bar-code photothermal probe triggered multi-signal readout sensing system for nontoxic detection of mycotoxins

Herein, a photothermal triggered multi-signal readout (MSR) system was innovatively established with great convenience for low-cost and sensitive point-of-care testing (POCT). In this sensing system, an intelligent multi-signal readout interface (MSRI) with multidimensional response-ability to thermal stimulus was developed and utilized as a sensing element. A bio-bar-code photothermal probe peptides@H2N-HCNTs acted as a target associated photothermal agent anchored on MSRI via competitive reaction. The multi-signal assay of target was realized under the driven of 808 nm laser, photo-to-thermal conversion effect of photothermal probe caused dramatically thermal energy increase on MSRI. As a result, the competitive recognition events were translated into several detectable signals on MSRI, including a local temperature elevation, a visual color change from blue to green as well as weight loss on MSRI, all of these signals were proportional to the target concentration. This assay has been successfully applied in field work for detecting zearalenone (ZEN), a common mycotoxin in grain food, with linear ranger from 10−7 ng/mL to 10−1 ng/mL and detection limits of 1.06 × 10−7 ng/mL. Combination of the different signal principles was expected to result in more reliable and precise results. Accordingly, this creatively designed MSR-system not only provided a platform for sensitive monitor of mycotoxin but also offered new method for reliable and affordable personal assays in daily life and low-resource setting.

Photothermal and colorimetric dual mode detection of nanomolar ferric ions in environmental sample based on in situ generation of prussian blue nanoparticles

Iron ions play a key role in many physiological processes, which can provide feedback for the evaluation of biological systems and environmental processes. New strategies for portable determination of Fe3+ therefore are still in urgent need. Here, through an in situ generation of prussian blue nanoparticles (PB NPs) in aqueous solution, we developed a bimodal method for photothermal and colorimetric detection of Fe3+. The sensing mechanism is based on the effective oxidation etching of Au–Cu core-shell nanocubes induced by Fe3+, accompanied by the in situ generation of PB NPs. It can be attributed to the specific reaction between ferrous ions (Fe2+) from the reduction of Fe3+ and potassium ferricyanide (K3[Fe(CN)6]) in the reaction solution. The in situ produced PB NPs show distinct bare-eye-detectable readouts with highly sensitive colorimetric and photothermal responses and thus can be used for Fe3+ determination. Such colorimetric change signals of characteristic absorbance at 740 nm in the UV–vis spectra showed a sensitive response to Fe3+ with a LOD of 210 nM. Moreover, as a sensitive photothermal probe, PB NPs generated in our Fe3+-enabled reaction system also exhibited a sensitive response to Fe3+ with a LOD of 70 nM. In addition, the standard addition experiments demonstrate our photothermal and colorimetric probe has good applicability for Fe3+ detection in the river water sample. What’s more, the proposed strategy opens a new horizon for affordable detection of metal ions using a common thermometer, and therefore has a great potential for analytical chemistry and some important applications such as environmental monitoring, disease diagnostics and food analysis.

Colorimetric and photothermal dual-mode immunoassay for tumour marker detection based on a Ag2CO3@Ag nanocomposite

Abstract Under the limitations of advanced instruments and professional operations, straightforward readouts play an increasingly vital role in immunoassays. Herein, a Ag2CO3@Ag nanocomposite-mediated colorimetric and photothermal immunoassay was developed to detect carcinoembryonic antigen (CEA). The Ag2CO3@Ag nanocomposites could oxidize 3,3’,5,5’-tetramethylbenzidine to form blue oxidation products (TMBox) due to the acidic dissolution of Ag2CO3 under acidic conditions. TMBox presented a strong photothermal effect driven by a near-infrared (NIR) laser. Therefore, TMBox could act as a photothermal probe to convert immunoassay signals into thermal signals. The Ag2CO3@Ag nanocomposite was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). Then, a sandwich-type immunoassay was built on the surface of a magnetic bead, and CEA was quantified using a common thermometer based on the photothermal effect. Under optimal conditions, the temperature increased with increase of CEA concentrations in the range of 0.1 ng/mL–5 ng/mL. More importantly, this system exhibited high selectivity, good repeatability and outstanding stability.

Thermoplasmonic Effect of Surface-Enhanced Infrared Absorption in Vertical Nanoantenna Arrays

Thermoplasmonics is a method for increasing temperature remotely using focused visible or infrared laser beams interacting with plasmonic nanoparticles. Here, local heating induced by mid-infrared quantum cascade laser illumination of vertical gold-coated nanoantenna arrays embedded into polymer layers is investigated by infrared nanospectroscopy and electromagnetic/thermal simulations. Nanoscale thermal hotspot images are obtained by a photothermal scanning probe microscopy technique with laser illumination wavelength tuned at the different plasmonic resonances of the arrays. Spectral analysis indicates that both Joule heating by the metal antennas and surface-enhanced infrared absorption (SEIRA) by the polymer molecules located in the apical hotspots of the antennas are responsible for thermoplasmonic resonances, that is, for strong local temperature increase. At odds with more conventional planar nanoantennas, the vertical antenna structure enables thermal decoupling of the hotspot at the antenna apex ...

Exploration of Nanoparticle-Mediated Photothermal Effect of TMB-H2O2 Colorimetric System and Its Application in a Visual Quantitative Photothermal Immunoassay.

The exploration of new physical and chemical properties of materials and their innovative application in different fields are of great importance to advance analytical chemistry, material science, and other important fields. Herein, we, for the first time, discovered the photothermal effect of an iron oxide nanoparticles (NPs)-mediated TMB (3,3',5,5'-tetramethylbenzidine)-H2O2 colorimetric system, and applied it toward the development of a new NP-mediated photothermal immunoassay platform for visual quantitative biomolecule detection using a thermometer as the signal reader. Using a sandwich-type proof-of-concept immunoassay, we found that the charge transfer complex of the iron oxide NPs-mediated one-electron oxidation product of TMB (oxidized TMB) exhibited not only color changes, but also a strong near-infrared (NIR) laser-driven photothermal effect. Hence, oxidized TMB was explored as a new sensitive photothermal probe to convert the immunoassay signal into heat through the near-infrared laser-driven photothermal effect, enabling simple photothermal immunoassay using a thermometer. Based on the new iron oxide NPs-mediated TMB-H2O2 photothermal immunoassay platform, prostate-specific antigen (PSA) as a model biomarker can be detected at a concentration as low as 1.0 ng·mL-1 in normal human serum. The discovered photothermal effect of the colorimetric system and the developed new photothermal immunoassay platform open up a new horizon for affordable detection of disease biomarkers and have great potential for other important material and biomedical applications of interest.

Heat transfer through soldered and bonded joints of multilayer semiconductor devices studied by laser photothermal beam-deflection method

Thermal wave propagation through solid-solid non-ideal interfaces in multilayer semiconductor devices is considered. A theoretical model is developed for thermal wave propagation, and the laser photothermal probe beam deflection method is used for experimental study of heat transport through multilayered samples with vertical joint interfaces. Experimental and theoretical results are presented for bonded and soldered joints. It is shown that, in general case, both the thermal resistance and the heat capacity of the joint should be considered to describe adequately experimental data and to determine thermophysical properties of a separate layer. It is shown that the real thermal resistance of a soldered joint may be much higher than the predicted one basing on tabulated characteristics. The paper demonstrates that the laser photothermal beam-deflection methods can be applied for testing the thermal contact quality between elements of multilayered semiconductor structures, for example, a multijunction solar cell, assembling by various technologies. These methods make possible to evaluate quantitatively the thermal resistance and heat capacity of thermal contacts at the micrometer scale.

Adaptive laser conditioning of reflective thin film based on photo thermal lens probe.

A novel laser conditioning (LC) concept that performs adaptive control of exposure fluence is proposed. As photo-thermal absorption effect can discover defects responsible for laser-induced damage of reflective thin film, in situ photo-thermal lens probe is introduced in conventional LC procedure to detect defects during raster-scanning. The absorptance signal is fed back to guide the adaptive control of exposure fluence. By this method, the damage risk accompanying with LC can be reduced to a rather low level. In order to test the performance of adaptive laser conditioning (ALC), an experimental setup has been built, and several film samples have been tested. The results show that ALC is effective at reducing laser damage risk.

A plasmonic photo-thermal probe for thermoablation of post-operative breast cancer cells

Thermoablation of cancerous cells using probe-based strategies has received a lot of attention because it provides a localised minimally invasive strategy that minimizes injuries to collateral tissues. Although radiofrequency ablation is the most widely used probe-based method, skin injuries at the site of the grounding pad are a major complication that limits its efficacy. This paper presents a novel plasmonic photo-thermal probe that has the potential to achieve reasonable lesion sizes without skin burns. First, the concept and its embodiment are presented. Then, its performance is investigated using a 3-D finite-element method (FEM) model. The FEM model was tested for its validity using an analytical model. Lesions are shown to have an ellipsoidal shape and their sizes controlled by the length of the active tip of the probe. The comparison with the analytical model showed reasonably good agreement to within 2%. Our predictions demonstrate the feasibility of our novel probe to achieve reasonable lesion ...

Nanoparticle-mediated photothermal effect enables a new method for quantitative biochemical analysis using a thermometer.

A new biomolecular quantitation method, nanoparticle-mediated photothermal bioassay, using a common thermometer as the signal reader was developed. Using an immunoassay as a proof of concept, iron oxide nanoparticles (NPs) captured in the sandwich-type assay system were transformed into a near-infrared (NIR) laser-driven photothermal agent, Prussian blue (PB) NPs, which acted as a photothermal probe to convert the assay signal into heat through the photothermal effect, thus allowing sensitive biomolecular quantitation using a thermometer. This is the first report of biomolecular quantitation using a thermometer and also serves as the first attempt to introduce the nanoparticle-mediated photothermal effect for bioassays.

Low-Power Photothermal Probing of Single Plasmonic Nanostructures with Nanomechanical String Resonators

We demonstrate the direct photothermal probing and mapping of single plasmonic nanostructures via the temperature-induced detuning of nanomechanical string resonators. Single Au nanoslits and nanorods are illuminated with a partially polarized focused laser beam (λ = 633 nm) with irradiances in the range of 0.26-38 μW/μm(2). Photothermal heating maps with a resolution of ∼375 nm are obtained by scanning the laser over the nanostructures. Based on the string sensitivities, absorption efficiencies of 2.3 ± 0.3 and 1.1 ± 0.7 are extracted for a single nanoslit (53 nm × 1 μm) and nanorod (75 nm × 185 nm). Our results show that nanomechanical resonators are a unique and robust analysis tool for the low-power investigation of thermoplasmonic effects in plasmonic hot spots.

Environmentally Benign Synthesis of Bi<SUB>2</SUB>S<SUB>3</SUB> Quantum Dot Using Microwave-Assisted Approach

Oleic acid (OA) capped Bi2S3 quantum dots were successfully synthesized using 180 watt microwave power for 5 minutes in water-ethanol mixed solvents containing oleic acid as capping agent. In this approach, the reaction was conducted in ambient air and a much lower temperature than hot injection approach. The OA capped Bi2S3 QDs were characterized by using XRD, TEM, FTIR, UV-Vis and PL. The OA capped Bi2S3 QDs can be readily modified with sodium dodecyl sulfate (SDS) via hydrophobic interaction to improve their solubility in aqueous solution. According to optical properties of the QDs, the modified QD revealed the additional features, such as photothermal therapeutic agent and fluorescent probe.

Thermal conductivity of transparent thin films/substrates measured by photothermal reflectivity probing method

In this article the photothermal reflectivity probing method is used to evaluate the thermal properties of a transparent thin film deposited on an opaque substrate. In this method the thin film is illuminated with a modulated and focused laser beam, which induces thermal waves penetrated into the sample. The resulted temperature oscillations and surface vibrations can be measured using a probe laser beam through optical reflectivity variations. According to the analytical formulas for the reflectivity of light focused on a transparent thin film/opaque substrate structure, the thermal conductivity of the thin film can be obtained by fitting the experimental frequency dependence of the reflectance signal. The validity of the method is proved by application to thin transparent ZnO films on opaque silicon substrates.

A simple theoretical extension to the analysis of photothermal deflection signal for low thermal diffusivity evaluation

A modified amplitude method to analyze the photothermal probe beam deflection signal for the determination of low thermal diffusivity values of materials is proposed. This simple theoretical model, which is an extension of the amplitude method proposed by Quelin et al., takes into account the dependence of the photothermal signal on the height of the probe beam above the sample surface which affects mirage measurements when the thermal diffusivity of the coupling medium is greater than that of the sample. The present work is similar to the modification to the phase method proposed by Bertolotti et al. for determination of low thermal diffusivity. The method can be applied irrespective of whether the sample is optically transparent or optically opaque and is independent of thickness.

Photothermal probing of inhomogeneously modulated transparent thin films

The problem of the photothermal modulation of optical beams passing through multilayer films is an extremely complex one owing to the inhomogeneously modulated refractive index combined with multiple optical reflections inside the sample. This problem has so far not been given an exact analytical treatment in the field of photothermal probing. We consider here such a treatment for normal-incidence optical probing in reflectance of photothermally modulated single-layer thin-film samples with arbitrary optical constants. The validity of the method is demonstrated by application to a thin transparent film of silica on a silicon substrate.

Microelectronic circuit characterization via photothermal radiometry of scribeline recombination lifetime

Three-dimensional (3D) photothermal radiometric microscopic imaging and laser-intensity-modulation frequency scans have been used for the non-contact, non-intrusive measurement of electronic transport properties of integrated circuits in patterned 4″ Si wafers. The experimental data showed that carrier recombination lifetimes along each scribeline remain constant. However, variations in surface recombination velocities and carrier diffusion coefficients were found. It was further found that such variations are related to the presence of highly doped poly-Si structures adjacent to the scribeline. As a result of these measurements, it is concluded that scribeline photothermal radiometric probing can be used effectively for monitoring local values of the carrier recombination lifetime and, through those, wafer contamination and damage during device fabrication processing.

Effects of optothermal nonlinearities on photothermal beam deflection

The usual theory of the photothermal probe beam deflection, which is normally used for the thermal characterization of solids, is based on the assumption that the optical refractive index of the air surrounding the heated sample behaves linearly with the temperature. Here we study the effects of the nonlinear variation of the refractive index with higher air temperatures in front of the sample. These optothermal nonlinearities become important, when the photothermal probe beam deflection is applied at higher temperatures to analyze the effects of thermal ablation and erosion of heated surfaces. Examples of measurements in front of a heated vertical plate are presented and compared with theory.

Photothermal measurement of bulk and surface absorption of transparent infrared optical elements

Photothermal probe beam deflection spectroscopy is used to separately measure bulk and surface absorption of transparent IR optical elements. Different approaches of this technique are considered. One approach consists in variation of the laser beam heat modulation frequency in the condition that the heating beam component is transverse to the path of the probe beam. Another approach consists in varying the heat and probe cross section measuring point position within the tested optical sample. It is theoretically and experimentally shown that in the second case, the spatial resolution and measurement locality are determined by the size of laser beam spots and the thermal diffusion length in a sample. The relative contribution of surface and bulk absorption to summary absorption can be derived from the ratio of the probe beam deflection signal, measured both near the surface and within the sample volume far from the surface, to thermal wavelength. Absolute calibration of absorption measurements can be carried out using laser calorimetry. A comparison between deflection and calorimetry data on volume absorption in a number of ZnSe laser optical elements is made and shows a good correlation.

Cracks detection by a moving photothermal probe

Using a mobile photothermal probe we show that it is possible to detect rapidly different type of cracks (emerging ones or not), their width being a few micrometers and their depth being some hundredths of micrometers.

Thermal conductivity analysis of polymeric crystal by mirage effect

Photothermal Techniques are based on the conversion of the modulated light energy into heat within the sample. Using the Photothermal Probe Beam Technique, where the analysis of a laser beam deflected by the mirage effect near the sample leads to the thermal properties of this sample, we have determined the three components of the thermal conductivity tensor of an orthorhombic polydiacetylene single crystal. A numerical simulation of the probe beam deflection is also presented and compared to the experimental data.