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Application of Quartz Tuning Fork in Photodetector Based on Photothermal Effect
摘要： A photodetector with a commercial quartz tuning fork (QTF) based on photothermal effect was demonstrated. Unlike the commonly used thermosensitive elements, a QTF with the mechanical resonance ability and the piezoelectric effect was used to amplify the photothermal signal. Operating at the optimal operating distance and modulation signal duty ratio selected for the photodetector, the photodetector achieved a good linear response at the wavelength of 1550 nm and 980 nm. And the photoresponsivity of the photodetector reach up to 515 mV/mW at the wavelength of 1550 nm. More important, the detection sensitivity of 0.75 pW at 203 s integration time has been achieved by using the Allan deviation analysis.
关键词： photothermal effect,Photodetector,quartz tuning fork
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Quantitative Phase Microscopy with Molecular Vibrational Sensitivity
摘要： Quantitative phase imaging (QPI) has become a valuable tool for studying optically transparent samples such as biological cells and tissues. It yields the sample-specific optical path-length delay at each spatial point of the field of view with a nanometer resolution, enabling high-contrast and objective analysis. The major advantage of QPI is its wide-field, label-free measurement capability of the transparent morphology. This allows for high-speed imaging limited by the image sensor’s frame rate while reducing optical and/or chemical damages to the sample which are troublesome in other imaging techniques such as fluorescence and Raman imaging. To date, QPI has been used for pathology diagnosis, phenotyping of live cancer cells, non-destructive measurement of cellular volume and dry-mass, study of cellular membrane dynamics, to just name a few. However, QPI lacks chemical sensitivity which limits its application to morphology-based diagnosis. Here, we report on our wide-field label-free molecular-vibrational (MV) microscopy method realized in the framework of QPI utilizing mid-infrared (MIR) photothermal effect. We measure local changes in the optical phase delay occurring upon absorption of the MIR light in the vicinity of the MV-resonant molecules, which is called photothermal effect, by means of QPI. This imaging scheme yields high-molecular-detection sensitivity based on MV-resonant MIR absorption having ~8 orders of magnitude larger cross-section compared to Raman scattering. Meanwhile, it also maintains the visible-light spatial resolution, high temporal resolution limited by the image sensor’s frame rate, and low photodamage to the sample with the wide-field, low-fluence optical illumination. Notably, our wide-field, parallelized detection scheme could even surpass the imaging speed of conventional label-free imaging methods such as coherent Raman imaging by an order of magnitude, as they typically employ a point-scanning mechanism for image synthesis. Our MV-sensitive QPI (MV-QPI) could offer new insights for optically-transparent complex dynamics by enabling high-speed, label-free cross-correlative analysis based on the quantitative morphology and the MV-spectroscopic chemical contrasts.
关键词： molecular-vibrational microscopy,Quantitative phase imaging,chemical sensitivity,label-free imaging,mid-infrared photothermal effect
更新于2025-09-12 10:27:22
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Atomic Force Microscope Guided SERS Spectra Observation for Au@Ag-4MBA@PVP Plasmonic Nanoparticles
摘要： Recently polymer encapsulated surface-enhanced-Raman-scattering (SERS) probes with internal noble metal core–shell structure has found growing applications in biomedical applications. Here we studied the SERS spectra of Au@Ag–4MBA@PVP (4MBA: 4-mercaptobenzoic acid; PVP: polyvinylpyrrolidone) plasmonic nanoparticles produced from a chemical reduction method. By linking the atomic force microscope (AFM) with the homebuilt confocal Raman spectrometer thus to use AFM images as guidance, we realized the measurement of the SERS spectra from separated nanoparticles. We investigated the cases for single nanoparticles and for dimer structures and report several observed results including SERS spectra linearly scaled with laser power, abrupt boosting and abnormal shape changing of SERS spectra for dimer structures. Based on the finite element method simulation, we explained the observed ratio of SERS signals between the dimer structure and the single nanoparticle, and attributed the observed abnormal spectra to the photothermal effect of these plasmonic nanoparticles. Our study provides valuable guidance for choosing appropriate laser power when applying similar SERS probes to image biological cells.
关键词： SERS probes,AFM imaging,confocal Raman spectrometer,SERS spectra,photothermal effect,plasmonic nanoparticles
更新于2025-09-11 14:15:04
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Photothermal Microfluidic Sensing Platform Using Near-Infrared Laser-Driven Multiplexed Dual-Mode Visual Quantitative Readout
摘要： The application of different sensing principles in microfluidic devices opens up further possibilities for the development of point-of-care testing (POCT). Herein, the photothermal sensing principle is introduced in microfluidic paper-based analytical devices (μPADs) to develop a photothermal microfluidic sensing platform using near-infrared (NIR) laser-driven multiplexed dual-mode visual quantitative readout. Prussian blue (PB) as the analyte-associated photothermal agent was in-situ synthesized in thermoresponsive poly(N-isopropylacrylamide) hydrogels to serve as the on-chip photothermal sensing element. NIR laser-driven photothermal effect of PB triggered not only on-chip dose-dependent heat generation but also phase transition-induced dye release from the hydrogels, simultaneously enabling both thermal image- and distance-based dual-mode visual quantitative readout of the analyte concentration in a multiplexed manner. Both the on-chip temperature elevation value of the hydrogels and the traveling distance of released dye solutions were proportional to the concentration of PB. Using the detection of silver ions in environmental water as a proof-of-concept study, the photothermal μPAD can detect silver ions at a concentration as low as 0.25 μM with high selectivity and satisfactory accuracy. The photothermal microfluidic sensing platform holds great potential for POCT with promising integratability and broad applicability, owing to the combination of synergistic advantages of the photothermal sensing principle, μPADs and photothermally responsive hydrogels.
关键词： Microfluidic device,Photothermal effect,Visual readout,Point-of-care testing,Thermoresponsive hydrogel
更新于2025-09-11 14:15:04
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Optical fiber-based manipulation of microparticles in microfluidic channel through thermal convection
摘要： We demonstrate a simple optical fiber microfluidic control device based on photothermal effect induced convection, which can realize flexible manipulation and particle sorting in range of hundreds of microns. Three single-mode optical fibers arranged regularly were utilized for the realization of the particle capture function, which simplifies the complex equipment and reduces the cost in traditional optical tweezers. We also display a unique control mode: horizontal manipulation of particles by moving the fiber vertically. It is hopefully to be applied in biomedical, chemical analysis, material testing and other fields.
关键词： optical fiber,photothermal effect,trapping,microfludic
更新于2025-09-11 14:15:04
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Responsive Smart Windows Enabled by the Azobenzene Copolymer Brush with Photothermal Effect
摘要： An azobenzene side chain liquid crystalline copolymer (MAzo-co-GMA) is successfully synthesized through copolymerizing monomer 6-{4-[(4-butylphenyl)diazenyl]phenoxy} hexyl methacrylate (MAzo) with glycidyl methacrylate (GMA). The obtained MAzo-co-GMA copolymer can form stabilized polymer brush on the surface after thermal annealing. The obtained polymer brush not only induces the alignment of liquid crystals but also shows photothermal effect under UV light irradiation due to the azobenzene side group. On basis of these results, the LC cell with this polymer brush as the substrate is further used to fabricate the polymer-stabilized liquid crystal (PSLC) smart window. The resultant PSLC smart window shows the transparent state because the homeotropic alignment in SmA* phase of PSLC is induced by the polymer brush on the surface of LC cell. The opaque state can be achieved in the scattering N* phase by UV light irradiation or heating. The response time of PSLC smart window can be regulated by adjusting the concentration of MAzo-co-GMA copolymer brush and the intensity of UV light. This kind of PSLC smart window with both thermal and UV response shows good reversibility and stability, which endows enormous promising applications in energy-saving devices.
关键词： UV response,photothermal effect,polymer brush,smart window
更新于2025-09-11 14:15:04
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Plasmonic photothermal heating of gold nanostars in a real-size container: multiscale modelling and experimental study
摘要： The ability of noble metal nanoparticles (NPs) to convert light into heat has triggered a lot of scientific interest due to the numerous potential applications, including, e.g. photothermal therapy or laser-based nanopatterning. In order for such applications to be practically implemented, the heating behaviour of NPs embedded in their surrounding medium has to be thoroughly understood, and theoretical models capable of predicting this behaviour must be developed. Here we propose a multiscale approach for modelling the photothermal response of a large ensemble of nanoparticles contained within a cm-scale, real size container. Electromagnetic field, ray tracing and heat transfer simulations are combined in order to model the response of and analyzing the heating efficiency and temperature dynamics upon laser irradiation of nanostars and nanospheres suspensions contained within a common Eppendorf tube. To validate the model, gold nanostars are then synthesised and characterized by electron microscopy and optical spectroscopy. Laser-induced heating experiments are conducted by irradiating colloid-filled Eppendorf tubes with a 785 nm continuous wave laser and monitoring by a thermographic camera. The experimental results confirm that the proposed model has potential for predicting plasmonic nanoparticle suspensions in real-scale containers, at cm3 volumes.
关键词： multiscale model,gold nanoparticle,photothermal effect,gold nanostar,surface plasmon
更新于2025-09-11 14:15:04
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Photothermal-enhanced synthetic melanin inks for near-infrared imaging
摘要： Synthetic melanin has been increasingly exploited as a new class of functional ink materials due to its promising properties such as ultrahigh reflective index and blackness, and good stability in aqueous solution. Whilst the promising photothermal conversion feature of synthetic melanin has been well devoted, the relatively low near-infrared (NIR) light absorption limited their further application as the NIR imaging inks. Herein, we developed a series of synthetic melanin nanoparticles (SMNPs) inks doped with different kinds of metal ions and found that all the products exhibited enhanced light absorption ability and total photothermal effect compared to the undoped sample. Interestingly, it was also found that these properties could be improved correspondingly with the increase of metal ion concentration. This study not only provides a comprehensive understanding of the metal ion-loaded SMNPs with enhanced photothermal effect, but also paves the way towards fabricating new SMNP inks for NIR imaging applications.
关键词： enhanced photothermal effect,Synthetic melanin,ink
更新于2025-09-11 14:15:04
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Enhancing Photothermal Effect and Stability of Plasmonic Pd/Ag‐Nanosheet by Nanoassembly for Efficient Light‐Driven Catalytic Organic Hydrogenation
摘要： Due to the ability to harness surface plasmons to promote solar-to-chemical energy conversion, plasmonic nanoparticles with finely-controlled structure and optical properties hold great promise for light-activated catalysis. Herein, we prepared a strong plasmonic nanostructure, by assembling Pd/Ag nanosheets (NSs) with varied Pd/Ag ratio onto the surface of polystyrene (PS) microsphere to form a spherical nanoassembly (NAs). The as-prepared Pd/Ag-PS NAs showed better photothermal performance than the precursor Pd/Ag NSs of the same concentration. More importantly, the as-prepared Pd/Ag-PS NAs can be used to boost light-driven organic hydrogenation reactions, in which Pd nanocomponent acts as hydrogenation reaction active sites and Pd/Ag-NSs can convert light efficiently into heat. Under room temperature conditions, the light-driven catalytic hydrogenation efficiency under 50 mW/cm2 full-spectrum irradiation proved to be comparable to that of thermally (70 °C) driven reactions. Moreover, the as-prepared Pd/Ag-PS NAs has better photostability than Pd/Ag NSs. The results proved that the photothermal effect rather than the transfer of hot electrons is responsible for enhanced photocatalytic hydrogenation performance. The strong plasmon coupling between closely-packed Pd/Ag NSs enhances the electromagnetic field intensity and scattering intensity and increase Vis-NIR light trapping and high density hot spots generation, which lead to an overall better photocatalytic efficiency.
关键词： photocatalytic hydrogenation,photothermal effect,hot-electron,surface plasmon resonant coupling,Pd/Ag-nanosheet nanoassembly
更新于2025-09-11 14:15:04
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Optical control of polarized terahertz waves using dye-doped nematic liquid crystals
摘要： We propose an optically tunable terahertz (THz) polarization converter based on use of a dye-doped nematic liquid crystal (LC). The dye-doped LC exhibits a photothermally-induced nematic-isotropic phase transition under irradiation by a laser beam with a wavelength that lies within the absorption band of the dye. We investigate the transmission spectra and the polarization-conversion properties of the dye-doped LC cell with twisted alignment using THz time-domain spectroscopy. The polarization state of a THz wave transmitted through the proposed dye-doped LC cell can be controlled using the laser beam irradiation based on the photothermal effect. The experimental results also demonstrate that optical control of this dye-doped LC cell offers an advantage in terms of response speed when compared with voltage-based control of LC cells via their electrodes. The dye-doped LC proposed in this study presents the possibility that a variety of LC-based THz elements with optical tunability may be realized.
关键词： terahertz,polarization converter,liquid crystal,optical control,photothermal effect
更新于2025-09-10 09:29:36