Thermoplasmonic Effect Research Articles

Concurrent photothermal therapy and nuclear magnetic resonance imaging with plasmonic–magnetic nanoparticles: A numerical study

Background and Objective: Theranostics is the combination of the diagnostic and therapeutic phases. Here we focus on simultaneous use of photothermal therapy and magnetic resonance imaging, employing a contrast-photothermal agent that converts incident light into heat and affects the transverse relaxation time, a key magnetic resonance imaging parameter. Our work considers a gold–magnetite nanoshell platform to gauge the feasibility of magnetic resonance imaging monitoring of the heating associated with phototherapy, by studying the modification of the transverse relaxation rate induced by laser illumination of a solution containing these hybrid nanoparticles. Methods:We simulate a system composed of an aqueous solution with hybrid nanoshells under continuous laser irradiation, enabling the evaluation of spatial variations of the transverse relaxation rate within the sample. We work with the hybrid nanoshell platform comprising a metal/gold shell for thermoplasmonic effects and a magnetite core for magnetic resonance imaging contrast enhancement. The optical properties of the nanoshells are first obtained through simulations using the finite element method. Next, the heating generated by the laser illumination is calculated by numerical integration. Finally, the transverse relaxation rate is obtained through the application of an analytical model. Additionally, we conduct an optimization of the nanoshell geometry to fulfill requirements of both magnetic resonance imaging and phototherapy techniques. Results:Our findings demonstrate a narrow range of nanoshell sizes exhibiting both a plasmonic absorption peak in the human biological window and a high response to laser illumination of the transverse relaxation rate. Furthermore, the illumination can induce up to a 30% modification in transverse relaxation rate compared to the non-illuminated scenario in this range of nanoshell sizes. Conclusions:In this work we establish the numerical understanding of the interplay between phototherapy and nuclear magnetic resonance imaging when employed concurrently. This allows magnetic resonance imaging monitoring of the heating associated with phototherapy.

Thermoplasmonic Effect Enables Indirect ON-OFF Control over the Z-E Isomerization of Azobenzene-Based Photoswitch.

Proper formulation of systems containing plasmonic and photochromic units, such as gold nanoparticles and azobenzene derivatives, yields materials and interfaces with synergic functionalities. Moreover, gold nanoparticles are known to accelerate the Z-E isomerization of azobenzene molecules in the dark. However, very little is known about the light-driven, plasmon-assisted Z-E isomerization of azobenzene compounds. Additionally, most of the azobenzene-gold hybrids are prepared with nanoparticles of small, isotropic shapes and azobenzene ligands covalently linked to the surface of nanostructures. Herein, a formulation of an innovative system combining azobenzene derivative, gold nanorods, and cellulose nanofibers is proposed. The system's structural integrity relies on electrostatic interactions among components instead of covalent linkage. Cellulose, a robust scaffold, maintains the material's functionality in water and enables monitoring of the material's plasmonic-photochromic properties upon irradiation and at elevated temperatures without gold nanorods aggregation. Experimental evidence supported by statistical analysis suggests that the optical properties of plasmonic nanometal enable indirect control over the Z-E isomerization of the photochromic component with near-infrared irradiation by triggering the thermoplasmonic effect. The proposed hybrid material's dual plasmonic-photochromic functionality, versatility, and ease of processing render a convenient starting point for further advanced azobenzene-related research and 3D printing of macroscopic light-responsive structures.

Choreographing Oscillatory Hydrodynamics with DNA-Coated Gold Nanoparticles.

Periodic responses to nonperiodic energy inputs, such as oscillations, are hallmarks of living systems. Nanoparticle-based systems have largely remained unexplored in the generation of oscillatory features. Here, we demonstrate a nanosystem featuring hierarchical response to light, where thermoplasmonic effects and reversible DNA-hybridization generate thermal convective forces and ultimately, oscillatory hydrodynamic flows. The slow aggregation of gold nanoparticles (AuNPs) serves as a positive feedback, while fast photothermal disassembly acts as negative feedback. These asymmetric feedback loops, combined with thermal hysteresis for time-delay, are essential ingredients for orchestrating an oscillating response.

Optical and thermo-plasmonic properties of spherical and hollow gold nanoparticles injected in cell organelles

The advent of nanotechnology has profoundly altered many traditional treatment approaches, due to the beneficial physicochemical and functional characteristics of gold nanoparticles (AuNPs). These gold nanostructures are attracting particular interest in a wide range of biomedical applications, such as thermotherapy, diagnostics, detection, and drug delivery. Due to their exceptional characteristics, AuNPs have long been considered as a potential means of combating cancer. These features include surface plasmon resonance (SPR), surface chemistry and multi-functionalization. In addition to targeting tissues and cancer cells, AuNPs with the ability to specifically target organelles are attracting growing interest and are seen as the next evolutionary step in nanomedicine, forming the third generation of this technology. Subcellular targeting offers unique advantages over free targeting, as it enables specific delivery of encapsulated NPs to the intracellular site of action. This translates into greater therapeutic efficacy with a reduced dose and, above all, the ability to overcome immune resistance. AuNPs act as small heat sources taking advantage of SPR phenomenon, enabling targeted heating of specific organelles. The thermoplasmonic effect disrupts organelle function in targeted cancer cells, leading to their destruction. In this work, we used the finite element method (FEM) to examine the properties associated with the SPR of both spherical and hollow AuNPs when they are embedded in the main cellular components, including the lysosome, cell membrane, mitochondria, nucleus, cytoplasm and extracellular medium. In order to predict the thermal destructive power of solid spheres (SAuNPs) and hollow (HAuNPs) gold nanoparticles embedded in these different organelles, we simulated their absorption capacity, field enhancement effect and temperature distribution. The results obtained show that the thermoplasmonic effect is very important for HAuNPs compared with SAuNPs. In addition, the optical and thermoplasmonic properties of SAuNPs and HAuNPs show differential behavior for different cell organelles.

Portable microfluidic plasmonic chip for fast real-time cardiac troponin I biomarker thermoplasmonic detection.

Acute myocardial infarction is one of the most serious cardiovascular pathologies, impacting patients' long-term outcomes and health systems worldwide. Significant effort is directed toward the development of biosensing technologies, which are able to efficiently and accurately detect an early rise of cardiac troponin levels, the gold standard in detecting myocardial injury. In this context, this work aims to develop a microfluidic plasmonic chip for the fast and accurate real-time detection of the cardiac troponin I biomarker (cTnI) via three complementary detection techniques using portable equipment. Furthermore, the study focuses on providing a better understanding of the thermoplasmonic biosensing mechanism taking advantage of the intrinsic photothermal properties of gold nanoparticles. Specifically, a plasmonic nanoplatform based on immobilized gold nanobipyramids was fabricated, exhibiting optical and thermoplasmonic properties that promote, based on a sandwich-like immunoassay, the "proof-of-concept" multimodal detection of cTnI via localized surface plasmon resonance, surface enhanced Raman spectroscopy and thermoplasmonic effects under simulated conditions. Furthermore, after the integration of the plasmonic nanoplatform in a microfluidic channel, the determination of cTnI in 16 real plasma samples was successfully realized via thermoplasmonic detection. The results are compared with a conventional high-sensitivity enzyme-linked immunosorbent clinical assay (ELISA), showing high sensitivity (75%) and specificity (100%) as well as fast response features (5 minutes). Thus, the proposed portable and miniaturized microfluidic plasmonic chip is successfully validated for clinical applications and transferred to clinical settings for the early diagnosis of cardiac diseases, leading towards the progress of personalized medicine.

Light blocking and phase modulation based on thermo-plasmonic hotspots in WS2 monolayer

Here we demonstrate light blocking and phase modulation in nano-plasmonic donate shape rings based on the thermo-plasmonic effect in these structures. For this purpose, we use a laser writing system to fabricate nanohole arrays and cover them with plasmonic gold thin film via a sputtering machine. The chemical vapor deposition method is also used to produce a WS2 layer, which is suitable for light blocking and phase modulation due to the nonlinearity of this two-dimensional material. After theoretically and experimentally evaluating the plasmonic donate-shaped substrate, we use the ellipsometric method to characterize the optical modes of the samples and record the switching manner and light-blocking phenomena under the probe laser excitation set to 980 nm. Our results show phase modulation based on the thermo-plasmonic effect of nano gap in donated double rings and light blocking by thermal expansion of the WS2 layer, which can open new insight into plasmon and two-dimensional material-based devices.

Enhancement of photothermal effect using a hierarchical plasmonic structure

The photothermal effect exhibited by plasmonic structures has garnered considerable attention because of its versatile application prospects. However, the conversion efficiency of broadband light sources and large area fabrication still pose challenges. Herein, a hierarchical plasmonic structure was proposed as a photothermal substrate, which integrated a two-dimensional periodic microstructure with a disordered nanostructure. The microstructure and nanostructure were obtained through litho-etching and metal-assisted chemical etching technologies, respectively. Titanium nitride was deposited on the hierarchical structure as the mediator between the irradiation and generation of heat. The metallic nanostructure on the hierarchical structure played a crucial role in generating the thermoplasmonic effect. Moreover, the type (vertical and tapered shapes) of the microstructure and morphology (porous texture and deep trench) of the nanostructure were also altered to investigate the photothermal effect. The addition of deeper nanotrenches on the tapered microstructure exhibited a synergistic effect on the photothermal efficiency. The hierarchical plasmonic structures were experimentally demonstrated to exhibit a 3.6 times greater photothermal efficiency (change in temperature) compared to a titanium nitride film. These engineered hierarchical structures have remarkable potential for use as non-classical photothermal devices.

Tunable all-optical liquid crystal lens based on the thermo-plasmonic effect

Surface plasmon resonance (SPR) thermal effects have been the focus of researchers lately and are commonly used in sensors, micro heaters in integrated circuits, and other applications. In this study, a new type of tunable all-optical liquid crystal (LC) lens is fabricated by employing the SPR thermal effects. Due to the absorption of pump light by gold nanoparticles, the generated heat is transferred to the surrounding LC layer, leading a radial gradient distribution of LC molecules. Passing a probe light through the center of the fabricated cell, a lens shaped optical phase retardation observed. The temperature increase with intensification of the pump light power has been numerically calculated. In addition, the focal length of the lens reduces from 157.8 to 13.1 cm during this process. The tunable all-optical LC lens is a fascinating new concept that could open up new horizons and has numerous applications. It has a simpler and cheaper structure compared to electronic lenses, provides greater stability than other all-optical counterparts, and allows for optical control of the focal length.

Synergistically photothermal Au Nanoprisms@MXene enable adaptive solar modulation of HA-PNIPAM hydrogels for smart window

Smart windows are highly desired as emerging optical devices based on appealing sunlight modulation, however, some prevailing limitations remain with low photothermal conversion and narrow spectral adjusting ranges, which drastically restrict energy-saving performance. Herein, a strategically designed smart window achieves significant breakthroughs, containing photothermal fillers of Au nanoprisms (AuNPRs) hybrid MXene nanosheets, and copolymerized thermochromic poly(N-isopropyl acrylamide)-doped hyaluronic acid (HA) hydrogels. By harness of AuNPR@MXene nanocomposites as photo-trapped nanoheaters, stimulating thermo-responsive behaviors of hydrogels boosts solar transmittance switching. The compelling photothermal features depend on the amalgamation: thermoplasmonic effect of AuNPRs, broad-band-absorbed AuNPRs endowed by MXene, and thermal conductivity from AuNPRs to MXene, generating synergistic effects. We maximize the advancing transmittance regulation by controlling the proportion gain of HA to increase hydrogen-bonded interaction. The resulting device with low-loadings AuNPR@MXene composites (0.9 wt% and 0.98 vol%) is capable of allowing 78 % of the maximum visible light through before thermochromism and blocking 98.04 % of sunlight penetration when photothermal stimulation. Besides, outdoor measurements show an achievable great indoor temperature drop of about 7 °C only 30 min irradiation, and a skin-cooling performance in the wearable, illustrating the potential of adaptive solar modulation application.

White light thermoplasmonic activated gold nanorod arrays enable the photo-thermal disinfection of medical tools from bacterial contamination.

The outspread of bacterial pathogens causing severe infections and spreading rapidly, especially among hospitalized patients, is worrying and represents a global public health issue. Current disinfection techniques are becoming insufficient to counteract the spread of these pathogens because they carry multiple antibiotic-resistance genes. For this reason, a constant need exists for new technological solutions that rely on physical methods rather than chemicals. Nanotechnology support provides novel and unexplored opportunities to boost groundbreaking, next-gen solutions. With the help of plasmonic-assisted nanomaterials, we present and discuss our findings in innovative bacterial disinfection techniques. Gold nanorods (AuNRs) immobilized on rigid substrates are utilized as efficient white light-to-heat transducers (thermoplasmonic effect) for photo-thermal (PT) disinfection. The resulting AuNRs array shows a high sensitivity change in refractive index and an extraordinary capability in converting white light to heat, producing a temperature change greater than 50 °C in a few minute interval illumination time. Results were validated using a theoretical approach based on a diffusive heat transfer model. Experiments performed with a strain of Escherichia coli as a model microorganism confirm the excellent capability of the AuNRs array to reduce the bacteria viability upon white light illumination. Conversely, the E. coli cells remain viable without white light illumination, which also confirms the lack of intrinsic toxicity of the AuNRs array. The PT transduction capability of the AuNRs array is utilized to produce white light heating of medical tools used during surgical treatments, generating a temperature increase that can be controlled and is suitable for disinfection. Our findings are pioneering a new opportunity for healthcare facilities since the reported methodology allows non-hazardous disinfection of medical devices by simply employing a conventional white light lamp.

The Effect of Femtosecond Laser Irradiation and Plasmon Field on the Degree of Conversion of a UDMA-TEGDMA Copolymer Nanocomposite Doped with Gold Nanorods.

In this work, the effects of femtosecond laser irradiation and doping with plasmonic gold nanorods on the degree of conversion (DC) of a urethane dimethacrylate (UDMA)-triethylene glycol dimethacrylate (TEGDMA) nanocomposite were investigated. The UDMA-TEGDMA photopolymer was prepared in a 3:1 weight ratio and doped with dodecanethiol- (DDT) capped gold nanorods of 25 × 75 or 25 × 85 nm nominal diameter and length. It was found that the presence of the gold nanorods alone (without direct plasmonic excitation) can increase the DC of the photopolymer by 6-15%. This increase was found to be similar to what could be achieved with a control heat treatment of 30 min at 180 °C. It was also shown that femtosecond laser impulses (795 nm, 5 mJ pulse energy, 50 fs pulse length, 2.83 Jcm-2 fluence), applied after the photopolymerization under a standard dental curing lamp, can cause a 2-7% increase in the DC of undoped samples, even after thermal pre-treatment. The best DC values (12-15% increase) were obtained with combined nanorod doping and subsequent laser irradiation close to the plasmon resonance peak of the nanorods (760-800 nm), which proves that the excited plasmon field can directly facilitate double bond breakage (without thermoplasmonic effects due to the short pulse length) and increase the crosslink density independently from the initial photopolymerization process.

Hybrid polymeric therapeutic microcarriers for thermoplasmonic-triggered release of resveratrol

Diabetic retinopathy (DR) is a severe ocular complication that causes retinal damage, being one of the leading causes of blindness globally, thus the development of new strategies to prevent and treat DR as well as other degenerative diseases is highly desired. This work is focused on the design and fabrication of an ingenious model of polymeric microcapsules (MC) for controlled drug delivery in human retina cells able to carry therapeutic resveratrol (RSV) molecules in tandem with active anisotropic gold bipyramidal nanoparticles (AuBPs) as efficient photothermal agents. Specifically, MC were developed via a Layer-by-Layer deposition technique, by successively adding oppositely charged polyelectrolytes on a RSV-conjugated calcium carbonate (CaCO3) core. For the monitorization and localization of the as-formed spherical fluorescent MC inside human retina pigmented epithelial (RPE) D407 cells, fluorescein isothiocyanate, a Food and Drug Administration approved fluorophore, was attached between the polyelectrolytes layers. High-performance liquid chromatography analysis revealed a loading efficiency of over 90% of RSV on the CaCO3 core and demonstrates its release upon NIR irradiation as a consequence of the thermoplasmonic effect of MC. The cytotoxicity of the RSV-carrying MC inside human retina cells was assessed by WST-1 assay. Finally, cellular internalization and localization of the MC inside living RPE cells were monitored via Conventional Fluorescence and Re-Scanning Confocal Fluorescence Microscopy. This research seeks to take use of the novel MC and implement them as potential intraocular RSV delivery vehicles for the therapy of DR.

Thermoplasmonic Regulation of the Mitochondrial Metabolic State for Promoting Directed Differentiation of Dental Pulp Stem Cells.

Regulating stem cell differentiation in a controllable way is significant for regeneration of tissues. Herein, we report a simple and highly efficient method for accelerating the stem cell differentiation of dental pulp stem cells (DPSCs) based on the synergy of the electromagnetic field and the photothermal (thermoplasmonic) effect of plasmonic nanoparticles. By simple laser irradiation at 50 mW/cm2 (10 min per day, totally for 5 days), the thermoplasmonic effect of Au nanoparticles (AuNPs) can effectively regulate mitochondrial metabolism to induce the increase of mitochondrial membrane potential and further drive energy increase during the DPSC differentiation process. The proposed method can specifically regulate DPSCs' cell differentiation toward odontoblasts, with the differentiation time reduced to only 5 days. Simultaneously, the molecular profiling change of mitochondria within DPSCs during the cell differentiation process is revealed by in situ surface-enhanced Raman spectroscopy. It clearly demonstrates that the expression of hydroxyproline and glutamate gradually increases with prolonging of the differentiation days. The developed method is simple, robust, and rapid for stem cell differentiation of DPSCs, which would be beneficial to tissue engineering and regenerative medicine.

Toward SERS based localized thermometry of Polymer-Supported silver and gold nanostructures

In order to accurately account for the contribution of different plasmon mediated phenomena when developing materials for applications in photothermal therapy, photovoltaics, or photocatalysis reliable, precise, and localized temperature measurements are required. In this work we applied two surface-enhanced Raman scattering (SERS) spectroscopy based methods to measure the local temperature increase due to the thermoplasmonic effect in gold and silver nanoparticles on thin polystyrene films. The first method relies on the temperature dependence of the anti-Stokes to Stokes Raman bands intensity ratio for a label Rhodamine 6G deposited on the nanostructures. We found that the method enables good measurements in the 20–60 °C temperature range but becomes less reliable at higher temperatures when the system undergoes transformations and the plasmonic response of the nanoparticles changes with heating. The second method makes use of the temperature dependent adsorption geometry of phenyl isocyanide (PIC) and a corresponding shift of ν(C≡N) vibration. The method demonstrates greater temperature sensitivity of gold nanoparticles than silver. The difference in sensing capability is related to the difference in molecular adsorption geometry of PIC on Au compared to Ag. We conclude that for universal thermometry of the nanoparticle/ thin film composite a combination of the two methods provides more precise localized temperature measurements.

Hybrid Nanoparticles as Theranostics Platforms for Glioblastoma Treatment: Phototherapeutic and X-ray Phase Contrast Tomography Investigations

Glioblastoma multiforme (GBM) is one of the deadliest and most aggressive cancers, remarkably resilient to current therapeutic treatments. Here, we report preliminary in vivo studies of GBM treatments based on photo-nanotherapeutics to activate synergistic killing mechanisms. Core-shell nanoparticles have been weaponized by combining photophysical properties of a new generation PDT agent (Ir(III) complex) with the thermoplasmonic effects of resonant gold nanospheres. In order to investigate the damages induced in GBM treated with these photoactivable nanosystems, we employed X-ray phase-contrast tomography (XPCT). This high-resolution three-dimensional imaging technique highlighted a vast devascularization process by micro-vessels disruption, which is indicative of tumor elimination without relapse.

In Situ Single-Cell Surgery and Intracellular Organelle Manipulation Via Thermoplasmonics Combined Optical Trapping.

Microsurgery and biopsies on individual cells in a cellular microenvironment are of great importance to better understand the fundamental cellular processes at subcellular and even single-molecular levels. However, it is still a big challenge for in situ surgery without interfering with neighboring living cells. Here, we report a thermoplasmonics combined optical trapping (TOT) technique for in situ single-cell surgery and intracellular organelle manipulation, without interfering with neighboring cells. A selective single-cell perforation was demonstrated via a localized thermoplasmonic effect, which facilitated further targeted gene delivery. Such a perforation was reversible, and the damaged membrane was capable of being repaired. Remarkably, a targeted extraction and precise manipulation of intracellular organelles were realized via the optical trapping. This TOT technique represents a new way for single-cell microsurgery, gene delivery, and intracellular organelle manipulation, and it provides a new insight for a deeper understanding of cellular processes as well as to reveal underlying causes of diseases associated with organelle malfunctions at a subcellular level.

Analysis of thermo-plasmonic lab-on-fiber probes in liquid environments

Lab-on-fiber (LOF) optrodes are recently emerging not only as valid platforms for biosensing, but also as promising light-controlled actuators in drug-delivery, optical trapping and thermo-ablation systems. In this regard, the thermo-plasmonic effect has been recognized as an intriguing tool for conferring to the optical fiber the capability of interacting with the external environment through the fine control of local overheating actuated by light in the range of few mW. However, the evaluation of the thermo-plasmonic overheating on small areas such as that of a standard single mode fiber tip is not trivial, especially in liquid solutions, where these probes typically operate. Here we demonstrate that by functionalizing the metallic nanostructure of LOF devices with a thermoresponsive smart materials, it is possible to measure the light-induced overheating on the fiber tip. Specifically, we monitored the plasmonic resonance wavelength shift induced by the temperature-dependent swelling dynamics of different microgel films deposited on the nanostructure. We find a local overheating of about 8 °C mW−1, i.e. also in line with our theoretical predictions based on numerical simulations. Our results demonstrate that the proposed approach is a valid methodology for the direct and continuous monitoring of the temperature changes in LOF devices induced by the input optical power in liquid environment. Our findings lay the basis for the analysis of thermo-plasmonic optical fiber probes exploitable in many applications, especially for the life science sector.

Thermoplasmonic Patterning of Silver Nanocrystal/Polymer Composite Thin Films (Adv. Mater. Interfaces 19/2021)

Thermoplasmonic Patterning of Silver Nanocrystals on Polymer Films Absorption of light by plasmonic nanoparticles can result in local temperature increase due to the thermoplasmonic effect. In article number 2100738, Daniel Prezgot, Anatoli Ianoul, and co-workers use this phenomenon to achieve the controlled nano/micro scale lithographic patterning of a nanocomposite of silver nanocrystals on thin polystyrene films using a continuous-wave, visible laser.

Exploiting Thermoplasmonic Effects for Laser‐Assisted Preparation of Au Nanoparticles/InZnO Thin Film with Visible Range Photodetection Properties

AbstractHere, a new method is proposed for preparing gold nanoparticles (Au NPs)/indium‐zinc‐oxide (IZO) nanocomposite thin films based on photothermal mechanisms with near‐Infrared (NIR) laser annealing, which allows integrating the nanomaterial on fragile substrates such as thin glass, plastic sheets, or 3D printed pieces. The Au NPs are first prepared by NIR laser dewetting of a thin Au layer. Then, the Au NPs are used to locally cure the semiconductor material and provide suitable electronic properties owing to their efficient thermoplasmonic effects under the NIR laser annealing conditions. Finally, the electronic properties of the Au NPs/IZO thin films are characterized in the dark and under light excitation. Good photoresponsivity at 410 nm (UV, >100 A W−1) is demonstrated, but interestingly, the presence of Au NPs significantly improves the detection ability to a longer wavelength range, such as to 515 nm (green, ≈5 × 10−3 A W−1), even extending to 630 nm (red, ≈5 × 10−4 A W−1), and 780 nm (NIR, ≈10−4 A W−1). In addition, with the critical evaluation of dynamic light detection and lifetime trace (>22 d), the laser‐annealed Au NPs/IZO photodetectors demonstrate useful operating reliability and stability.

Microscale Thermophoresis in Liquids Induced by Plasmonic Heating and Characterized by Phase and Fluorescence Microscopies

Thermophoresis denotes the motion of particles along temperature gradients. Insignificant in most daily-life observations, this peculiar effect can become dominant in applications involving nano- and microscale heating in fluids. Recent studies in nanoplasmonics observed significant thermophoresis of molecules and particles, in particular in plasmonic trapping, SERS, and biosensing. Evidencing the presence of thermophoresis is not obvious and quantifying its magnitude is even less accessible considering existing techniques. In this article, we introduce a method capable of quantifying the thermophoresis of particles in the context of nanoplasmonic applications. A gold nanoparticle array under illumination is used to create microscale temperature gradients, and a dual fluorescence-phase microscopy technique is used to map both temperature and concentration in parallel. This association enables the determination of Soret coefficients for a wide range of temperatures from a single image acquisition. This metrology technique paves the way for broader fundamental research in microscale thermophoresis in liquids and better-controlled applications in nanophotonics involving thermoplasmonic effects.