Search

When illuminated by a resonant laser, noble metal nanoparticles immersed in liquids can efficiently produce a huge amount of heat and rapidly vaporize surrounding liquid, leading to the nucleation of plasmonic bubbles. Plasmonic bubbles are gaining increasing attention and emerged in numerous applications due to their unique properties and excellent controllability, such as microfabrication, micromanipulation, robot propulsion, molecule enrichment, and clinical therapies. In this review paper, the research progress of plasmonic bubbles in the past decade is summarized, including the plasmonic effect‐induced heat generation, experimental methods of plasmonic bubble observation, growth dynamics of plasmonic bubbles, approaches of optomechanical energy conversion via plasmonic bubbles, as well as their applications. This work provides a comprehensive understanding of the state of the art in the field and inspires researchers to explore more promising applications of plasmonic bubbles in different fields, like biology, microfluidics, and micromanufacturing. [ABSTRACT FROM AUTHOR]

Plasmonic nanoparticles play a pivotal role in various research areas due to their exceptional optical and thermo‐optical properties, like high spectral tunability and efficient light‐to‐heat conversion. Gold, with its biocompatibility, low cytotoxicity, and tunable resonances , makes gold nanoparticles ideal for photothermal therapies. Geometries, including spheres, core–shells, rods, disks, stars, nanocages, and nanotoroids, are extensively studied, with the gold nanodoughnut emerging as one of the most promising ones due to its ability to produce high temperatures and rotational stability. Nevertheless, the fabrication of metallic toroidal shapes remains a challenge. Recent advances in DNA‐based nanotechnology, especially DNA‐origami techniques, provide feasible route for the fabrication of this geometry through metallization reactions or attachment of metal nanoparticles. However, particles manufactured using this method possess a DNA core that influences their thermoplasmonic performance. In this work, a theoretical investigation is conducted on the thermoplasmonic response of DNA‐origami‐based core/shell toroids (CSTs) for photothermal applications. Key parameters that optimize the CST thermoplasmonic response are identified, and compared with their solid counterparts and discrete metallic coatings. Additionally, the CSTs tolerance to random rotations is assessed, providing insights into their behavior in fluidic environments and implications for its practical consideration. [ABSTRACT FROM AUTHOR]

This work reveals the rules of using figures of merit on selecting efficient plasmonic nanoheaters. Here, a size dependence of plasmonic nanoparticle optical heating was disclosed. The continuous laser heating of gold nanospheres is evaluated exploring a theoretical approach and thermal lens spectroscopy, which allowed identifying micro-degree temperature changes of laser heated colloidal gold nanospheres of varying sizes. Our findings indicate that the temperature of photoheating colloidal particles rises according to the Joule number values. The optimal gold nanospheres diameter for efficient colloidal laser heating was identified to be 50 nm. Moreover, we demonstrated that long-time domain measurements of colloidal sample enable the identification of single-particle intermediate steady-state temperature. Considering a single particle, nanospheres with diameter larger than 80 nm exhibit superior heating performance than smaller particles, revealing that the optimal particle size for single-particle optical heating applications is different from the optimal particle size for collective heating of nanoparticles. Our results pave the way for the rational use of plasmonic nanoheaters in photothermal applications. [ABSTRACT FROM AUTHOR]

The opto-thermal properties of Au- and Ag-coated core–shell hybrid nanoparticles (NPs) have been thoroughly investigated by using the PyMieLab V1.0 simulation tool based on electrodynamics modelling. We, specifically, investigated the plasmonic resonance tunability and spatial temperature profiles of Au- and Ag-coated composed hybrid core–shell nanospheres as optimized combinations of alloy core (viz. Au0.25Ag0.75, Au0.25Cu0.75, Au0.75Al0.25, Ag0.75Cu0.25 and Ag0.75Al0.25) immersed in the local water (n = 1.33) media. In the present core–shell nanostructure configuration, the alloy core radius (r ) has been changed from 5 to 50 nm (with 5-nm step-size) and shell thickness, t = 5 , and 10 nm is kept the same with varying core radii. The localized surface plasmon resonance (LSPR) of Au- and Ag-coated optimized alloys composed of hybrid core–shell nanospheres is tuned between 238–545 nm and 347–531 nm, respectively, and lies under the ultraviolet–visible segment of the electromagnetic band. The temperature recorded at the surface of core–shell NPs (i.e. alloy core@gold/silver shell) lies between the range of 0.20 and 2.38 °C (for Au-coated alloys) and 0.64–2.44 °C (for Ag-coated alloy) with different core/shell size ratios. The present results are of paramount importance for using these alloy core–plasmonic shell NPs in several types of thermoplasmonic applications. [ABSTRACT FROM AUTHOR]

Here, we investigate the correlation between the heat generated by gold nanoparticles, in particular nanospheres and nanobipyramids, and their plasmonic response manifested by the presence of Localized Surface Plasmon Resonances (LSPRs). Using a tunable laser and a thermal camera, we measure the temperature increase induced by colloidal nanoparticles in an aqueous solution as a function of the excitation wavelength in the optical regime. We demonstrate that the photothermal performances of the nanoparticles are strongly related not only to their plasmonic properties but also to the size and shape of the nanoparticles. The contribution of the longitudinal and transversal modes in gold nanobipyramids is also analyzed in terms of heat generation. These results will guide us to design appropriate nanoparticles to act as efficient heat nanosources. [ABSTRACT FROM AUTHOR]

This study addresses the fabrication of microporous plasmonic nanocomposites (NCs) by using plasmonic nanoparticles (i.e., gold bipyramids, AuB) as seeds to grow microporous shells, specifically, metal–organic frameworks (MOF) PCN‐224 of increasing thickness from 69 to 138 nm. This method is based on using a previously synthesized Zr6‐oxo cluster and unfolds at room temperature. Notably, it is demonstrated that the concentration of the AuB seeds determines both the yield of NCs and the resultant thickness of the PCN‐224 shell, illustrating the seeded growth mechanism. Furthermore, it is found that the thermoplasmonic response of the NCs is dominated by the thickness of the microporous shell, with thicker shells having enhanced thermal confinement properties than thinner ones. As a proof of concept, the NCs are loaded with cresyl violet (CV), a lysosomal fluorescent marker. This serves to demonstrate the thermoplasmonic‐induced intracellular release of CV by the photostimulation of the AuB's plasmonic near‐infrared (NIR) band. Moreover, the NCs display exceptional efficacy as photodynamic agents when photostimulated at the PCN‐224's Soret band. In summary, this study offers a facile, efficient, and reproducible methodology for the fabrication of NCs with a controlled geometry while unlocking new possibilities in the field of nanoMOFs as multifunctional theranostic probes. [ABSTRACT FROM AUTHOR]

Halide perovskites belong to an important family of semiconducting materials with electronic properties that enable a myriad of applications, especially in photovoltaics and optoelectronics. Their optical properties, including photoluminescence quantum yield, are affected and notably enhanced at crystal imperfections where the symmetry is broken and the density of states increases. These lattice distortions can be introduced through structural phase transitions, allowing charge gradients to appear near the interfaces between phase structures. In this work, we demonstrate controlled multiphase structuring in a single perovskite crystal. The concept uses cesium lead bromine (CsPbBr3) placed on a thermoplasmonic TiN/Si metasurface and enables single-, double-, and triple-phase structures to form on demand above room temperature. This approach promises application horizons of dynamically controlled heterostructures with distinctive electronic and enhanced optical properties.

The use of photothermal processes has been proven effective in the control of microbial infections. Simultaneously, the localized surface plasmon resonance phenomena in metallic nanoparticles have been explored as an alternative strategy to achieve highly efficient localized heating. In this work, we propose the use of selected nanoheaters to improve the efficiency of fungal photothermal inactivation of Candida albicans through size optimization of plasmonic gold nanorods. Here, the optical heating of polyethylene glycol coated gold nanorods of varying sizes is evaluated, both theoretically and experimentally. A size-dependent computational approach was applied to identify metallic nanorods with maximized thermal performance at 800 nm, followed by the experimental comparison of optimal and suboptimal nanoheaters. Comparison among samples show temperatures of up to 53.0 °C for 41×10 nm gold nanorods against 32.3 °C for 90×25 nm, a percentage increase of ∼63% in photothermal inactivation assessments. Our findings reveal that gold nanorods of 41×10 nm exhibit superior efficiency in near-infrared (800 nm) photothermal inactivation of fungi, owing to their higher light-thermal conversion efficiency. The identification of high performance metallic nanoheaters may lead to the reduction of the nanoparticle dose used in plasmonic-based procedures and decrease the laser exposure time needed to induce cell death. Moreover, our results provide insights to better exploit plasmonic nanoparticles on photothermal inactivation protocols.

Plasmonic nanoparticles play a pivotal role in various research areas due to their exceptional optical and thermo‐optical properties, like high spectral tunability and efficient light‐to‐heat conversion. Gold, with its biocompatibility, low cytotoxicity, and tunable resonances , makes gold nanoparticles ideal for photothermal therapies. Geometries, including spheres, core–shells, rods, disks, stars, nanocages, and nanotoroids, are extensively studied, with the gold nanodoughnut emerging as one of the most promising ones due to its ability to produce high temperatures and rotational stability. Nevertheless, the fabrication of metallic toroidal shapes remains a challenge. Recent advances in DNA‐based nanotechnology, especially DNA‐origami techniques, provide feasible route for the fabrication of this geometry through metallization reactions or attachment of metal nanoparticles. However, particles manufactured using this method possess a DNA core that influences their thermoplasmonic performance. In this work, a theoretical investigation is conducted on the thermoplasmonic response of DNA‐origami‐based core/shell toroids (CSTs) for photothermal applications. Key parameters that optimize the CST thermoplasmonic response are identified, and compared with their solid counterparts and discrete metallic coatings. Additionally, the CSTs tolerance to random rotations is assessed, providing insights into their behavior in fluidic environments and implications for its practical consideration.

We developed an unconventional seed-mediated in situ synthetic method, whereby gold nanostars are formed directly on the internal walls of microfluidic reactors. The dense plasmonic substrate coatings were grown in microfluidic channels with different geometries to elucidate the impacts of flow rate and profile on reagent consumption, product morphology, and density. Nanostar growth was found to occur in the flow-limited regime and our results highlight the possibility of creating shape gradients or incorporating multiple morphologies in the same microreactor, which is challenging to achieve with traditional self-assembly. The plasmonic-microfluidic platforms developed herein have implications for a broad range of applications, including cell culture/sorting, catalysis, sensing, and drug/gene delivery.

This study showcases an experimental demonstration of near‐field optical trapping and dynamic manipulation of an individual extracellular vesicle. This is accomplished through the utilization of a plasmonic dielectric nanoantenna designed to support an optical anapole state—a non‐radiating optical state resulting from the destructive interference between electric and toroidal dipoles in the far‐field, leading to robust near‐field enhancement. To further enhance the field intensity associated with the optical anapole state, a plasmonic mirror is incorporated, thereby boosting trapping capabilities. In addition to demonstrating near‐field optical trapping, the study achieves dynamic manipulation of extracellular vesicles by harnessing the thermoelectric effect. This effect is induced in the presence of an ionic surfactant, cetyltrimethylammonium chloride, combined with plasmonic heating. Furthermore, the thermoelectric effect improves trapping stability by a deep trapping potential. In summary, the hybrid plasmonic‐dielectric trapping platform offers a versatile approach for actively transporting, stably trapping, and dynamically manipulating individual extracellular vesicles. [ABSTRACT FROM AUTHOR]

This study addresses the fabrication of microporous plasmonic nanocomposites (NCs) by using plasmonic nanoparticles (i.e., gold bipyramids, AuB) as seeds to grow microporous shells, specifically, metal–organic frameworks (MOF) PCN‐224 of increasing thickness from 69 to 138 nm. This method is based on using a previously synthesized Zr6‐oxo cluster and unfolds at room temperature. Notably, it is demonstrated that the concentration of the AuB seeds determines both the yield of NCs and the resultant thickness of the PCN‐224 shell, illustrating the seeded growth mechanism. Furthermore, it is found that the thermoplasmonic response of the NCs is dominated by the thickness of the microporous shell, with thicker shells having enhanced thermal confinement properties than thinner ones. As a proof of concept, the NCs are loaded with cresyl violet (CV), a lysosomal fluorescent marker. This serves to demonstrate the thermoplasmonic‐induced intracellular release of CV by the photostimulation of the AuB's plasmonic near‐infrared (NIR) band. Moreover, the NCs display exceptional efficacy as photodynamic agents when photostimulated at the PCN‐224's Soret band. In summary, this study offers a facile, efficient, and reproducible methodology for the fabrication of NCs with a controlled geometry while unlocking new possibilities in the field of nanoMOFs as multifunctional theranostic probes.

Metallic nanoparticles possess strong photothermal responses, especially when illuminated as ensembles due to collective effects. However, accurately quantifying the temperature increase remains a significant challenge, impeding progress in several applications. Anti Stokes thermometry offers a promising solution by enabling direct and non‐invasive temperature measurements of the metal without the need for labeling or prior calibration. While Anti Stokes thermometry is successfully applied to individual nanoparticles, its potential to study light‐to‐heat conversion with plasmonic ensembles remains unexplored. In this study, the theoretical framework and the conditions that must be fulfilled for applying Anti Stokes thermometry to ensembles of nanoparticles are discussed. Then, this technique is implemented to measure the light‐induced heating of square arrays of Au nanodisks. The obtained temperature measurements are validated using wavefront microscopy, demonstrating excellent agreement between the two thermometry methods. These results showcase the extension of Anti Stokes thermometry to plasmonic ensembles, highlighting its potential for implementation in the diverse photothermal applications involving these systems. [ABSTRACT FROM AUTHOR]

Optical heating in solids is fundamentally related to the dissipation of energy during absorption. The absorption of light can nevertheless be enhanced through the excitation of optical resonances (e.g., plasmon, Mie, and Fano). The authors investigate the amplification of light absorption in nanostructured silicon via excitation of the optical near field in the gap between the tip of a silicon probe and a gold film. [ABSTRACT FROM AUTHOR]

While often life‐saving, surgical resectioning of diseased tissues puts patients at risk for post‐operative complications. Sutures and staples are well‐accepted and routinely used to reconnect tissues, however, their mechanical mismatch with biological soft tissue and invasiveness contribute to wound healing complications, infections, and post‐operative fluid leakage. In principle, laser tissue soldering offers an attractive, minimally‐invasive alternative for seamless soft tissue fusion. However, despite encouraging experimental observations, including accelerated healing and lowered infection risk, critical issues related to temperature monitoring and control during soldering and associated complications have prevented their clinical exploitation to date. Here, intelligent laser tissue soldering (iSoldering) with integrated nanothermometry is introduced as a promising yet unexplored approach to overcome the critical shortcomings of laser tissue soldering. It demonstrates that adding thermoplasmonic and nanothermometry nanoparticles to proteinaceous solders enables heat confinement and non‐invasive temperature monitoring and control, offering a route to high‐performance, leak‐tight tissue sealing even at deep tissue sites. The resulting tissue seals exhibit excellent mechanical properties and resistance to chemically‐aggressive digestive fluids, including gastrointestinal juice. The iSolder can be readily cut and shaped by surgeons to optimally fit the tissue defect and can even be applied using infrared light from a medically approved light source, hence fulfilling key prerequisites for application in the operating theatre. Overall, iSoldering enables reproducible and well‐controlled high‐performance tissue sealing, offering new prospects for its clinical exploitation in diverse fields ranging from cardiovascular to visceral and plastic surgery. [ABSTRACT FROM AUTHOR]

Here, we investigate the correlation between the heat generated by gold nanoparticles, in particular nanospheres and nanobipyramids, and their plasmonic response manifested by the presence of Localized Surface Plasmon Resonances (LSPRs). Using a tunable laser and a thermal camera, we measure the temperature increase induced by colloidal nanoparticles in an aqueous solution as a function of the excitation wavelength in the optical regime. We demonstrate that the photothermal performances of the nanoparticles are strongly related not only to their plasmonic properties but also to the size and shape of the nanoparticles. The contribution of the longitudinal and transversal modes in gold nanobipyramids is also analyzed in terms of heat generation. These results will guide us to design appropriate nanoparticles to act as efficient heat nanosources.

Heat generation by means of plasmonic structures, which is at the heart of thermoplasmonics, has stimulated intense research on the manipulation of matter in liquid environments. Tiny noble metal structures with dimensions of a few tens of nanometers thereby serve as heat sources generating large temperature gradients. As a result, thermophoretic drifts occur, concentration fields form, or charge separation takes place. But also hydrodynamic boundary flows, which play an important role in microfluidic environments, can be induced. These processes remotely triggered by optically generated local dynamic temperature fields offer novel possibilities for manipulating and studying not only colloids but in particular also single molecules and their aggregates in solution. [ABSTRACT FROM AUTHOR]

An experimental study on an innovative contrast agent is presented. This work demonstrates that copper sulfide in the form of small-sized nanoparticles can be exploited in photoacoustic imaging. An advantage of this material is strong light absorption in the near-infrared range, especially in the transparency windows of biological tissues. In order to yield a proper contrast, light absorption must be followed by heat release with high efficiency. Therefore, it is important to evaluate the photochemical conversion efficiency of the material. We applied a method that is strictly related to photoacoustic applications. The nanoparticles were produced according to a well-established synthesis. Subsequently, they were diluted in pure water to obtain an extinction <0.2/cm at 1064 nm. The photoacoustic signals, generated by 1064 nm laser excitation, were analyzed as a function of concentration and incident laser energy below 70 μJ /pulse. The signals were carefully compared with those of a reference aqueous solution, containing a light-absorbing ionic solute. Data analysis yielded a light-to-heat conversion efficiency 1.0 (±0.1). We discuss this result by comparison with related studies on other types of copper sulfide nanoparticles, where the conversion efficiency reportedly varied from 33% to 93%. The high value determined in the present study possibly indicates that resonant light scattering and luminescence are negligible for our material system. [ABSTRACT FROM AUTHOR]

Under the action of light under the conditions of plasmon resonance, metal nanoparticles induce nanoscale heating. This effect forms the basis for thermoplasmon probing of phase changes occurring in the nanoscale systems whose investigation is the key problem in the modern materials science. Despite an evident simplicity of such an approach, intensive absorption of light by resonance nanostructures does not ensure the desired optical heating in the cases when the thermal conduction of the medium significantly exceeds that of the plasmonic nanostructure. We propose the approach to creation of the controlled heating of plasmonic nanostructures by nanostructuring the thermostat surface, which is demonstrated with the help of the thermoplasmonic metasurface, which is an array of TiN:Si voxels—the vertical system of nanostructures of titanium nitride (TiN) and silicon (Si) on a silicon substrate. The plasmonic nanostructures of TiN play the role of nanoheaters, while varying the height of silicon thermal conductors makes it possible to control the temperature of heating of the voxels at a fixed value of pump intensity owing to the control of heat localization. The possibility of probing phase transitions in the nanoscale systems is demonstrated by an example of thin polymer films with the use of thermoplasmonic metasurface and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Water and energy are two strategic drivers of sustainable development, intimately interlaced and vital for a secure future of humanity. Given that water resources are limited, whereas global population and energy demand are exponentially growing, the competitive balance between these resources, referred to as the water-energy nexus, is receiving renewed focus. The desalination industry alleviates water stress by producing freshwater from saline sources, such as seawater, brackish or groundwater. Since the last decade, the market has been dominated by membrane desalination technology, offering significant advantages over thermal processes, such as lower energy demand, easy process control and scale-up, modularity for flexible productivity, and feasibility of synergic integration of different membrane operations. Although seawater reverse osmosis (SWRO) accounts for more than 70% of the global desalination capacity, it is circumscribed by some significant technological limitations, such as: (i) the relatively low water recovery factor (around 50%) due to the negative impact of osmotic and polarization phenomena; (ii) an energy consumption in the range of 3–5 kWh m ^−3 , still far from the theoretical energy demand (1.1 kWh m ^−3 ) to produce potable water from seawater (at 50% water recovery factor). Ultimately, desalination is an energy intensive practice and research efforts are oriented toward the development of alternative and more energy-efficient approaches in order to enhance freshwater resources without placing excessive strain on limited energy supplies. Recent years have seen a relevant surge of interest in membrane distillation (MD), a thermally driven membrane desalination technology having the potential to complement SWRO in the logic of Process Intensification and Zero Liquid Discharge paradigm. Due to its peculiar transport mechanism and negligibility of osmotic phenomena, MD allows high-quality distillate production (theoretically, non-volatile species are completely rejected) with a recovery factor of up to 80% at a relatively low operative temperature (typically 60 °C–80 °C). Although low operative temperatures make MD technology attractive for renewable power applications (e.g. solar thermal, wind or geothermal energy sources) or for efficient exploitation of low-grade or waste heat streams, the low energy efficiency intrinsically due to heat losses—and specifically to temperature polarization—has so far hindered the application at industrial scale. Nowadays, photothermal materials able to absorb and convert natural or artificial irradiation into heat have gained great attention, demonstrating the potential to mitigate the ‘anthropic’ energy input to MD and to mitigate the impact of thermal inefficiencies. On this road, a step-change improvement in light-to-heat conversion is expected through high-throughput computational screening over thermoplasmonic materials based on electronic and optical properties of advanced materials including novel topological phases of matter used as nanofillers in polymeric membranes. Coherently with the concept of Circular Economy, waste hypersaline solutions rejected from desalination process (referred as ‘brine’) are now the subject of valorization activities along two main exploitation routes: (1) recovery of valuable minor and trace metals and minerals, with special focus on critical raw materials (including, among others, Mg, Na, Ca, K, Sr, Li, Br, B, and Rb); (2) production of salinity gradient power (SGP) renewable energy resulting from the recovery of the Gibbs energy of mixing (mainly represented by the entropic contribution) of two solutions having different ionic concentration. The exciting new frontier of sustainable mining of seawater concentrates is accelerating the appearance of a plethora of innovative membrane materials and methods for brine dehydration and selective extraction of trace ions, although under the sword of Damocles represented by cost feasibility for reliable commercial application. On the other hand, among several emerging technologies, reverse electrodialysis (SGP-RED) was already proven capable—at least at the kW scale–of turning the chemical potential difference between river water, brackish water, and seawater into electrical energy. Efforts to develop a next generation of ion exchange membranes exhibiting high perm-selectivity (especially toward monovalent ions) and low electrical resistance, to improve system engineering and to optimize operational conditions, pursue the goal of enhancing the low power density so far achievable (in the order of a few W per m ^2 ). This Roadmap takes the form of a series of short contributions written independently by worldwide experts in the topic. Collectively, such contributions provide a comprehensive picture of the current state of the art in membrane science and technology at the water-energy nexus, and how it is expected to develop in the future. In addition, this Roadmap acknowledges the challenges and advances in membrane systems, particularly emphasizing the interplay of material innovation and system optimization, which collectively contribute to advancing the desalination field within the water-energy nexus framework.

In this work, we establish a new paradigm on identifying optimal arbitrarily shaped metallic nanostructures for photothermal applications. Crucial thermo-optical parameters that rule plasmonic heating are appraised, exploring a nanoparticle size-dependence approach. Our results indicate two distinct figures of merit for the optimization of metallic nanoheaters, under both non-cumulative femtosecond and continuum laser excitation. As a case study, gold nanorods are evaluated for infrared photothermal conversion in water, and the influence of the particle length and diameter are depicted. For non-cumulative femtosecond pulses, efficient photothermal conversion is observed for gold nanorods of small volumes. For continuous wave (CW) excitation at 800 nm and 1064 nm, the optimal gold nanorod dimensions (in water) are, respectively, 90 × 25nm and 150 × 30 nm. Figure of Merit (FoM) variations up to 700% were found considering structures with the same peak wavelength. The effect of collective heating is also appraised. The designing of high-performance plasmonic nanoparticles, based on quantifying FoM, allows a rational use of nanoheaters for localized photothermal applications. [ABSTRACT FROM AUTHOR]

The current COVID-19 pandemic has resulted in an urgent need for methods to decontaminate respirators masks for reuse while keeping them intact and functional. The severe shortage of professional masks such as N95 and FFP2 has necessitated their reuse over long periods. A very promising method is the pasteurization of these masks by thermoplasmonic heat generated by plasmonics nanoparticles when they are irradiated by light. Under illumination at its plasmonic resonance, a metal nanoparticle features enhanced light absorption, turning it into an ideal nano-source of heat, remotely controllable using light. In this work, we propose a numerical study based on the finite element method (FEM) of the thermoplasmonic properties of silver nanoparticles (AgNPs) decorating polypropylene (PP) fibers which is a basic material for the manufacture of these masks. The surface plasmon resonance (SPR) of these nanostructures was investigated through the computation of the complex effective dielectric permittivity and the absorption cross section in the near UV–visible (NUV-Vis) range. First, the SPR characteristics of AgNPs for different morphologies are determined from the absorption spectra, including the SPR-peak position λmax and the electric field enhancement. Second, we determine the power absorbed by an individual AgNP of different morphologies. From this, we calculate the internal temperature increase of the particle at the plasmonic resonance. The last step is devoted to the determination of the temperature profile in the surrounding medium in order to better understand and design the plasmon-assisted heating processes at the nanometric scale. [ABSTRACT FROM AUTHOR]

We propose an approach to controlling the heating of plasmonic nanostructures by nanostructuring the thermostat surface. We demonstrate this using a two-dimensional array of TiN:Si voxels, which are a system of stacked titanium nitride and silicon nanocylinders. The optical heating of plasmon nanostructures can be directly controlled by the height of silicon columns at a fixed value of the pump intensity. The height of silicon nanopillar sets the operating temperature range, while the pumping intensity allows one to control the temperature in this range. We register this effect using Raman thermometry. Using plasmonic metasurface with array of TiN:Si voxels, we demonstrate the detection of the such phase transitions in nanoconfined polymers as the glass transition temperature and melting temperature at the nanoscale using Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Having full control of light propagation in free space represents the ultimate goal for an imaging system. Spatial Light Modulators (SLMs), featuring the ability to actively control the spatial distribution of light components, are usually limited either to performing small and continuous adjustments to imaging aberrations or to rapidly shifting discrete segments of the wavefront with severe diffraction artifacts. Here a photothermally modulated optical structure is introduced as a highly responsive SLM capable of producing arbitrarily shaped wavefront patterns with smooth as well as step‐like features. The phase‐shift inducing temperature profile within the plasmonic metamaterial at the core of the SLM structure replicates closely the pattern of illuminating light intensity avoiding the common speed and spatial gradient limitations. As a result, the SLM concept is insensitive to polarization, free of diffraction artifacts, and offers sub‐millisecond response time and high transmittance >80%. The dynamic generation of a set of common optical functions is demonstrated, including low‐order Zernike polynomials patterns, phase grating, or vortex, which build an essential phase modulation toolbox across different imaging applications. [ABSTRACT FROM AUTHOR]

The plasmonic properties of asymmetric nanoparticles have an important role in a wide range of applications such as photonics, sensing, and catalysis. In this work, we break the symmetry of the hexagonal nano-ring dimers (HNDs). Our results show that the HNDs can confine light in subwavelength volumes and, consequently, achieve intense local electric field enhancement at resonance wavelengths. Three categories of multimodal resonances i.e. resonances that are hybrids of different multiples were studied here. On the other hand, while asymmetric nanoparticles have been mainly studied for their plasmonic properties, recently they have been used for increasing local thermal-induced processes in different fields such as bio-imaging and medical therapy. In line with this goal, we studied the thermoplasmonic properties of HNDs. We find that the maximum temperature is strongly dependent on the symmetry of nanorings i.e. the distance between the center of the cavity and the nanoparticles (d). The lowest temperature changes occur when the cavity is located in the middle of the nanoparticles due to the lowest asymmetry (ΔTmax = 22 °C). Moreover, by increasing the value of d, due to increased hybridization, the second and third plasmonic modes are formed and the temperature increases in all three modes. The result of this work opens new possibilities for controlling photo-thermal processes such as chemical and metabolic thermal activation and local melting. [ABSTRACT FROM AUTHOR]

Shortage of freshwater is a global challenge related to population growth, changes in climate conditions and industrial and agricultural needs. Thus, sustainable freshwater production through desalination and wastewater treatment is essential for various human purposes. Membrane distillation (MD) is a recent thermal driven membrane based purification technology with capability to eliminate the limitations of traditional desalination technologies by a synergistic exploitation of the nexus between water and energy. Though MD is recognized as an ecofriendly technology, input heat energy utilization and its efficient management remains a challenge influencing the economic viability of the technology and hindering its realistic applications. To solve this problem, it requires an integrative approach involving materials chemistry, physical chemistry, polymer science, and materials engineering. In addition to the use of robust wetting and fouling resistant membranes, employing the newly developed self-surface heating membranes such as photothermal, joule heating and induction heating membranes have not only minimized energy requirement and fouling issues of MD technology but also enabled it to be considered as potential and economically viable approach for producing high-quality freshwater with negligible carbon footprint. Specifically, recent studies on self-surface heating membranes, utilizing nanomaterials with photothermal, conductive, and magnetic properties, have revealed new possibilities for renewable energy utilization in MD technology. Through direct irradiation or photovoltaic energy conversion, nanomaterial-integrated membranes significantly enhance MD's energy efficiency and productivity without compromising cost-effectiveness, opening avenues for sustainable desalination and water purification technologies. Here, we furnish a comprehensive state of the art overview on (1) the progress of conventional antifouling MD membranes and (2) the opportunities, challenges and limitations of the emerging field of self-surface heated MD (i.e., photothermal MD (PMD), Joule-heating MD and Induction heated MD). We also discuss the exceptional physicochemical properties, antifouling properties, fabrication and scalability of self-surface heating membranes, as well as the strategies for their deployment into MD modules enabling localization of heat at the membrane surface for direct feed heating, thereby leading to sustainable freshwater production. [ABSTRACT FROM AUTHOR]

• A size-dependent optimization approach is explored to identify gold nanorods as high performance nanoheaters. • The collective optical heating mediated by gold nanorods for hyperthermia is discussed. • Cytotoxicity of different concentrations of gold nanorods is evaluated. • Optimized size of gold nanorod for yeast near-infrared photothermal inactivation is identified. [Display omitted] The use of photothermal processes has been proven effective in the control of microbial infections. Simultaneously, the localized surface plasmon resonance phenomena in metallic nanoparticles have been explored as an alternative strategy to achieve highly efficient localized heating. In this work, we propose the use of selected nanoheaters to improve the efficiency of fungal photothermal inactivation of Candida albicans through size optimization of plasmonic gold nanorods. Here, the optical heating of polyethylene glycol coated gold nanorods of varying sizes is evaluated, both theoretically and experimentally. A size-dependent computational approach was applied to identify metallic nanorods with maximized thermal performance at 800 nm, followed by the experimental comparison of optimal and suboptimal nanoheaters. Comparison among samples show temperatures of up to 53. 0 °C for 41 × 10 nm gold nanorods against 32. 3 °C for 90 × 25 nm, a percentage increase of ∼ 63% in photothermal inactivation assessments. Our findings reveal that gold nanorods of 41 × 10 nm exhibit superior efficiency in near-infrared (800 nm) photothermal inactivation of fungi, owing to their higher light-thermal conversion efficiency. The identification of high performance metallic nanoheaters may lead to the reduction of the nanoparticle dose used in plasmonic-based procedures and decrease the laser exposure time needed to induce cell death. Moreover, our results provide insights to better exploit plasmonic nanoparticles on photothermal inactivation protocols. [ABSTRACT FROM AUTHOR]

Plasmonics offer unprecedented control over light and stimulate fundamental research and engineering applications in solar energy. The surface plasmon resonance is responsible for both enhanced light scattering and absorption. The plasmon excitations in nanostructures can be tuned to control the hot-carrier emission. The damping dissipation of the kinetic energy of surface plasmons releases heat at nanoscale, which can be used to create high-performance nano-heaters and/or radiators. Spectrally and/or thermally engineered plasmonic nanomaterials attract considerable attention for solar energy application due to their distinct thermoplasmonic properties. In light of these advances, this paper provides a critical review of current research in thermoplasmonics with focus on its physic mechanisms, structure tuning strategies and solar energy applications. Basic mechanism of thermoplasmonics is described from the photothermal conversion and heat transfer physics to thermal-induced processes. Structure tuning strategies including self-tunable plasmons, plasmon coupling strategies and active plasmons with tunable gap distances are then fully discussed in terms of their principles and structures. Based on the flourishing development of novel thermoplasmonic structures, potential applications ranging from solar collector, solar radiator, thermo-photovoltaic, solar desalination and sterilization, solar degradation and catalysis, to solar fuels, and solar fertilizers are additionally highlighted. The advantages of using plasmonics over the conventional technologies are identified, and the areas where important basics involved when the thermoplasmonics bringing into application are stressed throughout the text. Finally, we provide our views on future challenges in solar thermoplasmonics, together with a few suggestions for further developments of this technology. This work would bring new insights and inspire innovative works on designing thermoplasmonics for solar energy application. [ABSTRACT FROM AUTHOR]

Nanofocusing of electromagnetic (EM) energy is an emblematic effect that guides EM energy along plasmonic conical structures, effectively focusing it at its nanometer‐sized extremity. However, EM energy nanofocusing could also be accompanied by (often disregarded) heating. Here, rigorous 3D finite element method simulations of a plasmonic conical structure were performed with a finite‐size apex excited by a continuous wave radially polarized beam over visible and near‐infrared wavelengths. Together with broadband nanofocusing the presence of narrowband Fabry–Pérot (FP) like resonances is demonstrated. Importantly, FP‐like resonances yield strong temperature localization that adds to the broadband nanofocusing component, providing an extra degree of freedom in tuning the temperature localization through proper selection of the structure dimensions suitable for applications in Raman, electron emission spectroscopies or sharp‐tip nanofabrication strategies. [ABSTRACT FROM AUTHOR]

The linear electronic dispersion relation of graphene endows the atomically thin carbon layer with a large intrinsic optical nonlinearity, with regard to both parametric and photothermal processes. While plasmons in graphene nanostructures can further enhance nonlinear optical phenomena, boosting resonances to the technologically relevant mid- and near-infrared (IR) spectral regimes necessitates patterning on ∼10 nm length scales, for which quantum finite-size effects play a crucial role. Here we show that thermoplasmons in narrow graphene nanoribbons can be activated at mid- and near-IR frequencies with moderate absorbed energy density, and furthermore can drive substantial third-harmonic generation and optical Kerr nonlinearities. Our findings suggest that photothermal excitation by ultrashort optical pulses offers a promising approach to enable nonlinear plasmonic phenomena in nanostructured graphene that avoids potentially invasive electrical gating schemes and excessive charge carrier doping levels.

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., Competing Interests: Declaration of competing interest The authors have no competing interests to declare., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Gold nanoparticles possess unique photothermal properties and have gained considerable interest in biomedical research, particularly for photothermal therapy (PTT). This study focuses on evaluating the photothermal properties of gold nanorods (AuNRs) supported on glass substrates upon excitation with near-infrared (NIR) light. Two aspect ratios of AuNRs were electrostatically immobilized onto glass with controlled coverage. In situ X-ray diffraction (XRD) was performed to evaluate the photothermal behavior and morphological changes of the supported AuNRs during NIR laser irradiation. The XRD data sets were corroborated with scanning electron microscopy and Vis-NIR spectroscopy characterization. XRD revealed a linear temperature increase with laser power, aligning with theoretical predictions, and a slope dependent on the AuNR coverage, until the onset of morphology transformations around 120 °C. This study provides valuable insights into the photothermal properties of supported AuNRs, crucial for their application in PTT.

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., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

An experimental study on an innovative contrast agent is presented. This work demonstrates that copper sulfide in the form of small-sized nanoparticles can be exploited in photoacoustic imaging. An advantage of this material is strong light absorption in the near-infrared range, especially in the transparency windows of biological tissues. In order to yield a proper contrast, light absorption must be followed by heat release with high efficiency. Therefore, it is important to evaluate the photochemical conversion efficiency of the material. We applied a method that is strictly related to photoacoustic applications. The nanoparticles were produced according to a well-established synthesis. Subsequently, they were diluted in pure water to obtain an extinction

In this paper, the optical and thermoplasmonics properties of nanocomposites consisting of spherical gold nanoparticles (AuNPs) integrated in Al 2 O 3 matrix are determined using the Finite Element Method (FEM). Firstly, the refractive index (n) , extinction coefficient (κ) , absorption coefficient (μ a) , and optical conductivity (σ) are calculated from the effective complex permittivity obtained by solving the Laplace's equation for different size and concentration of nanoparticles. The surface plasmon resonance (SPR) properties of AuNPs are optimized from the peak presented in the absorption coefficient spectrum. The results show that the optical parameters n , κ , μ a , and σ undergo a strong variation around the wavelength λ max corresponding to the SPR phenomenon. The value of λ max increases from 560 to 600 n m when the radius of the particles varies between r = 5 and r = 30 n m . The effect of the AuNP concentration on the band gap energy E g (e V) of Au- Al 2 O 3 nanocomposites is also studied, a shift from E g = 5.34 to E g = 5.49 e V is observed when the concentration of the AuNPs increases from 0 to 0.82 % . The electric field enhancement induced by the AuNPs at plasmonic resonance is also determined depending to the particle size; the results show that the enhancement factor increases from g = 4.71 to g = 6.95 when the radius of the AuNPs increases from r = 5 to 30 n m . The thermal dissipation of the plasmonic energy of spherical of our system dispersed in the Al 2 O 3 matrix is determined considering the Joule effect which occurs by the oscillation of the charges at the plasmonic resonance. The generated thermal power by particles is calculated for different sizes, which allows to calculate the thermal power per gram of particles depending on the intensity of the incident electric field. The results show that the plasmonic thermal power is almost identical for small particles when the radius is less than r = 15 n m and increases considerably when the size increases from r = 15 to 30 n m . For a fixed size and incident field amplitude, we calculated the temperature change in the nanocomposites Au- Al 2 O 3 depending of time for different particle concentrations; the temperature variation curves obtained are linear as a function of time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Designing a smart window with an adaptive cooling performance up to ∼13.9 °C. • Extending high-efficiency spray assembly method for scale-up of smart windows. • Proving the pressure-dependent adsorption kinetic of Au NPs in spray assembly. Smart windows for adaptive solar modulation have attracted considerable attention because of their broad prospects in energy-saving buildings. Herein, energy-saving smart windows are fabricated by the high-efficiency spray assembly of thermoplasmonic gold nanoparticles (Au NPs). First, the adsorption kinetics of the Au NPs in the spray assembly are investigated based on a pseudo-first-order kinetics equation, which exhibit a spray-pressure dependency. The amount of adsorbed Au NPs after spraying at 30 psi for 20 s is up to ∼80% the saturation adsorption amount, demonstrating the high-speed characteristic of the spray assembly. The spray-assembled Au NP coating, as a solar heating surface, is used to construct smart windows for adaptive solar modulation with the thermochromic poly(N-isopropylacrylamide) hydrogel. The obtained smart window shields 76.6% of the total solar irradiation in the range 300–2500 nm and allows 80.3% of the visible light to enter indoors before optical switching by the hydrogel ensures visual comfort. The cooling performance of the smart window is determined to be ∼13.9 °C by a model house test under a stimulated solar irradiation of 2.8 kW·m−2 (2.8 suns). Moreover, the fabrication method is suitable for flexible substrates to prepare bendable smart windows. This work provides a speed-up fabrication strategy for the large-scale manufacturing of energy-saving smart windows. [ABSTRACT FROM AUTHOR]

Covalent-organic frameworks (COFs) hold promise for photocatalysis, but their efficiency is hindered by strong excitonic effects that limit charge separation and transfer. Here, we demonstrate a novel strategy to overcome this challenge by integrating thermoplasmonic TiN nanoparticles with a β -ketoenamine-linked COFs (TFP-BD). The enhanced local electromagnetic field generated by TiN promotes the separation of electron-hole pairs in TFP-BD. This enhancement is evidenced by a doubled carrier lifetime (∼0.99 ns) and photocurrent density (1.67 μA cm⁻²) in the 3% TiN@TFP-BD composite compared to pristine TFP-BD. Additionally, thermoplasmonic heating in 3% TiN@TFP-BD (69.2 °C) surpasses that of TFP-BD (62.15 °C), accelerating mass transport during the photocatalytic process. This synergistic effect leads to a remarkable hydrogen evolution rate (HER) of 37.59 mmol g⁻¹ h⁻¹, an 8.5-fold improvement over the pristine COFs. Our work highlights the potential of thermoplasmonic enhancement for solar fuel production and establishes a new approach to mitigate excitonic limitations in COF-based photocatalysts. [Display omitted] • Thermoplasmonic materials enhance photocatalytic semiconductors due to their superior local electromagnetic field and photothermal effect. • Covalent organic frameworks, with complementary absorption to plasmons and heat insulation, are ideal to study thermoplasmonic enhancement. • Benefiting from the synergistic effects of enhanced electromagnetic field and nano heat, an outstanding HER of 37.59 mmol g-1 h-1 is achieved. • This work highlights the thermoplasmonic enhancement for solar fuel production and offers a new approach to tackle COFs' excitonic effects. [ABSTRACT FROM AUTHOR]

In this work, we establish a new paradigm on identifying optimal arbitrarily shaped metallic nanostructures for photothermal applications. Crucial thermo-optical parameters that rule plasmonic heating are appraised, exploring a nanoparticle size-dependence approach. Our results indicate two distinct figures of merit for the optimization of metallic nanoheaters, under both non-cumulative femtosecond and continuum laser excitation. As a case study, gold nanorods are evaluated for infrared photothermal conversion in water, and the influence of the particle length and diameter are depicted. For non-cumulative femtosecond pulses, efficient photothermal conversion is observed for gold nanorods of small volumes. For continuous wave (CW) excitation at 800 nm and 1064 nm, the optimal gold nanorod dimensions (in water) are, respectively, 90 × 25nm and 150 × 30 nm. Figure of Merit (FoM) variations up to 700% were found considering structures with the same peak wavelength. The effect of collective heating is also appraised. The designing of high-performance plasmonic nanoparticles, based on quantifying FoM, allows a rational use of nanoheaters for localized photothermal applications.

Sunlight-to-electricity conversion using solar thermoelectric generators (STEGs) is a proven technology to meet our ever-growing energy demand. However, STEGs are often operated under a vacuum with customized thermoelectric materials to achieve high performance. In this work, the incorporation of plasmonic gold nanoparticle (AuNP) based solar absorbers enabled the efficient operation of STEGs under ambient conditions with commercially available thermoelectric devices. AuNPs enhanced the performance of STEG by ∼9 times, yielding an overall solar-to-electricity conversion efficiency of ∼9.6% under 7.5 W cm -2 solar irradiance at ambient conditions. Plasmonic heat dissipated by AuNPs upon solar irradiation was used as the thermal energy source for STEGs. High light absorptivity, photothermal conversion efficiency (∼95%), and thermal conductivity of AuNPs enabled the efficient generation and transfer of heat to STEGs, with minimal radiative and convective heat losses. The power generated from plasmon-powered STEGs is used to run electrical devices as well as produce green hydrogen via the electrolysis of water.

Tuning optical properties of plasmonic nanostructures, including their absorption, scattering, and local‐field distribution is of great interest for various applications that rely on optical energy regulated by plasmonic effects. Conventional plasmonic nanostructures enhance light scattering and absorption simultaneously, leading to compromise for either surface‐enhanced spectroscopy or thermoplasmonic applications. In this paper, a dual functional platform based on a hyperbolic meta particles (HMP) substrate that exhibits separate and tuneable wavelengths of absorption and scattering resonances for both thermoplasmonics and surface enhanced Raman spectroscopy (SERS), is demonstrated. Significantly, either light‐to‐heat conversion efficiency at the absorption resonance band or SERS performance at the scattering resonance band of the HMP substrate is improved in comparison to those of plasmonic gold nanoparticles. Taking advantage of the flexible control of the separate scattering and absorption channels, the influence of the absorption resonance band position on the SERS signal is also investigated. The platform shows unique potential for in vitro biosensing in thermal modulation and in situ monitoring. [ABSTRACT FROM AUTHOR]

There is great interest in the development of alternatives to noble metals for plasmonic nanostructures. Transition metal nitrides are promising due to their robust refractory properties. However, the photophysics of these nanostructures, particularly the hot carrier dynamics and photothermal response on ultrafast timescales, are not well understood. This limits their implementation in applications such as photothermal catalysis or solar thermophotovoltaics. In this study, the light‐induced relaxation processes in water‐dispersed HfN nanoparticles are, for the first time, elucidated by fs transient absorption, Lumerical FDTD and COMSOL Multiphysics simulations, and temperature‐dependent ellipsometry. It is unequivocally demonstrated that HfN nanoparticles convert absorbed photons into heat within <100 fs; no signature of hot charge carriers is observed. Interestingly, under high photon energy or intense irradiation stimulated Raman scattering characteristic of oxynitride surface termination is observed. These findings suggest that transition metal nitrides could offer benefits over noble metals in the field of plasmonic photothermal catalysis. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate that the plasmonic heat delivered by a single layer of homogeneously distributed gold nanoparticles (AuNPs), immobilized on a glass substrate, can be optically tuned by taking advantage of the properties of an organic layer based on azobenzene and nematic liquid crystal (NLC) molecules. The effect, which exploits the dependence of the NLC refractive index value on the molecular director orientation, is realized using the polarization-dependent, light-induced molecular reorientation of a thin film of photo-aligning material that the NLC is in contact with. The reversibility of the optically induced molecular director reorientation of the NLC enables an active modulation of the plasmonic photo-induced heat. [ABSTRACT FROM AUTHOR]

Aim: To realize and characterize a new generation of keratin-coated gold nanoparticles (Ker-AuNPs) as highly efficient photosensitive nanosized therapeutics for plasmonic photothermal (PPT) therapy. Materials & methods: The chemical, physical, morphological and photothermal properties of Ker-AuNPs are investigated using dynamic light scattering, ζ-potential, UV–Visible, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, transmission electron microscopy and high-resolution thermography. In vitro experiments are performed on a human glioblastoma cell line (i.e., U87-MG), using viability assays, transmission electron microscopy, fluorescence microscopy, cytometric analyses and PPT experiments. Results: Experiments confirm the excellent biocompatibility of Ker-AuNPs, their efficient cellular uptake and localized photothermal heating capabilities. Conclusion: The reported structural and functional properties pointed out these Ker-AuNPs as a promising new tool in the field of biocompatible photothermal agents for PPT treatments against cancer-related diseases. This work involves the synthesis and application of nanosized keratin-coated gold particles; a protein extracted from wool. Their effect against a specific type of brain cancer, glioblastoma, is investigated. Gold nanoparticles have been the subject of a lot of interest recently due to their ability to convert light energy into heat energy. When the keratin-coated nanoparticles were up taken into cancerous cells and exposed to light from a laser, they heated up and killed the cancer cells. The next step for this research is to conduct more detailed studies in animals, hopefully leading to a new generation of nanosized therapeutics in the fight against cancer. [ABSTRACT FROM AUTHOR]

Precise measurement and control of local heating in plasmonic nanostructures are vital for diverse nanophotonic devices. Despite significant efforts, challenges in understanding temperature-induced plasmonic nonlinearity persist, particularly in light absorption and near-field enhancement due to the absence of suitable measurement techniques. This study presents an approach allowing simultaneous measurements of light absorption and near-field enhancement through angle-resolved near-field scanning optical microscopy with iterative opto-thermal analysis. We revealed gold thin films exhibit sublinear nonlinearity in near-field enhancement due to nonlinear opto-thermal effects, while light absorption shows both sublinear and superlinear behaviors at varying thicknesses. These observations align with predictions from a simple harmonic oscillation model, in which changes in damping parameters affect light absorption and field enhancement differently. The sensitivity of our method was experimentally examined by measuring the opto-thermal responses of three-dimensional nanostructure arrays. Our findings have direct implications for advancing plasmonic applications, including photocatalysis, photovoltaics, photothermal effects, and surface-enhanced Raman spectroscopy.