Plasmonic Nanostructures for Photothermal Conversion

Immunomodulatory effects of metal nanoparticles: current trends and future prospects

The advent of nanotechnology has steered into a new era of medical advancements, with metal nanoparticles (MNPs) emerging as potent agents for precise regulation of the immune system. This review provides a comprehensive overview of the immunomodulatory roles of MNPs, including gold, silver, and metal oxide nanoparticles, in regulating innate and adaptive immunity. Additionally, we discuss the immunological effects of metal ions and metal complexes, offering a comparative analysis with nanoparticulate systems. We analyse cutting-edge strategies utilising MNPs to optimise vaccine efficacy, achieve targeted delivery to immune cells, and orchestrate inflammatory responses. Additionally, we discuss the therapeutic potential of MNPs in combating autoimmune diseases, cancers, and infectious agents, which is evaluated within the framework of precision medicine. Furthermore, we critically assess challenges such as biocompatibility, potential toxicity, and regulatory hurdles. Finally, we propose future directions for integrating MNPs with advanced delivery systems and other nanomaterials to propel the frontiers of immunotherapy. This review aims to provide a foundational understanding of MNP-mediated immunomodulation, inspiring further research and development in this burgeoning field.

Lignin-Based Photothermal Materials: Bridging Sustainability and High-Efficiency Energy Conversion

Photothermal materials can effectively absorb light and convert it into heat, providing sustainable solutions to mitigate environmental pollution and energy shortages. Compared to traditional photothermal materials, lignin has garnered significant attention due to its wide availability, low cost, biocompatibility, renewability, and sustainability. Consequently, lignin-based materials are considered ideal candidates for the development of eco-friendly photothermal systems, aligning well with the increasing demand for sustainable energy solutions. This review discusses the potential of lignin-based photothermal materials, highlighting their unique molecular structure and the photothermal properties imparted by their aromatic rings, which facilitate effective energy conversion through non-radiative vibrational relaxation. Discussed the latest advances in the applications of lignin photothermal materials in photothermal drive, solar desalination, and biomedicine. Despite the significant potential of lignin, challenges such as structural variability, long-term stability, and scalability remain critical. This paper integrates recent progress and proposes strategies to optimize the photothermal performance of lignin-based materials, while emphasizing important directions for sustainable development, thereby providing a roadmap to fully realize the potential of lignin in next-generation green technologies.

Superior photothermal conversion performance of black titanium-based materials

The application of photothermal conversion technology in the fields of seawater desalination and wastewater treatment stands as a potent approach to alleviating the global water scarcity crisis. In this research, we have successfully synthesized black titanium-based photothermal conversion materials utilizing the aluminothermic reduction method. The experimental results demonstrate that the crafted black TiO2 exhibits a notable overall solar energy absorptivity of 65.7% and a photothermal conversion efficiency of 87.5%. Notably, the black Magneli phase titanium oxide (Ti4O7 and Ti5O9), derived from nanorutile TiO2, exhibits an even more impressive overall solar absorptivity of 83.4% and a photothermal conversion efficiency of 93.8%. Under a light intensity of 5 kW/m2, this material achieves an evaporation rate of 4.4 kg m-2·h-1 and an evaporation efficiency of 63%, underscoring its vast potential for applications in wastewater purification and seawater desalination.

Molecular Engineering of a SICTERS Small Molecule with Superior In Vivo Raman Imaging and Photothermal Performance

Raman-based theranostics has demonstrated great potential for sensitive real-time imaging and treatment. However, these advanced materials, primarily depending on the SERS technique, encounter clinical concerns regarding substrate biosafety. Herein, we molecularly engineered a de novo substrate-free SICTERS small molecule, namely BTT-TPA (bis-thienyl-substituted benzotriazole selenadiazole derivative structures), possessing both ultrasensitive Raman signals and excellent photothermal effects based on self-stacking. The mechanistic studies confirm that BTT maintains the planar structure with polycyclic distorted vibrations required for SICTERS. TPA enhances the donor-acceptor interaction, yielding a Raman sensitivity of BTT higher than previously reported SICTERS molecules; it also acts as a molecular rotor, increasing the photothermal conversion efficiency to 67.44%, which is superior to most of the existing SERS-based photothermal materials. In the tumor model of mouse orthotopic colon cancer, BTT-TPA NPs demonstrate a great Raman imaging-guided photothermal therapy effect in eliminating primary and metastatic tumors, remarkably decreasing the recurrence rate. This work puts forward substrate-free SICTERS small molecules toward Raman-based theranostic applications in vivo.

Nanocomposite-based PCR reactors to enhance thermal rate and fluorescence intensity in hand-held qPCR device

A photonic quantitative polymerase chain reaction (qPCR) has usually implemented a polydimethylsiloxane (PDMS) based disposable inexpensive PCR reactor, worked as the photothermal cycler, to show potential as a point-of-care test (PoCT) for detection nucleic acids. However, the PoCT type photonic qPCR has to overcome the prolonged time for the fabrication of PDMS-based PCR reactors and enable a rapid thermal cycler to shorten diagnosis time with a strong fluorescence intensity. Here, we developed a room-temperature curable titanium dioxide (TiO2) nanoparticle dispersed PDMS (TiO2-PDMS) nanocomposite to reduce the fabrication time of the PCR reactor which enhanced the speed of photothermal cycles and fluorescence signal intensity of photonic qPCR. The TiO2-PDMS nanocomposite was formulated for rapid cross-linking at the room-temperature by introducing an optimized amount of Pt catalyst, resulting in the fabrication of a nanocomposite-based PCR reactor within 8 min at room-temperature. The nanocomposite-based PCR reactor enhanced the heating rate to 18.33 Cº/s and cooling rate to -3.11Cº/s because of the phonon scattering effect of TiO2 in the reactor and successfully amplified λ-DNA (amplicon size of 100 bp) within 10 min. Finally, we improved the qPCR efficiency by 2 cycle threshold (Ct) value compared with pristine PDMS reactor and quantified up to 10 copies/µL nucleic acids by fluorescence intensity enhancement resulting from light reflections property of TiO2. By using TiO2-PDMS nanocomposite-based PCR reactors, the fast and efficient nucleic acid assay was enabled without loss of sensitivity, and it can be practically used in the field of PoCT.

Nanostructured Surfaces with Plasmonic Activity and Superhydrophobicity: Review of Fabrication Strategies and Applications

Plasmonics and superhydrophobicity have garnered broad interest from academics and industry alike, spanning fundamental scientific inquiry and practical technological applications. Plasmonic activity and superhydrophobicity rely heavily on nanostructured surfaces, providing opportunities for their mutually beneficial integration. Engineering surfaces at microscopic and nanoscopic length scales is necessary to achieve superhydrophobicity and plasmonic activity. However, the dissimilar surface energies of materials commonly used in fabricating plasmonic and superhydrophobic surfaces and different length scales pose various challenges to harnessing their properties in synergy. In this review, an overview of various techniques and materials that researchers have developed over the years to overcome this challenge is provided. The underlying mechanisms of both plasmonics and superhydrophobicity are first overviewed. Next, a general classification scheme is introduced for strategies to achieve plasmonic and superhydrophobic properties. Following that, applications of multifunctional plasmonic and superhydrophobic surfaces are presented. Lastly, a future perspective is presented, highlighting shortcomings, and opportunities for new directions.

Photothermal Material-Based Solar-Driven Cogeneration of Water and Electricity: An Efficient and Promising Technology

With the increasing demand for fresh-water and electricity in modern society, various technologies are being explored to obtain fresh-water and electricity. Due to advances in materials science, solar-driven interfacial evaporation (SDIE) systems have attracted widespread attention because they require only solar energy, and possess a high evaporation rate and little pollution. The researchers combined energy harvesting measures into the system to output electricity, further improving energy utilization. However, more in-depth research and review remain on using SDIE systems for efficient water-electricity cogeneration. Therefore, the mechanisms of different photothermal materials that utilize solar energy to produce thermal energy are first summarized in this paper. Subsequently, the mechanism and application of thermal, mechanical, chemical, and evaporation energy to produce electrical power in SDIE water-electricity cogeneration systems are discussed. Concurrently, vital mathematical equations and widely used mathematical simulation methods for performance evaluation and practical applications are presented. The design and operation of water-electricity cogeneration systems based on photothermal materials are analyzed and summarized. Based on a review and in-depth understanding of these aspects, the future development direction of cogeneration is proposed to address the problems faced in basic research and practical applications.

Numerical Simulation of Light to Heat Conversion by Plasmonic Nanoheaters

Plasmonic nanoparticles are widely recognized as photothermal conversion agents, i.e., nanotransducers or nanoheaters. Translation of these materials into practical applications requires quantitative analyses of their photothermal conversion efficiencies (η). However, the value of η obtained for different materials is dramatically influenced by the experimental setup and method of calculation. Here, we evaluate the most common methods for estimating η (Roper's and Wang's) and compare these with numerical estimates using the simulation software ANSYS. Experiments were performed with colloidal gold nanorod solutions suspended in a hanging droplet irradiated by an 808 nm diode laser and monitored by a thermal camera. The ANSYS simulations accounted for both heating and evaporation, providing η values consistent with the Wang method but higher than the Roper approach. This study details methods for estimating the photothermal efficiency and finds ANSYS to be a robust tool where experimental constraints complicate traditional methods.

Nanostructure-Mediated Photothermal Effect for Reinforcing Physical Killing Activity of Nanorod Arrays

The physical killing of bacteria based on surface topography has attracted much attention due to the sustainable and safe prevention of biofilm formation. However, the antibacterial efficiency of biomedical implants derived solely from nanostructures or microstructures is insufficient to combat bacteria against common infections, such as methicillin-resistant Staphylococcus aureus with thick cell walls. Herein, photothermal therapy is carried out in the presence of nanorod arrays to mitigate infection of biomedical implants. Different from traditional photothermal therapy relying on a photosensitizer, the photothermal effect is mediated by light traps rendered by the nanorod arrays, and consequently, the photosensitizer is not needed. Finite element simulations and experiments are performed to elucidate the light-to-thermal conversion mechanism. This photothermal platform, in conjunction with thermosensitive nitric oxide therapy, is applied to treat titanium implant infection. The nanostructure-mediated photothermal effect destroys bacterial cell walls by inhibiting peptidoglycan synthesis and increasing the membrane permeability by affecting fatty acid synthesis. Furthermore, the nanorods synergistically puncture the bacterial membrane easily as demonstrated by experiments and transcriptome analysis. The results provide insights into the development of efficient antibacterial treatment of implants by combining nanostructures and photothermal therapy.

Manipulating Near-Infrared Absorption via Engineering Anisotropic Plasmonic Spiky Au Nanocubes for the Highly Efficient Dual-Response Immune Detection of T-2 Toxin

Integrating specific immune recognition, a desirable extinction coefficient, and conspicuous photothermal conversion ability into a single-immune probe to enhance the analysis performance represents an appealing yet significantly challenging task. Herein, by delicately manipulating the geometry of plasmonic nanoparticles from spherical to spiky, precise engineering approach-based spiky Au nanocubes (S-AuNCs) are employed to address this challenge, which fully exploits the plasmon resonance absorption-induced photothermal effect. The finite difference time domain (FDTD) method was employed to computationally simulate the electromagnetic and thermal fields while assessing the feasibility of regulating plasmon resonance for enhanced photothermal absorption. The optimized noble photothermal agent simultaneously exhibits acceptable near-infrared absorption (NIR), a significantly increased 808 nm extinction coefficient (145 times higher than that of AuNPs), favorable antibody coupling ability, and desirable photothermal conversion behavior. Consequently, the satisfactory performance of the S-AuNCs-guided colorimetric and photothermal lateral flow immunoassay (CPLFIA) is demonstrated for the sensitive detection of T-2 toxin. In comparison to spherical AuNPs (35.2 pg/mL), the dual-mode detection sensitivity was enhanced by 1.862-fold and 5.18-fold, respectively, achieving limits of detection at 18.9 pg/mL (colorimetric mode) and 6.8 pg/mL (photothermal mode). Therefore, S-AuNCs-guided CPLFIA holds great potential in advancing food mycotoxin safety control.

Femtosecond Laser-Induced Photothermal Effects of Ultrasmall Plasmonic Gold Nanoparticles on the Viability of Human Hepatocellular Carcinoma HepG2 Cells

Laser-induced photothermal therapy using gold nanoparticles (AuNPs) has emerged as a promising approach to cancer therapy. However, optimizing various laser parameters is critical for enhancing the photothermal conversion efficacy of plasmonic nanomaterials. In this regard, the present study investigates the photothermal effects of dodecanethiol-stabilized hydrophobic ultrasmall spherical AuNPs (TEM size 2.2 ± 1.1 nm), induced by a 343 nm wavelength ultrafast femtosecond-pulse laser with a low intensity (0.1 W/cm2) for 5 and 10 min, on the cell morphology and viability of human hepatocellular carcinoma (HepG2) cells treated in vitro. The optical microscopy images showed considerable alteration in the overall morphology of the cells treated with AuNPs and irradiated with laser light. Infrared thermometer measurements showed that the temperature of the cell medium treated with AuNPs and exposed to the laser increased steadily from 22 °C to 46 °C and 48.5 °C after 5 and 10 min, respectively. The WST-1 assay results showed a significant reduction in cell viability, demonstrating a synergistic therapeutic effect of the femtosecond laser and AuNPs on HepG2 cells. The obtained results pave the way to design a less expensive, effective, and minimally invasive photothermal approach to treat cancers with reduced side effects.

Laser Irradiation Induced Electronic Structure Modulation of the Palladium-Based Nanosheets for Efficient Electrocatalysts

Palladium nanosheets (Pd NSs) are widely used as electrocatalysts due to their high atomic utilization efficiency, and long-term stability. Here, the electronic structure modulation of the Pd NSs is realized by a femtosecond laser irradiation strategy. Experimental results indicate that laser irradiation induces the variation in the atomic structures and the macrostrain effects in the Pd NSs. The electronic structure of Pd NSs is modulated by laser irradiation through the balancing between Au-Pd charge transfer and the macros-strain effects. Finite element analysis (FEA) indicates that the lattice of the nanostructures undergoes fast heating and cooling during laser irradiation. The structural evolution mechanism is disclosed by a combined FEA and molecule dynamics (MD) simulation. These results coincide well with the experimental results. The L-AuPd NSs exhibit excellent mass activity and specific activity of 7.44 A mg-1 Pd and 18.70 mA cm-2 toward ethanol oxidation reaction (EOR), 4.3 and 4.4 times higher than the commercial Pd/C. The 2500-cycle accelerated durability (ADT) test confirms the outstanding catalytic stability of the L-AuPd NSs. Density functional theory (DFT) calculations reveal the catalytic mechanism. This unique strategy provides a new pathway to design the ultrathin nanosheet-based materials with excellent performance.

Generating Immunological Memory Against Cancer by Camouflaging Gold-Based Photothermal Nanoparticles in NIR-II Biowindow for Mimicking T-Cells

Photothermal therapy (PTT) against cancer not only directly ablates tumors but also induces tumor immunogenic cell death (ICD). However, the antitumor immune response elicited by ICD is insufficient to prevent relapse and metastasis because of the immunosuppressive tumor microenvironment (TME). A biomimetic nanoplatform (bmNP) mimicking cytotoxic lymphocytes (CTLs) for combinational photothermal-immunotherapy to effectively regulate the immunosuppressive TME is reported here. The bmNP is constructed by wrapping the T-cell membrane onto a new type of photothermal agents, spherical Au-based PNCs (sAuPNCs). Similar to T-cells, the bmNP enhanced accumulation at the tumor site by targeting the tumor via adhesion proteins on T-cell membrane. The obtained sAuPNCs have a wide absorption band in the second near-infrared (NIR-II) region with a high photothermal conversion efficiency (PCE) up to about 75% and excellent photostability. The bmNP with a smaller size is more superior compete with T-cells to bond with tumor cells via PD-1/PD-L1 interaction to effectively block the PD-1 checkpoint of T-cells for preventing T-cell exhaustion. Furthermore, in vivo studies reveal the immunological memory effect is significantly elicited in mice received bmNPs therapy. Collectively, bmNPs show great potential in photothermal-enhanced immunotherapy.

Nickel-Induced Dual Carbon Networks Encapsulating Phase Change Materials for Photothermal Conversion and Storage

Bifunctional phase change materials (PCMs) with efficient energy storage and photothermal conversion capabilities have tremendous potential to be applied in advanced thermal management. However, classical organic PCMs with high latent heat are challenged by poor light harvesting, low thermal conductivity, and leakage risks. Here, we design a unique dual-carbon network with Ni nanoparticles (NPs), confined carbon nanotubes (CNTs) shuttling in carbon honeycombs (CH), namely, CH@Ni-CNTs, to encapsulate paraffin wax (PW) that can facilitate the light capture and photothermal conversion dynamics. Benefiting from the physical adsorption of the hierarchical porous structure, the obtained PW/CH@Ni-CNTs composite PCMs show a high phase change enthalpy of 131.0 J g-1 and long-lasting thermal stability of up to 300 heating-cooling cycles. Moreover, an outstanding photothermal energy conversion efficiency of 96.9% is achieved due to the synergistic effect of the dual carbon network and confined Ni NPs. The CNTs shuttled CH network affords multiple reflection chambers and a thermal conductive pathway, while the localized surface plasmon resonance (LSPR) effects of Ni NPs concentrate the incident light energy to generate and accelerate the transport of active "hot electron", thus collectively contributing to the excellent photothermal properties of the composite PCMs. This study presents a bifunctional Ni-induced dual-carbon network system for the controllable preparation of composite PCMs, and it sheds light on the photothermal conversion mechanisms.

Photo-thermal effects initiate multi-level energy conversion in "solid-solid" phase-changing fibers

The current textiles primarily employ passive heat barriers to minimize heat loss and achieve effective thermal insulation for human beings. Accordingly, intelligent fibers with energy storage and temperature control capabilities have garnered significant attention due to their potential to revolutionize textile technology. The study integrates the photo-thermal effect and phase change energy storage materials onto a fiber, thereby fabricating a fully intelligent energy storage fiber. This innovation enables the multi-level conversion of sunlight: "Optical energy - Thermal energy - Phase transition energy - Thermal energy". The intelligent fiber efficiently converts solar energy into heat energy through the photo-thermal coupling of CuNPs, subsequently inducing a spatial conformational change in the solid-solid phase change material within the fiber for effective heat storage. The hybrid fiber possesses enhanced mechanical properties but also exhibits a significantly high phase transition enthalpy value of 49.75 J g-1 and a phase transition temperature suitable for human body temperature (20.19-30.21 °C), especially the fiber is more durable. The photo-thermal conversion test vividly demonstrates the systematic transformation of four distinct forms of energy within the composite fiber. This approach holds significant potential for advancing the field of smart fiber technology.

Plasmonic Particle Integration into Near-Infrared Photodetectors and Photoactivated Gas Sensors: Toward Sustainable Next-Generation Ubiquitous Sensing

Current challenges in environmental science, medicine, food chemistry as well as the emerging use of artificial intelligence for solving problems in these fields require distributed, local sensing. Such ubiquitous sensing requires components with 1) high sensitivity, 2) power efficiency, 3) miniaturizability, and 4) the ability to directly interface with electronic circuitry, i.e., electronic readout of sensing signals. Over the recent years, several nanoparticle-based approaches have found their way into this field and have demonstrated high performance. However, challenges remain, such as the toxicity of many of today's narrow bandgap semiconductors for NIR detection and the high energy consumption as well as low selectivity of state-of-the-art commercialized gas sensors. With their unique light-matter interaction and ink-based fabrication schemes, plasmonic nanostructures provide potential technological solutions to these challenges, leading also to better environmental performance. In this perspective recent approaches of using plasmonic nanoparticles are discussed for the fabrication of NIR photodetectors and light-activated, energy-efficient gas sensing devices. In addition, new strategies implying computational approaches are pointed out for miniaturizable spectrometers, exploiting the wide spectral tunability of plasmonic nanocomposites, and for selective gas sensors, utilizing dynamic light activation. The benefits of colloidal approaches for device fabrication are discussed with regard to technological advantages and environmental aspects, which are barely considered so far.

Ultrafast Laser Manipulation of In-Lattice Plasmonic Nanoparticles

Plasmonic nanoparticles enable manipulation and enhancement of light fields at deep subwavelength scales, leading to structures and devices for diverse applications in optics. Despite hybrid plasmonic materials display remarkable optical properties due to interactions between components in nanoproximity, scalable production of plasmonic nanostructures within a single-crystalline matrix to achieve an ideal plasmon-crystal interface remains challenging. Here, a novel approach is presented to realize efficient manipulation of in-lattice plasmonic nanoparticles. Employing ultrafast-laser-driven plasmonic nanolithography, metallic nanoparticles with controllable morphology are precisely defined in the crystalline lattice of yttrium aluminum garnet (YAG) crystal. Through direct ion implantation, hybrid plasmonic material composed of nanoparticles embedded in a sub-surface amorphous YAG layer is created. Subsequently, femtosecond laser pulses guide formation and reshaping of plasmonic nanoparticles from the amorphous layer into the single-crystalline matrix along direction of light propagation, facilitated by a plasmon-mediated evolution of laser energy deposition. By tailoring resonance modes and optimizing the coupling between structured particle assemblies, a range of applications including polarization-dependent absorption and nonlinearity, controllable photoluminescence, and structural color generation is demonstrated. This research introduces a new approach for fabricating advanced optical materials featuring in-lattice plasmonic nanostructures, paving the way for the development of diverse functional photonic devices.

Recent Applications of Photothermal Conversion in Organic Synthesis

Photothermal conversion is a novel heating method that has emerged in recent years, wherein certain species can convert light to heat with great efficiency. These photothermal agents have shown immense promise for generating nanoscale thermal gradients under mild, visible light irradiation, providing a pathway for combining photochemistry with thermally driven reactivity. While this novel heating mechanism has been leveraged to great effect for applications such as photothermal therapeutics and steam water purification, it has seen limited use in organic synthesis. This outlook explores instances wherein the photothermal effect was used directly or as a synergistic component to drive organic reactions and postulates how it may be used moving forward.

Reversible Modulation of Plasmonic Coupling of Gold Nanoparticles Confined within Swellable Polymer Colloidal Spheres

Dynamic optical modulation in response to stimuli provides exciting opportunities for designing novel sensing, actuating, and authentication devices. Here, we demonstrate that the reversible swelling and deswelling of crosslinked polymer colloidal spheres in response to pH and temperature changes can be utilized to drive the assembly and disassembly of the embedded gold nanoparticles (AuNPs), inducing their plasmonic coupling and decoupling and, correspondingly, color changes. The multi-responsive colloids are created by depositing a monolayer of AuNPs on the surface of resorcinol-formaldehyde (RF) nanospheres, then overcoating them with an additional RF layer, followed by a seeded growth process to enlarge the AuNPs and reduce their interparticle separation to induce significant plasmonic coupling. This configuration facilitates dynamic modulation of plasmonic coupling through the reversible swelling/deswelling of the polymer spheres in response to pH and temperature changes. The rapid and repeatable transitions between coupled and decoupled plasmonic states of AuNPs enable reversible color switching when the polymer spheres are in colloidal form or embedded in hydrogel substrates. Furthermore, leveraging the photothermal effect and stimuli-responsive plasmonic coupling of the embedded AuNPs enables the construction of hybrid hydrogel films featuring switchable anticounterfeiting patterns, showcasing the versatility and potential of this multi-stimuli-responsive plasmonic system.

Dynamical Janus-Like Behavior Excited by Passive Cold-Heat Modulation in the Earth-Sun/Universe System: Opportunities and Challenges

The utilization of solar-thermal energy and universal cold energy has led to many innovative designs that achieve effective temperature regulation in different application scenarios. Numerous studies on passive solar heating and radiation cooling often operate independently (or actively control the conversion) and lack a cohesive framework for deep connections. This work provides a concise overview of the recent breakthroughs in solar heating and radiation cooling by employing a mechanism material in the application model. Furthermore, the utilization of dynamic Janus-like behavior serves as a novel nexus to elucidate the relationship between solar heating and radiation cooling, allowing for the analysis of dynamic conversion strategies across various applications. Additionally, special discussions are provided to address specific requirements in diverse applications, such as optimizing light transmission for clothing or window glass. Finally, the challenges and opportunities associated with the development of solar heating and radiation cooling applications are underscored, which hold immense potential for substantial carbon emission reduction and environmental preservation. This work aims to ignite interest and lay a solid foundation for researchers to conduct in-depth studies on effective and self-adaptive regulation of cooling and heating.

Hierarchical Carbon Nanocages as Superior Supports for Photothermal CO2 Catalysis

The exploitation of hierarchical carbon nanocages with superior light-to-heat conversion efficiency, together with their distinct structural, morphological, and electronic properties, in photothermal applications could provide effective solutions to long-standing challenges in diverse areas. Here, we demonstrate the discovery of pristine and nitrogen-doped hierarchical carbon nanocages as superior supports for highly loaded, small-sized Ru particles toward enhanced photothermal CO2 catalysis. A record CO production rate of 3.1 mol·gRu-1·h-1 with above 90% selectivity in flow reactors was reached for hierarchical nitrogen-doped carbon-nanocage-supported Ru clusters under 2.4 W·cm-2 illumination without external heating. Detailed studies reveal that the enhanced performance originates from the strong broadband sunlight absorption and efficient light-to-heat conversion of nanocage supports as well as the excellent intrinsic catalytic reactivity of sub-2 nm Ru particles. Our study reveals the great potential of hierarchical carbon nanocages in photothermal catalysis to reduce the fossil fuel consumption of various industrial chemical processes and stimulates interest in their exploitation for other demanding photothermal applications.

Layer-By-Layer Designed Spark-Type AuCuPt Alloy with Robust Broadband Absorption to Enhance Sensitivity in Flexible Detection of Estriol by a Lateral Flow Immunoassay

Excessive intake of estrogen poses significant health risks to the human body; hence, there is a necessity to develop rapid detection methods to monitor its levels of addition. Gold nanoparticles (AuNPs), commonly utilized as colorimetric signal labels, find extensive application in lateral flow immunoassay (LFIA). However, the detection sensitivity of traditional AuNPs-LFIA is typically constrained by low molar extinction coefficients and reliance on a single signal. Herein, in this work, unique spark-type AuCuPt nanoflowers modified with tannic acid (AuCuPt@TA) were precisely designed by reasonable layer-by-layer element composition and green modification. The obtained AuCuPt displays robust broadband absorption spanning the visible to near-infrared spectrum, showcasing a notable molar extinction coefficient of 2.38 × 1012 M-1 cm-1 and a photothermal conversion efficiency of 48.5%. Based on this, selecting estriol (E3) as a model analyte, colorimetric/photothermal dual-signal LFIA (CLFIA and PLFIA) was developed. Limits of detection (LOD) of the CLFIA and PLFIA were achieved at 0.033 ng mL-1 and 0.021 ng mL-1, respectively, which represent a 9.3- and 14.6-fold improvement compared to the visual LOD of AuNPs-LFIA. Moreover, the application feasibility of the immunoassay was further evaluated in the milk and pork with satisfactory recoveries ranging from 86.21% to 117.91%. Thus, this work has enhanced the performance of LFIA for E3 detection and exhibited enormous potential for other sensing platform construction.

Efficient Photothermal Sensor Based on Coral-Like Hollow Gold Nanospheres for the Sensitive Detection of Sulfonamides

Gold nanoparticles (AuNPs), universally regarded as colorimetric signal reporters, are widely employed in lateral flow immunoassays (LFIAs). However, it is difficult for AuNPs-LFIA to achieve a wide range and sensitive detection. Herein, novel coral-like hollow gold nanospheres (CHGNPs) are synthesized. The growth of gold nanospheres can be regulated to obtain a multibranched and hollow construction. The obtained CHGNPs possess intense broadband absorption across the visible to near-infrared region, exhibiting a high molar extinction coefficient of 14.65 × 1011 M-1 cm-1 and a photothermal conversion efficiency of 79.75%. Thus, the photothermal/colorimetric dual-readout LFIA is developed based on CHGNPs (CHGNPs-PT-LFIA and CHGNPs-CM-LFIA) to effectively improve the detection sensitivity and broaden the detection range in regard to sulfonamides (SAs). The limits of detection of the CHGNPs-PT-LFIA and CHGNPs-CM-LFIA reached 1.9 and 2.8 pg mL-1 for the quantitative detection of sulfaquinoxaline, respectively, which are 6.3-fold and 4.3-fold lower than that of the AuNPs-LFIA. Meanwhile, the CHGNPs-PT-LFIA broadened the detection range to three orders of magnitude, which ranged from 2.5 to 5000 pg mL-1. The synthesized photothermal CHGNPs have been proven effective in improving the performance of the LFIA and provide a potential option for the construction of sensing platforms.

Supramolecular dye nanoassemblies for advanced diagnostics and therapies

Dyes have conventionally been used in medicine for staining cells, tissues, and organelles. Since these compounds are also known as photosensitizers (PSs) which exhibit photoresponsivity upon photon illumination, there is a high desire towards formulating these molecules into nanoparticles (NPs) to achieve improved delivery efficiency and enhanced stability for novel imaging and therapeutic applications. Furthermore, it has been shown that some of the photophysical properties of these molecules can be altered upon NP formation thereby playing a major role in the outcome of their application. In this review, we primarily focus on introducing dye categories, their formulation strategies and how these strategies affect their photophysical properties in the context of photothermal and non-photothermal applications. More specifically, the most recent progress showing the potential of dye supramolecular assemblies in modalities such as photoacoustic and fluorescence imaging, photothermal and photodynamic therapies as well as their employment in photoablation as a novel modality will be outlined. Aside from their photophysical activity, we delve shortly into the emerging application of dyes as drug stabilizing agents where these molecules are used together with aggregator molecules to form stable nanoparticles.

Application of photothermal effects of nanomaterials in food safety detection

Numerous nanomaterials endowed with outstanding light harvesting and photothermal conversion abilities have been extensively applied in various fields, such as photothermal diagnosis and therapy, trace substance detection, and optical imaging. Although photothermal detection methods have been established utilizing the photothermal effect of nanomaterials in recent years, there is a scarcity of reviews regarding their application in food safety detection. Herein, the recent advancements in the photothermal conversion mechanism, photothermal conversion efficiency calculation, and preparation method of photothermal nanomaterials were reviewed. In particular, the application of photothermal nanomaterials in various food hazard analyses and the newly established photothermal detection methods were comprehensively discussed. Moreover, the development and promising future trends of photothermal nanomaterial-based detection methods were discussed, which provide a reference for researchers to propose more effective, sensitive, and accurate detection methods.

An Ultra-broadband Metallic Plasmonic Antenna for Ultrasensitive Molecular Fingerprint Identification

Near-field enhanced mid-infrared light-matter interactions via metallic plasmonic antennae (PA) have attracted much attention but are inevitably limited by the detuning between their narrow band and the broad applied spectral range. Here, we develop a new low-temperature incubation synthetic method to acquire uniform Ag microparticles (MPs) with numerous hotspots. Their plasmonic band is remarkably extended by the plasmonic coupling of numerous hotspots and covers the entire mid-infrared range (400-4000 cm-1). Hence, the almost complete molecular fingerprint of 4-mercaptobenzonitrile was successfully probed for the first time via resonant surface-enhanced infrared absorption (rSEIRA), and the rSEIRA spectra of different essential amino acids were further detected and exhibit a high spectral identification degree assisted by machine learning. This work changes the inertia perception of "narrow band and large size but small hotspot area" of mid-infrared metallic PA and paves the way for the ultrasensitive mid-infrared optical sensing.

Supra-Photothermal CO2 Methanation over Greenhouse-Like Plasmonic Superstructures of Ultrasmall Cobalt Nanoparticles

Improving the solar-to-thermal energy conversion efficiency of photothermal nanomaterials at no expense of other physicochemical properties, e.g., the catalytic reactivity of metal nanoparticles, is highly desired for diverse applications but remains a big challenge. Herein, a synergistic strategy is developed for enhanced photothermal conversion by a greenhouse-like plasmonic superstructure of 4 nm cobalt nanoparticles while maintaining their intrinsic catalytic reactivity. The silica shell plays a key role in retaining the plasmonic superstructures for efficient use of the full solar spectrum, and reducing the heat loss of cobalt nanoparticles via the nano-greenhouse effect. The optimized plasmonic superstructure catalyst exhibits supra-photothermal CO2 methanation performance with a record-high rate of 2.3 mol gCo -1 h-1 , close to 100% CH4 selectivity, and desirable catalytic stability. This work reveals the great potential of nanoscale greenhouse effect in enhancing photothermal conversions through the combination with conventional promoting strategies, shedding light on the design of efficient photothermal nanomaterials for demanding applications.

Dual-Readout Ultrasensitive Lateral Flow Immunosensing of Salmonella typhimurium in Dairy Products by Doping Engineering-Powered Nanoheterostructure with Enhanced Photothermal Performance

The photothermal lateral flow immunoassay (LFIA) is of great significance to suitable for on-site semiquantitative detection, which has the upper hand in further constructing detection methods for low-concentration targets. Herein, we presented a doping engineering-powered nanoheterostructure with an enhanced photothermal performance strategy, employing bimetallic nanocuboid Pt3Sn (PSNCs) as a proof of concept. With the help of finite element simulation analysis, the contrast of direct temperature experiment, and the evaluation of photothermal conversion efficiency (η), the distinguished and enthusiastic photothermal feedback of PSNCs is proved. Based on steady bright black of colorimetric and superior photothermal performance, the PSNCs were employed to construct an ultrasensitive model LIFA for detecting Salmonella typhimurium (S. typhimurium), which achieved the double-signal semiquantitative detection, the detection limit reached 103 cfu mL-1 (colorimetric mode) and 102 cfu mL-1 (photothermal mode), which is 100 times higher than that of the traditional colloidal gold method. In addition, the method was effective for the detection of targets in dairy samples only through a simple dilution treatment, which was completed within 15 min. Meanwhile, this PSNCs dual-signal LFIA demonstrated the sensitive detection of S. typhimurium due to the excellent colorimetric signal and significant photothermal performance, which provides a broad spectrum for the future detection of foodborne pathogens.

Regulation of the upconversion effect to promote the removal of biofilms on a titanium surface via photoelectrons

Biofilms on public devices and medical instruments are harmful. Hence, it is of great importance to fabricate antibacterial surfaces. In this work, we target the preparation of an antibacterial surface excited by near-infrared light via the coating of rare earth nanoparticles (RE NPs) on a titanium surface. The upconverted luminescence is absorbed by gold nanoparticles (Au NPs, absorber) to produce hot electrons and reactive oxygen species to eliminate the biofilms. The key parameters in tuning the upconversion effect to eliminate the biofilms are systematically investigated, which include the ratios of the sensitizer, activator, and matrix in the RE NPs, or the absorber Au NPs. The regulated RE NPs exhibit an upconversion quantum yield of 3.5%. Under illumination, photogenerated electrons flow through the surface to bacteria, such as E. coli, which disrupt the breath chain and eventually lead to the death of bacteria. The mild increase of the local temperature has an impact on the elimination of biofilms on the surface to a certain degree as well. Such a configuration on the surface of titanium exhibits a high reproducibility on the removal of biofilms and is functional after the penetration of light using soft tissue. This work thus provides a novel direction in the application of upconversion materials to be used in the fabrication of antibacterial surfaces.

NIR-II photothermal conversion and imaging based on a cocrystal containing twisted components

On account of the scarcity of molecules with a satisfactory second near-infrared (NIR-II) response, the design of high-performance organic NIR photothermal materials has been limited. Herein, we investigate a cocrystal incorporating tetrathiafulvalene (TTF) and tetrachloroperylene dianhydride (TCPDA) components. A stable radical was generated through charge transfer from TTF to TCPDA, which exhibits strong and wide-ranging NIR-II absorption. The metal-free TTF-TCPDA cocrystal in this research shows high photothermal conversion capability under 1064 nm laser irradiation and clear photothermal imaging. The remarkable conversion ability-which is a result of twisted components in the cocrystal-has been demonstrated by analyses of single crystal X-ray diffraction, photoluminescence and femtosecond transient absorption spectroscopy as well as theoretical calculations. We have discovered that space charge separation and the ordered lattice in the TTF-TCPDA cocrystal suppress the radiative decay, while simultaneously strong intermolecular charge transfer enhances the non-radiative decay. The twisted TCPDA component induces rapid charge recombination, while the distorted configuration in TTF-TCPDA favors an internal non-radiative pathway. This research has provided a comprehensive understanding of the photothermal conversion mechanism and opened a new way for the design of advanced organic NIR-II photothermal materials.

Photoelectrons Sequentially Regulate Antibacterial Activity and Osseointegration of Titanium Implants

Titanium implants are widely used ; however, implantation occasionally fails due to infections during the surgery or poor osseointegration after the surgery. To solve the problem, an intelligent functional surface on titanium implant that can sequentially eradicate bacteria biofilm at the initial period and promote osseointegration at the late period of post-surgery time is designed. Such surfaces can be excited by near infrared light (NIR), with rare earth nanoparticles to upconvert the NIR light to visible range and adsorb by Au nanoparticles, supported by titanium oxide porous film on titanium implants. Under NIR irradiation, the implant converts the energy of phonon to hot electrons and lattice vibrations, while the former flows directly to the contact substance or partially reacts with the surrounding to generate reactive oxygen species, and the latter leads to the local temperature increase. The biofilm or microbes on the implant surface can be eradicated by NIR treatment in vitro and in vivo. Additionally, the surface exhibits superior biocompatibility for cell survival, adhesion, proliferation, and osteogenic differentiation, which provides the foundation for osseointegration. In vivo implantation experiments demonstrate osseointegration is also promoted. This work thus demonstrates NIR-generated electrons can sequentially eradicate biofilms and regulate the osteogenic process, providing new solutions to fabricate efficient implant surfaces.

Multiscale Bioresponses of Metal Nanoclusters

Metal nanoclusters (NCs) are well-recognized novel nano-agents that hold great promise for applications in nanomedicine because of their ultrafine size, low toxicity, and high renal clearance. As foreign substances, however, an in-depth understanding of the bioresponses to metal NCs is necessary but is still far from being realized. Herein, this review is deployed to summarize the biofates of metal NCs at various biological levels, emphasizing their multiscale bioresponses at the molecular, cellular, and organismal levels. In the parts-to-whole schema, the interactions between biomolecules and metal NCs are discussed, presenting typical protein-dictated nano-bio interfaces, hierarchical structures, and in vivo trajectories. Then, the accumulation, internalization, and metabolic evolution of metal NCs in the cellular environment and as-imparted theranostic functionalization are demonstrated. The organismal metabolism and transportation processes of the metal NCs are subsequently distilled. Finally, this review ends with the conclusions and perspectives on the outstanding issues of metal NC-mediated bioresponses in the near future. This review is expected to provide inspiration for tailoring the customization of metal NC-based nano-agents to meet practical requirements in different sectors of nanomedicine.

High Freshwater Flux Solar Desalination via a 3D Plasmonic Evaporator with an Efficient Heat-Mass Evaporation Interface

Passive solar desalination with interfacial heating is a promising technique to utilize solar energy to convert seawater into fresh water through evaporation and condensation. However, the current freshwater flux of solar desalination is much below industrial requirements (> 20 L m-2  h-1 ). Herein, it is demonstrated that a 3D plasmonic evaporator with an efficient heat-mass evaporation interface (HM-EI) achieves a freshwater flux of 29.1 L m-2  h-1 for 3.5 wt.% NaCl, which surpasses the previous solar evaporators and approaches the level of reverse osmosis (the highest installed capacity in industrial seawater desalination technology). The realization of high freshwater flux solar desalination comes from the efficient HM-EI comprising a grid-like plasmonic macrostructure for enhanced energy utilization in heat properties and a large-pore microstructure for accelerated ion transport in mass properties. This work provides a new direction for designing next-generation solar evaporators with high freshwater flux for industrial requirements.

The energetic and physical concept of gold nanorod-dependent fluorescence in cancer treatment and development of new photonic compounds|review

The optical features of gold nanorods (GNR) may be precisely controlled by manipulating their size, shape, and aspect ratio. This review explores the impact of these parameters on the optical tuning of (GNR). By altering the experimental conditions, like the addition of silver ions during the seed-mediated growth process, the aspect ratio of (GNR) may be regulated. The shape is trans from spherical to rod-like structures resulting in noticeable changes in the nanoparticles surface plasmons resonance (SPR) bands. The longitudinal SPR band, associated with electron oscillations along the long axis, exhibits a pronounced red shift into the (NIR) region as the aspect ratio increases. In contrast, the transverse SPR band remains relate unchanged. Using computational methods like the discrete dipole approximation (DDA) allows for analyzing absorption, scattering, and total extinction features of gold (G) nanoparticles. Studies have shown that increasing the aspect ratio enhances the scattering efficiency, indicating a higher scattering quantum yield (QY). These findings highlight the importance of size, shape, and aspect ratio in controlling the optical features of (GNR) providing valuable insights for various uses in nanophotonics and plasmonic-dependent fluorescence in cancer treatment and developing new photonic compound NRs.

Advances in photothermal regulation strategies: from efficient solar heating to daytime passive cooling

Photothermal regulation concerning solar harvesting and repelling has recently attracted significant interest due to the fast-growing research focus in the areas of solar heating for evaporation, photocatalysis, motion, and electricity generation, as well as passive cooling for cooling textiles and smart buildings. The parallel development of photothermal regulation strategies through both material and system designs has further improved the overall solar utilization efficiency for heating/cooling. In this review, we will review the latest progress in photothermal regulation, including solar heating and passive cooling, and their manipulating strategies. The underlying mechanisms and criteria of highly efficient photothermal regulation in terms of optical absorption/reflection, thermal conversion, transfer, and emission properties corresponding to the extensive catalog of nanostructured materials are discussed. The rational material and structural designs with spectral selectivity for improving the photothermal regulation performance are then highlighted. We finally present the recent significant developments of applications of photothermal regulation in clean energy and environmental areas and give a brief perspective on the current challenges and future development of controlled solar energy utilization.

Material Design Strategies for Recovery of Critical Resources from Water

Population growth, urbanization, and decarbonization efforts are collectively straining the supply of limited resources that are necessary to produce batteries, electronics, chemicals, fertilizers, and other important products. Securing the supply chains of these critical resources via the development of separation technologies for their recovery represents a major global challenge to ensure stability and security. Surface water, groundwater, and wastewater are emerging as potential new sources to bolster these supply chains. Recently, a variety of material-based technologies have been developed and employed for separations and resource recovery in water. Judicious selection and design of these materials to tune their properties for targeting specific solutes is central to realizing the potential of water as a source for critical resources. Here, the materials that are developed for membranes, sorbents, catalysts, electrodes, and interfacial solar steam generators that demonstrate promise for applications in critical resource recovery are reviewed. In addition, a critical perspective is offered on the grand challenges and key research directions that need to be addressed to improve their practical viability.

Influence of plasmons on the luminescence properties of solvatochromic merocyanine dyes with different solvatochromism

The effect of localized surface plasmon resonance (LSPR) of a system consisting of a highly dipolar merocyanine dye and a silver nanoparticle (NP) was studied experimentally and theoretically. A theoretical model for estimating the fluorescence quantum yield (φfl) using quantum chemical calculations of intramolecular and intermolecular electronic transition rate constants was developed. Calculations show that the main deactivation channels of the lowest excited singlet state of the studied merocyanines are internal conversion (kIC(S1 → S0)) and fluorescence (kr(S1 → S0)). The intersystem-crossing transition has a low probability due to the large energy difference between the singlet and triplet levels. In the presence of plasmonic NPs, the fluorescence quantum yield is increased by a factor of two according to both experiment and computations. The calculated values of φfl, when considering changes in kr(S1 → S0) and the energy-transfer rate constant (ktransfer) from the dye to the NP was also twice as large at distances of 6-8 nm between the NP and the dye molecule. We also found that the LSPR effect can be increased or decreased depending on the value of the dielectric constant (εm) of the environment.

Broadband and Spectrally Selective Photothermal Conversion through Nanocluster Assembly of Disordered Plasmonic Metasurfaces

Plasmonic metasurfaces have been realized for efficient light absorption, thereby leading to photothermal conversion through nonradiative decay of plasmonic modes. However, current plasmonic metasurfaces suffer from inaccessible spectral ranges, costly and time-consuming nanolithographic top-down techniques for fabrication, and difficulty of scale-up. Here, we demonstrate a new type of disordered metasurface created by densely packing plasmonic nanoclusters of ultrasmall size on a planar optical cavity. The system either operates as a broadband absorber or offers a reconfigurable absorption band right across the visible region, resulting in continuous wavelength-tunable photothermal conversion. We further present a method to measure the temperature of plasmonic metasurfaces via surface-enhanced Raman spectroscopy (SERS), by incorporating single-walled carbon nanotubes (SWCNTs) as an SERS probe within the metasurfaces. Our disordered plasmonic system, generated by a bottom-up process, offers excellent performance and compatibility with efficient photothermal conversion. Moreover, it also provides a novel platform for various hot-electron and energy-harvesting functionalities.

Boosting Water Evaporation by Construction of Photothermal Materials with a Biomimetic Black Soil Aggregate Structure

Solar-driven interfacial evaporation is considered an efficient way to get fresh water from seawater. However, the low evaporation rate, surface salt crystallization, and low energy collection of the photothermal evaporation layer limit its further application in an outdoor freshwater field. And the aggregate structure design of the material itself is often ignored in solar-driven water evaporation. Black soil (BS), with a unique soil aggregate structure, is rich in tubular pores, which can be used for multilevel sunlight utilization and good capillary water transport. Based on the extraordinary photothermal properties and pumping capacity of BS, a reasonable unidirectional salt-collecting device is designed, which can realize long-term collection of mineral salts and continuous evaporation of seawater and generate electric energy in the continuous evaporation. Inspired by the unique aggregate structure, the photothermal material doping of halloysite and nigrosin will simulate the generation of this aggregate structure and retain a good water transport effect while obtaining multistage utilization of sunlight. The solar-driven evaporation rate of a nigrosin-halloysite solar steam generator is 1.75 kg m-2 h-1 under 1 kW m-2 mimic solar radiation; it can achieve stable salt leaching-induced voltage generation of 240 mV. This work demonstrates not only a solar evaporator that can continuously achieve desalination but also the design strategy of BS-like aggregate photothermal materials, which promotes the development of low-cost resource recovery and energy generation for practical outdoor seawater desalination.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

Synthesis of Linear Black Gold Nanostructures Processable as Sunlight and Low-Energy Light Collecting Films for Photo-Thermoelectricity

As one of the effort to cope with the energy crisis and carbon neutrality, utilization of low-grade energy generated indoors (e.g., light) is imperative because this saves building and house energy, which accounts for ≈40% of total energy consumption. Although photovoltaic devices could contribute to energy savings, it is also necessary to harvest heat from indoor lights to generate electricity because the light absorbed by materials is mostly transformed into heat. For daily life uses, materials should not only have high absorptance and low emittance but also be easily processed into various forms. To this end, this work synthesizes black aqueous suspensions containing winding and bent linear gold nanostructures with diameters of 3-5 nm and length-to-diameter ratios of ≈4-10. Their optical and photo-thermal characteristics are understood through experimental and theoretical investigations. Black gold nanostructures are conveniently processed into metal-dielectric films on metal, glass, and flexible substrates. The film on copper has an absorptance of 0.97 and an emittance of 0.08. Under simulated sunlight and indoor LED light illumination, the film has equivalent photo-thermal and photo-thermoelectric performances to a top-tier sunlight-collecting film. This work attempts to modify the film structure to generate more usable electricity from low-energy indoor light.

Quantitative Analysis of the Shape Effect of Thermoplasmonics in Gold Nanostructures

The shape effect of thermoplasmonic properties of Au nanostructures remains largely unexplored. Herein, we report a systematic investigation on the photothermal effects of Au nanoparticles (NPs) of different shapes: nanosphere, nanocube, nanorod, nanostar, and nanobipyramid. The Joule (Jo) number (absorption cross section normalized by the particulate volume) is utilized for quantitatively assessing the photothermal properties of these different shaped Au NPs. It is shown that the Jo number of Au NPs greatly varies with the geometric shape and localized surface plasmon resonance (LSPR) wavelength. Specifically, the Jo number decreases with the red-shifting of the LSPR wavelength in these Au NPs, and the Au NPs of sharp structural features such as Au nanorod, nanostar and nanobipyramid have a much larger Jo number, indicative of their exceptional light-to-heat conversion ability. We further demonstrate the close correlation of the Jo number of Au NPs of different shapes with their optical absorption power density.

Rapid controllable synthesis of branched Au superparticles: formation mechanism of toggling the growth mode and their applications in optical broadband absorption

We develop a tunable, ultrafast (5 seconds), and mass-producible seed-mediated synthesis method to prepare branched Au superparticles consisting of multiple small Au island-like nanoparticles by a wet chemical route. We reveal and confirm the toggling formation mechanism of Au superparticles between the Frank-van der Merwe (FM) growth mode and the Volmer-Weber (VW) growth mode. The key factor of this special structure is the frequent toggling between the FM (layer by layer) growth mode and the VW (island) growth mode induced by 3-aminophenol, which is continuously absorbed on the surface of newborn Au nanoparticles, leading to a relatively high surface energy during the overall synthesis process, thus achieving an island on island growth. Such Au superparticles demonstrate broadband absorption from visible to near-infrared regions due to their multiple plasmonic coupling and hence they have important applications in sensors, photothermal conversion and therapy, etc. We also exhibit the excellent properties of Au superparticles with different morphologies, such as NIR-II photothermal conversion and therapy and SERS detection. The photothermal conversion efficiency under 1064 nm laser irradiation was calculated to be as high as 62.6% and they exhibit robust photothermal therapy efficiency. This work provides insight into the growth mechanism of plasmonic superparticles and develops a broadband absorption material for highly efficient optical applications.

Hollow Nanomaterials in Advanced Drug Delivery Systems: From Single- to Multiple Shells

Hollow-structured nanomaterials (HSNMs) have attracted increased interest in biomedical fields, owing to their excellent potential as drug delivery systems (DDSs) for clinical applications. Among HSNMs, hollow multi-shelled structures (HoMSs) exhibit properties such as high loading capacity, sequential drug release, and multi-functionalized modification and represent a new class of nanoplatforms for clinical applications. The remarkable properties of HoMS-based DDS can simultaneously satisfy and enhance DDSs for delivering small molecular drugs (e.g., antibiotics, chemotherapy drugs, and imaging agents) and macromolecular drugs (e.g., protein/peptide- and nucleic acid-based drugs). First, the latest research advances in delivering small molecular drugs are summarized and highlight the inherent advantages of HoMS-based DDSs for small molecular drug targeting, combining continuous therapeutic drug delivery and theranostics to optimize the clinical benefit. Meanwhile, the macromolecular drugs DDSs are in the initial development stage and currently offer limited delivery modes. There is a growing need to analyze the deficiency of other HSNMs and integrate the advantages of HSNMs, providing solutions for the safe, stable, and cascade delivery of macromolecular drugs to meet vast treatment requirements. Therefore, the latest advances in HoMS-based DDSs are comprehensively reviewed, mainly focusing on the characteristics, research progress by drug category, and future research prospects.

Single-Probe-Based Colorimetric and Photothermal Dual-Mode Identification of Multiple Bacteria

Effective identification of multiple pathogenic bacteria in unknown samples is important for disease prevention and control but remains a challenge yet. A single-mode array-based sensing approach is simple and sensitive, but it usually relies on the use of multiple cross-reactive receptors to construct sensor arrays, which is cumbersome and insufficiently accurate. Here, we developed a sensor array with colorimetric and photothermal dual mode of differentiating multiple pathogenic bacteria. The sensor array was based on boronic acid-functionalized Au-Fe₃O₄ nanoparticles (BA-GMNPs), which not only possess localized surface plasmon resonance properties, showing a burgundy color similar to that of AuNPs, but also exhibit mild superparamagnetism, allowing for the differentiation of bacteria before and after binding to the nanoparticles. Immobilization of BA-GMNPs on the bacterial cell surface by covalent bonding would diminish NaCl-induced assembly of BA-GMNPs. Different BA-GMNPs@bacterial complexes differed in their ability to resist assembly and produced different colorimetric and photothermal response signals. A unique molecular fingerprint of each bacterium was obtained by linear discriminant analysis of the response patterns, demonstrating an effective differentiation among the six species studied. Compared with single-mode sensing arrays based on multiple receptors, this method only requires the preparation of a single nanomaterial, which produces two signal outputs for the identification of multiple bacteria with better differentiation. It can distinguish not only multiple pathogenic bacteria but also Gram-negative and Gram-positive bacteria, and, more importantly, it can perform preliminary discrimination of unknown samples.

Self-Healing Polymeric Soft Actuators

Natural evolution has provided multicellular organisms with sophisticated functionalities and repair mechanisms for surviving and preserve their functions after an injury and/or infection. In this context, biological systems have inspired material scientists over decades to design and fabricate both self-healing polymeric materials and soft actuators with remarkable performance. The latter are capable of modifying their shape in response to environmental changes, such as temperature, pH, light, electrical/magnetic field, chemical additives, etc. In this review, we focus on the fusion of both types of materials, affording new systems with the potential to revolutionize almost every aspect of our modern life, from healthcare to environmental remediation and energy. The integration of stimuli-triggered self-healing properties into polymeric soft actuators endow environmental friendliness, cost-saving, enhanced safety, and lifespan of functional materials. We discuss the details of the most remarkable examples of self-healing soft actuators that display a macroscopic movement under specific stimuli. The discussion includes key experimental data, potential limitations, and mechanistic insights. Finally, we include a general table providing at first glance information about the nature of the external stimuli, conditions for self-healing and actuation, key information about the driving forces behind both phenomena, and the most important features of the achieved movement.

Tungsten-based Nanomaterials in the Biomedical Field: A Bibliometric Analysis of Research Progress and Prospects

Tungsten-based nanomaterials (TNMs) with diverse nanostructures and unique physicochemical properties have been widely applied in the biomedical field. Although various reviews have described the application of TNMs in specific biomedical fields, there are still no comprehensive studies that summarize and analyze research trends of the field as a whole. To identify and further promote the development of biomedical TNMs, a bibliometric analysis method is used to analyze all relevant literature on this topic. First, general bibliometric distributions of the dataset by year, country, institute, referenced source, and research hotspots are recognized. Next, a comprehensive review of the subjectively recognized research hotspots in various biomedical fields, including biological sensing, anticancer treatments, antibacterials, and toxicity evaluation, is provided. Finally, the prospects and challenges of TNMs are discussed to provide a new perspective for further promoting their development in biomedical research.

Polysaccharide-based hydrogel with photothermal effect for accelerating wound healing

Polysaccharide-based hydrogel has excellent biochemical function, abundant sources, good biocompatibility and other advantages, and has a broad application prospect in biomedical fields, especially in the field of wound healing. With its inherent high specificity and low invasive burden, photothermal therapy has shown great application prospect in preventing wound infection and promoting wound healing. Combining polysaccharide-based hydrogel with photothermal therapy (PTT), multifunctional hydrogel with photothermal, bactericidal, anti-inflammatory and tissue regeneration functions can be designed, so as to achieve better therapeutic effect. This review first focuses on the basic principles of hydrogel and PTT, and the types of polysaccharides that can be used to design hydrogels. In addition, according to the different materials that produce photothermal effects, the design considerations of several representative polysaccharide-based hydrogels are emphatically introduced. Finally, the challenges faced by polysaccharide-based hydrogels with photothermal properties are discussed, and the future prospects of this field are put forward.

Antibacterial Properties of Gold Nanoparticles in the Modification of Medical Implants: A Systematic Review

The widespread occurrence of bacterial infections and their increased resistance to antibiotics has led to the development of antimicrobial coatings for multiple medical implants. Owing to their desirable properties, gold nanoparticles (AuNPs) have been developed as antibacterial agents. This systematic investigation sought to analyze the antibacterial effects of implant material surfaces modified with AuNPs. The data from 27 relevant studies were summed up. The included articles were collected from September 2011 to September 2021. According to the retrieved literature, we found that medical implants modified by AuNPs have good antibacterial effects against gram-positive and gram-negative bacteria, and the antibacterial effects would be improved by near-infrared (NIR) radiation.