Photothermal conversion of light into heat energy is an intrinsic optical property of metal nanoparticles when irradiated using near-infrared radiation. However, the impact of size and shape on the photothermal behaviour of gold nanomakura particles possessing optical absorption within 600-700 nm as well as on incorporation in hydrogels is not well reported. In this study, nanomakura-shaped anisotropic gold nanoparticles (AuNMs) were synthesized via a surfactant-assisted seed-mediated protocol. Quaternary cationic surfactants having variable carbon tail length (n = 16, 14, 12) were used as capping for tuning the plasmon peak of gold nanomakura within a 600-700 nm wavelength. The aspect ratio as well as anisotropy of synthesized gold nanomakura can influence photothermal response upon near-infrared irradiation. The role of carbon tail length was evident via absorption peaks obtained from longitudinal surface plasmon resonance analysis at 670, 650, and 630 nm in CTAB-AuNM, MTAB-AuNM, and DTAB-AuNM, respectively. Furthermore, the impact of morphology and surrounding milieu of the synthesized nanomakuras on photothermal conversion is investigated owing to their retention of plasmonic stability. Interestingly, we found that photothermal conversion was exclusively assigned to morphological features (i.e., nanoparticles of higher aspect ratio showed higher temperature change and vice versa irrespective of the surfactant used). To enable biofunctionality and stability, we used kappa-carrageenan- (k-CG) based hydrogels for incorporating the nanomakuras and further assessed their photothermal response. Nanomakura particles in association with k-CG were also able to show photothermal conversion, depicting their ability to interact with light without hindrance. The CTAB-AuNM, MTAB-AuNM, and DTAB-AuNM after incorporation into hydrogel beads attained up to ≈17.2, ≈17.2, and ≈15.7 °C, respectively. On the other hand, gold nanorods after incorporation into k-CG did not yield much photothermal response as compared to that of AuNMs. The results showed a promising platform to utilize nanomakura particles along with kappa-carrageenan hydrogels for enabling usage on nanophotonic, photothermal, and bio-imaging applications.

Colloidal gold particles have been extensively studied for their potential in hyperthermia treatment due to their ability to become excited in the presence of an external laser. However, their light-to-heat efficiency is affected by the physiologic environment. In this study, we aimed to evaluate the ability of gold sphere, rod, and star-shaped colloids to elevate the temperature of blood plasma and breast cancer-simulated fluid under laser stimulation. Additionally, the dependence of optical properties and colloid stability of gold nanostructures with physiological medium, particle shape, and coating was determined. The light-to-heat efficiency of the gold particle is shape-dependent. The light-to-heat conversion efficiency of a star-shaped colloid is 36% higher than that of sphere-shaped colloids. However, the raised temperature of the surrounding medium is the lowest in the star-shaped colloid. When gold nanostructures are exited with a laser stimulation in a physiological fluid, the ions/cations attach to the surface of the gold particles, resulting in colloidal instability, which limits electron oscillation and diminishes the energy generated by the plasmonic excitation. Fluorescein (Fl) and polyethylene glycol (PEG) attached to gold spheres enhances their colloidal stability and light-to-heat efficiency; post-treatment, they remand their optical properties.

Plasmonic systems are becoming a favourable alternative to dye molecules in the generation of photoacoustic signals for spectroscopy and imaging. In particular, inorganic nanoparticles are appealing because of their versatility. In fact, as the shape, size and chemical composition of nanoparticles are directly correlated with their plasmonic properties, the excitation wavelength can be tuned to their plasmon resonance by adjusting such traits. This feature enables an extensive spectral range to be covered. In addition, surface chemical modifications can be performed to provide the nanoparticles with designed functionalities, e.g., selective affinity for specific macromolecules. The efficiency of the conversion of absorbed photon energy into heat, which is the physical basis of the photoacoustic signal, can be accurately determined by photoacoustic methods. This review contrasts studies that evaluate photoconversion in various kinds of nanomaterials by different methods, with the objective of facilitating the researchers\' choice of suitable plasmonic nanoparticles for photoacoustic applications.

The aim of this paper is to achieve in situ photochemical synthesis of silver nanoclusters (AgNCs) stabilized by the multiple-amine groups of chitosan (Ch@AgNCs) with luminescent and photothermal properties. Ch@AgNCs were obtained by applying a fast and simple methodology previously described by our group. Direct functionalization of AgNCs with chitosan template provided new nanohybrids directly in water solution, both in the presence or absence of oxygen. The formation of hybrid AgNCs could be monitored by the rapid increase of the absorption and emission maximum band with light irradiation time. New Ch@AgNCs not only present photoluminescent properties but also photothermal properties when irradiated with near infrared light (NIR), transducing efficiently NIR into heat and increasing the temperature of the medium up to 23 °C. The chitosan polymeric shell associated to AgNCs works as a protective support stabilizing the metal cores, facilitating the storage of nanohybrids and preserving luminescent, photothermal and bactericide properties.

Photothermal conversion agents (PTCAs) based on π-conjugated polymers are promising for cancer therapy, but the alteration of bandgap energies toward boosted photothermal properties remains challenging. Herein, polymer PTCAs with heterojunctions of a binary optical component are developed by interface hybridization on porous particles. Specifically, polypyrrole (PPy) nanodomains are successfully hosted on the wet-adhesive surface of mesoporous polydopamine nanoparticles through the loading and polymerization of pyrrole in the confined pore space (≈5.0 nm). The near-infrared absorbing polymers in the heterojunctions possess similar five-membered heterocyclic rings and can interact mutually to generate photoinduced electron transfer (PET). Such a large-area optoelectronic interaction progressively reduces the bandgap energy (down to 0.56 eV) by increasing the doped amount of PPy, which consequently enhances the extinction coefficient and photothermal conversion efficiency by 4.6- and 2.2-fold, respectively. Notably, the hybrid PTCA exhibits good biocompatibility, photocytotoxicity, and great potential for cancer therapy.

We investigate, with a combination of ultrafast optical spectroscopy and semiclassical modeling, the photothermal properties of various water-soluble nanocrystal assemblies. Broadband pump-probe experiments with ∼100-fs time resolution in the visible and near infrared reveal a complex scenario for their transient optical response that is dictated by their hybrid composition at the nanoscale, comprising metallic (Au) or semiconducting ([Formula: see text]) nanostructures and a matrix of organic ligands. We track the whole chain of energy flow that starts from light absorption by the individual nanocrystals and subsequent excitation of out-of-equilibrium carriers followed by the electron-phonon equilibration, occurring in a few picoseconds, and then by the heat release to the matrix on the 100-ps timescale. Two-dimensional finite-element method electromagnetic simulations of the composite nanostructure and multitemperature modeling of the energy flow dynamics enable us to identify the key mechanism presiding over the light-heat conversion in these kinds of nanomaterials. We demonstrate that hybrid (organic-inorganic) nanocrystal assemblies can operate as efficient nanoheaters by exploiting the high absorption from the individual nanocrystals, enabled by the dilution of the inorganic phase that is followed by a relatively fast heating of the embedding organic matrix, occurring on the 100-ps timescale.

A new kind of fast near-infrared (NIR) light-responsive shape-memory polymer composites was prepared by introducing polydopamine particles (PDAPs) into commercial shape-memory polyurethane (SMPU). The toughness and strength of the polydopamine-particle-filled polyurethane composites (SMPU-PDAPs) were significantly enhanced with the addition of PDAPs due to the strong interface interaction between PDAPs and polyurethane segments. Owing to the outstanding photothermal effect of PDAPs, the composites exhibit a rapid light-responsive shape-memory process in 60 s with a PDAPs content of 0.01 wt%. Due to the excellent dispersion and convenient preparation method, PDAPs have great potential to be used as high-efficiency and environmentally friendly fillers to obtain novel photoactive functional polymer composites.

Phosphorene has attracted great interest due to its unique electronic and optoelectronic properties owing to its tunable direct and moderate band-gap in association with high carrier mobility. However, its intrinsic instability in air seriously hinders its practical applications, and problems of technical complexity and in-process degradation exist in currently proposed stabilization strategies. A facile pathway in obtaining and stabilizing phosphorene through a one-step, ionic liquid-assisted electrochemical exfoliation and synchronous fluorination process is reported in this study. This strategy enables fluorinated phosphorene (FP) to be discovered and large-scale, highly selective few-layer FP (3-6 atomic layers) to be obtained. The synthesized FP is found to exhibit unique morphological and optical characteristics. Possible atomistic fluorination configurations of FP are revealed by core-level binding energy shift calculations in combination with spectroscopic measurements, and the results indicate that electrolyte concentration significantly modulates the fluorination configurations. Furthermore, FP is found to exhibit enhanced air stability thanks to the antioxidation and antihydration effects of the introduced fluorine adatoms, and demonstrate excellent photothermal stability during a week of air exposure. These findings pave the way toward real applications of phosphorene-based nanophotonics.

Molybdenum disulfide (MoS2 ) nanosheets have attracted significant attention due to their photothermal properties, but the poor solubility and colloidal stability limited their further application in biomedical field. Here, we report a targeted photothermal controllable nanocarrier consisting of MoS2 nanosheets modified with block copolymer P(OEG-A)-b-P(VBA-co-KH570) and targeting ligand transferrin. P(OEG-A)-b-P(VBA-co-KH570) is synthesized by RAFT polymerization and utilized not only to improve the solubility of MoS2 nanosheets but also efficiently load the anti-cancer drug doxorubicin (DOX) through an acid-cleavable Schiff base linker. Thiol-functionalized transferrin (Tf-SH) is anchored onto the surface of MoS2 nanosheets by the formation of disulfide bonds, which could further enhance the cellular uptake of DOX and MoS2 to HepG2 cells for high-efficiency synergetic therapy. The drug release experiments exhibited the minimal release of DOX at room temperature and neutral pH, and the maximal drug release of 53 % at acidic tumor pH and hyperthermia condition after 48 h. In addition, the DOX-loaded, Tf-SH and P(OEG-A)-b-P(VBA-co-KH570) modified MoS2 (DOX-POVK-MoS2 -Tf) showed better a therapeutic effect than DOX-POVK-MoS2 and POVK-MoS2 , probably owing to the combined effects of target-directed uptake, acid-triggered drug release, and NIR induced localized heating, which suggest the designed MoS2 nanocarriers are promising for applications in multi-modal cancer therapy.