Novel Au–SiO2–WO3 Core–Shell Composite Nanoparticles for Surface‐Enhanced Raman Spectroscopy with Potential Application in Cancer Cell Imaging

With the rapid development of nanotechnology during the last decades, the ability to detect and control individual objects at the nanoscale has enabled us to deal with complex biomedical challenges. In cancer imaging, novel nanoparticles (NPs) offer promising potential to identify single cancer cells and precisely label larger areas of cancer tissues. Herein, a new class of size tunable core–shell composite (Au–SiO₂–WO₃) nanoparticles is reported. These nanoparticles display an easily improvable ≈10³ surface‐enhanced Raman scattering (SERS) enhancement factor with a double Au shell for dried samples over Si wafers and several orders of magnitude for liquid samples. WO₃ core nanoparticles measuring 20–50 nm in diameter are sheathed by an intermediate 10–60 nm silica layer, produced by following the Stöber‐based process and Turkevich method, followed by a 5–20 nm thick Au outer shell. By attaching 4‐mercaptobenzoic acid (4‐MBA) molecules as Raman reporters to the Au, high‐resolution Raman maps that pinpoint the nanoparticles' location are obtained. The preliminary results confirm their advantageous SERS properties for single‐molecule detection, significant cell viability after 24 h and in vitro cell imaging using coherent anti‐stokes Raman scattering. The long‐term objective is to measure SERS nanoparticles in vivo using near‐infrared light.     

Anisotropic Ag2S–Au Triangular Nanoprisms with Desired Configuration for Plasmonic Photocatalytic Hydrogen Generation in Visible/Near‐Infrared Region

Anisotropic Ag₂S‐edged Au‐triangular nanoprisms (TNPs) are constructed by controlling preferential overgrowth of Ag₂S as plasmonic photocatalysts for hydrogen generation. Under visible and near‐infrared light irradiation, Ag₂S‐edged Au‐TNPs exhibit almost fourfold higher efficiency (796 µmol h⁻¹ g⁻¹) than those of Ag₂S‐covered Au‐TNPs (216 µmol h⁻¹ g⁻¹) and pure Au‐TNPs in hydrogen generation. A single‐particle photoluminescence study demonstrates that the plasmon‐induced hot electrons transfer from Au‐TNPs to Ag₂S for hydrogen generation. Finite‐difference‐time‐domain simulations verify that the corners/edges of Au‐TNPs are high‐curvature sites with maximum electric field distributions facilitating hot electron generation and transfer. Therefore, Ag₂S‐edged Au‐TNPs are efficient plasmonic photocatalyst with the desired configurations for charge separation boosting hydrogen generation.     

Selective Pd Deposition on Au Nanobipyramids and Pd Site‐Dependent Plasmonic Photocatalytic Activity

The synthesis of anisotropic metal nanostructures is strongly desired for exploring plasmon‐enabled applications. Herein, the preparation of anisotropic Au/SiO₂ and Au/SiO₂/Pd nanostructures is realized through selective silica coating on Au nanobipyramids. For silica coating at the ends of Au nanobipyramids, the amount of coated silica and the overall shape of the coated nanostructures exhibit a bell‐shaped dependence on the cationic surfactant concentration. For both end and side silica coating on Au nanobipyramids, the size of the silica component can be varied by changing the silica precursor amount. Silica can also be selectively deposited on the corners or facets of Au nanocubes, suggesting the generality of this method. The blockage of the predeposited silica component on Au nanobipyramids enables further selective Pd deposition. Suzuki coupling reactions carried out with the different bimetallic nanostructures functioning as plasmonic photocatalysts indicate that the plasmonic photocatalytic activity is dependent on the site of Pd nanoparticles on Au nanobipyramids. Taken together, these results suggest that plasmonic hot spots play an important role in hot‐electron‐driven plasmonic photocatalysis. This study opens up a promising route to the construction of anisotropic bimetallic nanostructures as well as to the design of bimetallic plasmonic‐catalytic nanostructures as efficient plasmonic photocatalysts.     

Plasmon‐Promoted Electrochemical Oxygen Evolution Catalysis from Gold Decorated MnO2 Nanosheets under Green Light

The oxygen evolution reaction (OER) is of great importance for renewable energy conversion and storage; however, the intrinsic process is sluggish and suffers from severe efficiency loss as well as large overpotentials. In this work, with the introduction of the plasmonic effects by design of the Au‐MnO₂ hybrid catalysts, it is demonstrated that this photophysical phenomenon could largely promote the confinement of the outer electrons of Mn cations by plasmonic “hot holes” generated on gold surface. These “hot holes” work as the effective electron trapper to form the active Mnⁿ⁺ species which could provide active sites to extract electrons from OH^? and eventually facilitate the electrochemical OER catalysis under low laser power. By tuning the laser intensity from 100 to 200 mW, the overpotential is decreased from 0.38 to 0.32 V, which is comparable to IrO₂ and RuO₂ catalysts. These findings may provide insights into activation of plasmon‐promoted electrocatalysis under low power laser irradiation/treatment and the design of novel composite electrocatalysts.     

Piezotronic Effect Enhanced Plasmonic Photocatalysis by AuNPs/BaTiO3 Heterostructures

Piezopotential‐assisted catalysis is of great significance for low cost and efficient catalysis processes. Here, Au_x/BaTiO₃ plasmonic photocatalysts are fabricated by precipitating Au nanoparticles on piezoelectric BaTiO₃ nanocubes through a chemical approach. The Au nanoparticles (<8 nm) are decorated uniformly on the surface of BaTiO₃, which endows the heterostructure with a wide light absorption from 300 to 600 nm. The photocatalytic properties of the heterostructures are investigated in detail toward methyl orange (MO) degradation. The Au content, piezoelectric potential of the BaTiO₃ substrate, and surface plasmon resonance (SPR) are confirmed to be vital to the photocatalytic activity. The Au₄/BaTiO₃ shows an optimum photocatalytic performance for a complete degradation of MO in 75 min under full spectrum light irradiation with auxiliary ultrasonic excitation. The piezoelectric field originating from the deformation of BaTiO₃ further enhances the separation of photon‐generated carriers induced by SPR and promotes the formation of hydroxyl radicals, which results in a strong oxidizing ability of organic dyes. This work introduces the piezotronic effect to enhance plasmonic photocatalysis with Au_x/BaTiO₃ heterostructures, which is ready to extend to other catalytic systems and offers a new option to design high‐performance catalysts for pollutant treatment.     

Gold Nanoshell Nanomicelles for Potential Magnetic Resonance Imaging,Light‐Triggered Drug Release,and Photothermal Therapy

A novel multifunctional drug‐delivery platform is developed based on cholesteryl succinyl silane (CSS) nanomicelles loaded with doxorubicin, Fe₃O₄ magnetic nanoparticles, and gold nanoshells (CDF‐Au‐shell nanomicelles) to combine magnetic resonance (MR) imaging, magnetic‐targeted drug delivery, light‐triggered drug release, and photothermal therapy. The nanomicelles show improved drug‐encapsulation efficiency and loading level, and a good response to magnetic fields, even after the formation of the gold nanoshell. An enhancement for T₂‐weighted MR imaging is observed for the CDF‐Au‐shell nanomicelles. These nanomicelles display surface plasmon absorbance in the near‐infrared (NIR) region, thus exhibiting an NIR (808 nm)‐induced temperature elevation and an NIR light‐triggered and stepwise release behavior of doxorubicin due to the unique characteristics of the CSS nanomicelles. Photothermal cytotoxicity in vitro confirms that the CDF‐Au‐shell nanomicelles cause cell death through photothermal effects only under NIR laser irradiation. Cancer cells incubated with CDF‐Au‐shell nanomicelles show a significant decrease in cell viability only in the presence of both NIR irradiation and a magnetic field, which is attributed to the synergetic effects of the magnetic‐field‐guided drug delivery and the photothermal therapy. Therefore, such multicomponent nanomicelles can be developed as a smart and promising nanosystem that integrates multiple capabilities for effective cancer diagnosis and therapy.     

Rational Assembly of Optoplasmonic Hetero‐nanoparticle Arrays with Tunable Photonic–Plasmonic Resonances

Metallic and dielectric nanoparticles (NPs) have synergistic electromagnetic properties but their positioning into morphologically defined hybrid arrays with novel optical properties still poses significant challenges. A template‐guided self‐assembly strategy is introduced for the positioning of metallic and dielectric NPs at pre‐defined lattice sites. The chemical assembly approach facilitates the fabrication of clusters of metallic NPs with interparticle separations of only a few nanometers in a landscape of dielectric NPs positioned hundreds of nanometers apart. This approach is used to generate two‐dimensional interdigitated arrays of 250 nm diameter TiO₂ NPs and clusters of electromagnetically strongly coupled 60 nm Au NPs. The morphology‐dependent near‐ and far‐field responses of the resulting multiscale optoplasmonic arrays are analyzed in detail. Elastic and inelastic scattering spectroscopy in combination with electromagnetic simulations reveal that optoplasmonic arrays sustain delocalized photonic–plasmonic modes that achieve a cascaded E‐field enhancement in the gap junctions of the Au NP clusters and simultaneously increase the E‐field intensity throughout the entire array.     

An Acceptor–Donor–Acceptor Structured Small Molecule for Effective NIR Triggered Dual Phototherapy of Cancer

Dual phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is regarded as a more effective method for cancer treatment than single PDT or PTT. However, development of single component and near‐infrared (NIR) triggered agents for efficient dual phototherapy remains a challenge. Herein, a simple strategy to develop dual‐functional small‐molecules‐based photosensitizers for combined PDT and PTT treatment is proposed through: 1) finely modulating HOMO–LUMO energy levels to regulate the intersystem crossing (ISC) process for effective singlet oxygen (¹O₂) generation for PDT; 2) effectively inhibiting fluorescence via strong intramolecular charge transfer (ICT) to maximize the conversion of photo energy to heat for PTT or ISC process for PDT. An acceptor–donor–acceptor (A‐D‐A) structured small molecule (CPDT) is designed and synthesized. The biocompatible nanoparticles, FA‐CNPs, prepared by encapsulating CPDT directly with a folate functionalized amphipathic copolymer, present strong NIR absorption, robust photostability, cancer cell targeting, high photothermal conversion efficiency as well as efficient ¹O₂ generation under single 808 nm laser irradiation. Furthermore, synergistic PDT and PTT effects of FA‐CNPs in vivo are demonstrated by significant inhibition of tumor growth. The proposed strategy may provide a new approach to reasonably design and develop safe and efficient photosensitizers for dual phototherapy against cancer.     

Self‐Assembly of Nanoparticle‐Spiked Pillar Arrays for Plasmonic Biosensing

Plasmonic biosensors have demonstrated superior performance in detecting various biomolecules with high sensitivity through simple assays. Scaled‐up, reproducible chip production with a high density of hotspots in a large area has been technically challenging, limiting the commercialization and clinical translation of these biosensors. A new fabrication method for 3D plasmonic nanostructures with a high density, large volume of hotspots and therefore inherently improved detection capabilities is developed. Specifically, Au nanoparticle‐spiked Au nanopillar arrays are prepared by utilizing enhanced surface diffusion of adsorbed Au atoms on a slippery Au nanopillar arrays through a simple vacuum process. This process enables the direct formation of a high density of spherical Au nanoparticles on the 1 nm‐thick dielectric coated Au nanopillar arrays without high‐temperature annealing, which results in multiple plasmonic coupling, and thereby large effective volume of hotspots in 3D spaces. The plasmonic nanostructures show signal enhancements over 8.3 × 10⁸‐fold for surface‐enhanced Raman spectroscopy and over 2.7 × 10²‐fold for plasmon‐enhanced fluorescence. The 3D plasmonic chip is used to detect avian influenza‐associated antibodies at 100 times higher sensitivity compared with unstructured Au substrates for plasmon‐enhanced fluorescence detection. Such a simple and scalable fabrication of highly sensitive 3D plasmonic nanostructures provides new opportunities to broaden plasmon‐enhanced sensing applications.     

Plasmonic Electrically Functionalized TiO2 for High‐Performance Organic Solar Cells

Optical effects of the plasmonic structures and the materials effects of the metal nanomaterials have recently been individually studied for enhancing performance of organic solar cells (OSCs). Here, the effects of plasmonically induced carrier generation and enhanced carrier extraction of the carrier transport layer (i.e., plasmonic‐electrical effects) in OSCs are investigated. Enhanced charge extraction in TiO₂ as a highly efficient electron transport layer by the incorporation of metal nanoparticles (NPs) is proposed and demonstrated. Efficient device performance is demonstrated by using Au NPs incorporated TiO₂ at a plasmonic wavelength (560–600 nm), which is far longer than the originally necessary UV light. By optimizing the concentration ratio of the Au NPs in the NP‐TiO₂ composite, the performances of OSCs with various polymer active layers are enhanced and efficiency of 8.74% is reached. An integrated optical and electrical model, which takes into account plasmonic‐induced hot carrier tunneling probability and extraction barrier between TiO₂ and the active layer, is introduced. The enhanced charge extraction under plasmonic illumination is attributed to the strong charge injection of plasmonically excited electrons from NPs into TiO₂. The mechanism favors trap filling in TiO₂, which can lower the effective energy barrier and facilitate carrier transport in OSCs.     

Rattle‐Type Fe3O4@CuS Developed to Conduct Magnetically Guided Photoinduced Hyperthermia at First and Second NIR Biological Windows

A therapeutic carrier in the second near‐infrared (NIR) window is created that features magnetic target, magnetic resonance imaging (MRI) diagnosis, and photothermal therapy functions through the manipulation of a magnet and NIR laser. A covellite‐based CuS in the form of rattle‐type Fe₃O₄@CuS nanoparticles is developed to conduct photoinduced hyperthermia at 808 and 1064 nm of the first and second NIR windows, respectively. The Fe₃O₄@CuS nanoparticles exhibit broad NIR absorption from 700 to 1300 nm. The in vitro photothermal results show that the laser intensity obtained using 808 nm irradiation required a twofold increase in its magnitude to achieve the same damage in cells as that obtained using 1064 nm irradiation. Because of the favorable magnetic property of Fe₃O₄, magnetically guided photothermal tumor ablation is performed for assessing both laser exposures. According to the results under the fixed laser intensity and irradiation spot, exposure to 1064 nm completely removed tumors showing no signs of relapse. On the other hand, 808 nm irradiation leads to effective inhibition of growth that remained nearly unchanged for up to 30 d, but the tumors are not completely eliminated. In addition, MRI is performed to monitor rattle‐type Fe₃O₄@CuS localization in the tumor following magnetic attraction.     

Near‐Infrared SERS Nanoprobes with Plasmonic Au/Ag Hollow‐Shell Assemblies for In Vivo Multiplex Detection

For the effective application of surface‐enhanced Raman scattering (SERS) nanoprobes for in vivo targeting, the tissue transparency of the probe signals should be as high as it can be in order to increase detection sensitivity and signal reproducibility. Here, near‐infrared (NIR)‐sensitive SERS nanoprobes (NIR SERS dots) are demonstrated for in vivo multiplex detection. The NIR SERS dots consist of plasmonic Au/Ag hollow‐shell (HS) assemblies on the surface of silica nanospheres and simple aromatic Raman labels. The diameter of the HS interior is adjusted from 3 to 11 nm by varying the amount of Au³⁺ added, which results in a red‐shift of the plasmonic extinction of the Au/Ag nanoparticles toward the NIR (700–900 nm). The red‐shifted plasmonic extinction of NIR SERS dots causes enhanced SERS signals in the NIR optical window where endogenous tissue absorption coefficients are more than two orders of magnitude lower than those for ultraviolet and visible light. The signals from NIR SERS dots are detectable from 8‐mm deep in animal tissues. Three kinds of NIR SERS dots, which are injected into live animal tissues, produce strong SERS signals from deep tissues without spectral overlap, demonstrating their potential for in vivo multiplex detection of specific target molecules.     

Plasmonic Janus‐Composite Photocatalyst Comprising Au and C–TiO2 for Enhanced Aerobic Oxidation over a Broad Visible‐Light Range

Asymmetric Janus nanostructures containing a gold nanocage (NC) and a carbon–titania hybrid nanocrystal (AuNC/(C–TiO₂)) are prepared using a novel and facile microemulsion‐based approach that involves the assistance of ethanol. The localized surface plasmon resonance of the Au NC with a hollow interior and porous walls induce broadband visible‐light harvesting in the Janus AuNC/(C–TiO₂). An acetone evolution rate of 6.3 μmol h^?1 g^?1 is obtained when the Janus nanostructure is used for the photocatalytic aerobic oxidation of iso‐propanol under visible light (λ = 480–910 nm); the rate is 3.2 times the value of that obtained with C–TiO₂, and in photo‐electrochemical investigations an approximately fivefold enhancement is obtained. Moreover, when compared with the core–shell structure (AuNC@(C–TiO₂) and a gold–carbon–titania system where Au sphere nanoparticles act as light‐harvesting antenna, Janus AuNC/(C–TiO₂) exhibit superior plasmonic enhancement. Electromagnetic field simulation and electron paramagnetic resonance results suggest that the plasmon–photon coupling effect is dramatically amplified at the interface between the Au NC and C–TiO₂, leading to enhanced generation of energetic hot electrons for photocatalysis.     

Bottom‐Up Tailoring of Plasmonic Nanopeapods Making Use of the Periodical Topography of Carbon Nanocoil Templates

Au nanoparticle chains embedded in helical Al₂O₃ nanotubes (“nanopeapods”) are synthesized by annealing carbon nanocoils coated with Au by sputtering and Al₂O₃ by atomic layer deposition. Regular spacing between nanoparticles with a sharp size distribution is achieved by fragmentation of the Au coating in agreement with the pitch of the nanocoils arising from three‐dimensional periodical topography of the carbon nanocoil templates. A strong plasmonic resonance behavior of the fabricated nanopeapods manifests itself in confocal laser scanning microscopy by a clear polarization contrast at red wavelengths, which is absent in the blue. Numerical simulations confirm an incisive resonance enhancement for longitudinal polarization and suggest the nanopeapods as promising candidates for highly efficient, ultrathin waveguides. The waveguiding properties of the nanopeapods are investigated by electron energy‐loss spectroscopy and energy‐filtered TEM imaging.     

Highly Efficient Plasmonic Membrane Flow Reactor

A plasmonic flow reactor, consisting of thin Au film at exits of monolithic anodized aluminum oxide (AAO) membranes under LED illumination is demonstrated. The system shows over 200% quantum efficiency (QE) for peroxide activation and the ability to limit to single oxidation reaction by controlling residence time with flow rate and pore geometry. Periodic pore arrays (20–200 nm diameter) with 25 nm thick Au on AAO are modeled by finite-difference time-domain (FDTD) simulations and predicted largest E-field enhancements for the larger 200 nm pore diameters. Peroxide activation, as measured by O₂ generation is most efficient with a 200 nm pore diameter system under 523 nm LED illumination. The optimal wavelength falls near the absorption peak of Au@AAO with 200 nm pore diameter suggesting that hot electron generated from gold plasmonic response is the primary mechanism for activation of H₂O₂. QE for gold plasmonic flow system calculated from O₂ generation experiments is as high as 250%, which indicates a mechanism of hot-electron activation of peroxide that leaves a still energetic hot-electron to catalytically activate multiple reactions. The formation of Au surface oxides that are catalytically active in dark is also observed and must be accounted for in Au plasmonic photochemical studies.     

Si and Ge nanocluster formation in silica matrix

High resolution transmission electron microscopy, scanning transmission electron microscopy, and cathodoluminescence have been used to investigate Si and Ge cluster formation in amorphous silicon-dioxide layers. Commonly, cathodoluminescence emission spectra of pure SiO₂ are identified with particular defect centers within the atomic network of silica including the nonbridging oxygen hole center associated with the red luminescence at 650 nm (1.9 eV) and the oxygen deficient centers with the blue (460 nm; 2.7 eV) and ultraviolet band (295 nm; 4.2 eV). In Ge⁺ ion-implanted SiO₂, an additional violet emission band appears at 410 nm (3.1 eV). The strong increase of this violet luminescence after thermal annealing is associated with formation of low-dimension Ge aggregates such as dimers, trimers, and higher formations, further growing to Ge nanoclusters. On the other hand, pure silica layers were modified by heavy electron beam irradiation (5 keV; 2.7 A/cm²), leading to electronic as well as thermal dissociation of oxygen and the appearance of under-stoichiometric SiO_x. This SiO_x will undergo a phase separation and we observe Si cluster formation with a most probable cluster diameter of 4 nm. Such largely extended Si clusters will diminish the SiO₂-related luminescence and Si-crystal-related luminescence in the near IR. The text was submitted by the authors in English.     

Assembly of Au Plasmonic Photothermal Agent and Iron Oxide Nanoparticles on Ultrathin Black Phosphorus for Targeted Photothermal and Photodynamic Cancer Therapy

Photodynamic therapy (PDT), as a minimally invasive and high‐efficiency anticancer approach, has received extensive research attention recently. Despite plenty of effort devoted to exploring various types of photodynamic agents with strong near‐infrared (NIR) absorbance for PDT and many encouraging progresses achieved in the area, effective and safe photodynamic photosensitizers with good biodegradability and biocompatibility are still highly expected. In this work, a novel nanocomposite has been developed by assembly of iron oxide (Fe₃O₄) nanoparticles (NPs) and Au nanoparticles on black phosphorus sheets (BPs@Au@Fe₃O₄), which shows a broad light absorption band and a photodegradable character. In vitro and in vivo assay indicates that BPs@Au@Fe₃O₄ nanoparticles are highly biocompatible and exhibit excellent tumor inhibition efficacy owing to a synergistic photothermal and photodynamic therapy mediated by a low‐power NIR laser. Importantly, BPs@Au@Fe₃O₄ can anticipatorily suppress tumor growth by visualized synergistic therapy with the help of magnetic resonance imaging (MRI). This work presents the first combination application of the photodynamic and photothermal effect deriving from black phosphorus nanosheets and plasmonic photothermal effect from Au nanoparticles together with MRI from Fe₃O₄ NPs, which may open the new utilization of black phosphorus nanosheets in biomedicine, optoelectronic devices, and photocatalysis.     

Design and Synthesis of “All‐in‐One” Multifunctional FeS2 Nanoparticles for Magnetic Resonance and Near‐Infrared Imaging Guided Photothermal Therapy of Tumors

The ideal theranostic nanoplatform for tumors is a single nanoparticle that has a single semiconductor or metal component and contains all multimodel imaging and therapy abilities. The design and preparation of such a nanoparticle remains a serious challenge. Here, with FeS₂ as a model of a semiconductor, the tuning of vacancy concentrations for obtaining “all‐in‐one” type FeS₂ nanoparticles is reported. FeS₂ nanoparticles with size of ≈30 nm have decreased photoabsorption intensity from the visible to near‐infrared (NIR) region, due to a low S vacancy concentration. By tuning their shape/size and then enhancing the S vacancy concentration, the photoabsorption intensity of FeS₂ nanoparticles with size of ≈350 nm (FeS₂‐350) goes up with the increase of the wavelength from 550 to 950 nm, conferring the high NIR photothermal effect for thermal imaging. Furthermore, this nanoparticle has excellent magnetic properties for T₂‐weighted magnetic resonance imaging (MRI). Subsequently, FeS₂‐350 phosphate buffer saline (PBS) dispersion is injected into the tumor‐bearing mice. Under the irradiation of 915‐nm laser, the tumor can be ablated and the metastasis lesions in liver suffer significant inhibition. Therefore, FeS₂‐350 has great potential to be used as novel “all‐in‐one” multifunctional theranostic nanoagents for MRI and NIR dual‐modal imaging guided NIR‐photothermal ablation therapy (PAT) of tumors.     

Phase‐Change Materials Based Nanoparticles for Controlled Hypoxia Modulation and Enhanced Phototherapy

Tumor hypoxia strengthens tumor resistance to different therapies especially oxygen involved strategies, such as photodynamic therapy (PDT). Herein, the thermal responsive phase change materials (PCM) are utilized to coencapsulate ultrasmall manganese dioxide (sMnO₂) and organic photosensitizer IR780 to obtain IR780‐sMnO₂‐PCM nanoparticles for controlled tumor hypoxia modulation and enhanced phototherapy. The thermal responsive protective PCM layer can not only prevent IR780 from photodegradation, but also immediately release sMnO₂ to decompose endogenous H₂O₂ and generate enough oxygen for PDT under laser irradiation. Owing to the efficient accumulation of IR780‐sMnO₂‐PCM nanoparticles in tumor under intravenous injection as revealed by both florescence imaging and photoacoustic imaging, the tumor hypoxia is greatly relieved. Furthermore, in vivo combined photothermal therapy (PTT) and PDT, IR780‐sMnO₂‐PCM nanoparticles, compared to IR780‐PCM nanoparticles, exhibit better performance in inhibiting tumor growth. The results highlight the promise of IR780‐sMnO₂‐PCM in controlled modulation of tumor hypoxia to overcome current limitations of cancer therapies.     

Ultrasonication‐Induced Self‐Assembled Fixed Nanogap Arrays of Monomeric Plasmonic Nanoparticles inside Nanopores

Monomeric gold (Au) and silver (Ag) nanoparticle (NP) arrays are self‐assembled uniformly into anodized aluminium oxide (AAO) nanopores with a high homogeneity of greater than 95%, using ultrasonication. The monomeric metal NP array exhibits asymmetric plasmonic absorption due to Fano‐like resonance as interpreted by finite‐difference time‐domain (FDTD) simulation for the numbers up to 127 AuNPs. To examine gap distance‐dependent collective‐plasmonic resonance, the different dimensions of S, M, and L arrays of the AuNP diameters/the gap distances of ≈36 nm/≈66 nm, ≈45 nm/≈56 nm, and ≈77 nm/≈12 nm, respectively, are prepared. Metal NP arrays with an invariable nanogap of ≈50 nm can provide consistent surface‐enhanced Raman scattering (SERS) intensities for Rhodamine 6G (Rh6G) with a relative standard deviation (RSD) of 3.8–5.4%. Monomeric arrays can provide an effective platform for 2D hot‐electron excitation, as evidenced by the SERS peak‐changes of 4‐nitrobenzenethiol (4‐NBT) adsorbed on AgNP arrays with a power density of ≈0.25 mW µm^‐2 at 514 and 633 nm. For practical purposes, the bacteria captured by 4‐mercaptophenylboronic acid are found to be easily destroyed under visible laser excitation at 514 nm with a power density of ≈14 mW µm^‐2 for 60 min using Ag due to efficient plasmonic‐electron transfer.