Au Nanoshells Research Articles

Magnetoplasmonic Metasurface-Modulated Electrochemiluminescence Strategy for Extracellular Vesicle Detection.

Due to the ideal optical manipulation ability, the metasurface has broad prospects in the development of novel optical research. In particular, an active metasurface can control optical response through external stimulus, which has attracted great research interest. However, achieving effective modulation of the optical response is a significant challenge. In this work, we have developed a novel electrochemiluminescence (ECL) signal modulation strategy by an active magnetoplasmonic metasurface under an external magnetic field. The magnetoplasmonic metasurface was assembled based on yolk-shell Fe3O4@Au nanoparticles (Fe3O4@Au YS-NPs). On the one hand, the yolk-shell structure of Fe3O4@Au YS-NPs possessed the surface plasmon coupling effect and cavity-based Purcell effect, which provided high-intensity electromagnetic hot spots in the magnetoplasmonic metasurface. On the other hand, due to the strong magnetic response of the Fe3O4 core, the local magnetic field was induced by the external magnetic field, which further generated Lorentz force acting on the free electrons of Au nanoshells with strong optical anisotropy. The plasmon frequency of the metasurface can be effectively modulated by the Lorentz force effect. As a result, the ECL signal of nitrogen dots (N dots) was dynamically modulated and significantly enhanced at a specific polarization angle by the magnetoplasmonic metasurface under the variable external magnetic field. Based on the luminescence modulation ability and structure feature, the magnetoplasmonic metasurface was further established successfully as a sensing interface for gastric cancer (GC) extracellular vesicle (EV) detection. This study illustrated that the electromagnetic response of the active metasurface can effectively improve the optical modulation ability and luminescence sensing performance.

Rapid quantitative PCR equipment using photothermal conversion of Au nanoshell

The emergence of infectious diseases worldwide necessitates rapid and precise diagnostics. Using gold nanoshells in the PCR mix, we harnessed their unique photothermal properties in the near-infrared regime to attain efficient heating, reaching ideal photothermal PCR cycle temperature profile. Our photothermal PCR method expedited DNA amplification while retaining its detection sensitivity. Combining photothermal quantitative PCR with real-time fluorometry and non-invasive temperature measurement, we could amplify the target DNA within just 25 min, with a minimum detectable DNA amount of 50 picograms. This innovation in photothermal qPCR, leveraging the photothermal properties of gold nanoshells, will pave the way for immediate point-of-care diagnostics of nucleic acid biomarkers.

Modulating Kerr nonlinearity and optical bistability in a monolayer graphene nanoribbon nanoresonator coupled to a metallic nanoshell

A scheme for modulating Kerr nonlinearity and optical bistability (OB) based on a monolayer graphene nanoribbon nanoresonator (NR) and a metallic nanoshell (MNS) is proposed. The MNS is made of an Au nanoshell and a dielectric core. Here, we not only demonstrate that the spectrum of the Kerr coefficient can switch from a four-peaked structure to a two-peaked structure by increasing the shell thickness of the MNS, but also plot bistability phase diagrams in the system’s parameter subspace, revealing that the bistable effect can be controlled via zero-channel, one-channel or two-channels by only changing the shell thickness in a strong exciton-phonon coupling regime. Additionally, the calculated results also show that the material of the core of MNS plays an essential role in tuning OB when the shell thickness is fixed. The findings pave a new way for developing optical Kerr switches and high-flexible bistable nanodevices.

High-density Au nanoshells assembled onto Fe3O4 nanoclusters for integrated enrichment and photothermal/colorimetric dual-mode detection of SARS-CoV-2 nucleocapsid protein

Traditional lateral flow immunoassays (LFIA) suffer from insufficient sensitivity, difficulty for quantitation, and susceptibility to complex substrates, limiting their practical application. Herein, we developed a polyethylenimine (PEI)-mediated approach for assembling high-density Au nanoshells onto Fe3O4 nanoclusters (MagAushell) as LFIA labels for integrated enrichment and photothermal/colorimetric dual-mode detection of SARS-CoV-2 nucleocapsid protein (N protein). PEI layer served not only as “binders” to Fe3O4 nanoclusters and Au nanoshells, but also “barriers” to ambient environment. Thus, MagAushell not only combined magnetic and photothermal properties, but also showed good stability. With MagAushell, N protein was first separated and enriched from complex samples, and then loaded to the strip for detection. By observation of the color stripes, qualitative detection was performed with naked eye, and by measuring the temperature change under laser irradiation, quantification was attained free of sophisticated instruments. The introduction of Fe3O4 nanoclusters facilitated target purification and enrichment before LFIA, which greatly improved the anti-interference ability and increased the detection sensitivity by 2 orders compared with those without enrichment. Moreover, the high loading density of Au nanoshells on one Fe3O4 nanocluster enhanced the photothermal signal of the nanoprobe significantly, which could further increase the detection sensitivity. The photothermal detection limit reached 43.64 pg/mL which was 1000 times lower than colloidal gold strips. Moreover, this method was successfully applied to real samples, showing great application potential in practice. We envision that this LFIA could serve not only for SARS-CoV-2 detection but also as a general test platform for other biotargets in clinical samples.

Monodisperse Sub-100 nm Au Nanoshells for Low-Fluence Deep-Tissue Photoacoustic Imaging.

Nanoparticles with high absorption cross sections will advance therapeutic and bioimaging nanomedicine technologies. While Au nanoshells have shown great promise in nanomedicine, state-of-the-art synthesis methods result in scattering-dominant particles, mitigating their efficacy in absorption-based techniques that leverage the photothermal effect, such as photoacoustic (PA) imaging. We introduce a highly reproducible synthesis route to monodisperse sub-100 nm Au nanoshells with an absorption-dominant optical response. Au nanoshells with 48 nm SiO2 cores and 7 nm Au shells show a 14-fold increase in their volumetric absorption coefficient compared to commercial Au nanoshells with dimensions commonly used in nanomedicine. PA imaging with Au nanoshell contrast agents showed a 50% improvement in imaging depth for sub-100 nm Au nanoshells compared with the smallest commercially available nanoshells in a turbid phantom. Furthermore, the high PA signal at low fluences, enabled by sub-100 nm nanoshells, will aid the deployment of low-cost, low-fluence light-emitting diodes for PA imaging.

Templated Out‐of‐Equilibrium Self‐Assembly of Branched Au Nanoshells (Small 12/2023)

Branched Au Nanoshells Out-of-equilibrium self-assembly of metal nanoparticles achieving 3D structures with controlled morphology is still rare. In article number 2206712, Claudia Pigliacelli, Pierangelo Metrangolo, and co-workers adopt a peptide-gold superstructure as template to control the out-of-equilibrium self-assembly of Au nanoparticles, obtaining a transient 3D branched Au-nanoshell stabilized by surfactant. The nanoshell dismantles upon concentration gradient equilibration, leading to disassembly and regression to the template.

NIR‐triggered Synergetic Photothermal and Chemotherapy Cancer Treatment Based on SiO2@Au@SiO2@QDs‐DOX Composite Structural Particles

AbstractThis paper reports the synthesis of multi‐layer SiO2@Au@SiO2@QDs nanoparticles with a dual‐functionality of simultaneous heating and temperature sensing and their applications to in vitro chemo‐thermal therapy. The heating is activated by a NIR‐light through resonance excitation of surface plasma while in‐situ thermal sensing is accomplished by the QDs photoluminescent (PL) effect. These dual function nanoparticles are used as a drug carrier for in vitro chemotherapy‐photothermal co‐treatment for malignant cells. A comparative study of drug release profiles was performed with and without 808 nm laser irradiation. The drug release rate was accelerated by a rise of temperature, which is induced by plasmonic heat generation associated with Au nanoshells; while the temperature change is monitored by the QD nanoparticles at the same time. The results showed that SiO2@Au@SiO2@QDs‐DOX platform enabled the combination of local specific chemotherapy with external near‐infrared (NIR) photothermal therapy and significantly improved the efficacy of cancer treatment. This combined treatment demonstrated synergistic chemotherapeutic‐thermal effects compared to chemotherapy or photothermal therapy alone, resulting in higher efficacy.

Templated Out-of-Equilibrium Self-Assembly of Branched Au Nanoshells.

Out-of-equilibrium self-assembly of metal nanoparticles (NPs) has been devised using different types of strategies and fuels, but achieving finite 3D structures with a controlled morphology through this assembly mode is still rare. Here, a spherical peptide-gold superstructure (PAuSS) is used as a template to control the out-of-equilibrium self-assembly of Au NPs, obtaining a transient 3D-branched Au-nanoshell (BAuNS) stabilized by sodium dodecyl sulphate (SDS). The BAuNS dismantles upon SDS concentration gradient equilibration over time in the sample solution, leading to NPs disassembly and regression to PAuSS. Notably, BAuNS assembly and disassembly promotes temporary interparticle plasmonic coupling, leading to reversible and tunable changes of their plasmonic properties, a highly desirable behavior in the development of optoelectronic nanodevices.

Strong-Field Control of Plasmonic Properties in Core–Shell Nanoparticles

The strong-field control of plasmonic nanosystems opens up new perspectives for nonlinear plasmonic spectroscopy and petahertz electronics. Questions, however, remain regarding the nature of nonlinear light-matter interactions at sub-wavelength spatial and ultrafast temporal scales. Addressing this challenge, we investigated the strong-field control of the plasmonic response of Au nanoshells with a SiO$_2$ core to an intense laser pulse. We show that the photoelectron energy spectrum from these core-shell nanoparticles displays a striking transition between the weak and strong-field regime. This observed transition agrees with the prediction of our modified Mie-theory simulation that incorporates the nonlinear dielectric nanoshell response. The demonstrated intensity-dependent optical control of the plasmonic response in prototypical core-shell nanoparticles paves the way towards ultrafast switching and opto-electronic signal modulation with more complex nanostructures.

Magnetic Nanotag-Based Colorimetric/SERS Dual-Readout Immunochromatography for Ultrasensitive Detection of Clenbuterol Hydrochloride and Ractopamine in Food Samples.

Direct and sensitive detection of multiple illegal additives in complex food samples is still a challenge in on-site detection. In this study, an ultrasensitive immunochromatographic assay (ICA) using magnetic Fe3O4@Au nanotags as a capture/detection difunctional tool was developed for the direct detection of β2-adrenoceptor agonists in real samples. The Fe3O4@Au tag is composed of a large magnetic core (~160 nm), a rough Au nanoshell, dense surface-modified Raman molecules, and antibodies, which cannot only effectively enrich targets from complex solutions to reduce the matrix effects of food samples and improve detection sensitivity, but also provide strong colorimetric/surface-enhanced Raman scattering (SERS) dual signals for ICA testing. The dual readout signals of the proposed ICA can meet the detection requirements in different environments. Specifically, the colorimetric signal allows for rapid visual detection of the analyte, and the SERS signal is used for the sensitive and quantitative detection modes. The proposed dual-signal ICA can achieve the simultaneous determination of two illegal additives, namely, clenbuterol hydrochloride and ractopamine. The detection limits for the two targets via colorimetric and SERS signals were down to ng mL−1 and pg mL−1 levels, respectively. Moreover, the proposed assay has demonstrated high accuracy and stability in real food samples.

NIR-Absorbing Mesoporous Silica-Coated Copper Sulphide Nanostructures for Light-to-Thermal Energy Conversion.

Plasmonic nanostructures, featuring near infrared (NIR)-absorption, are rising as efficient nanosystems for in vitro photothermal (PT) studies and in vivo PT treatment of cancer diseases. Among the different materials, new plasmonic nanostructures based on Cu2−xS nanocrystals (NCs) are emerging as valuable alternatives to Au nanorods, nanostars and nanoshells, largely exploited as NIR absorbing nanoheaters. Even though Cu2−xS plasmonic properties are not linked to geometry, the role played by their size, shape and surface chemistry is expected to be fundamental for an efficient PT process. Here, Cu2−xS NCs coated with a hydrophilic mesoporous silica shell (MSS) are synthesized by solution-phase strategies, tuning the core geometry, MSS thickness and texture. Besides their loading capability, the silica shell has been widely reported to provide a more robust plasmonic core protection than organic molecular/polymeric coatings, and improved heat flow from the NC to the environment due to a reduced interfacial thermal resistance and direct electron–phonon coupling through the interface. Systematic structural and morphological analysis of the core-shell nanoparticles and an in-depth thermoplasmonic characterization by using a pump beam 808 nm laser, are carried out. The results suggest that large triangular nanoplates (NPLs) coated by a few tens of nanometers thick MSS, show good photostability under laser light irradiation and provide a temperature increase above 38 °C and a 20% PT efficiency upon short irradiation time (60 s) at 6 W/cm2 power density.

Photothermal bistability in the molecular energy transfer near a VO2@Au nanoshell triggered by the continuous-wave laser

The thermally triggered semiconductor-metal phase transition of vanadium dioxide (VO2) is a frequent subject in the study of nanostructure responses due to the high speed of the transition. Here we report on the molecular energy transfer near a hybrid VO2@Au nanoshell during the VO2 phase transition when induced by a continuous-wave (CW) laser. The presence of VO2 causes a bistable and reversible change in the optical response of the nanoshell through the thermo-optical process at the resonance wavelength of the VO2@ Au nanoshell. This behavior is achieved by controlling the laser intensity during the heating and cooling processes. In this paper we couple the thermodynamics with the Forster-Dexter theory of energy transfer between molecules which is generalized to use a nearby VO2@Au nanoshell. The bistable and reversible change in the response of the nanoshell causes the molecular energy transfer in the same manner over an intensity range of 1.52 (GW/m2) <I< 4.39 (GW/m2). This work also provides general guidelines for designing switchable surface plasmon based biosensors, switchable molecular junction devices and switching the energy exchange between proteins.

Analysis and optimization of the photothermal properties of Au nanoshells and nanospheroids

The investigations on the photothermal properties of nanoparticles present the following two problems. Firstly, approximate models and theories are used to calculate the optical properties of nanoparticles. Secondly, the optimal size parameters of the nanoparticles that correspond to the best photothermal properties are not given. To solve the above-mentioned problems, the effects of the light wavelength and the particle size on the photothermal properties of Au nanoshells and nanospheroids were analyzed by using the time-dependent heat transfer equation and the accurate light scattering theory (Mie theory and T-matrix). The maximum steady-state temperature changes at four different typical wavelengths (800 nm, 808 nm, 820 nm, and 1064 nm) in the near-infrared region and the corresponding optimal particle sizes were obtained. The optimized Au nanoparticles can be used as an ideal heat source in photothermal therapy.

Enhanced refractive index sensitivity of localized surface plasmon resonance inflection points in single hollow gold nanospheres with inner cavity

Hollow gold nanoparticles have great potential for localized surface plasmon resonance (LSPR) sensing. In this study, we investigated the refractive index (RI) sensitivities of single hollow gold nanosphere (HAuNS) with thin Au shell and inner cavity and single solid gold nanosphere (AuNS) in media with different RIs. The HAuNS exhibited a remarkable improvement in the RI sensitivity than the AuNS of similar size. The increased RI sensitivity of HAuNSs was ascribed to plasmon coupling between the inner and outer surface of the Au nanoshell. We then investigated the homogeneous LSPR scattering inflection points (IFs) to better understand the RI sensitivity of single HAuNS. The LSPR IF at the long wavelength side exhibited a better RI sensitivity compared to the wavelength shift of its counterpart LSPR maximum peak. Furthermore, the single HAuNS showed a remarkable improvement in the RI sensitivity at the LSPR IFs when compared to the AuNS of similar size. Therefore, we provided a new insight into the effect of inner cavity of HAuNS on the RI sensitivity of homogeneous LSPR IFs for use in LSPR-based biosensors.

Enzyme-Based Mesoporous Nanomotors with Near-Infrared Optical Brakes.

As one of the most important parameters of the nanomotors' motion, precise speed control of enzyme-based nanomotors is highly desirable in many bioapplications. However, owing to the stable physiological environment, it is still very difficult to in situ manipulate the motion of the enzyme-based nanomotors. Herein, inspired by the brakes on vehicles, the near-infrared (NIR) "optical brakes" are introduced in the glucose-driven enzyme-based mesoporous nanomotors to realize remote speed regulation for the first time. The novel nanomotors are rationally designed and fabricated based on the Janus mesoporous nanostructure, which consists of the SiO2@Au core@shell nanospheres and the enzymes-modified periodic mesoporous organosilicas (PMOs). The nanomotor can be driven by the biofuel of glucose under the catalysis of enzymes (glucose oxidase/catalase) on the PMO domain. Meanwhile, the Au nanoshell at the SiO2@Au domain enables the generation of the local thermal gradient under the NIR light irradiation, driving the nanomotor by thermophoresis. Taking advantage of the unique Janus nanostructure, the directions of the driving force induced by enzyme catalysis and the thermophoretic force induced by NIR photothermal effect are opposite. Therefore, with the NIR optical speed regulators, the glucose-driven nanomotors can achieve remote speed manipulation from 3.46 to 6.49 μm/s (9.9-18.5 body-length/s) at the fixed glucose concentration, even after covering with a biological tissue. As a proof of concept, the cellar uptake of the such mesoporous nanomotors can be remotely regulated (57.5-109 μg/mg), which offers great potential for designing smart active drug delivery systems based on the mesoporous frameworks of this novel nanomotor.

Synergistic H2O2 self-supplying and NIR-responsive drug delivery nanoplatform for chemodynamic-photothermal-chemotherapy

Developing effectively synergistic multi-mode drug delivery nanoplatform for cancer treatment is of great significance but still challenging. Here, we construct core-shell (CaO2@Au nanoshells) nanoparticles coated with doxorubicin-loaded hyaluronic acid. The developed platform can be used as synergistic H2O2 self-supplying and near-infrared-enhanced reactive oxygen species producer for chemodynamic-photothermal-chemotherapy multi-mode drug delivery. In this platform, the CaO2 possesses a high capacity of self-supplying H2O2 in acidic conditions, while retains desired stability under physiological conditions. The in-situ deposited Au nanoshells not only provide a remarkable photothermal therapy, but function as peroxidase mimics to catalyze H2O2 to produce hydroxyl radical to afford highly efficient chemodynamic therapy. Furthermore, the outer layer hyaluronic acid can load doxorubicin and target overexpressed receptor CD44 of cancer cell, meanwhile, trigger release of DOX in photothermal condition and acidic tumor microenvironment. The results of in vitro cell viability and in vivo tumor inhibition indicate that the developed synergistic nanoplatform hold the potential as an efficient strategy for chemodynamic-photothermal-chemotherapy combination therapy of cancer.

Analysis and Optimization of Au Nanoshell Photothermal Properties

Analysis and Optimization of Au Nanoshell Photothermal Properties

Photothermal induced bistability in the spontaneous decay rate of an emitter near a hybrid VO2–Au nanoshell

We theoretically investigate the bistable spontaneous emission behavior of a single emitter in the vicinity of a hybrid V O 2 –Au nanoshell. The hybrid nanoshell is illuminated by a continuous wave pump laser. The incident beam generates heat through light absorption and causes the V O 2 to undergo a phase change from semiconductor to metallic mode. Our calculation shows that for certain values, over a range of incident laser intensity [ 0.25 ( G W / m 2 ) &lt; I &lt; 0.84 ( G W / m 2 )], at the resonance wavelength of the V O 2 (semiconductor)–Au nanoshell ( λ = 630 n m ), there is a reasonable bistable contrast for the two spontaneous emission rate values: the radiative and nonradiative decay rates. Our results provide important general guidelines for enabling platforms for optical switching sources and tunable sensors.

Tuning and Exploitation of the Surface Plasmon Resonance on Gold/Cadmium Sulfide Nanoshell for Performanance Enhancement in Photocatalytic

Core-shell nanoparticles based on Au or Ag nanoshell core and cadmium sulfide semiconductor shell with differents size have been simulated using Mie and Drude approach. The results show that gold nanosphere coated by cadmium sulphide results has a maximum wavelength at 530 nm. This plasmon peak correspond to a ratio equal of 1.66. The optimised nanoshell allow light absorption in the visible region before cadmium sulfide coating. Thus, theses materials Au/CdS especially are good candidates for the design of functional nanocomposites used for photocatalytic application due mainly to its good light transparency.

Identifying high performance gold nanoshells for singlet oxygen generation enhancement

Metallic nanostructures can improve the production of singlet oxygen (1O2) of a photosensitizer during photodynamic therapy (PDT) . Engineering a high performance nanoparticle is mandatory for an appropriate use of plasmonic nanostructures in PDT. Metal enhanced singlet oxygen generation requires the use of nanoparticles with high scattering efficiency, capable of inducing a significant electric field enhancement and with plasmon peak overlapping the photosensitizer absorption spectrum. Herein, we report the optimization of nanoshells structure (silica core radius and gold shell thickness) to increase the singlet oxygen production by Methylene Blue photosensitizer. A 3D Full-wave field analysis was used to evaluate the plasmonic spectrum, scattering efficiency and localized field intensity of Au nanoshells as a function of their dimensions. The 40/20 core radius/shell thickness optimized gold nanoshell showed 75% scattering efficiency and field enhancement up to 35 times. Metal-enhanced singlet oxygen generation was observed and quantified for Methylene Blue water solution with gold nanoshell particles. Moreover, the influence of the irradiation time and the metallic nanostructures concentration on metal enhanced singlet oxygen generation were also appraised. The experimental results showed that the use of gold nanoshell improved 320% the 1O2 production in a MB solution. The approach used to select a high performance metallic nanoparticle provides insights on engineering plasmonic structures for metal enhanced singlet oxygen generation for PDT.