Silica-coated Gold Nanorods Research Articles

Plasmon-enhanced NIR-II photoluminescence of rare-earth oxide nanoprobes for high-sensitivity optical temperature sensing.

With ongoing advancements in photothermal therapy, achieving efficient tumor cell eradication while minimizing damage to healthy tissues necessitates a highly effective and non-invasive real-time temperature monitoring technique for human tissues. Herein, we report a near-infrared (NIR)-II optical temperature sensing nanoprobe featuring rare-earth-doped gadolinium oxide nanocrystals (RENCs) attached to the dumbbell mesoporous silica-coated gold nanorods (AuNRs). The composite nanoprobe presents an intense absorption in the NIR region, and NIR-II photoluminescence (PL) increases by 97.2 to 102-fold compared to pure RENCs upon 980 nm irradiation. The localized electric field generated through surface plasmon resonance effects of AuNRs demonstrated a dumbbell-shaped distribution that aligns with the structure of nanoprobes, maximizing the PL enhancement of RENCs. Moreover, the NIR-II emissions are changed with the rising temperature, with an exceptional relative sensitivity of 7.25% K-1 at 338 K based on PL lifetime, indicating the nanoprobe is highly potential for optical temperature sensing.

A "Talking" between Gold Nanoparticle and a Luminescent Iridium(III) Complex: A Study of the Effect Due to the Interaction between Plasmon Resonance and a Fluorophore.

This paper explores a novel synthesis and characterization of silica-coated gold nanorods (AuNRs) embedding a highly emissive cyclometalated iridium(III) complex, denoted as Ir1. We investigate the optical properties and the interplay between the metal compound and gold plasmon, observing how the emission of Ir1 incorporated into the nanoparticles shows two emission bands, one in the blue and the other in the green-orange range of the visible spectrum. To obtain a clearer picture of what we were observing, we synthesized analogous nanosystems, from which it was possible to highlight the effect of different features. Based on what we observed, we proposed that the fraction of the iridium(III) complex in direct contact with the surface of the gold nanoparticle undergoes a "demixing" of the excited state, which, for cyclometalated iridium complexes, is generally considered a mixed LC+MLCT state. This preliminary study sheds light on the complexity of the "talking" between a fluorophore and a plasmonic system, highlighting the importance of considering the emitter typology when modeling such systems.

Fluorinated triphenylamine phthalocyanine @ silica-coated gold nanorods: A photoactivated lysosome escape and targeting mitochondria two-photon probe for imaging-guided photothermal synergistic photodynamic therapy in cancer cells

The timely evasion of nanomedicines from lysosomes is essential to avert premature degradation under the acidic and hydrolytic conditions characteristic of these cellular compartments. However, the development of effective strategies has been hindered by the complexity of design material and the scarcity of practical methods. In this study, we have synthesized a novel nanoparticle, designated as TPA-BPAF-SiPc@AuNR@SiO2. This nanoparticle was prepared by encapsulating near-infrared fluorinated triphenylamine-substituted silicon phthalocyanines (TPA-BPAF-SiPc) within mesoporous silica-coated gold nanorods (AuNR@SiO2). TPA-BPAF-SiPc@AuNR@SiO2 functions as a dual-function two-photon probe, facilitating photoactivated lysosome escape and targeting mitochondria. The inherent aggregation-induced emission (AIE) two-photon fluorescence of TPA-BPAF-SiPc is notably bright when encapsulated in AuNR@SiO2 nanocarriers, a phenomenon not observed in polymer nanocarriers composed of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG2000) or in THF/water mixtures. Upon irradiation, this nanoparticle autonomously escapes from lysosomes and selectively targets mitochondria, a process can be visually monitored in real-time through the two-photon AIE fluorescence of TPA-BPAF-SiPc. Moreover, upon activation, TPA-BPAF-SiPc@AuNR@SiO2 produces a substantial quantity of reactive oxygen species (ROS) and induces hyperthermia effects, showcasing its potential for effective photodynamic therapy (PDT) in conjunction with synergistic hyperthermia. Flow cytometry data corroborate the induction of tumor cell death through both necrosis and apoptosis pathways by TPA-BPAF-SiPc@AuNR@SiO2. This study underscores the potential of TPA-BPAF-SiPc@AuNR@SiO2 as a multifunctional probe capable of enabling lysosome escape, mitochondria targeting, and two-photon fluorescence imaging-guided photothermal synergistic photodynamic therapy, specifically tailored for the treatment of breast cancer.

Fabrication and evaluation of a plasmonic biosensor based on silica-coated gold nanorods for highly-sensitive detection of anti-Müllerian hormone

Anti-müllerian hormone is a crucial biomarker for reproductive potential, but current detection methods are not cost-effective or time-efficient. In this study, we set out to develop a biosensor using gold nanorods (Au-NRs) coated with a functionalized silica network. The biosensor structure was completed by covalently binding the anti-Müllerian hormone antibody to SiO2@Au-NRs. We confirmed the proper coating of the gold nanorods using HR-TEM, EDS/EDAX, zeta potential, and FT-IR analysis. To assess the sensitivity of SiO2@Au-NRs, we analyzed the LSPR peak position redshift in different concentrations of ethylene glycol. The biosensor was then used to recognize the AMH antigen and determine the limit of detection (LoD) and quantification (LoQ) for the biosensor. Our research has shown that the SiO2@Au-NRs have a suitable thickness. The SiO2@Au-NRs demonstrated impressive sensitivity as a nano biosensor. The AMH antigen identification results indicated that the nano biosensor was highly sensitive. The LoD and LoQ values were 0.086 and 0.262 ng ml−1, respectively, very close to the values obtained by the ELISA kit. Furthermore, LSPR biosensors have reduced detection costs and measurement time. Their high sensitivity makes them excellent candidates for use in diagnostic kits.

Sequential release of drugs from dual-delivery plasmonic nanogels containing lipid-gated mesoporous silica-coated gold nanorods

Nanosystems that enable the sequential delivery of various drugs with different targets are desired for improved cancer therapy. However, current strategies are mainly dependent on the tumour microenvironment, such as low pH or enzyme-triggered release. In this work, a nanosystem design strategy for near infrared (NIR) light-triggered sequential delivery based on lipid-gated mesoporous silica-coated gold nanorods and chitosan/alginate nanogels was developed. The mesoporous silica particles (99 ± 11 nm) were loaded with methotrexate, and further coated with a thermoresponsive phospholipid bilayer that works as gatekeeper. These particles were then incorporated in a chitosan/alginate nanogel matrix containing doxorubicin. The plasmonic nanogels exhbited high loading efficiencies of ∼90 % and ∼85 for methotrexate and doxorubicin, respectively. Notably, this system displayed average hydrodynamic diameters near 300 nm, low polidispersity, highly negative zeta potential (∼−30 mV), and a sustained release of both drugs under acidic and neutral conditions. Upon NIR laser irradiation, an enhanced release of both drugs was observed, with doxorubicin exhibiting a faster release rate than methotrexate under acidic conditions. This design strategy of NIR-triggered sequential delivery holds promise for different drug combinations against multiple targets in tumour microenvironment in the field of multimodal cancer therapy.

Progress of Mesoporous Silica Coated Gold Nanorods for Biological Imaging and Cancer Therapy.

For unique surface plasmon absorption and fluorescence characteristics, gold nanorods have been developed and widely employed in the biomedical field. However, limitations still exist due their low specific surface area, instability and tendency agglomerate in cytoplasm. Mesoporous silica materials have been broadly applied in field of catalysts, adsorbents, nanoreactors, and drug carriers due to its unique mesoporous structure, highly comparative surface area, good stability and biocompatibility. Therefore, coating gold nanorods with a dendritic mesopore channels can effectively prevent particle agglomeration, while increasing the specific surface area and drug loading efficiency. This review discusses the advancements of GNR@MSN in synthetic process, bio-imaging technique and tumor therapy. Additionally, the further application of GNR@MSN in imaging-guided treatment modalities is explored, while its promising superior application prospect is highlighted. Finally, the issues related to in vivo studies are critically examined for facilitating the transition of this promising nanoplatform into clinical trials.

Accurately Controlled Tumor Temperature with Silica-Coated Gold Nanorods for Optimal Immune Checkpoint Blockade Therapy.

Photothermal therapy (PTT) at mild temperatures ranging from 44 to 45 °C holds tremendous promise as a strategy for inducing potent immunogenic cell death (ICD) within tumor tissues, which can reverse the immunosuppressive tumor microenvironment (ITM) into an immune-responsive milieu. However, accurately and precisely controlling the tumor temperature remains a formidable challenge. Here, we report the precision photothermal immunotherapy by using silica-coated gold nanorods (AuNR@SiO2), and investigating the optimal administration routes and treatment protocols, which enabled to achieve the sustained and controlled mild heating within the tumor tissues. First, the highest photothermal performance of AuNR@SiO2 with 20-nm silica shell thickness than 5 or 40 nm was confirmed invitro and invivo. Then, the optimal conditions for precision immunotherapy were further investigated to produce mild temperature (44 to 45 °C) accurately in tumor tissues. The optimal conditions with AuNR@SiO2 result in a distinct cell death with high early/late apoptosis and low necrosis, leading to very efficient ICD compared to lower or higher temperatures. In colon tumor-bearing mice, intratumorally injected AuNR@SiO2 efficiently promotes a mild temperature within the tumor tissues by local irradiation of near-infrared (NIR) laser. This mild PTT substantially increases the population of mature dendritic cells (DCs) and cytotoxic T cells (CTLs) within tumor tissues, ultimately reversing the ITM into an immune-responsive milieu. Furthermore, we found that the combination mild PTT with AuNR@SiO2 and anti-PD-L1 therapy could lead to the 100% complete regression of primary tumors and immunological memory to prevent tumor recurrence. Collectively, this study demonstrates that AuNR@SiO2 with a robust methodology capable of continuously inducing mild temperature accurately within the ITM holds promise as an approach to achieve the precision photothermal immunotherapy.

Bottom-Up Then Top-Down Synthesis of Gold Nanostructures Using Mesoporous Silica-Coated Gold Nanorods.

Gold nanostructures were synthesized by etching away gold from heat-treated mesoporous silica-coated gold nanorods (AuNR@mSiO2), providing an example of top-down modification of nanostructures made using bottom-up methodology. Twelve different types of nanostructures were made using this bottom-up-then-top-down synthesis (BUTTONS), of which the etching of the same starting nanomaterial of AuNR@mSiO2 was found to be controlled by how AuNR@mSiO2 were heat treated, the etchant concentration, and etching time. When the heat treatment occurred in smooth moving solutions in round-bottomed flasks, red-shifted longitudinal surface plasmon resonance (LSPR) was observed, on the order of 10-30 min, indicating increased aspect ratios of the gold nanostructures inside the mesoporous silica shells. When the heat treatment occurred in turbulent solutions in scintillation vials, a blue shift of the LSPR was obtained within a few minutes or less, resulting from reduced aspect ratios of the rods in the shells. The influence of the shape of the glassware, which may impact the flow patterns of the solution, on the heat treatment was investigated. One possible explanation is that the flow patterns affect the location of opened pores in the mesoporous shells, with the smooth flow of solution mainly removing CTAB surfactants from the pores along the cylindrical body of mSiO2, therefore increasing the aspect ratios after etching, and the turbulent solutions removing more surfactants from the pores of the two ends or tips of the silica shells, hence decreasing the aspect ratios after etching. These new stable gold nanostructures in silica shells, bare and without surfactant protection, may possess unique chemical properties and capabilities. Catalysis using heat-treated nanomaterials was studied as an example of potential applications of these nanostructures.

Effective Distribution of Gold Nanorods in Ordered Thick Mesoporous Silica: A Choice of Noninvasive Theranostics.

Porous silica coated gold nanorod core-shell structures demonstrate a multifunctional role in bioimaging, drug delivery, and cancer therapeutics applications. Here, we address a new approach for effective distribution of gold nanorods (GNRs) in a mesoporous silica (MS) shell, viz., one nanorod in one silica particle (GMS). We have studied that silica coating presents major advantages for the better biocompatibility and stability of GNRs. In this study, two different thicknesses of silica shell over GNRs have been discussed as per the application's need; GNRs in thin silica (11 nm) are fit for phototherapy and bioimaging, whereas thick and porous silica (51 nm) coated gold nanorods are suitable for triggered drug delivery and theranostics. However, effective distribution of GNRs in ordered architecture of thick mesoporous silica (MS, more than 50 nm thickness) with high surface area (more than 1000 m2/g) is not well understood so far. Here, we present methodical investigations for uniform and highly ordered mesoporous silica coating over GNRs with tunable thickness (6 to 51 nm). Judicious identification and optimization of different reaction parameters like concentrations of silica precursor (TEOS, 1.85-43.9 mM), template (CTAB, 0.9-5.7 mM), effect of temperature, pH (8.6-10.8), stirring speed (100-400 rpm), and, most importantly, the mode of addition of TEOS with GNRs have been discussed. Studies with thick, porous silica coated GNRs simplify the highest ever reported surface area (1100 m2/g) and cargo capacity (57%) with better product yield (g/batch). First and foremost, we report a highly scalable (more than 500 mL) and rapid direct deposition of an ordered MS shell around GNRs. These engineered core-shell nanoparticles demonstrate X-ray contrast property, synergistic photothermal-chemotherapeutics, and imaging of tumor cell (96% cell death) due to released fluorescent anticancer drug molecules and photothermal effect (52 °C) of embedded GNRs. A deeper insight into their influence on the architectural features and superior theranostics performances has been illustrated in detail. Hence, these findings indicate the potential impact of individual GMS for image guided combination therapeutics of cancer.

Gold Nanorods with Mesoporous Silica Shell: A Promising Platform for Cisplatin Delivery.

The versatile combination of metal nanoparticles with chemotherapy agents makes designing multifunctional drug delivery systems attractive. In this work, we reported cisplatin's encapsulation and release profile using a mesoporous silica-coated gold nanorods system. Gold nanorods were synthesized by an acidic seed-mediated method in the presence of cetyltrimethylammonium bromide surfactant, and the silica-coated state was obtained by modified Stöber method. The silica shell was modified first with 3-aminopropyltriethoxysilane and then with succinic anhydride to obtain carboxylates groups to improve cisplatin encapsulation. Gold nanorods with an aspect ratio of 3.2 and silica shell thickness of 14.74 nm were obtained, and infrared spectroscopy and ζ potential studies corroborated surface modification with carboxylates groups. On the other hand, cisplatin was encapsulated under optimal conditions with an efficiency of ~58%, and it was released in a controlled manner over 96 h. Furthermore, acidic pH promoted a faster release of 72% cisplatin encapsulated compared to 51% in neutral pH.

Quantitative 3D Investigation of Nanoparticle Assemblies by Volumetric Segmentation of Electron Tomography Data Sets

Morphological characterization of nanoparticle assemblies and hybrid nanomaterials is critical in determining their structure-property relationships as well as in the development of structures with desired properties. Electron tomography has become a widely utilized technique for the three-dimensional characterization of nanoparticle assemblies. However, the extraction of quantitative morphological parameters from the reconstructed volume can be a complex and labor-intensive task. In this study, we aim to overcome this challenge by automating the volumetric segmentation process applied to three-dimensional reconstructions of nanoparticle assemblies. The key to enabling automated characterization is to assess the performance of different volumetric segmentation methods in accurately extracting predefined quantitative descriptors for morphological characterization. In our methodology, we compare the quantitative descriptors obtained through manual segmentation with those obtained through automated segmentation methods, to evaluate their accuracy and effectiveness. To show generality, our study focuses on the characterization of assemblies of CdSe/CdS quantum dots, gold nanospheres and CdSe/CdS encapsulated in polymeric micelles, and silica-coated gold nanorods decorated with both CdSe/CdS or PbS quantum dots. We use two unsupervised segmentation algorithms: the watershed transform and the spherical Hough transform. Our results demonstrate that the choice of automated segmentation method is crucial for accurately extracting the predefined quantitative descriptors. Specifically, the spherical Hough transform exhibits superior performance in accurately extracting quantitative descriptors, such as particle size and interparticle distance, thereby allowing for an objective, efficient, and reliable volumetric segmentation of complex nanoparticle assemblies.

Precise Tailoring of Mesoporous Silica-Coated Gold Nanorods for Laser Ignition at 1064 nm

Precise Tailoring of Mesoporous Silica-Coated Gold Nanorods for Laser Ignition at 1064 nm

Machine Learning Predicting Optimal Preparation of Silica-Coated Gold Nanorods for Photothermal Tumor Ablation.

Gold nanorods (GNRs) coated with silica shells are excellent photothermal agents with high surface functionality and biocompatibility. Understanding the correlation of the coating process with both structure and property of silica-coated GNRs is crucial to their optimizing preparation and performance, as well as tailoring potential applications. Herein, we report a machine learning (ML) prediction of coating silica on GNR with various preparation parameters. A total of 306 sets of silica-coated GNRs altogether were prepared via a sol-gel method, and their structures were characterized to extract a dataset available for eight ML algorithms. Among these algorithms, the eXtreme gradient boosting (XGboost) classification model affords the highest prediction accuracy of over 91%. The derived feature importance scores and relevant decision trees are employed to address the optimal process to prepare well-structured silica-coated GNRs. The high-throughput predictions have been adopted to identify optimal process parameters for the successful preparation of dumbbell-structured silica-coated GNRs, which possess a superior performance to a conventional cylindrical core-shell counterpart. The dumbbell silica-coated GNRs demonstrate an efficient enhanced photothermal performance in vivo and in vitro, validated by both experiments and time domain finite difference calculations. This study epitomizes the potential of ML algorithms combined with experiments in predicting, optimizing, and accelerating the preparation of core-shell inorganic materials and can be extended to other nanomaterial research.

Multifunctional Mesoporous Silica-Coated Gold Nanorods Mediate Mild Photothermal Heating-Enhanced Gene/Immunotherapy for Colorectal Cancer.

Colorectal cancer (CRC) is the third most common cancer worldwide and the second leading cause of cancer-related deaths in the world. It is urgent to search for safe and effective therapies to address the CRC crisis. The siRNA-based RNA interference targeted silencing of PD-L1 has extensive potential in CRC treatment but is limited by the lack of efficient delivery vectors. In this work, the novel cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs)/siPD-L1 co-delivery vectors AuNRs@MS/CpG ODN@PEG-bPEI (ASCP) were successfully prepared by two-step surface modification of CpG ODNs-loading and polyethylene glycol-branched polyethyleneimine-coating around mesoporous silica-coated gold nanorods. ASCP promoted dendritic cells (DCs) maturation by delivering CpG ODNs, exhibiting excellent biosafety. Next, mild photothermal therapy (MPTT) mediated by ASCP killed tumor cells and released tumor-associated antigens, further promoting DC maturation. Furthermore, ASCP exhibited mild photothermal heating-enhanced performance as gene vectors, resulting in an increased PD-L1 gene silencing effect. Enhanced DCs maturity and enhanced PD-L1 gene silencing significantly promoted the anti-tumor immune response. Finally, the combination of MPTT and mild photothermal heating-enhanced gene/immunotherapy effectively killed MC38 cells, leading to strong inhibition of CRC. Overall, this work provided new insights into the design of mild photothermal/gene/immune synergies for tumor therapy and may contribute to translational nanomedicine for CRC treatment.

Simulation of Optical Characteristics of a Breast Tumor Incorporated with Silica Coated Gold Nanorods

Simulation of Optical Characteristics of a Breast Tumor Incorporated with Silica Coated Gold Nanorods

In situ reversible tuning of chemical interface damping in mesoporous silica-coated gold nanorods via direct adsorption and removal of thiol.

Chemical interface damping (CID) is a recently proposed plasmon decay channel in gold nanoparticles. However, thus far, a very limited number of studies have focused on controlling CID in single gold nanoparticles. Herein, we describe a new simple method for reversible tuning of CID in single gold nanorods coated with a mesoporous silica shell (AuNRs@mSiO2). We used 1-alkanethiols with two different carbon chain lengths (1-butanethiol and 1-decanethiol) as adsorbates to induce CID. In addition, NaBH4 solution was used to remove the attached thiol from the AuNR surface. We confirmed the adsorption and removal of 1-alkanethiols on single AuNRs@mSiO2 and the corresponding changes in localized surface plasmon resonance (LSPR) peak wavelengths and linewidths. Furthermore, we investigated the effect of immersion time in NaBH4 solution on thiol removal from AuNRs@mSiO2. Therefore, the LSPR properties and CID can be controlled, thereby paving the way for in situ reversible tuning of CID by repeated adsorption and desorption of thiol molecules on single AuNRs@mSiO2.

Silica-coated gold nanorods biofunctionalization for localized surface plasmon resonance (LSPR) biosensing

We introduce here the engineering of nanobiosensors designed from gold nanorods coated with an ultrathin layer of silica (AuNR@SiO2) and biofunctionalized with antibodies for the Localized Surface Plasmon Resonance (LSPR) biosensing of proteins. Despite the outstanding properties of AuNRs, their use for LSPR biosensing is limited due to the presence of the surfactant cetyltrimethylammonium bromide (CTAB) – mandatory for their synthesis - which forms a strongly-bounded and positively-charged bilayer at their surface and significantly complicates their bio-functionalization. When coated with a thin layer of silica, these nanomaterials exhibit an improved sensitivity to refractive index change which augurs for better analytical performances. Here, we undertook an in-depth investigation of the biofunctionalization of AuNR@SiO2via three different routes to design and test a label-free LSPR biosensor operating in solution. In the first route, we took advantage of the negatively charged external silica shell to immobilize anti-rabbit IgG antibody by electrostatic physisorption. In the second and third routes, the silica surface was reacted with thiol or aldehyde terminated silanes, subsequently utilized to covalently attach anti-rabbit IgG antibody to the surface. The resulting nanoprobes were characterized by a wide range of physical methods (TEM, XPS, DLS, ELS and UV-Visible spectroscopy) then tested for the biosensing of rabbit-IgG. The three nanobiosensors maintain an excellent colloidal stability after analyte recognition and exhibit extremely high analytical performances in terms of specificity and dynamic range, with an LoD down to 12 ng/mL.

Methylene Blue-Loaded Mesoporous Silica-Coated Gold Nanorods on Graphene Oxide for Synergistic Photothermal and Photodynamic Therapy.

Photo-nanotheranostics integrates near-infrared (NIR) light-triggered diagnostics and therapeutics, which are combined into a novel all-in-one phototheranostic nanomaterial that holds great promise for the early detection and precise treatment of cancer. In this study, we developed methylene blue-loaded mesoporous silica-coated gold nanorods on graphene oxide (MB-GNR@mSiO2-GO) as an all-in-one photo-nanotheranostic agent for intracellular surface-enhanced Raman scattering (SERS) imaging-guided photothermal therapy (PTT)/photodynamic therapy (PDT) for cancer. Amine functionalization of the MB-GNR@mSiO2 surfaces was performed using 3-aminopropyltriethoxysilane (APTES), which was well anchored on the carboxyl groups of graphene oxide (GO) nanosheets uniformly, and showed a remarkably higher photothermal conversion efficiency (48.93%), resulting in outstanding PTT/PDT for cancer. The in vitro photothermal/photodynamic effect of MB-GNR@mSiO2-GO with laser irradiation showed significantly reduced cell viability (6.32%), indicating that MB-GNR@mSiO2-GO with laser irradiation induced significantly more cell deaths. Under laser irradiation, MB-GNR@mSiO2-GO showed a strong SERS effect, which permits accurate cancer cell detection by SERS imaging. Subsequently, the same Raman laser can focus on highly detected MDA-MB-23l cells for a prolonged time to perform PTT/PDT. Therefore, MB-GNR@mSiO2-GO has great potential for precise SERS imaging-guided synergistic PTT/PDT for cancer.

Surface Plasmon-Enhanced NIR-II Fluorescence in a Multilayer Nanoprobe for Through-Skull Mouse Brain Imaging.

Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) holds great potential for the accurate visualization of deeply located biological structures in vivo. However, the weak fluorescence of current NIR-II fluorophores remains a long-standing challenge for the ever-growing imaging demand. Here, we describe a surface plasmon-enhanced NIR-II fluorescence strategy by incorporating silica-coated gold nanorods (GNRs) and polymer dots (Pdots) into a multilayer nanostructure. Precise manipulation of the silica spacing layer thickness signifies an optimum distance of 8.6 nm, where an enhancement factor of up to 6.4 is achieved in the NIR-II imaging window. The surface plasmon enhancement approach is successfully extended to several types of Pdots fluorophores with NIR-II emission. We finally perform outer-layer encapsulation and PEGylation for the multilayer probes and demonstrate surface plasmon-enhanced NIR-II fluorescence for mouse brain imaging through the skull, which exhibits a refined signal-to-background ratio and penetration depth as compared to the clinically approved ICG dye.

Improved refractive index sensitivity of localized surface plasmon resonance inflection points in amalgamated gold nanorods with mesoporous silica shell

Mesoporous silica coated gold nanorods (AuNRs@mSiO2) are very promising as multifunctional localized surface plasmon resonance (LSPR) sensors. Here, we described the refractive index (RI) sensitivities of single AuNRs@mSiO2 before and after mercury (Hg) amalgamation without their structural deformation. The amalgamated AuNRs@mSiO2 showed significant improvement in the RI sensitivity than the AuNRs@mSiO2 before the Hg amalgamation with the respect to RI changes of local environments. LSPR scattering inflection points (IFs) were then investigated to determine the LSPR sensing performance of single AuNRs@mSiO2 before and after Hg amalgamation. The RI sensitivity at the LSPR IF in the low-energy side was higher than the wavelength shifts in the conventional LSPR maximum peak. Furthermore, the amalgamated AuNRs@mSiO2 exhibited better RI sensitivity at the LSPR IFs than non-amalgamated AuNRs@mSiO2. Thus, we provide a deeper understanding of how Hg amalgamation affects RI sensitivity in single AuNRs@mSiO2.