Synthesis of Multibranched Gold Nanoechinus Using a Gemini Cationic Surfactant and Its Application for Surface Enhanced Raman Scattering

Hotspots in action: near-infrared light mediated photoelectrochemical oxygen evolution on high index faceted plasmonic gold nanoarchitectures

Photo-induced electrochemical water splitting is a fascinating approach to overcome the present energy demands as well as environmental issues. To this end, near-infrared (NIR) photocatalysts stand out as promising candidates (where 53% of the solar light is NIR light) to solve the present energy crisis but the lack of NIR-activated photocatalysts has remained a great challenge for decades. Herein, for the first time, we report the synthesis of high-index faceted plasmonic Au nano-branched 12 tip nanostars, which can absorb the whole spectral region of electromagnetic radiation (UV-vis-NIR), for efficient water splitting. Moreover, the plasmonic hot spots on the Au 12 tip nanostars significantly promote the photoelectrochemical oxygen evolution reaction (OER) under NIR light (915 nm) with long-term stability. Remarkably, the Au 12 tip nanostars exhibit 250-fold enhancement of activity under 915 nm laser irradiation and 6.5-fold enhancement of activity under 532 nm laser irradiation, as compared to the Au NPs. Furthermore, the Finite-Difference Time-Domain (FDTD) study confirmed that the significant photoelectrochemical (PEC) enhancement in the NIR light region could be attributed to the hot-electron injection/plasmonic hot spot mechanism upon localized surface plasmonic resonance (LSPR) excitation. Overall, we anticipate that the present work would help to develop new NIR photoelectrocatalysts for meeting future energy demands.

Ag and Au Nanoparticles as Color Indicators for Monomer/Micelle-Nanoparticle Interactions

Ag and Au nanoparticles (NPs) were used as color indicators to determine the monomer/micelle adsorption on the NP surface. A simple methodology based on the color change of Ag/Au NPs upon interacting with surface-active molecules was developed. A contrasting color change occurred when NPs interact with the monomer/micelle. This was demonstrated by monitoring the adsorption behavior of a series of Gemini surfactants. UV-visible measurements showed a large change in the intensity and wavelength of Ag/Au NP absorbance upon the surface adsorption of the monomer/micelle of Gemini surfactants. The mechanism of surface adsorption and molecular orientation on the solid-liquid interface of NPs was determined by performing the FT-IR and XPS measurements. Results demonstrated that sharp color changes from yellow to red for Ag NPs and red to purple for Au NPs happened when the Gemini surfactant monomer/micelle adsorbs on the NP surface. This colorimeter-based methodology highlighted the applicability of Ag/Au NPs in complex media where such NPs frequently encounter surface-active molecules.

Spiky yolk-shell AuAg bimetallic nanorods with uniform interior gap for the SERS detection of thiram residues in fruit juice

By using gold nanorods with silver coating as the sacrificial templates, we prepared spiky yolk-shell AuAg bimetallic nanorods with uniform interior gap via galvanic replacement reaction. The length and number of Au tips of the spiky yolk-shell AuAg nanorods can be tuned simultaneously by altering HAuCl₄ volume. The influence of HAuCl₄ volume and the sliver layer thickness on the SERS activity of spiky yolk-shell AuAg nanorods are studied. When the sliver layer is thin, the interior gap has not been shielded completely and the outer shell has obvious tips, thus the surface-enhanced Raman scattering (SERS) activity has the strongest enhancement with an enhancement factor (EF) of 4.9 × 10⁵. The spiky yolk-shell AuAg nanorods with the strongest SERS activity are used as SERS substrates to detect thiram. The results demonstrate that the SERS intensity increases linearly with the logarithmic concentration of thiram in the range of 10^-3 M to 10^-7 M. The detection limit is as low as 97 nM, which is lower than the maximum pesticide residue limit (29 µM) in fruits stipulated by the US Environmental Protection Agency (EPA). Therefore, the spiky yolk-shell AuAg bimetallic nanorods have important practical application value in pesticide detection.

Au Nanoflowers for Catalyzing and In Situ Surface-Enhanced Raman Spectroscopy Monitoring of the Dimerization of p-Aminothiophenol

In this work, we demonstrated a facile approach for fabrication of Au nanoflowers (Au NFs) using an amino-containing organosilane, 3-aminopropyltriethoxysilane (APTES), as a shape-directing agent. In this approach, the morphology of the Au particles evolved from sphere-like to flower-like with increasing the concentration of APTES, accompanied by a red shift in the localized surface plasmon resonance peak from 520 to 685 nm. It was identified that the addition of APTES is profitable to direct the preferential growth of the (111) plane of face-centered cubic gold and promote the formation of anisotropic Au NFs. The as-prepared Au NFs, with APTES on their surface, presented effective catalytic and surface-enhanced Raman scattering (SERS) performances, as evidenced by their applications in catalyzing the dimerization of p-aminothiophenol and monitoring the reaction process via in situ SERS analysis.

Preparing Alumina-Supported Gold Nanowires for Alcohol Oxidation

The development of shape-controlled noble metal nanocrystals such as nanowires (NWs) is progressing steadily owing to their potentially novel catalytic properties and the ease with which they can be prepared by reducing the metal ions in a particular solution as capping agents. Recently, many reports have been presented on the preparation of shape-controlled Au nanocrystals, such as nanostars and nanoflowers, by a one-pot method using 2-[4-(2-hydroxyethyl)-1-piperazinyl] ethanesulfonic acid (HEPES) as capping and reducing agents. The catalytic activity is depressed due to the adsorption of the capping agent onto a Au surface. Since HEPES has low binding affinities on the Au surface, shape-controlled nanocrystals obtained using HEPES are effective for application as nanocatalysts because HEPES was easily removed from the Au surface. In this study, we report the preparation of AuNWs, with an average diameter of 7.7 nm and lengths of a few hundred nanometers, in an aqueous solution containing HEPES and sodium borohydride. A γ-Al2O3-supported AuNW (AuNW/γ-Al2O3) catalyst was obtained using catalytic supporters and a water extraction method that removed HEPES from the Au surface without morphological changes. AuNW/γ-Al2O3 was then utilized to catalyze the oxidation of 1-phenylethyl alcohol to acetophenone. The formation rate of acetophenone over AuNW/γ-Al2O3 was 3.2 times that over γ-Al2O3-supported spherical Au nanoparticles (AuNP/γ-Al2O3) with almost the same diameter.

Synthesis of sea urchin-shaped Au nanocrystals by double-strand diblock oligonucleotides for surface-enhanced Raman scattering and catalytic application

It is of great significance to construct specially designed gold nanocrystals (AuNCs) with precisely controllable size and morphology to achieve an excellent physicochemical performance. In this work, sea urchin-shaped AuNCs with tunable plasmonic property were successfully synthesized by the hybridized double-strand poly adenine (dsPolyA) DNA-directed self-assembly technique. Hybridized dsPolyA as the directing template had suitable rigidity and upright conformation, which benefited the controllable formation of these anisotropic multi-branched AuNCs with the assistance of surfactant. The effects of essential conditions influencing the synthesis and precise morphology control were investigated in detail. COMSOL simulation was used to evaluate their electromagnetic field distribution according to their morphologies, and the result suggested that sea urchin-shaped AuNCs had abundant 'hot spots' for surface-enhanced Raman scattering (SERS) detection due to their regular nanoprotuberance structure. Finally, sea urchin-shaped AuNCs with excellent SERS and catalytic performance were applied for the quantitative analysis of food colorant and catalytic degradation of potential pollutants. The SERS enhancement factor of sea urchin-shaped AuNCs was up to 5.27 × 10⁶, and the catalytic degradation rate for 4-NP by these AuNCs was up to -0.13min^-1.

Metal Nanoparticles-Enhanced Biosensors: Synthesis, Design and Applications in Fluorescence Enhancement and Surface-enhanced Raman Scattering

Metal nanoparticles (NP) that exhibit localized surface plasmon resonance play an important role in metal-enhanced fluorescence (MEF) and surface-enhanced Raman scattering (SERS). Among the optical biosensors, MEF and SERS stand out to be the most sensitive techniques to detect a wide range of analytes from ions, biomolecules to macromolecules and microorganisms. Particularly, anisotropic metal NPs with strongly enhanced electric field at their sharp corners/edges under a wide range of excitation wavelengths are highly suitable for developing the ultrasensitive plasmon-enhanced biosensors. In this review, we first highlight the reliable methods for the synthesis of anisotropic gold NPs and silver NPs in high yield, as well as their alloys and composites with good control of size and shape. It is followed by the discussion of different sensing mechanisms and recent advances in the MEF and SERS biosensor designs. This includes the review of surface functionalization, bioconjugation and (directed/self) assembly methods as well as the selection/screening of specific biorecognition elements such as aptamers or antibodies for the highly selective bio-detection. The right combinations of metal nanoparticles, biorecognition element and assay design will lead to the successful development of MEF and SERS biosensors targeting different analytes both in-vitro and in-vivo. Finally, the prospects and challenges of metal-enhanced biosensors for future nanomedicine in achieving ultrasensitive and fast medical diagnostics, high-throughput drug discovery as well as effective and reliable theranostic treatment are discussed.

Accompanying photocytotoxic activity of gold nanoechinus and zinc phthalocyanine on cancerous cell lines

BACKGROUND

Near-infrared triggered photodynamic therapy (NIR-PDT) has been introduced as a relatively deep tumor treatment modality. The gold Nanoechinus (Au NE) is a rare type of nanostructures that act as a transducer to change NIR wavelength to ultraviolet (UV) and visible lights. During the photodynamic process, Au nanoechinus (Au NE) converts the irradiation of 980 nm to 674 nm which is absorbed by Zn(II) Phthalocyanine tetrasulfonic acid (ZnPcS). In this study the cooperation effect of Au NE and ZnPcS in PDT on MCF7 and Hela cells was investigated.

METHODS

Cytotoxicity and phototoxicity of the composition having different concentrations of Au NE and ZnPcS upon irradiation of 980 nm NIR light were evaluated against MCF7 and Hela cells after two different incubation times and irradiating with two different power densities of laser.

RESULTS

Among different experimental groups, in MCF7 cells, which were incubated for 48 h with 50 μg/mL Au NE+2μM ZnPcS and were treated by 980 nm laser with a power density of 200 mW cm^-2 for 15 and 30 min, 48 and 38% cell viability were recorded. No appreciable result was observed due to PDT of Hela cells.

CONCLUSIONS

Comparing to other PDT modalities against MCF7 cells, NIR-PDT procedure suggested in this study with the synergistic effect of Au NE and ZnPcS could be a secure promising modality in the treatment of deep-seated tumors. Carefully increasing the power density and ambient temperature, to the extent of skin tolerance threshold value, seems to be efficient in the treatment of Hela cells.

Graphene oxide-highly anisotropic noble metal hybrid systems for intensified surface enhanced Raman scattering and direct capture and sensitive discrimination in PCBs monitoring

Graphene oxide (GO)-anisotropic noble metal hybrid systems were developed as highly sensitive and reproducible surface enhanced Raman scattering (SERS) platform, in which ultrathin GO was embedded between two metallic layers of flower-like Ag nanoparticles (AgNFs) and gold nanostars (AuNSts). Due to multi-dimensional plasmonic coupling effect, the well-designed AgNFs-GO-AuNSts sandwich structures possessed ultrahigh sensitivity with the detection limit of R6G as low as 1.0 × 10^-13 M and high enhancement factor of 2.59 × 10⁷. Additionally, the GO interlayer could function as protective shell to suppress the oxidation of bottom silver layer and efficiently position the target analytes within hot spots. These features endow the substrate with high stability and excellent reproducibility (Signal variations < 7%). Particularly, the GO sandwiched substrate can be explored for the direct capture and sensitive detection of polychlorinated biphenyls (PCBs) without any organic modifier as molecule harvester. This minimum detected concentration was estimated as low as 3.4 × 10^-6 M. The detection method based on GO mediated sandwich substrate avoids complicated surface modification manipulations and improves the substrate cleanness. Moreover, the resultant sandwich substrates can be used to recognize fingerprint peaks of different PCBs in their complex mixture, revealing great potential applications in SERS-based simultaneous detection of multiple pollutants with low affinity.

Present and Future of Surface-Enhanced Raman Scattering

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

Recent advances in cancer bioimaging using a rationally designed Raman reporter in combination with plasmonic gold

Gold nanomaterials (AuNMs) have been widely implemented for the purpose of bioimaging of cancer and tumor cells in combination with Raman spectral markers.

Bovine serum albumin assisted preparation of ultra-stable gold nanoflowers and their selective Raman response to charged dyes

In this work, we demonstrated a facile, one-pot approach for preparation of gold nanoflowers by using tetrachloroauric acid as a gold precursor, ascorbic acid as a reductant, and bovine serum albumin (BSA) as a ligand. It was found that the morphology of the as-prepared gold nanoparticles (Au NPs) was dependent on the concentration of BSA introduced into the reaction solutions. It is identified that BSA directed the preferential growth along the 〈111〉 direction, which contributed to the anisotropic growth of Au NPs and thus the formation of Au nanoflowers. An increased concentration of BSA reduced the reactivity of the gold precursor, leading to the formation of Au nanoflowers with increased size, which could also be obtained by decreasing the amount of reductant added. The Au nanoflowers were ultra-stable in the presence of chloride ions under acidic pH, making them suitable for selective detection of oppositely charged dyes via surface-enhanced Raman scattering according to the isoelectric point (∼4.7) of BSA capped on their surface.

Magnetic Gemini Surfactants

A homologous series of Gemini surfactants, dimethylene-1,2-bis(alkyldimethyl-ammonium bromide) (referred to as n-2-n·2Br, n = 14, 16, and 18) and Fe- or lanthanide metal-based magnetic Gemini surfactants (abbreviated as n-2-n·2X, X = Fe, Ce, and Gd), were first synthesized. Measurements of surface tension and electrical conductivity determine the physical quantities related to the surface activities of n-2-n·2Br and n-2-n·2X, and the magnetic behaviors of n-2-n·2X are elucidated by superconducting quantum interference device magnetometry. Thermogravimetric analysis and differential scanning calorimetry have been used to investigate thermotropic liquid crystalline properties of all aforementioned surfactants, and the liquid crystal textures were further observed via polarizing optical microscopy. These results reveal that for magneto-responsive Gemini surfactants, both magnetic counterions and alkyl chain lengths have certain effect on surface activities, magnetism, and thermotropic phase behavior. We summed up these changes and discussed the causes, which could provide a new insight into controlling the properties of magnetic surfactants.

Au-Ag Nanoflower Catalysts with Clean Surfaces for Alcohol Oxidation

Shape-controlled metal nanocrystals, such as nanowires and nanoflowers, are attractive owing to their potentially novel catalytic properties and bimetallic nanocrystals composed of two distinct metals are expected to act as highly active catalysts. However, their catalytic activities are limited because of the capping agents adsorbed on the metal surfaces, which are necessary for the preparation and dispersion of these nanocrystals in solvents. Therefore, the preparation of bimetallic shape-controlled noble metal nanocrystals with clean surfaces, devoid of almost all capping agents, are expected to have high catalytic activity. Herein, we report the preparation of bimetallic Au-Ag nanoflowers using melamine as the capping agent. The bimetallic Au-Ag nanoflowers with a clean surface were subsequently obtained by a support and extraction method. The bimetallic nanoflowers with a clean surface were then used for the aerobic oxidation of 1-phenylethyl alcohol and they exhibited high rates for the formation of acetophenone compared to Au nanoflowers and spherical nanoparticles with almost the same size and Au/Ag ratio. We also show that Au-Ag nanoflowers containing only 1 % Ag (Au₉₉ -Ag₁ NFs) exhibit the highest rate of acetophenone formation among Au-Ag nanoflowers with different Au/Ag ratios owing to an increase in the electron density of the Au atoms that act as active sites for the oxidation of 1-phenylethyl alcohol.

One-Pot Synthesis of Multi-Branch Gold Nanoparticles and Investigation of Their SERS Performance

Gold nanoparticles with multiple branches have attracted intensive studies for their application in sensing of low trace molecules. A large number of the merits found on the gold nanoparticles for the above applications are attributed to the strong localized surface plasmon resonance excited by the incident radiation. However, a facile and flexible way of synthesizing the multi-branch gold nanoparticles with tunable localized surface plasmon resonance frequency is still a challenge for the plasmonic research field. Herein, we report an efficient one-pot synthesis of multi-branch gold nanoparticles method that resembles a seed-medicated approach while using no further chemicals except chloroauric acid, ascorbic acid and 4-(2-Hydroxyethyl)-1-piperazinyl]-ethanesulfonic acid. By controlling the amounts of ascorbic acid volumes in the reaction mixture, the morphology and the localized surface plasmon resonance frequency of the synthesized multi-branch gold nanoparticles can be manipulated conveniently. Moreover, using the 4-Mercaptobenzoic acid as the Raman reporter, the multi-branch gold nanoparticles show superior surface-enhanced Raman spectroscopy characteristics that can be potentially used in chemical and biological sensing.

Gold-nanobranched-shell based drug vehicles with ultrahigh photothermal efficiency for chemo-photothermal therapy

Development of combined chemo-photothermal nanoplatform is of great interest for enhancing antitumor efficacy. Herein, a multifunctional drug delivery system was synthesized based on gold-nanobranched coated betulinic acid liposomes (GNBS-BA-Lips) for chemo-photothermal synergistic therapy. In this system, GNBS-BA-Lips exhibited broad near-infrared (NIR) absorption, preferable photothermal response and good photostability under NIR irradiation. Importantly, the gold-nanobranched nanostructure possessed high photothermal conversion efficiency (η = 55.7%), and the temperature change (ΔT) reached 43.2 °C after laser irradiation for 5 min. Upon NIR irradiation, the nanocarriers apparently endowed higher cell uptake, resulting in an enhanced intracellular drug accumulation. Furthermore, the tumor growth inhibition ratio achieved from chemo-photothermal therapy of GNBS-BA-Lips was 86.9 ± 1.1%, which was higher than that of the chemotherapy or photothermal therapy alone, showing an outstanding synergistic anticancer effect. Our data suggested that the nanoplatform should be considered as a critical platform in the development of cancer multi-mode therapies.

Developing Hollow-Channel Gold Nanoflowers as Trimodal Intracellular Nanoprobes

Gold nanoparticles-enabled intracellular surface-enhanced Raman spectroscopy (SERS) provides a sensitive and promising technique for single cell analysis. Compared with spherical gold nanoparticles, gold nanoflowers, i.e., flower-shaped gold nanostructures, can produce a stronger SERS signal. Current exploration of gold nanoflowers for intracellular SERS has been considerably limited by the difficulties in preparation, as well as background signal and cytotoxicity arising from the surfactant capping layer. Recently, we have developed a facile and surfactant-free method for fabricating hollow-channel gold nanoflowers (HAuNFs) with great single-particle SERS activity. In this paper, we investigate the cellular uptake and cytotoxicity of our HAuNFs using a RAW 264.7 macrophage cell line, and have observed effective cellular internalization and low cytotoxicity. We have further engineered our HAuNFs into SERS-active tags, and demonstrated the functionality of the obtained tags as trimodal nanoprobes for dark-field and fluorescence microscopy imaging, together with intracellular SERS.

Lipid Bilayer-Enabled Synthesis of Waxberry-like Core-Fluidic Satellite Nanoparticles: Toward Ultrasensitive Surface-Enhanced Raman Scattering Tags for Bioimaging

Herein, we presented waxberry-like core-satellite (C-S) nanoparticles (NPs) prepared by an in situ growth of satellite gold NPs on spherical phospholipid bilayer-coated gold cores. The fluidic lipid bilayer cross-linker was reported for the first time, which imparted several novel morphological and optical properties to the C-S NPs. First, it regulated the anisotropic growth of the satellite NPs into vertically oriented nanorods on the core NP surface. Thus, an interesting waxberry-like nanostructure could be obtained, which was different from the conventional raspberry-like C-S structures decorated with spherical satellite NPs. Second, the satellite NPs were "soft-landed" on the lipid bilayer and could move on the core NP surface under certain conditions. The movement induced tunable plasmonic features in the C-S NPs. Furthermore, the fluidic lipid bilayer was capable of not only holding an abundance of reporter molecules but also delivering them to the hotspots at the junctions between the core and satellite NPs, which made the C-S NPs an excellent candidate for preparing ultrasensitive surface-enhanced Raman scattering (SERS) tags. The bioimaging capabilities of the C-S NP-based SERS tags were successfully demonstrated in living cells and mice. The developed SERS tags hold great potential for bioanalysis and medical diagnostics.

A novel trimeric cationic surfactant as a highly efficient capping agent for the synthesis of trisoctahedral gold nanocrystals

A trimeric cationic surfactant, even at a very low concentration of 0.2 mM, enables the formation of trisoctahedral Au nanocrystals.

Formation of Au Nanoparticles in Liquid Cell Transmission Electron Microscopy: From a Systematic Study to Engineered Nanostructures

In this work, a systematic study of the effect of electron dose rate, solute concentration, imaging mode (broad beam vs scanning probe mode), and liquid cell setup (static vs flow mode) on the growth mechanism and the ultimate morphology of Au nanoparticles (NPs) was performed in chloroauric acid (HAuCl₄) aqueous solutions using in situ liquid-cell TEM (LC-TEM). It was found that a diffusion limited growth dominates at high dose rates, especially for the solution with the lowest concentration (1 mM), resulting in formation of dendritic NPs. Growth of 2D Au plates driven by a reaction limited mechanism was only observed at low dose rates for the 1 mM solution. For the 5 mM and 20 mM solutions, reaction limited growth can still be induced at higher dose rates, due to abundance of the precursor available in the solutions, leading to formation of 2D plates or 3D faceted NPs. As a proof-of-concept, an Au nanostructure with a 3D faceted particle core and a dendritic shell can be in situ produced by simply tuning the electron dose in the 1 mM solution irradiated in a flow cell setup in the STEM mode. This work paves the way to study the growth of complex heteronanostructures composed of multiple elements in LC-TEM.

Seedless synthesis and SERS characterization of multi-branched gold nanoflowers using water soluble polymers

We report for the first time, the aqueous-based synthesis of multibranched, monodispersed gold nanoflowers (AuNFs) using pyromellitic dianhydride-p-phenylene diamine - PPDDs at room temperature. AuNF synthesis was achieved using PPDDs that converts Au precursor (Au³⁺) into AuNFs while serving as both the reducing and directional agent. The resulting branched AuNFs exhibited different degrees of anisotropy and protuberance lengths obtained by modulating the ratio of PPDDs and HAuCl₄·3H₂O. The surface roughness obtained ranged from small bud-like protuberances to elongated spikes, which enabled the tuning of the optical properties of the nanoparticles from ∼450 to 1100 nm. Systematic analysis revealed that the generation of urchin-like particles as well as their size depended on the PPDDs/HAuCl₄·3H₂O ratio. At a medium concentration of the precursor, spherical nanoparticles were formed. Whereas at lower precursor concentrations, urchin-like nanoparticles were obtained with their size and protuberances length increasing at even lower HAuCl₄·3H₂O concentration. Increasing the temperature to 100 °C resulted in the enhancement of the anisotropy of the AuNFs. The resulting gold nanoflowers exhibited an enhanced performance in surface-enhanced Raman scattering (SERS). This work provides a unique approach for anisotropic particle synthesis using water soluble polymer and greener approaches. The fabricated AuNFs exhibited variable UV-vis absorption and SERS enhancement as a function of branch morphology, indicating their potential application in biolabeling, biosensing, imaging, and therapeutic applications.

Gold nanorod-based poly(lactic-co-glycolic acid) with manganese dioxide core-shell structured multifunctional nanoplatform for cancer theranostic applications

Recently, photothermal therapy has become a promising strategy in tumor treatment. However, the therapeutic effect was seriously hampered by the low tissue penetration of laser. Therefore, in this study, radiofrequency (RF) with better tissue penetration was used for tumor hyperthermia. First, one type of gold nanorods (AuNRs) suitable for RF hyperthermia was selected. Then, poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with AuNRs and docetaxel (DTX) (PLGA/AuNR/DTX) NPs were constructed. Finally, manganese dioxide (MnO2) ultrathin nanofilms were coated on the surfaces of PLGA/AuNR/DTX NPs by the reduction of KMnO4 to construct the PLGA/AuNR/DTX@MnO2 drug delivery system. This drug delivery system can not only be used for the combined therapy of chemotherapy and RF hyperthermia but can also produce Mn2+ to enable magnetic resonance imaging. Furthermore, the RF hyperthermia and the degradation of MnO2 can significantly promote the controlled drug release in a tumor region. The in vitro and in vivo results suggested that the PLGA/AuNR/DTX@MnO2 multifunctional drug delivery system is a promising nanoplatform for effective cancer theranostic applications.

Rapid synthesis of hierarchical, flower-like Ag microstructures with a gemini surfactant as a directing agent for SERS applications

Various hierarchical Ag microstructures, including sensitive SERS substrate flower-like structures, can be designed and rapidly synthesized under different conditions.