Au Nanorods Research Articles

RecJf exonuclease-catalyzed signal amplified aptasensor for sensitive detection of atrazine using Ni6MnO8@C/Au nanorods and COF@MOF nanohybrids

Atrazine (ATZ) represents an endocrine-disrupting pesticide posing significant threats to both the environment and human well-being. In this study, a novel turn-on electrochemical aptasensor was successfully developed for highly sensitive ATZ detection. It relied on Ni6MnO8@C/Au nanorods (Ni6MnO8@C/AuNR) and covalent-metal organic framework nanohybrids (MCA@Ce-MOF) with RecJf-catalyzed target recycling amplification. Notably, this marks the first instance of utilizing this strategy for ATZ detection. The substrate material, ultrathin Ni6MnO8@C/AuNR nanosheets, enhanced the specific surface area, conductivity, and biocompatibility, thereby facilitating biomolecule attachment and improving sensitivity. The scaffolds, hierarchically porous MCA@Ce-MOF, not only elevated the loading efficiency and surface concentration of signal molecules, but also strengthened the binding firmness of biomolecules. RecJf-catalyzed target recycling was triggered in the presence of ATZ, further magnifying electrochemical signals. Leveraging these unique attributes, the developed aptasensor exhibited exceptional ATZ detection performance with a low detection limit of 4.9 fg·mL−1, a wide linear range of 4 × 10−5–4 ng·mL−1, and a satisfactory recovery of 93.3–99.6% in corn samples. With its diverse signal amplification capabilities, this aptasensor holds promise for detecting various analytes in environmental monitoring applications.

Optical and thermal characterization of a nanofluid of MPA-functionalized CdSe nanocrystals and Au nanorods: An energy transfer process analysis

This study investigates the optical and energy transfer properties of mercaptopropionic acid (MPA)-functionalized CdSe nanocrystals (NCs) and gold nanorods (AuNRs) into aqueous solution. CdSe NCs of different sizes exhibit size-dependent excitonic transitions, with larger sizes resulting in red shifted absorption and emission peaks. MPA surface modification induces deep trap emissions in CdSe NCs. Thermal lens measurements reveal that the addition of CdSe NCs decreases the thermal diffusivity, while the presence of AuNRs increases it. The energy transfer efficiency between CdSe NCs and AuNRs in the nanofluids was observed, with CdSe1+Au60 showing the highest energy transfer efficiency of 0.75. These findings emphasize the significance of MPA functionalization in enhancing energy transfer efficiency between NCs and AuNRs, with implications for improving the performance of photovoltaic systems.

Varying aspect ratios of Au nanorods with LSPR effect for efficient enhanced upconversion luminescence

Varying aspect ratios of Au nanorods with LSPR effect for efficient enhanced upconversion luminescence

Engineering Near‐Infrared Plasmonic Spiky Gold Nanostructures for Highly Efficient Surface‐Enhanced Raman Spectroscopy‐Guided Cancer Hyperthermia Therapy

AbstractCancer phototheranostics utilizing plasmonic materials is attracting considerable interest due to its high spatiotemporal precision and specificity, remote controllability, superior therapeutic efficacy, and low systemic side effects. Exploring new plasmonic materials with excellent plasmonic and photothermal properties is at the frontier of cancer phototheranostics. Herein, this work systematically investigates the plasmonic and photothermal properties of spiky Au nanoparticles (NPs) with different shaped central cores – spiky Au nanosphere , spiky Au nanocube and spiky Au nanorod (AuNR). It is shown that the shape of the central core in spiky Au NPs has significant effects on their surface‐enhanced Raman spectroscopy (SERS) and photothermal performances, and spiky Au NPs of a spherical or cubic core are much superior for near‐infrared (NIR) SERS detection and hyperthermia therapy in comparison with spiky AuNRs. The spiky Au NP‐based SERS probes demonstrate the remarkable capability for SERS imaging of live cells and dynamic visualization of tumors in a 4T1 breast tumor mouse model after intravenous administration. Moreover, in vivo studies show exceptional hyperthermia therapeutic effects of such SERS probes against 4T1 breast tumors under NIR irradiation. This study suggests the potential utility of spiky Au NP‐based SERS probes for efficient SERS‐guided cancer hyperthermia therapy.

Facilitating H+ ion heterolysis using lattice strained Pd-tipped Au nanorods for direct H2O2 synthesis in pure water

Direct H2O2 synthesis (DHS) from H2 and O2 over Pd catalyst is a potentially rewarding strategy to replace the industrial anthraquinone method, but the sluggish hydrogenation process seriously impedes production efficiency in pure water. Here, we report a lattice strained Pd catalyst which is formed on Au nanorods (NRs) tips by taking advantage of curvature. The lattice strained Pd tipped Au NRs (PTA) is found to be able to facilitate the H+ ion heterolysis, in particular with light illumination, thereby remarkably enhancing the DHS performance. The lattice strain effect together with light-induced hot electrons enables a production rate of 0.12 mol/g/h for H2O2 generation, which is 3.11 and 3.56 times higher than that of no light assistance or strain effect ones, respectively. Finally, a porous PTA film was assembled, which achieves a H2O2 concentration of ∼2.3% within 24 h that is expected to make for direct medical use (＜3%).

Plasmonic Dodecahedral-Walled Elongated Nanoframes for Surface-Enhanced Raman Spectroscopy.

Here, elongated pseudohollow nanoframes composed of four rectangular plates enclosing the sides and two open-frame ends with four ridges pointing at the tips for near-field focusing are reported. The side facets act as light-collecting domains and transfer the collected light to the sharp tips for near-field focusing. The nanoframes are hollow inside, allowing the gaseous analyte to penetrate through the entire architecture and enabling efficient detection of gaseous analytes when combined with Raman spectroscopy. The resulting nanostructures are named Au dodecahedral-walled nanoframes. Synthesis of the nanoframes involves shape transformation of Au nanorods with round tips to produce Au-elongated dodecahedra, followed by facet-selective Pt growth, etching of the inner Au, and regrowth steps. The close-packed assembly of Au dodecahedral-walled nanoframes exhibits an attomolar limit of detection toward benzenethiol. This significant enhancement in SERS is attributed to the presence of a flat solid terrace for a large surface area, sharp edges and vertices for strong electromagnetic near-field collection, and open frames for effective analyte transport and capture. Moreover, nanoframes are applied to detect chemical warfare agents, specifically mustard gas simulants, and 20 times higher sensitivity is achieved compared to their solid counterparts.

Hydrogel Micropillar Array for Temperature Sensing in Fluid.

Localized temperature sensing and control on a micron-scale have diverse applications in biological systems. We present a micron-sized hydrogel pillar array as potential temperature probes and actuators by exploiting sensitive temperature dependence of their volume change. Soft lithography-based molding processes were presented to fabricate poly N-isopropyl acrylamide (p-NIPAAm)-based hydrogel pillar array on a glass substrate. Au nanorods as light-induced heating elements were embedded within the hydrogel pillars, and near-infrared (NIR) light was used to modulate temperature in a local area. First, static responses of the micro-pillar array were characterized as a function of its temperature. It was shown that the hydrogel had a sensitive volume transition near its low critical solution temperature (LCST). Furthermore, we showed that LCST could be readily adjusted by utilizing copolymerizing with acrylamide (AAM). To demonstrate the feasibility of spatiotemporal temperature mapping and modulation using the presented pillar array, pulsed NIR light was illuminated on a local area of the hydrogel pillar array, and its responses were recorded. Dynamic temperature change in water was mapped based on the abrupt volume change characteristics of the hydrogel pillar, and its potential actuation using NIR light was successfully demonstrated. Considering that the structure can be arrayed in a two-dimensional pixel format with high spatial resolution and high sensitive temperature characteristics, the presented method and the device structure can have diverse applications to change and sense local temperatures in liquid. This is particularly useful in biological systems, where their physiological temperature can be modulated and mapped with high spatial resolution.

Influence of l-Dopa adsorption time and concentration on Au nanorods aggregation for SERS quantitative analysis

Levodopa (l-Dopa) is an important neurotransmitter from the amino acid family and is also associated with the treatment of Parkinson's disease. The obtention of the l-Dopa SERS signal in colloid is a challenge due to the zwitterionic charge promoting repulsion from nanoparticle surface and leading to poor or not active SERS signal. In this work, SERS signal of l-Dopa was successfully obtained using Au nanorods (AuNRs) covered with a cationic lipid bilayer and using the 785 nm laser line. The UV–Vis extinction, dynamic light scattering, and zeta potential results indicated an influence of l-Dopa adsorption time and l-Dopa concentration on AuNRs aggregation. The SERS signal followed this time dependence, being the characteristic l-Dopa band observed only after 30 min. The l-Dopa quantitative analysis using the standard addition method presented a linear SERS signal at 439 cm−1 with a limit of detection of 6.7 × 10−7 mol L−1 for peak intensity, and 7.9 × 10−7 mol L−1 for band integrated area.

Large-scale assembly of geometrically diverse metal nanoparticles-based 3D plasmonic DNA nanostructures for SERS detection of PNK in cancer cells

The organization of geometrically diverse metal nanoparticles into a core/satellite structure at a large scale is a promising strategy for improve SERS performance due to hot spots localized enrichment and signal increase. However, due to the lack of extensional frames and strong electrostatic repulsion between plasma NPs, the fabrication of such 3D architectures with a high-density periodic hotspot in the focus volume has proven exceedingly difficult. Herein, we demonstrate a facile large-scale assembly of geometrically diverse metal nanoparticles strategy for constructing spatially extended 3D plasmonic nanostructures resembling “signal towers” based on RCA-mediated periodic organization of gold nanospheres (GNS) surrounding gold nanorods (GNRs). Using cancer cell T4 PNK as a model, a padlock probe with 5′- hydroxyl (P-circle) was designed as the T4 PNK substrate. The center Au nanorod was coated with P1 and served as a “pedestal” to allow substantial loading of P-circle after target phosphorylation to initiate the rolling ring amplification reaction (RCA). The resultant DNA nanowire serves as an “antenna” to successively lock numerous Raman reporter P2 (Cy3-P2-SH) through base pairing at regular intervals. Finally, the 3D plasma DNA nanostructures that resemble “signal towers” could be obtained by placing a large number of GNS with a strong affinity for Au–S. The proposed 3D SERS sensor exhibited a sensitivity of LOD as low as 0.274 mU/mL, which was attributed to a substantial electromagnetic field enhancement at the inter-nanoparticle gaps between the adjacent pedestal and antenna. Moreover, by exploiting the synergistic effect of the periodically extended DNA scaffold generated by RCA amplification and the co-assembly of thiol ligand, the loaded GNS can be extended to three-dimensional space, forming a high-density periodic hotspot in the focal volume, thereby ensuring high enhancement and high reproducibility of Raman signals. In addition, this method can be used to quantify T4 PNK in HeLa cells, demonstrating its applicability in diagnosing and estimating PNK-related diseases in complex fluids.

Enhanced Modulation Bandwidth by Integrating 2D Semiconductor and Quantum Dots for Visible Light Communication

Light‐emitting devices present a tremendous potential for visible light communication (VLC) due to their dual functionality as both communication and lighting devices. Herein this study, the significant enhancement in VLC modulation bandwidth by integrating two‐dimensional (2D) semiconductor and quantum dots (QDs) emitter is reported. Generally, the modulation bandwidth of CdSe‐based QDs is limited to only less than 25 MHz; however, with the proposed hybrid emitter, a maximum modulation bandwidth of 130 MHz for CdSe/ZnS QDs emitter is able to be achieved. The WSe2 monolayer is integrated into an Au–nanorod–decorated CdSe/ZnS QDs emitter to achieve high modulation performance. The modulation bandwidth of the hybrid QD–Au–WSe2 emitter (130 MHz) is found to be higher than those of the pristine QDs and QD–WSe2 heterostructure without Au nanorods (79 and 91 MHz, respectively). A significant increase is observed in the transition rate of QDs excitons when they are integrated with Au nanorods and WSe2 monolayer, which is substantiated by a reduction in average carrier lifetime from time‐resolved photoluminescence analysis. This approach and the findings open an opportunity to apply 2D semiconductors into the next‐generation miniature VLC devices, for high‐speed optical communications.

Multiplex metal enhanced fluorescence (MEF) effect on porous Au nanorod for highly sensitive multi-microRNA (miRNA) detection

MicroRNA (miRNA) is an important biomarker for early diagnosis or progression of a disease because the type and amount of its release can vary depending on the type or condition of the cell. However, since microRNAs exist at low concentrations in the body with several microRNAs released, it is necessary to develop a biosensor that can sensitively measure multiple miRNAs. In this study, a metal-enhanced fluorescence (MEF)-based highly sensitive nanobiosensor for measuring multiple miRNAs was developed. To extend the plasmonic-based MEF phenomenon to fluorescent materials with various emission wavelengths, porous gold (Au) nanorods with a wide absorption wavelength were synthesized. Using this, two different miRNAs were simultaneously measured sensitively and selectively. The proposed sensing method is a highly sensitive, rapid, simple, and one-step way for multiplex detection of miRNAs. It can be used for early diagnosis of cancer and other nucleic acid-related diseases.

Absorption characteristics and solar absorption capacity of Au core NR coated with various shell material

Au nanorods (NRs) can be used to improve the performance of direct absorption solar collectors (DASCs), however, the solar absorption of Au NRs should be further improved because the absorption of Au NRs in near-infrared range is strong while the absorption in visible range is relatively weak where the solar spectrum intensity is the strongest. Based on this tissue, a composite nanostructure composed of Au core NR and Mg shell is proposed to improve the solar absorption capacity. The choice of Mg material as the shell composition is explained. By optimizing the composition structure, the enhancement effect on the absorption properties of Au@Mg NR from visible range to near-infrared range is proven by the finite element method. Furthermore, the effect of imperfect shell on absorption capacity of Au@Mg NR is discussed. Finally, the DASCs performance based on optimal Au@Mg NR nanofluids is evaluated. The results show that when the volume fraction is lower than 2 ppm and the collector depth is 2 cm, the highest solar energy harvesting capacity (>92%) using Au@Mg NRs nanofluids can be obtained, showing an excellent Au-based material for DASCs application.

Sensitive and reproducible on-chip SERS detection by side-polished fiber probes integrated with microfluidic chips

The combination of surface-enhanced Raman scattering (SERS) and microfluidic technology offers a promising solution to improve the reproducibility and reliability of SERS detection. Optical fiber SERS probes, as an important class of SERS substrates, provide a large SERS interaction area and flexible integration with microfluidic chips. In this article, a side-polished multimode fiber (SPMF) SERS probe is prepared by depositing Au nanorods on a planar polished fiber surface and integrating it into a microfluidic channel to form a glass-based microfluidic-SERS chip. The impact of SPMF residual thickness on SERS performance is thoroughly investigated, and the optimized residual thickness of 62 μm is determined by considering the evanescent wave intensity, transmission loss, and experimental feasibility. The optimized microfluidic-SERS chip shows low detection limits (as low as 10-8 M for MG) and good spectral reproducibility (RSD less than 10%) due to the large SERS interaction area provided by the SPMF SERS probe and the stable liquid flow in the microfluidic channel. The chip is furtherly used to detect pesticide and antibiotic residues in tap water, with the detection limits of 10-9 M for thiram and 10-6 M for levofloxacin. This work provides an effective way to realize highly sensitive and reproducible SERS detection, and may find important applications in environmental science, food safety, and biomedicine.

Gold-Based Nanostructures for Antibacterial Application.

Bacterial infections have become a fatal threat because of the abuse of antibiotics in the world. Various gold (Au)-based nanostructures have been extensively explored as antibacterial agents to combat bacterial infections based on their remarkable chemical and physical characteristics. Many Au-based nanostructures have been designed and their antibacterial activities and mechanisms have been further examined and demonstrated. In this review, we collected and summarized current developments of antibacterial agents of Au-based nanostructures, including Au nanoparticles (AuNPs), Au nanoclusters (AuNCs), Au nanorods (AuNRs), Au nanobipyramids (AuNBPs), and Au nanostars (AuNSs) according to their shapes, sizes, and surface modifications. The rational designs and antibacterial mechanisms of these Au-based nanostructures are further discussed. With the developments of Au-based nanostructures as novel antibacterial agents, we also provide perspectives, challenges, and opportunities for future practical clinical applications.

Dual-targeting multifunctional hyaluronic acid ligand-capped gold nanorods with enhanced endo-lysosomal escape ability for synergetic photodynamic-photothermal therapy of cancer.

Au nanorods (AuNRs) have attracted considerable interest as drug delivery systems because of their enhanced cell internalization and stronger drug-loading ability. In addition, the incorporation of photodynamic therapy (PDT) and photothermal therapy (PTT) into one nanosystem presents great promise to defect multiple drawbacks in cancer therapy. Herein, we fabricated a multifunctional and dual-targeting nanoplatform based on hyaluronic acid-grafted-(mPEG/triethylenetetramine-conjugated-lipoic acid/tetra(4-carboxyphenyl)porphyrin/folic acid) polymer ligand capped AuNRs (AuNRs@HA-g-(mPEG/Teta-co-(LA/TCPP/FA)) for combined photodynamic-photothermal therapy of cancer. The prepared nanoparticles displayed high TCPP loading capacity and excellent stability in different biological media. Furthermore, AuNRs@HA-g-(mPEG/Teta-co-(LA/TCPP/FA)) not only could produce a localized hyperthermia to conduct PTT, but also generate cytotoxic singlet oxygen (1 O2 ) to perform PDT under laser irradiation. Confocal imaging results disclosed that this nanoparticle endowing the specific function of polymeric ligand could enhance cellular uptake, accelerate endo/lysosomal escape, as well as produce higher reactive oxygen species. Importantly, this combination therapy strategy could also induce higher anticancer potential than PDT or PTT only against MCF-7 tumor cells in vitro. Therefore, this work presented an AuNRs-based therapeutic nanoplatform with great potential in dual-targeting and photo-induced combination therapy of cancer.

Nanowire-based smart windows combining electro- and thermochromics for dynamic regulation of solar radiation

Smart window is an attractive option for efficient heat management to minimize energy consumption and improve indoor living comfort owing to their optical properties of adjusting sunlight. To effectively improve the sunlight modulation and heat management capability of smart windows, here, we propose a co-assembly strategy to fabricate the electrochromic and thermochromic smart windows with tunable components and ordered structures for the dynamic regulation of solar radiation. Firstly, to enhance both illumination and cooling efficiency in electrochromic windows, the aspect ratio and mixed type of Au nanorods are tuned to selectively absorb the near-infrared wavelength range of 760 to 1360 nm. Furthermore, when assembled with electrochromic W18O49 nanowires in the colored state, the Au nanorods exhibit a synergistic effect, resulting in a 90% reduction of near-infrared light and a corresponding 5 °C cooling effect under 1-sun irradiation. Secondly, to extend the fixed response temperature value to a wider range of 30–50 °C in thermochromic windows, the doping amount and mixed type of W-VO2 nanowires are carefully regulated. Last but not the least, the ordered assembly structure of the nanowires can greatly reduce the level of haze and enhance visibility in the windows.

Mulberry-like porous-hollow AuPtAg nanorods for electrochemical immunosensing of biomarker myoglobin.

Mulberry-like AuPtAg porous hollow nanorods (PHNR) were facilely synthesized for the first time via a wet chemical method, where Au nanorods (Au NR) behaved as sacrificed template. The anisotropic oriented growth and etching process are involved in this synthesis. Theirstructural and electronic characteristics were scrutinously examined by TEM, EDS, XPS, and electrochemical techniques. The AuPtAg PHNR provided a large specific surface area and exposed a large number of active sites, showing highly enhanced catalytic activity. On thisfoundation, a label-free electrochemical immunosensor was developed for myoglobin (Myo) assay based on the AuPtAg PHNR. Further, the built sensor exhibited fast and ultrasensitive responses in a linear range of 0.0001 ~ 1000ngmL-1 with a low limit of detection (LOD = 0.46pgmL-1, S/N = 3), and enabled efficient application to human serum samples with acceptable results. Consequently, the developed AuPtAg PHNR-based platform has a broad prospect in practically monitoring Myo and other biomarkers in clinics.

Photothermal Heating of Au Nanorods and Nanospheres: Temperature Characteristics and Strength of Convective Forces

Photothermal Heating of Au Nanorods and Nanospheres: Temperature Characteristics and Strength of Convective Forces

Plasmon driven super-high HER activity of electronic structure and lattice strain engineered single atomic layer Pd@Au nanorods

The development of efficient catalysts with low energy consumption has always been a key issue for sustainable hydrogen energy. Here, we report a catalyst comprising a single atomic Pd layer deposited on Au nanorods (ML-Pd@Au NRs) that shows a super-high HER activity and ultra-low overpotential under localized surface plasmon resonance condition. The Au NR plays triple determining roles in HER performance via adjusting the electronic structure and lattice strain of Pd that effectively reduces the adsorption energy of H-adatoms, eliminating the penetration of H adatoms in multilayer Pd crystal that decreases the H adatoms diffusion kinetics, and providing high energetic hot charge carriers under near-IR light irradiation that decreases the activation energy and onset potential of HER. The single atomic Pd layer on Au NRs ensures the hot electron transfer as the main dissipation pathway of the plasmonic hot charge carriers for HER. Thus, under near-IR light irradiation, HER on ML-Pd@Au NRs occurs with a high mass activity of 17.47 mA mg−1 at 100 mV and a very low overpotential of 13 mV at 10 mA cm−2, which are superior to the commercial Pd/C and commercial Pt/C catalysts under the same conditions.

A biomimetic nanoplatform for precise reprogramming of tumor-associated macrophages and NIR-II mediated antitumor immune activation.

The therapeutic effects of photothermal therapy (PTT) are dependent on the photothermal conversion efficiency of photothermal agents (PTAs) in tumors and the subsequent activation of the antitumor immune system. However, the insufficient tumor accumulation of current PTAs and the inevitable recruitment of tumor-associated macrophages (TAMs) could further compromise the antitumor activities of PTT. To address these issues, a biomimetic photothermal nanoplatform Au@Fe-PM is developed for the targeted remodeling of TAMs, which promotes the antitumor immunity of PTT. Au nanorods with second near-infrared (NIR-II) absorptions are fabricated to serve as PTAs to induce immunogenic cell death in tumor cells. The ferric hydroxide shell coated on Au nanorods can release iron ions to repolarize M2-like TAMs into the tumoricidal M1 phenotype via P38 and STAT1-mediated signaling pathways. Moreover, the surface decoration of platelet membranes endows biomimetic nanoplatform with enhanced tumor targeting ability for precise tumor ablation and TAM regulation. Consequently, Au@Fe-PM under NIR-II laser irradiation exhibits significantly higher inhibitory effects in a poor immunogenic 4T1 tumor-bearing mouse model with a 50% complete remission rate compared to conventional PTT (0%). By simultaneously reversing the immunosuppressive tumor microenvironment, this biomimetic nanoplatform offers a promising strategy for enhancing the antitumor efficacy of PTT. STATEMENT OF SIGNIFICANCE: The therapeutic effects of current photothermal therapy (PTT) are hindered by the insufficient tumor accumulation of conventional photothermal agents and the recruitment of immunosuppressive tumor-associated macrophages (TAMs) after PTT. Herein, we report a biomimetic iron-based second near-infrared (NIR-II) photothermal nanoplatform (Au@Fe-PM) for targeted TAMs reprogramming and NIR-II mediated anti-tumor immunity. Au@Fe-PM can actively target the tumor site with the help of surface-decorated platelet membranes. Meanwhile, iron ions would be released from Au@Fe-PM in acidic lysosomes to reprogram TAMs into tumoricidal M1-like macrophages, which promotes the antitumor responses elicited by NIR-II PTT, thereby contributing to remarkable tumor inhibitory effects, with 50% higher complete remission rate than that of conventional PTT.