Gold-silver Alloy Nanoparticles Research Articles

Creation of Silver-Gold Alloy Nanoparticles Using Citrus sinensis Peel Extract and Their Antibacterial Efficacy

Creation of Silver-Gold Alloy Nanoparticles Using Citrus sinensis Peel Extract and Their Antibacterial Efficacy

Engineering the Hot-Spots in Au-Ag Alloy Nanoparticles through Meniscus-Confined 3D Printing for Microplastic Detection.

The escalating concern surrounding microplastic (MP) pollution necessitates urgent attention and the development of rapid techniques for quantifying extremely low concentrations. Surface-enhanced Raman spectroscopy (SERS) has emerged as a promising method due to its simplicity, high sensitivity, and rapid quantification capabilities. Herein, the efficacy of gold-silver alloy nanoparticles (3DPAu-Ag) substrates for detecting poly(methyl methacrylate) (PMMA) and polystyrene (PS) MPs is investigated. The 3DPAu-Ag SERS substrates are fabricated using the meniscus-confined electrochemical 3D printing (MC-E3DP) process, employing a nozzle of 0.8 mm size with 2.5 V potential at a printing speed of 0.4 mm s-1. The proposed SERS substrates exhibit exceptional sensitivity and are capable of detecting PMMA concentrations as low as 0.2 μg mL-1 and PS concentrations of 1.2 μg mL-1 within the ranges of 1-103 μg mL-1 and 10-104 μg mL-1, respectively. Remarkable enhancement factors (EFs) of up to 3.2 × 104 for PMMA and 9.3 × 103 for PS are achieved, underscoring the substrates' effectiveness. Furthermore, the investigation demonstrates outstanding uniformity and reproducibility of the 3DPAu-Ag substrates, with relative standard deviation (RSD) values of only 4.1 and 6.4%, respectively, across 31 and 5 measurements. Additionally, a minimal 17% decrease in the initial SERS signal value after 5 weeks highlights the substrates' high stability. This not only highlights the superior quality of the substrates but also positions them ahead of previously reported works in the literature. Moreover, this study also comes up with a plausible mechanism for MPs SERS detection facilitated by the 3DPAu-Ag substrates, offering insights into the underlying processes. Overall, 3DPAu-Ag substrates show promise for sensitive, stable MP detection, which is crucial for environmental monitoring.

Hot carriers from intra- and interband transitions in gold-silver alloy nanoparticles

Hot electrons and holes generated from the decay of localised surface plasmons in metallic nanoparticles can be harnessed for applications in solar energy conversion and sensing. In this paper, we study the generation of hot carriers in large spherical gold-silver alloy nanoparticles using a recently developed atomistic modelling approach that combines a solution of Maxwell’s equations with large-scale tight-binding simulations. We find that hot-carrier properties depend sensitively on the alloy composition. Specifically, nanoparticles with a large gold fraction produce hot carriers under visible light illumination while nanoparticles with a large silver fraction require higher photon energies to produce hot carriers. Moreover, most hot carriers in nanoparticles with a large gold fraction originate from interband transitions which give rise to energetic holes and ‘cold’ electrons near the Fermi level. Increasing the silver fraction enhances the generation rate of hot carriers from intraband transitions which produce energetic electrons and ‘cold’ holes. These findings demonstrate that alloy composition is a powerful tuning parameter for the design of nanoparticles for applications in solar energy conversion and sensing that require precise control of hot-carrier properties.

One-step synthesized multisize AuAg alloy nanoparticles with high SERS sensitivity in directly detecting SARS-CoV-2 spike protein

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in widespread disease transmission, challenging the stability of global healthcare systems. Surface-enhanced Raman scattering (SERS) as an easy operation, fast, and low-cost technology illustrates a good potential in detecting SARS-CoV-2. In the study, one-step fabrication of gold-silver alloy nanoparticles (AuAgNPs) with adjustable metal proportions and diameters is employed as SERS substrates. The angiotensin-converting enzyme 2 (ACE2) functionalized AuAgNPs are applied as sensor surfaces to detect SARS-CoV-2 S protein. By optimizing the SERS substrates, ACE2/Au35Ag65NPs illustrate higher performance in detecting the SARS-CoV-2 S protein with a limit of detection (LOD) of 10 fg/mL in both phosphate-buffered saline (PBS) and pharyngeal swabs solution (PSS). It also provides excellent reproducibility with a relative standard deviation (RSD) of 7.7 % and 7.9 %, respectively. This easily preparable and highly reproducible SERS substrate has good potential in the practical application of detecting SARS-CoV-2.

Tailoring the Reaction Pathway for Control of Size and Composition of Silver–Gold Alloy Nanoparticles

Tailoring the Reaction Pathway for Control of Size and Composition of Silver–Gold Alloy Nanoparticles

Anti-biofilm properties of laser-synthesized, ultrapure silver–gold-alloy nanoparticles against Staphylococcus aureus

Staphylococcus aureus biofilm-associated infections are a common complication in modern medicine. Due to inherent resilience of biofilms to antibiotics and the rising number of antibiotic-resistant bacterial strains, new treatment options are required. For this purpose, ultrapure, spherical silver–gold-alloy nanoparticles with homogenous elemental distribution were synthesized by laser ablation in liquids and analyzed for their antibacterial activity on different stages of S. aureus biofilm formation as well as for different viability parameters. First, the effect of nanoparticles against planktonic bacteria was tested with metabolic activity measurements. Next, nanoparticles were incubated with differently matured S. aureus biofilms, which were then analyzed by metabolic activity measurements and three dimensional live/dead fluorescent staining to determine biofilm volume and membrane integrity. It could be shown that AgAu NPs exhibit antibacterial properties against planktonic bacteria but also against early-stage and even mature biofilms, with a complete diffusion through the biofilm matrix. Furthermore, AgAu NPs primarily targeted metabolic activity, to a smaller extend membrane integrity, but not the biofilm volume. Additional molecular analyses using qRT-PCR confirmed the influence on different metabolic pathways, like glycolysis, stress response and biofilm formation. As this shows clear similarities to the mechanism of pure silver ions, the results strengthen silver ions to be the major antibacterial agent of the synthesized nanoparticles. In summary, the results of this study provide initial evidence of promising anti-biofilm characteristics of silver–gold-alloy nanoparticles and support the importance of further translation-oriented analyses in the future.

Multiplexed immunolabelling of cancer using bioconjugated plasmonic gold-silver alloy nanoparticles.

Reliable protein detection methods are vital for advancing biological research and medical diagnostics. While immunohistochemistry and immunofluorescence are commonly employed, their limitations underscore the necessity for alternative approaches. This study introduces immunoplasmonic labelling, utilizing plasmonic nanoparticles (NPs), specifically designed gold and gold-silver alloy NPs (Au:Ag NPs), for multiplexed and quantitative protein detection. These NPs, when coupled with antibodies targeting proteins of interest, enable accurate counting and evaluation of protein expression levels while overcoming issues such as autofluorescence. In this study, we compare two nanoparticle functionalization strategies-one coating based on thiolated PEG and one coating based on calix[4]arenes-on gold and gold-silver alloy nanoparticles of varying sizes. Overall results tend to demonstrate a greater versatility for the calix[4]arene-based coating. With this coating and using the classical EDC/sulfo-NHS cross-linking procedure, we also demonstrate the successful multiplexed immunolabelling of Her2, CD44, and EpCAM in breast cancer cell lines (SK-BR-3 and MDA-MB-231). Furthermore, we introduce a user-friendly software for automatic NP detection and classification by colour, providing a promising proof-of-concept for the practical application of immunoplasmonic techniques in the quantitative analysis of biopsies in the clinical setting.

Targeted color design of silver-gold alloy nanoparticles.

This research article focuses on the targeted color design of silver-gold alloy nanoparticles (NPs), employing a multivariate optimization approach. NP synthesis involves interconnected process parameters, making independent variation challenging. Data-based property-process relationships are established to optimize optical properties effectively. We define a color target, employ a green chemical co-reduction method at room temperature and optimize process parameters accordingly. The CIEL*a*b* color space (Commission Internationale de l'Éclairage - International Commission on Illumination) and Euclidean distances facilitate accurate color matching to establish the property-process relationship. Concurrently, theoretical Mie calculations explore the structure-property relationship across particle sizes, concentrations, and molar gold contents. The theoretically optimal structure agrees very well with experimental particle structures at the property-process relationship's optimum. The data-driven property-process relationship provides valuable insights into the formation mechanism of a complex particle system, sheds light on the role of relevant process parameters and allows to evaluate the practically available property space. Model validation beyond the original grid demonstrates its robustness, yielding colors close to the target. Additionally, Design of Experiments (DoE) methods reduce experimental work by threefold with slight accuracy trade-offs. Our novel methodology for targeted color design demonstrates how data-based methods can be utilized alongside structure-property relationships to unravel property-process relationships in the design of complex nanoparticle systems and paves the way for future developments in targeted property design.

Glasses with biocompatible Au/Ag NPs of governed composition

Silver-gold alloy nanoparticles were grown using heat treatment of soda-lime glass slides with depercolated gold film subjected to silver-to-sodium ion exchange. Varying the regime of the heat treatment allows one to control the proportion of silver in the nanoparticles and adjust the spectral position of their local surface plasmon resonance (LSPR) in the spectral range between the resonances of gold and silver nanoparticles. The position of LSPR in gold nanoparticles can be shifted by 15% via their dilution by silver in 50 wt % concentration. This shift is accompanied by only a 3% decrease in HeLa cell viability on the slides with alloy nanoparticles on the surface and by a slight decrease in the cell functionality/adhesion (FA) that show the biocompatibility of these nanoparticles. On the contrary, a notable decrease in the viability and ∼100% drop of FA were registered for the slides with purely silver nanoparticles.

The Origin of the Intracellular Silver in Bacteria: A Comprehensive Study using Targeting Gold-Silver Alloy Nanoparticles.

The bactericidal effects of silver nanoparticles (Ag NPs) against infectious strains of multiresistant bacteria is a well-studied phenomenon, highly relevant for many researchers and clinicians battling bacterial infections. However, little is known about the uptake of the Ag NPs into the bacteria, the related uptake mechanisms, and how they are connected to antimicrobial activity. Even less information is available on AgAu alloy NPs uptake. In this work, the interactions between colloidal silver-gold alloy nanoparticles (AgAu NPs) and Staphylococcus aureus (S. aureus) using advanced electron microscopy methods are studied. The localization of the nanoparticles is monitored on the membrane and inside the bacterial cells and the elemental compositions of intra- and extracellular nanoparticle species. The findings reveal the formation of pure silver nanoparticles with diameters smaller than 10nm inside the bacteria, even though those particles are not present in the original colloid. This finding is explained by a local RElease PEnetration Reduction (REPER) mechanism of silver cations emitted from the AgAu nanoparticles, emphasized by the localization of the AgAu nanoparticles on the bacterial membrane by aptamer targeting ligands. These findings can deepen the understanding of the antimicrobial effect of nanosilver, where the microbes are defusing the attacking silver ions via their reduction,and aid in the development of suitable therapeutic approaches.

Silver-Gold Alloy Nanoparticles (AgAu NPs): Photochemical Synthesis of Novel Biocompatible, Bimetallic Alloy Nanoparticles and Study of Their In Vitro Peroxidase Nanozyme Activity.

Facile synthesis of metal nanoparticles with controlled physicochemical properties using environment-friendly reagents can open new avenues in biomedical applications. Nanomaterials with controlled physicochemical properties have opened new prospects for a variety of applications. In the present study, we report a single-step photochemical synthesis of ~5 nm-sized silver (Ag) and gold (Au) nanoparticles (NPs), and Ag-Au alloy nanoparticles using L-tyrosine. The physicochemical and surface properties of both monometallic and bimetallic NPs were investigated by analytical, spectroscopic, and microscopic techniques. Our results also displayed an interaction between L-tyrosine and surface atoms that leads to the formation of AgAu NPs by preventing the growth and aggregation of the NPs. This method efficiently produced monodispersed NPs, with a narrow-sized distribution and good stability in an aqueous solution. The cytotoxicity assessment performed on breast cancer cell lines (MCF-7) revealed that the biofriendly L-tyrosine-capped AgNPs, AuNPs, and bimetallic AgAu NPs were biocompatible. Interestingly, AgAu NPs have also unveiled controlled cytotoxicity, cell viability, and in vitro peroxidase nanozyme activity reliant on metal composition and surface coating.

Plasmonic internal standard-decorated nitrocellulose membranes for duplex detection of circulating tumor biomarkers

Surface-enhanced Raman spectroscopy (SERS) technology has been increasingly integrated with lateral flow immunoassay (SERS-LFA) to enable sensitive and quantitative detection, but SERS-LFA still faces notable challenges. One of the biggest problems is signal variations caused by random distributions of plasmonic SERS immunoprobes. Herein, we develop a sensitive, accurate quantification platform that overcomes this problem with a plasmonic internal standard (PIS), referred to as PIS-LFA. The PIS is achieved by decorating nitrocellulose membranes with Raman reporter molecule-embedded silver-gold alloy nanoparticles. By simultaneously measuring signals of plasmonic immunoprobes and IS and calculating their intensity ratios for signal normalization, we can mitigate signal variations and improve assay sensitivity. Comparing with SERS-LFA in carcinoembryonic antigen (CEA) detection, we show that PIS-LFA achieves a 1.8-fold higher uniformity and 3.2-fold lower limit of detection. We further demonstrate that PIS-LFA exhibits accurate quantification capability in duplex detection of CEA and neuron-specific enolase (NSE) in human sera by performing spike-recovery experiments and validating with electrochemiluminescence immunoassays. As a proof-of-concept, PIS-LFA differentiates levels of serum CEA and NSE between 12 early-stage lung cancer patients and 12 healthy individuals. We believe that PIS-LFA will open up avenues for affordable, rapid, and non-invasive disease screening in point-of-care settings.

Two-Step Synthesis of Large Gold–Silver Alloy Nanoparticles via the Combination of Seeded Growth and Citrate Co-reduction

We report a novel two-step method for the synthesis of uniform quasi-spherical and monodisperse gold–silver alloy nanoparticles with diameters of approximately 80 nm. In step one, gold–silver alloy seeds (G0) with diameters of approximately 30 nm are synthesized by citrate co-reduction of gold acetate and silver nitrate. In step two, the seeds grow into large alloy nanoparticles with diameters of approximately 80 nm by the combination of seeded growth and citrate co-reduction of gold and silver precursors. Our method makes use of gold acetate (rather than chloroauric acid) as a gold precursor to avoid the formation of silver chloride precipitates during synthesis. To our knowledge, we are the first to prepare gold–silver alloy nanoparticles with diameters of above 70 nm using gold acetate as a gold precursor. The alloy seeds and seed-grown nanoparticles show good control of size and composition, which enables tuning of the plasmonic band of these gold–silver alloy nanoparticles. Gold and silver are distributed uniformly within the cores of all Au-Ag alloy nanoparticles, while the surface is enriched in silver. This silver-enriched surface layer is thicker and more prominent for 25% Au alloy nanoparticles than for 50% and 75% Au alloy nanoparticles.

SERS Reveals the Presence of Au–O–O–H and Enhanced Catalytic Activity of Electrochemically Dealloyed AgAu Nanoparticles

Due to their high surface-to-volume ratio and large proportion of low coordinated surface atoms, dealloyed nanoparticles have gained increasing attention as porous catalysts for the electrochemical oxygen evolution reaction (OER). Here, we characterize and rationalize the physical and chemical properties of operando gold-enriched porous nanoparticles fabricated by electrochemical dealloying of citrate-capped silver gold alloy nanoparticles in 250 mM KNO3. We combine surface-enhanced Raman spectroscopy (SERS) with electrochemistry for catalyst tracking. With SERS, we observe at 1.05 V (vs platinum quasi-reference electrode) the formation of Au–O–O–H species, a known intermediate of OER, while this is not observed for monometallic gold nanoparticles or bare electrodes. In agreement, qualitative measurements of the catalytic activity prove that appreciable OER currents are detected at lower potentials for gold-enriched porous nanoparticles compared to gold nanoparticles of the same size. Our results pave the way for the application of dealloying-derived nanoparticles as promising catalyst materials.

Disproportional surface segregation in ligand-free gold-silver alloy solid solution nanoparticles, and its implication for catalysis and biomedicine.

Catalytic activity and toxicity of mixed-metal nanoparticles have been shown to correlate and are known to be dependent on surface composition. The surface chemistry of the fully inorganic, ligand-free silver-gold alloy nanoparticle molar fraction series, is highly interesting for applications in heterogeneous catalysis, which is determined by active surface sites which are also relevant for understanding their dissolution behavior in biomedically-relevant ion-release scenarios. However, such information has never been systematically obtained for colloidal nanoparticles without organic surface ligands and has to date, not been analyzed in a surface-normalized manner to exclude density effects. For this, we used detailed electrochemical measurements based on cyclic voltammetry to systematically analyze the redox chemistry of particle-surface-normalized gold-silver alloy nanoparticles with varying gold molar fractions. The study addressed a broad range of gold molar fractions (Ag90Au10, Ag80Au20, Ag70Au30, Ag50Au50, Ag40Au60, and Ag20Au80) as well as monometallic Ag and Au nanoparticle controls. Oxygen reduction reaction (ORR) measurements in O2 saturated 0.1 M KOH revealed a linear reduction of the overpotential with increasing gold content on the surface, probably attributed to the higher ORR activity of gold over silver, verified by monometallic Ag and Au controls. These findings were complemented by detailed XPS studies revealing an accumulation of the minor constituent of the alloy on the surface, e.g., silver surface enrichment in gold-rich particles. Furthermore, highly oxidized Ag surface site enrichment was detected after the ORR reaction, most pronounced in gold-rich alloys. Further, detailed CV studies at acidic pH, analyzing the position, onset potential, and peak integrals of silver oxidation and silver reduction peaks revealed particularly low reactivity and high chemical stability of the equimolar Au50Ag50 composition, a phenomenon attributed to the outstanding thermodynamic, entropically driven, stabilization arising at this composition.

Influence of swift heavy ion irradiation on bimetallic gold-silver nanoparticles in dielectric matrices and their optical properties

Nanosized gold-silver (AuAg) alloy nanoparticles (NPs) of sizes, 2 nm -25 nm embedded in fused quartz are synthesized using sequential implantation and post annealing at 900℃ for 1 h in Argon environment. The post annealed film is irradiated using swift heavy ions (SHI), 120 MeV Ag ions to investigate the effect of electronic energy deposition, (Se×ϕ), on size, shape and composition of the alloy NPs. Transmission electron microscopy (TEM) analysis of the as- implanted AuAg film reveals the formation of small sized, 1.8 nm-3.5 nm, bimetallic AuAg NPs. Rutherford backscattering spectroscopy (RBS) spectra along with its fitted graph convey the annealing induced out diffusion, mixing and formation of larger sized, 2 nm -25 nm, alloy NPs through Ostwald ripening. SHI irradiation results in deformation in shape from spherical to ellipsoidal alloy NPs with major axis align along the beam direction and the average aspect ratio is about 1.20. RBS analysis results convey the formation of Ag enriched alloy NPs after irradiation. The smaller nanoparticles are found dissolved while larger ones grow and elongate along the ion beam direction. SPR properties are modified by SHI induced processes of melting, sputtering and re-precipitation in the ion tracks.The un-irradiated film exhibits a single intense SPR peak at 536 nm, while the irradiated film gives rise two SPR peaks: Ist, a blue shifted SPR peak from 536 nm to 515 nm with significantly reduced intensity and much wider FWHM; and, IInd, a small SPR peak around 460 nm. SHI induced modifications on the NPs are understood in terms of thermal spike model. The detailed analysis shows that SHI can be used as a tool to tailor size, shape and composition of the bimetallic AuAg alloy NPs and their SPR properties.

Green room temperature synthesis of silver-gold alloy nanoparticles.

Metallic alloy nanoparticles (NPs) exhibit interesting optical, electrical and catalytic properties, dependent on their size, shape and composition. In particular, silver-gold alloy NPs are widely applied as model systems to better understand the syntheses and formation (kinetics) of alloy NPs, as the two elements are fully miscible. Our study targets product design via environmentally friendly synthesis conditions. We use dextran as the reducing and stabilizing agent for the synthesis of homogeneous silver-gold alloy NPs at room temperature. Our approach is a one-pot, low temperature, reaction-controlled, green and scalable synthesis route of well-controlled composition and narrow particle size distribution. The composition over a broad range of molar gold contents is confirmed by scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (STEM-EDX) measurements and auxiliary inductively coupled plasma-optical emission spectroscopy measurements (ICP-OES). The distributions of the resulting particles in size and composition are obtained from multi-wavelength analytical ultracentrifugation using the optical back coupling method and further confirmed by high-pressure liquid chromatography. Finally, we provide insight into the reaction kinetics during the synthesis, discuss the reaction mechanism and demonstrate possibilities for scale-up by a factor of more than 250 by increasing the reactor volume and NP concentration.

Hollow silver-gold alloy nanoparticles for enhanced photothermal/photodynamic synergetic therapy against bacterial infection and acceleration of wound healing.

Bacterial infection seriously restricts the wound healing process due to severe inflammation and delayed wound healing. Unfortunately, the overuse or improper use of antibiotics leads to the advent of multidrug-resistant strains and intractable biofilms, severely affecting the therapeutic effect. Therefore, there is an urgent need to develop antibiotic-free strategies to accelerate the healing process of wounds with bacterial infection. Considering that single photothermal therapy (PTT) or photodynamic therapy (PDT) cannot fully meet the requirements of clinical sterilization and accelerating wound healing, herein, hollow silver-gold alloy nanoparticles immobilized with the photosensitizer molecule Ce6 (Ag@Au-Ce6 NPs) integrated with PTT and PDT are proposed for killing bacteria and accelerating wound healing. The photothermal conversion properties of Ag@Au-Ce6 NPs are obtained using an infrared thermal imager, and the generation of singlet oxygen (1O2) is verified with an 1O2 fluorescent probe DCFH-DA. Manipulated by near-infrared laser triggered mild hyperthermia and limited ROS amount, Ag@Au-Ce6 NPs could effectively kill bacteria that are free and colonized on the surface of wounded skin, promoting epithelium migration and vascularization, further accelerating wound healing, which showed great promise for biomedical application.

Correlation notice on the electrochemical dealloying and antibacterial properties of gold-silver alloy nanoparticles.

Galvanic replacement reaction was used in the synthesis of bimetallic gold-silver alloy nanoparticles (Au-Ag NPs), where pre-synthesized Ag nanoparticles-polyvinylpyrrolidone (AgNPs-PVP) were used to reduce the aryldiazonium tetrachloroaurate(III) salt in water. TEM images and EDS elemental analysis showed the formation of spherical Au-Ag NPs with sizes of 12.8 ± 4.9nm and 25.6 ± 14.4nm for corresponding Au-Ag ratios and termed as Au0.91Ag0.09 and Au0.79Ag0.21, respectively, with different concentrations of the gold precursor. The hydrodynamic sizes measured using dynamic light scattering are 46.4nm and 74.8nm with corresponding zeta potentials of - 44.56 and - 25.09mV in water, for Au0.91Ag0.09 and Au0.79Ag0.21 respectively. Oxidative leachability of Ag ion studies from the starting AgNPs-PVP in 1M NaCl showed a significant decrease in the plasmon peak after 8h, indicating the complete dissolution of Ag ions, however, there is enhanced oxidation resistivity of Ag from Au-Ag NPs even after 24h. Electrochemical studies on glassy carbon electrodes displayed a low oxidation peak in aqueous solutions of 20mM KCl at 0.16V and KNO3 at 0.33V vs. saturated calomel electrode (SCE). We studied the antibacterial activity of Au-Ag alloy nanoparticles against gram-positive Staphylococcus aureus, Staphylococcus epidermidis, Enterococcusfaecalis, and gram-negative Escherichia coli, Salmonella typhimurium, and Pseudomonas aeruginosa. Our findings demonstrated superior antibacterial activity of Au-Ag NPs compared with AgNPs-PVP. Moreover, the nanoparticles inhibited the S. epidermidis biofilm formation.

Direct Laser Writing of SERS Hollow Fibers.

We report the direct laser writing (DLW) of surface-enhanced Raman scattering (SERS) structures on the inner wall of a hollow fiber. Colloidal gold–silver alloy nanoparticles (Au–Ag ANPs) are firstly coated onto the inner wall of a hollow fiber. A green laser beam is focused through the outer surface of the hollow fiber to interact with colloidal Au–Ag ANPs so that they become melted and aggregated on the surface of the inner wall with strong adhesion. Such randomly distributed plasmonic nanostructures with high density and small gaps favor the SERS detection of low-concentration molecules in liquids flowing through the hollow fiber. Such a SERS device also supplies a three-dimensional microcavity for the interaction between excitation laser and the target molecules. The DLW system consists mainly of the flexible connection between the motor shaft and the hollow fiber, the program-controlled translation of the hollow fiber along its symmetric axis and rotation about the axis, as well as the mechanical design and the computer control system. This DLW technique enables high production, high stability, high reproducibility, high precision, and a high-flexibility fabrication of the hollow fiber SERS device. The resultant microcavity SERS scheme enables the high-sensitivity detection of R6G molecules in ethanol with a concentration of 10−7 mol/L.