Localized Surface Plasmon Resonance Signal Research Articles

Polydopamine-Assisted Fabrication of Stable Silver Nanoparticles on Optical Fiber for Enhanced Plasmonic Sensing

We present a facile and effective method for fabrication of the localized surface plasmon resonance (LSPR) optical fiber sensor assisted by two polydopamine (PDA) layers with enhanced plasmonic sensing performance. The first PDA layer was self-polymerized onto the bare optical fiber to provide the catechol groups for the reduction from Ag+ to Ago through chelating and redox activity. As the reduction of Ag+ proceeds, Ag nanoparticles (NPs) were grown in-situ on the PDA layer with uniform distribution. The second PDA layer was applied to prevent Ag NPs from oxidating and achieve an improvement of LSPR signal. The PDA/Ag/PDA-based optical fiber sensor has an enhanced LSPR sensitivity of 961 nm/RIU and excellent oxidation resistance. The stable PDA/Ag/PDA-based LSPR sensor with high optical performance is very promising for future application in optical sensing field.

Quantifying Cell Confluency by Plasmonic Nanodot Arrays to Achieve Cultivating Consistency.

The determination of cell confluency and subculture timing for cell culture consistency is crucial in the field of cell-based research, but there is no universal standard concerning optimal confluence. In this study, gold nanodot arrays on glass substrates were used as culture substrates, and their spectral shifts of localized surface plasmon resonance (LSPR) were employed to monitor cell growth and quantify cell confluency. Experiments including cell counting, metabolic activity, focal adhesion, and cell cycle were also performed to confirm the cell growth monitoring accuracy of the LSPR signals. The LSPR signal exhibited the same trends like the increase of cell numbers and cell metabolic activity and reached the maximum as the cell growth achieved confluency, suggesting its great capability as an effective indicator to predict suitable subculture timing. The proposed sensing approach is a noninterventional, nondestructive, real-time, and useful tool to help biologists quantify the optimal subculture timing, achieve cell culture consistency, and obtain reproducible experimental results efficiently.

Highly sensitive and wide-range nanoplasmonic detection of fibrinogen using erythrocyte membrane-blanketed nanoparticles

Fibrinogen, which is a glycoprotein that circulates in the blood, plays various important biological roles, e.g., in blood coagulation, fibroblast proliferation, angiogenesis, and wound healing. Abnormal levels of fibrinogen in plasma have been identified as a key biomarker of a variety of disorders from cardiovascular diseases to hemophilia. Therefore, the development of a quantitative assay for fibrinogen in the blood has emerged as an important issue for the prevention and diagnosis of these diseases. Meanwhile, it is well known that erythrocytes can selectively capture fibrinogen because of the fibrinogen receptor expressed on their plasma membrane. Inspired by these biological interactions, herein, we devised an erythrocyte membrane (EM)-blanketed biosensor based on localized surface plasmon resonance (LSPR) for highly sensitive detection of fibrinogen. By placing the EM onto a nanoparticle-on-substrate, we enhanced the LSPR signal, achieving highly sensitive and selective detection of fibrinogen. We demonstrated that fibrinogen detection is possible over a wide concentration range, 0.001–5.000 mg/mL, which can cover normal and pathological blood fibrinogen levels. In addition, it was verified that the biosensor selectively detects fibrinogen in comparison with other human-blood-plasma components. The nanoplasmonic sensor blanketed with the EM opens up new opportunities for the development of a robust fibrinogen-sensing technology.

A localized surface plasmon resonance-amplified immunofluorescence biosensor for ultrasensitive and rapid detection of nonstructural protein 1 of Zika virus.

Among the members of flaviviruses, the Zika virus (ZIKV) remains a potent infectious disease agent, with its associated pandemic prompting the World Health Organization (WHO) to declare it a global public health concern. Thus, rapid and accurate diagnosis of the ZIKV is needed. In this study, we report a new immunofluorescence biosensor for the detection of nonstructural protein 1 (NS1) of the ZIKV, which operates using the localized surface plasmon resonance (LSPR) signal from plasmonic gold nanoparticles (AuNPs) to amplify the fluorescence intensity signal of quantum dots (QDs) within an antigen-antibody detection process. The LSPR signal from the AuNPs was used to amplify the fluorescence intensity of the QDs. For ultrasensitive, rapid, and quantitative detection of NS1 of the ZIKV, four different thiol-capped AuNPs were investigated. Our biosensor could detect the ZIKV in a wide concentration range from 10–107 RNA copies/mL, and we found that the limit of detection (LOD) for the ZIKV followed the order Ab-L-cysteine-AuNPs (LOD = 8.2 copies/mL) > Ab-3-mercaptopropionic acid-AuNPs (LOD = 35.0 copies/mL). Immunofluorescence biosensor for NS1 exhibited excellent specificity against other negative control targets and could also detect the ZIKV in human serum.

Molybdenum Oxide Nanosheets with Tunable Plasmonic Resonance: Aqueous Exfoliation Synthesis and Charge Storage Applications

AbstractHerein, a simple aqueous‐exfoliation strategy is introduced for the fabrication of a series of MoO3−x nanosheets (where x stands for oxygen vacancies) using two commercial molybdenum oxide precursors, MoO2 and MoO3. The nanosheets offer a localized surface plasmon resonance (LSPR) effect which is dependent on the structure and local environment of the nanosheets. The LSPR can be efficiently tuned by changing the weight ratio between the molybdenum oxide precursor(s) and/or by solar light irradiation using a low‐energy UV lamp (36 W). For the pristine MoO3−x nanosheets, the highest LSPR signal is obtained for nanosheets prepared using 80% MoO2. On the contrary, after solar light irradiation, the nanosheets prepared using pure MoO3 offer the highest LSPR response. The nanosheets also show an outstanding rate capability when used as binder‐free supercapacitor electrodes in an acidified Na2SO4 electrolyte. The electrodes exhibit discharge capacities of 110 and 75 C g−1 at a scan rate of 20 and 1000 mV s−1, respectively. The MoO3−x nanosheets can likewise be used as a negative electrode material for lithium‐ion batteries. The efficient eco‐friendly synthesis and the ability to tune the photochemical and electrochemical properties of the nanosheets make this approach interesting to many energy‐related research fields.

Single-step detection of norovirus tuning localized surface plasmon resonance-induced optical signal between gold nanoparticles and quantum dots

A new method of label free sensing approach with superior selectivity and sensitivity towards virlabel-freeon is presented here, employing the localized surface plasmon resonance (LSPR) behavior of gold nanoparticles (AuNPs) and fluorescent CdSeTeS quantum dots (QDs). Inorganic quaternary alloyed CdSeTeS QDs were capped with L-cysteine via a ligand exchange reaction. Alternatively, citrate stabilized AuNPs were functionalized with 11-mercaptoundecanoic acid to generate carboxylic group on the gold surface. The carboxylic group on the AuNPs was subjected to bind covalently with the amine group of L-cysteine capped CdSeTeS QDs to form CdSeTeS QDs/AuNPs nanocomposites. The fluorescence of CdSeTeS QDs/AuNPs nanocomposite shows quenched spectrum of CdSeTeS QDs at 640 nm due to the close interaction with AuNPs. However, after successive addition of norovirus-like particles (NoV-LPs), steric hindrance-induced LSPR signal from the adjacent AuNPs triggered the fluorescence enhancement of QDs in proportion to the concentration of the target NoV-LPs. A linear range of 10−14 to 10−9 g mL−1 NoV-LPs with a detection limit of 12.1 × 10−15 g mL−1 was obtained. This method was further applied on clinically isolated norovirus detection, in the range of 102–105 copies mL−1 with a detection limit of 95.0 copies mL−1, which is 100-fold higher than commercial ELISA kit. The superiority of the proposed sensor over other conventional sensors is found in its ultrasensitive detectability at low virus concentration even in clinically isolated samples. This proposed detection method can pave an avenue for the development of high performance and robust sensing probes for detection of virus in biomedical applications.

Surface Plasmon Resonance Characteristics of Au Nanoparticles Layered Sensor Chip for Direct Detection of Stress Hormone Conjugated by Nanoparticles

In this study, localized surface plasmon resonance (LSPR) effect was characterized for immuneassay to detect cortisol conjugated nanoparticles (NPs) using a cuvette-compatible Au NPs layered sensor chip. A neuro stress hormone, cortisol, as target molecule was conjugated to 2 nm, 5 nm, 30 nm, and 40 nm Au NPs or 14 nm zinc oxide (ZnO) NPs to enhance the LSPR detection signals as plasmonic coupling elements with respect to cortisol monoclonal antibody (c-Mab) of probe molecule, which was immobilized on the Au NPs layered sensor. The cortisol conjugated 2 nm and 5 nm Au NPs and 14 nm ZnO NPs, which were selectively immune- bound to the c-Mab coated Au NPs sensor, showed LSPR effects to induce absorbance increases under UV-Vis spectroscopy. Also, the cortisol conjugated 2 nm, 5 nm, 30 nm and 40 nm Au NPs could show disparate plasmonic coupling effects to shift maximum absorbance wavelength peaks. Even though the cortisol conjugated 14 nm ZnO NPs could show increased absorbance only, the conjugation of cortisol to both Au and ZnO NPs was proved to enhance direct LSPR detection of the cortisol, which could not be explicitly sensed by itself for direct LSPR signal.

Biomolecule-templated photochemical synthesis of silver nanoparticles: Multiple readouts of localized surface plasmon resonance for pattern recognition

Silver nanoparticles (AgNPs) with distinct localized surface plasmon resonance (LSPR) absorption spectra can be synthesized using different proteins as templates upon irradiation by light. We utilized the multiple readouts of LSPR signals of AgNPs to construct sensor arrays for pattern recognition of proteins. Room temperature, aqueous solutions, and lack of harsh reducing reagents make the whole process inherently “green”. Meanwhile, the strategy efficiently simplified the process of array-receptor preparation and data acquisition, leading to lower time consumption, sample use, and cost. Furthermore, the system can differentiate proteins using flexible and alterable sensor elements by choosing different combinations of LSPR signals at different wavelengths. The principle of the sensor design can also be further extended to differentiate other biomolecules. The study provides a new method to construct feasible, economical, and general nanoparticle-based sensing arrays for pattern recognition.

LSPR and Interferometric Sensor Modalities Combined Using a Double-Clad Optical Fiber.

We report on characterization of an optical fiber-based multi-parameter sensor concept combining localized surface plasmon resonance (LSPR) signal and interferometric sensing using a double-clad optical fiber. The sensor consists of a micro-Fabry-Perot in the form of a hemispherical stimuli-responsive hydrogel with immobilized gold nanorods on the facet of a cleaved double-clad optical fiber. The swelling degree of the hydrogel is measured interferometrically using the single-mode inner core, while the LSPR signal is measured using the multi-mode inner cladding. The quality of the interferometric signal is comparable to previous work on hydrogel micro-Fabry-Perot sensors despite having gold nanorods immobilized in the hydrogel. We characterize the effect of hydrogel swelling and variation of bulk solution refractive index on the LSPR peak wavelength. The results show that pH-induced hydrogel swelling causes only weak redshifts of the longitudinal LSPR mode, while increased bulk refractive index using glycerol and sucrose causes large blueshifts. The redshifts are likely due to reduced plasmon coupling of the side-by-side configuration as the interparticle distance increases with increasing swelling. The blueshifts with increasing bulk refractive index are likely due to alteration of the surface electronic structure of the gold nanorods donated by the anionic polymer network and glycerol or sucrose solutions. The recombination of biotin-streptavidin on gold nanorods in hydrogel showed a 7.6 nm redshift of the longitudinal LSPR. The LSPR response of biotin-streptavidin recombination is due to the change in local refractive index (RI), which is possible to discriminate from the LSPR response due to changes in bulk RI. In spite of the large LSPR shifts due to bulk refractive index, we show, using biotin-functionalized gold nanorods binding to streptavidin, that LSPR signal from gold nanorods embedded in the anionic hydrogel can be used for label-free biosensing. These results demonstrate the utility of immobilizing gold nanorods in a hydrogel on a double-clad optical fiber-end facet to obtain multi-parameter sensing.

Fabrication and measurement of microtip-array-based LSPR sensor using bundle fiber

In this paper, we present a micro electro mechanical systems (MEMS)-technology-based localized surface plasmon resonance (LSPR) sensor using a uniformly distributed noble metal nanostructure array on a silicon microtip. The conventional LSPR sensor based on chemically synthesized metal nanoparticles exhibits a lack of reproducibility, which is caused by rearrangement and irregular sizes of metal nanoparticles. This problem strongly affects the LSPR sensing performance and reliability. To overcome this problem, we propose a novel fabrication process of the LSPR sensor using the microtip. The deposited gold is exposed using a self-aligned etching process at the tip end and it is used as gold nanoparticles. The whole process for the fabrication of the microtip is possible using a single photolithography mask. The detailed fabrication process is introduced and analyzed. In addition, the improved reproducibility in terms of fabrication and measurement of the fabricated sensor is assessed by reliability tests. Moreover, the LSPR signals with varying refractive indices of media are measured to verify the feasibility of the microtip-based LSPR sensor system.

An Assay Using Localized Surface Plasmon Resonance and Gold Nanorods Functionalized with Aptamers to Sense the Cytochrome-c Released from Apoptotic Cancer Cells for Anti-Cancer Drug Effect Determination.

To determine the degree of cancer cell killing after treatment with chemotherapeutic drugs, we have developed a sensitive platform using localized surface plasmon resonance (LSPR) and aptamers to detect the extracellular cytochrome-c (cyto-c), a mitochondrial protein released from cancer cells for the induction of apoptosis after treatment, to evaluate the effectiveness of cancer therapy. In this assay, a short single-stranded 76-mer DNA aptamer with a unique DNA sequence, which binds towards the cyto-c like an antibody with a high binding affinity and specificity, was conjugated to gold nanorods (AuNR) for LSPR sensing. Practically, cyto-c was first grabbed by a capturing antibody functionalized on the surface of micro-magnetic particles (MMPs). Subsequently, the AuNR-conjugated aptamer was added to form a complex sandwich structure with cyto-c (i.e., (MMP-Ab)-(cyto-c)-(AuNR-aptamer)) after washing away the non-target impurities, such as serum residues and intracellular contents, in a microfluidic chip. The sandwich complex led to formation of AuNR aggregates, which changed the LSPR signals in relation to the amount of cyto-c. With the LSPR signal enhancement effects from the AuNRs, the detection limit of cyto-c, sparked in human serum or culture medium, was found to be 0.1 ng/mL in our platform and the whole sensing process could be completed within two hours. Moreover, we have applied this assay to monitor the apoptosis in leukemia cancer cells induced by a potential anti-cancer agent phenylarsine oxide.

A highly sensitive and widely adaptable plasmonic aptasensor using berberine for small-molecule detection

Localized surface plasmon resonance (LSPR) biosensors allow label-free detection of small molecules in molecular binding events; however, they are limited by a relatively low sensitivity and narrow dynamic range. Here, we report highly sensitive small-molecule detection by LSPR peak shift exploiting the G-quadruplex (GQx) structure-binding characteristic of known GQx binders to enhance the LSPR signal of a plasmonic aptasensor. Six known GQx binders (thiazole orange, malachite green, crystal violet, zinc protoporphyrin IX, thioflavin T, and berberine) were tested for their ability to enhance the LSPR signal. Among these, berberine (BER) induced the largest LSPR peak shift by interacting with the GQx structure formed by the aptamer/target binding event on a gold nanorod surface. This specific binding performance was confirmed by the fluorescence signal of BER and through repeated cycles of BER addition and washing on the plasmonic sensing chip. The proposed plasmonic aptasensor respectively showed limit of detection (LOD) of 0.56, 0.63, 0.87 and 1.05 pM for ochratoxin A, aflatoxin B1, adenosine triphosphate and potassium ions, which was 1000-fold higher than that in BER-free condition, and a wide dynamic range from 10 pM to 10μM. In addition, the proposed LSPR aptasensor could effectively be used to quantitatively analyze small molecules in real samples.

Polarization dependence of tip-enhanced Raman and plasmon-resonance Rayleigh scattering spectra

Tip-enhanced Raman scattering (TERS) spectroscopy has high sensitivity and high spatial resolution, although it shows low reproducibility due to the variable optical properties of the tips. In the present study, polarized scattering spectra of localized surface plasmon resonance (LSPR) at the apex of the tip induced by conventional dark field illumination were compared with the corresponding TERS spectra, generated by excitation using polarization not only parallel and perpendicular to the tip, but also vertical to the sample plane (z-polarization). The polarization-dependence of LSPR was consistent with that of the TERS. Thus, the optical properties of the tip can be easily optimized before TERS measurement by excitation polarization that induces the largest LSPR signal.

Versatility of a localized surface plasmon resonance-based gold nanoparticle-alloyed quantum dot nanobiosensor for immunofluorescence detection of viruses

Flu infection, caused by the influenza virus, constitutes a serious threat to human lives worldwide. A rapid, sensitive and specific diagnosis is urgently needed for point-of-care treatment and to control the rapid spread of this disease. In this study, an ultrasensitive, rapid and specific localized surface plasmon resonance (LSPR)-induced immunofluorescence nanobiosensor has been developed for the influenza virus based on a gold nanoparticle (AuNP)-induced quantum dot (QD) fluorescence signal. Alloyed quaternary CdSeTeS QDs were synthesized via the hot-injection organometallic route and were subsequently capped with l-cysteine via a ligand exchange reaction. AuNPs were synthesized in HEPES buffer and thiolated with l-cysteine. The concept of the biosensor involves the conjugation of anti-neuraminidase (NA) antibody (anti-NA Ab) to thiolated AuNPs and the conjugation of anti-hemagglutinin (HA) antibody (anti-HA Ab) to alloyed quaternary l-cysteine-capped CdSeTeS QDs. Interaction of the antigens displaying on the surface of the influenza virus target with anti-NA Ab-conjugated AuNPs and anti-HA Ab-conjugated QDs induces an LSPR signal from adjacent AuNPs to trigger fluorescence-enhancement changes in the QDs in proportion to the concentration of the target virus. The detection limit for influenza H1N1 virus was 0.03pg/mL in deionized water and 0.4pg/mL in human serum; while, for the clinically isolated H3N2, the detection limit was 10PFU/mL. The detection of influenza virus H1N1 was accomplished with high sensitivity. The versatility of the biosensor was demonstrated for the detection of clinically isolated influenza virus H3N2 and norovirus-like particles (NoV-LPs).

Varying the morphology of silver nanoparticles results in differential toxicity against micro-organisms, HaCaT keratinocytes and affects skin deposition

The use of silver nanoparticles (Ag NPs) within the healthcare sector and consumer products is rapidly increasing. There are now a range of diverse-shaped Ag NPs that are commercially available and many of the products containing nanosilver are topically applied to human skin. Currently, there is limited data on the extent to which the antimicrobial efficacy and cytotoxicity of Ag NPs is related to their shape and how the shape of the Ag NPs affects their distribution in both intact and burn wounded human skin after topical application. In this study, we related the relative Ag NP cytotoxicity to potential skin pathogens and HaCaT keratinocytes in vitro with the shape of the Ag NPs. We employed multiphoton fluorescence lifetime imaging to map the distribution of the native and unlabeled Ag NPs after topical application to both intact and burn wounded human skin using the localized surface plasmon resonance signal of the Ag NPs. Truncated plate shaped Ag NPs led to the highest cytotoxicity against both bacteria (IC50 ranges from 31.25 to 125 μg/mL depending on the bacterial species) and HaCaT keratinocytes (IC50 78.65 μg/mL [95%CI 63.88, 96.83]) thus both with similar orders of magnitude. All Ag NPs were less cytotoxic than solutions of silver nitrate (IC50 of 7.85 μg/mL [95%CI 1.49, 14.69]). Plate-shaped Ag NPs displayed the highest substantivity within the superficial layers of the stratum corneum when topically applied to intact skin and the highest deposition into the wound bed when applied to burned ex vivo human skin relative to other Ag NP shapes.

Rapid and label-free bioanalytical method of alpha fetoprotein detection using LSPR chip

Alpha fetoprotein (AFP) is a cancer marker, particularly for hepatocellular carcinoma. Normal levels of AFP are less than 20ng/mL; however, its levels can reach more than 400ng/mL in patients with HCC. Enzyme linked immunosorbent assay (ELISA) and radioimmunoassay (RIA) have been employed for clinical diagnosis of AFP; however, these methods are time consuming and labor intensive. In this study, we developed a localized surface plasmon resonance (LSPR) based biosensor for simple and rapid detection of AFP. This biosensor consists of a UV–Vis spectrometer, a cuvette cell, and a biosensor chip nanopatterned with gold nanoparticles (AuNPs). In our LSPR biosensor, binding of AFP to the surface of the sensor chip led to an increasing magnitude of the LSPR signals, which was measured by an ultraviolet-visible (UV–Vis) spectrometer. Our LSPR biosensor showed sufficient detectability of AFP at concentrations of 1ng/mL to 1μg/mL. Moreover, the overall procedure for detection of AFP was completed within 20min. This biosensor could also be utilized for a point of care test (POCT) by employing a portable UV–Vis spectrometer. Owing to the simplicity and rapidity of the detection process, our LSPR biosensor is expected to replace traditional diagnostic methods for the early detection of diseases.

Simultaneous Electrochemical Impedance Spectroscopy and Localized Surface Plasmon Resonance in a Microfluidic Chip: New Insights into the Spatial Origin of the Signal.

A novel flow-through sensor based on electrochemical impedance spectroscopy (EIS) and localized surface plasmon resonance (LSPR) for analyzing biomolecular interactions under flow and static conditions is developed and characterized. The sensor consists of a double-side gold-coated perforated polycarbonate membrane as part of a microfluidic system made of poly(dimethylsiloxane) (PDMS). LSPR and EIS measurements are carried out simultaneously by applying media changes (water to NaCl solutions), unspecific adsorption of bovine serum albumin (BSA), or specific lectin binding on glycopolymer brushes. For BSA binding at the surface, EIS sensor signals mainly contain information from the binding activities at the sensor surface at low frequencies, whereas at high frequencies the change of bulk medium is the main contribution to the EIS signal. Here, the LSPR signal corresponds with EIS signal at high frequency. In contrast, in the case of lectin binding on glycopolymer brushes (3.4 nm thick), where the binding mainly takes place in the brush layer in the vicinity of the surface, LSPR data are correlated with the EIS signals at low frequencies. This leads to the conclusion that the origin of LSPR signals strongly depends on surface coverage and can be specified by simultaneously carrying out EIS measurements.

Monitoring the electrochemical responses of neurotransmitters through localized surface plasmon resonance using nanohole array

In this study, a novel spectroelectrochemical method was proposed for neurotransmitters detection. The central sensing device was a hybrid structure of nanohole array and gold nanoparticles, which demonstrated good conductivity and high localized surface plasmon resonance (LSPR) sensitivity. By utilizing such specially-designed nanoplasmonic sensor as working electrode, both electrical and spectral responses on the surface of the sensor could be simultaneously detected during the electrochemical process. Cyclic voltammetry was implemented to activate the oxidation and recovery of dopamine and serotonin, while transmission spectrum measurement was carried out to synchronously record to LSPR responses of the nanoplasmonic sensor. Coupling with electrochemistry, LSPR results indicated good integrity and linearity, along with promising accuracy in qualitative and quantitative detection even for mixed solution and in brain tissue homogenates. Also, the detection results of other negatively-charged neurotransmitters like acetylcholine demonstrated the selectivity of our detection method for transmitters with positive charge. When compared with traditional electrochemical signals, LSPR signals provided better signal-to-noise ratio and lower detection limits, along with immunity against interference factors like ascorbic acid. Taking the advantages of such robustness, the coupled detection method was proved to be a promising platform for point-of-care testing for neurotransmitters.

Investigation of enhancement of near-field probing for sensing at terahertz waveband

Enhancement of localized surface plasmon resonance (LSPR) for near-field probing working at terahertz waveband is an important issue. Optimization of an apertureless metallic probe is presented for the purpose of sensing and detection in high resolution. Numerical calculation is carried out for the purpose of design and optimization of the probe. Corresponding results demonstrate that performance enhancement of the probe at terahertz waveband is different from that of the visible regime. Unlike the visible case that the smaller size of the probe apex results in stronger LSPR, actually, it is opposite to the case of visible for the terahertz regime while the size of probe apex d is ranging from 0 to 20nm. The enhancement of the probe working at terahertz regime is mainly dominated by surface effect. In addition, the numerical results give a proof again that exciting SPP enhanced LSPR signal at near-field for the terahertz wavelength is surely difficult than that of the visible case.

Localized surface plasmon sensing based investigation of nanoscale metal oxidation kinetics

The localized surface plasmon resonance (LSPR) of nanoparticles can be a powerful and sensitive probe of chemical changes in nanoscale volumes. Here we have used the LSPR of silver (Ag) to study the oxidation kinetics of nanoscopic volumes of cobalt (Co) metal. Bimetal nanoparticles of the immiscible Co–Ag system prepared by pulsed laser dewetting were aged in ambient air and the resulting changes to the LSPR signal and bandwidth were used to probe the oxidation kinetics. Co was found to preferentially oxidize first. This resulted in a significant enhancement by a factor of 8 or more in the lifetime of stable Ag plasmons over that of pure Ag. Theoretical modeling based on optical mean field approximation was able to predict the oxidation lifetimes and could help design stable Ag-based plasmonic nanoparticles for sensing applications.