Silver Nanoprisms Research Articles

"All-in-One" Silver Nanoprism Platform for Targeted Tumor Theranostics.

Designing a multifunctional theranostic nanoplatform with optional therapeutic strategies is highly desirable to select the most suitable therapeutic manners for the patient's cancer treatment. Among all shapes of silver materials, a silver nanoprism was reported to have great potential in photothermal therapy (PTT) owing to its strong surface plasmon resonance band in the near-infrared region. However, its instability in physicochemical environments and its severe toxicity confined its further application. To overcome this, herein, we demonstrated a silver prism-polydopamine (PDA) hybrid nanoplatform for tumor treatment with three therapeutic strategies. Specifically, the PDA coating endows the silver prism with excellent stability, high photothermal conversion, long-term in vivo biocompatibility, ease of decorating targeting ligands, and drug delivery. Upon near-infrared laser irradiation (808 nm, 1 W/cm2), tumors can be eradicated by the as-prepared nanoparticle through monomodal PTT. Besides, when combined with a chemical drug, this nanoparticle is able to inhibit tumor growth via combined photochemotherapy under a lower laser treatment (0.7 W/cm2). Furthermore, by supplementing with an immune checkpoint blockade, the realized synergistic photochemoimmunotherapy exhibits high efficacy to inhibit tumor relapse and metastasis. Moreover, owing to the high photothermal conversion efficiency and great X-ray attenuation ability of the silver nanoprism, our designed nanoplatform can be used in photoacoustic, computed tomography, and infrared thermal multimodal imaging. Our study provides a multifunctional nanoparticle for tumor theranostics, and this therapeutic strategy-optional nanoplatform shows promise in future biomedicine.

Thermal performance and physicochemical stability of silver nanoprism-based nanofluids for direct solar absorption

To utilize nanofluids for direct absorption solar collectors (DASCs), they need to maintain their performance and physicochemical stability with exposure to solar radiation. In the present studies, three water-based nanofluids were characterized under light exposure, including silver nanoprisms (AgNPrs), silica coated silver nanoprisms (SiO2@AgNPr) and silica (SiO2) nanoparticles. Their temperature profiles and stability were monitored using simulated sunlight (SSL) and natural sunlight exposure (NSL), quantified by UV-vis spectroscopy and, in the case of SSL, characterized by transmission electron microscopy (TEM). With SSL both silver nanofluids showed an increase in maximum temperature of approximately 40–45 °C, with a photo-conversion efficiency of about three times greater than the SiO2 nanofluid and water base-fluid. Stability tests showed the SiO2@AgNPr nanomaterial to be morphologically unstable, with the AgNPrs etching over a period of several hours. The AgNPrs showed a higher tendency to aggregation than SiO2@AgNPr nanofluids when exposed to NSL sunlight over a two-week period. Contrarily, the latter exhibited notable changing in shape, consequently effecting the absorption band position. The results highlight strongly the need for stability trials under realistic conditions for the development of nanofluids for direct solar absorption.

Plasmonic Effects on the Growth of Ag Nanocrystals in Solution.

The light-stimulated transformation of ensembles of spherical nanoparticles into anisotropic metal nanostructures mediated by localized surface plasmon resonance (LSPR) excitation is an elegant way of synthesizing triangular silver nanoprisms with extraordinary control over size and shape. Generally, the transformation occurs in oxidizing environments along a pathway that involves the oxidative etching of small preexisting Ag seeds, followed by plasmon-mediated reduction of the resulting Ag ions and Ag0 incorporation into the anisotropic nanocrystals. Here, we investigate pathways toward Ag nanoprisms from initially homogeneous AgNO3 solutions held under reducing conditions. Observations using in situ electron microscopy show that reducing environments and high Ag precursor concentrations in the presence of sodium citrate favor two alternative transformation routes of initial spherical nuclei into anisotropic nanoprisms: (i) the aggregation of spherical nanoparticles and plasmon-mediated conversion of small clusters into triangular prisms; (ii) shape fluctuations of individual small nanoparticles. Simulated field distributions confirm that the coupling of the LSPR excitation between closely spaced nanoparticles causes significant field enhancements near the local plasmonic hot spots, which facilitates accelerated Ag incorporation and thus supports the transformation into nanoprisms.

Colorimetric captopril assay based on oxidative etching-directed morphology control of silver nanoprisms.

Oxidative etching is an effective approach to control the morphology of nanomaterials. Taking silver nanocrystals (AgNCs) as an example, oxidative etching-directed morphological transformation from a triangular prism shape to a disk shape is achieved and then applied to the determination of captopril. As a mediator, trace amount of halides play important roles in the shape-controlled evolution of AgNCs. Etching causes the color of the triangular silver nanoprims (AgNPRs) to change from blue to yellow on formation of round nanodisks. On addition of captopril, the oxidative etching of the AgNPRs is prevented owing to the protection by the drug via Ag-S bonding. In this case, the solution color does not change. This finding was used to design an assay of captopril that has a linear response in the 10-600nM concentration range and a 2nM limit of detection. This method also allows digital camera read-out. It was successfully applied to quality control of captopril in tablets. Graphical abstractOxidative etching-directed morphological transformation of silver nanocrystals is well manipulated and successfully applied in colorimetric determinationof captopril in tablets.

Resonant energy transfer and light scattering enhancement of plasmonic random lasers embedded with silver nanoplates.

The resonant energy transfer enhancement from a plasmonic random laser (PRL) has been investigated by means of a dye-covered PVA film with embedded silver nanoplates (DC-PVA/AgNPs). Different sizes and morphologies of AgNPs were adopted to shift the localized surface plasmon resonance (LSPR) and intensify recurrent light scattering between the AgNPs. For better overlap between surface plasmon resonance and the photoluminescence of fluorescent molecules with appropriately-sized silver nanoprisms, the slope efficiency of the PRL was greatly enhanced and the lasing threshold was obviously reduced. In addition, the photon lifetime for the DC-PVA/AgNPs film reveals an apparent decline around 1.39 ns owing to better coupling with LSPR. The stronger light scattering of samples with bigger-sized silver nanoprisms has been demonstrated by coherent back scattering measurements, which reveals a smaller transport mean free path around 3.3 μm. With α-stable analysis, it has been successfully demonstrated that the tail exponent α can be regarded as an identifier of the threshold of random lasing.

Optimized DNA-based biosensor for monitoring Leishmania infantum in human plasma samples using biomacromolecular interaction: a novel platform for infectious disease diagnosis.

Leishmania parasite identification is very important in clinical studies of leishmaniasis and its diagnosis. Though there are various clinical and epidemiological approaches to identifying Leishmania infantum, due to some limitations of the traditional methods, sensitive and specific techniques are needed and are in great demand. To achieve selective and rapid detection, a sensitive signal transducer with high surface area is necessary. In this work, a new paper sensor was fabricated using silver nanoprisms electrodeposited on the GQD conductive nano-ink (Ag NPr/GQDs nano-ink). A high surface area and suitable interface for anchoring biomolecules was achieved by electrodepositing gold nanoparticles (AuNPs) functionalized with cysteamine (AuNPs-CysA) on the surface of the paper sensor altered by Ag NPr/GQDs nano-ink. To prepare a sensitive and selective bio-device for the recognition of Leishmania in human plasma specimens, a DNA-thiol probe was stabilized on the surface of the platform. Hybridization of DNA was evaluated by chronoamperometry (ChA). The engineered DNA-based paper biosensor showed high sensitivity and selectivity for the identification of Leishmania genomic DNA. Under optimum circumstances, a linear range was obtained using photographic paper from 1 μM to 1 zM and an ivory sheet from 1 nM to 1 zM. The lower limits of quantitation (LLOQ) on the photographic paper and ivory sheet were 1 zM. In addition, the designed DNA-based biosensor revealed well-defined performance in the recognition of mismatched sequences (single base, two base and three base mismatches) and selectivity.

Optical properties of nanopatch antennas based on plasmonic nanoparticles and ruthenium complex

In this work, a significant reduction (up to 7 ns) of the excited states lifetime of the Ru dye (with a decay time of 850 ns) in an inhomogeneous «aluminium – silver nano-prism system (nano-patch antenna, NPA)», as well as an increase in the photoluminescence emitter to 2-3 times. The increase in the spontaneous emission rate of this substance is caused by the Purcell effect. The Purcell coefficient for the emitter in the cavity with hexagonal silver particles was 120. This decrease in the spontaneous emission decay time in the nano-patch antenna configuration is associated with an increase in the local density of photon states in the plasmon resonator, which increases the probability of a spontaneous transition from the excited state of the emitter. The results obtained by shortening the spontaneous emission time and increasing the intensity of the emitter radiation in a nano-patch antenna show possible prospects for using quantum dots and individual molecules with shorter luminescence times in nano-patch antennas. Such nano-patch antennas can form the basis for creating compact high-speed optical devices. Modeling in the mathematical package Comsol Multiphysics showed that the maximum values of the Purcell factors can exceed 104 in the NPA.

Enhancing Colorectal Cancer Radiation Therapy Efficacy using Silver Nanoprisms Decorated with Graphene as Radiosensitizers

Metal nanoparticles have significant interaction cross-sections with electromagnetic waves due to their large surface area-to-volume ratio, which can be exploited in cancer radiotherapy to locally enhance the radiation dose deposition in tumors. We developed a new type of silver nanoparticle composite, PEGylated graphene quantum dot (GQD)-decorated Silver Nanoprisms (pGAgNPs), that show excellent in vitro intracellular uptake and radiosensitization in radiation-sensitive HCT116 and relatively radiation-resistant HT29 colorectal cancer cells. Furthermore, following biodistribution analysis of intravenously injected nanoparticles in nude mice bearing HCT116 tumors radiosensitization was evaluated. Treatment with nanoparticles and a single radiation dose of 10 Gy significantly reduces the growth of colorectal tumors and increases the survival time as compared to treatment with radiation only. Our findings suggest that these novel nanoparticles offer a promising paradigm for enhancing colorectal cancer radiation therapy efficacy.

Plasmonic Nanocavity Metasurface Based on Laser-Structured Silver Surface and Silver Nanoprisms for the Enhancement of Adenosine Nucleotide Photoluminescence

A reliable photoluminescence (PL) spectroscopy and imaging of biomolecules at room temperature is a challenging and important problem of biophysics, biochemistry, and molecular genetics. A unique effect of strong plasmonic enhancement of the PL by metal nanostructures is one of the most effective approaches for this purpose. The highest enhancement is provided by metal nanostructures with densely packed sharp tips, periodically arranged metal nanostructures, and plasmonic cavities. All of these features have been realized in the plasmonic cavity metasurface based on the silver (Ag) laser-induced periodic surface structure and Ag triangular nanoprisms studied in the present work. The strong plasmon-enhanced PL of 5′-deoxyadenosine monophosphate deposited on such metasurfaces has been revealed at room temperature. The observed enhancement of more than 1000-fold has been interpreted as a result of synergetic action of the generation of a high concentration of hot spots near the sharp edges of the laser-induc...

Does engineering of nanoshapes have antibacterial synergy with magnetic signal exposure?

The widespread use of antibiotics in diverse areas led many bacterial strains to become highly resistant. Thus, considerable concerns were recently raised to overcome and/or to find other alternatives to the use of antibiotics. In this context, combining antibacterial effects of exposure to pulsed magnetic signals and supplying of silver nanoparticles recently indicated a significant bactericidal impact. The interplay between silver nanoshapes (spheres, rods and prisms) and exposure to pulsed magnetic signals (0·32 mT, 20 Hz–30 min) was studied to explore whether engineering of silver nanoshapes has a synergistic antibacterial effect against Klebsiella pneumoniae. In this regard, the bacterial growth rates, kinetics and enzymatic changes (protein leakage and lactate dehydrogenase levels) were investigated. The results confirmed that silver nanoprisms with a higher specific-area-to-volume ratio and appreciable analogy of charge distribution exhibit the highest synergistic inhibition effect with pulsed magnetic signals by 35% at 10 parts per million concentration. Moreover, the coupling of magnetic signals with nanoprisms showed significant cellular injuries and loss of membrane integrity as a consequence of the elevation of lactate dehydrogenase and protein leakage levels by more than fivefold and 15-fold, respectively. These new findings substantiate the antibacterial synergism of silver nanoparticles with pulsed magnetic signals in a shape-dependent manner.

Plasmonic Silver Nanoprism-Induced Emissive Mode Control between Fluorescence and Phosphorescence of a Phosphorescent Palladium Porphyrin Derivative.

We have succeeded in significantly enhancing fluorescence from intrinsically phosphorescent palladium octaethylporphyrin (Pd-porphyrin) that has an intersystem crossing efficiency of ∼1 by using silver nanoprisms (AgPRs). This was achieved by controlling the wavelength of the localized surface plasmon (LSP) resonance of AgPRs and the distance between the Pd-porphyrin molecules and the AgPR surfaces. In addition to enhancing phosphorescence by spectrally overlapping the phosphorescence band with the LSP resonance band, tuning the LSP wavelength to approximately 520 nm led to the appearance of a new emission band around the wavelength corresponding to the fluorescent radiation. The appearance of fluorescence suggests that the nonradiative energy transfer from the singlet excited state of Pd-porphyrin to the LSP of AgPRs overcame the ultrafast intramolecular intersystem crossing to the triplet excited state, manifesting the spectral properties of the singlet excited state of Pd-porphyrin. The fluorescence nature of this radiation was strongly supported by lifetime measurements of the hybrids of Pd-porphyrin and AgPRs. Furthermore, the dependence of the emissive intensities on the distance between the Pd-porphyrin molecules and the AgPR surfaces showed interesting opposite trends. The fluorescence intensity was increased as the distance between the molecules and the AgPRs was decreased from 10.5 to 1 nm, while the phosphorescence intensity was decreased, which indicates that the LSP-induced fluorescence radiation process from Pd-porphyrin near the AgPRs outweighed the quenching by the AgPRs, even though the phosphorescence significantly suffered quenching.

Green synthesis of photomediated silver nanoprisms via a light-induced transformation reaction and silver nanoprism-impregnated bacteria cellulose films for use as antibacterial wound dressings

Silver nanoprisms are used as antimicrobial agents for medical applications due to their large surface area, which provides better contact with microorganisms. However, silver nanoprisms are toxic to mammalian cells. To alleviate this problem, synthesis of silver nanoprisms via a light-induced transformation reaction with LED light was proposed. This reaction was ecofriendly and excluded hazards from the use of harmful oxidizing agents. Different shape and size of the as-grown silver nanocrystals could be distinguished by their colors. Results showed that the nano-octahedron photomediated silver nanoprisms showed the strongest bacterial inhibition with MIC and MBC value of 6.74, 6.74, 13.38, and 6.74 μg/mL against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and methicillin-resistant Staphylococcus aureus (MRSA), respectively. Silver nanoprisms were later impregnated within bacterial celluloses (BC) and the resulting composite films (PAgNPrs/BC) also exhibited the antibacterial activity against the four above microbes. Indirect cytotoxicity evaluation of the PAgNPrs/BC-composite films with human dermal fibroblasts proved that these films were non-toxic. All the results suggested that the PAgNPrs/BC-composite films could be used to care for certain infectious wounds.

Strategies for Surface Modification with Ag-Shaped Nanoparticles: Electrocatalytic Enhancement of Screen-Printed Electrodes for the Detection of Heavy Metals.

Screen-printed carbon nanofiber electrodes (SPCNFEs) represent an alternative with great acceptance due to their results, as well as their low impact on the environment. In order to improve their performance, in the present work they were modified with silver nanoparticles (Ag-NPs) and electrochemically characterized by using anodic stripping voltammetry. From the Ag-NP synthesis, silver seeds (Ag-NS) and silver nanoprisms (Ag-NPr) were obtained. The Ag-NP formation was confirmed by micrographs, where Ag-NPs with diameters of 12.20 ± 0.04 nm for Ag-NS and 20.40 ± 0.09 nm for Ag-NPr were observed. The electrodes were modified by using three different deposition methods—drop-casting, spin-coating, and in situ approaches—that offer different nanoparticle distribution and electrode modification times. It was observed that the last methodology showed a low amount of Ag-NS deposited on the electrode surface and deep alteration of this surface. Those facts suggest that the in situ synthesis methodology was not appropriate for the determination of heavy metals, and it was discarded. The incorporation of the nanoparticles by spin-coating and drop-casting strategies showed different spatial distribution on the electrode surface, as proved by scanning electron microscopy. The electrodes modified by these strategies were evaluated for the cadmium(II) and lead(II) detection using differential pulse anodic stripping voltammetry, obtaining detection limit values of 2.1 and 2.8 µg·L−1, respectively. The overall results showed that the incorporation route does not directly change the electrocatalytic effect of the nanoparticles, but the shape of these nanoparticles (spherical for seeds and triangular for prisms) has preferential electrocatalytic enhancement over Cd(II) or Pb(II).

Correlative Dark-Field and Photoluminescence Spectroscopy of Individual Plasmon–Molecule Hybrid Nanostructures in a Strong Coupling Regime

Light-matter interactions play a crucial role in several prominent nano-optical phenomena, such as plasmon-mediated fluorescence, nanoscale lasing, and strong plasmon-exciton coupling. The latter holds promise for the development of nanoscale nonlinear optical schemes and room-temperature polaritonic lasers. In recent years, strong coupling in nanoscale plasmon-exciton systems, also known as plasmon-exciton polaritons, has been thoroughly investigated using transmission, reflection, and dark-field scattering spectroscopies. However, only a few recent studies performed experiments using photoluminescence spectroscopy on the individual hybrid nanostructure level. The latter is important for the detailed understanding of intrinsic excited state dynamics in strongly coupled systems. Here, we use correlative dark-field scattering (DF) and photoluminescence (PL) measurements to study polaritonic states in individual silver nanoprisms surrounded by molecular J-aggregates. We investigate these systems under various experimental conditions, including temperatures in the range T = 4-300 K, laser excitation wavelengths at 532, 568, and 640 nm, and a broad range of plasmon-exciton detunings. Our findings indicate that the lower energy peak in PL emission closely follows the lower polariton band observed in DF, while the higher energy PL peak follows the emission of uncoupled J-aggregate molecules and incoherent states. These observations further improve the understanding of excited state dynamics in strongly coupled plasmon-exciton systems.

(Invited) Enhancement of Triplet-Triplet Annihilation-Based Upconversion Emission By Localized Surface Plasmon Resonance

The upconversion emission systems using triplet-triplet annihilation (TTA-UC emission) has attracted much attention because these systems can be driven by a noncoherent light with low intensity (e.g. sunlight). Namely, the achievement of efficient TTA-UC emission systems directly leads to the development of high-performance solar energy devices. On the other hand, since the Dexter energy transfer between the sensitizers and the emitters is contained in the process of TTA-UC emission, the emission efficiency is quite low in solid state. We have tried to enhance the emission in solid state TTA-UC systems by interacting with the localized surface plasmon (LSP) resonance of metal nanoparticles. The anisotropic triangular silver nanoplates (silver nanoprisms: AgPRs) were employed as a plasmonic metal nanoparticle because of the generating wavelength tunability of their LSP resonance and the generation of strong local electromagnetic fields. The hybrids of AgPRs and TTA-UC systems were fabricated by spin-coating the polymer solution containing the sensitizer (palladium(II) tetraphenyltetrabenzoporphyrin: Pd-TPTBP) and the emitter (9,10-bis(phenylethynyl)anthracene: BPEA) onto the AgPRs-immobilized glass plates. When the LSP resonance band of AgPRs spectrally overlapped with both the photoexcitation wavelength of Pd-TPTBP and the fluorescence band of BPEA, the TTA-UC emission was efficiently enhanced. It is reasonable to consider that the former spectral overlap provides the enhancement of TTA-UC emission through the photoexcitation enhancement of Pd-TPTBP (Figure 1). In addition, the threshold excitation intensity (the figure-of-merit in TTA-UC systems) significantly decreased by overlapping the LSP resonance band with the photoexcitation wavelength. Also, it was suggested by the fluorescence lifetime measurements that the enhancement of TTA-UC emission caused by overlapping with the fluorescence band was induced by the efficient nonradiative energy transfer from the singlet excited BPEA to the LSP of AgPRs (Figure 1). On the other hand, when the LSP resonance band overlapped well with the phosphorescence band of Pd-TPTBP, the TTA-UC emission was rather quenched. These results suggest that the nonradiative energy transfer by the LSP resonance from the triplet excited Pd-TPTBP to the LSP became dominant, as compared with the triplet-triplet energy transfer from the Pd-TPTBP to the BPEA. Namely, it was demonstrated that the LSP resonance of AgPRs has both of the positive and negative effects on the solid state TTA-UC emission systems.[1] Furthermore, we investigated the optical interaction between the singlet excited palladium porphyrin and the LSP resonance of AgPRs. Consequently, we will discuss the detailed effects of LSP resonance of the AgPRs on the complicated TTA-UC emission processes. [1] S. Jin, K. Sugawa et al., ACS Photon., 2018, 5, 5025-5037. Figure 1

Colorimetric probe for Ni2+ based on shape transformation of triangular silver nanoprisms upon H2O2 etching

In this article, a highly sensitive and selective colorimetric method for the detection of Ni2+ ions is presented on the basis of hydrogen peroxide etching of triangular silver nanoprisms (AgNPrs). Triangular AgNPrs were synthesized by a modified seed-mediated growth method, and upon addition of Ni2+ ions these triangular AgNPrs showed a significant colorimetric change from blue to reddish brown, and eventually yellow to as a function of the Ni2+ ion concentration. Ni2+ ion do not act as a selective etchant to triangular AgNPrs, but instead serve as a catalyst for the generation of H2O2 in a citrate-capped triangular AgNPr colloidal solution. The oxidative etching with H2O2 formed in the colloidal solution sculptured the sharp corners/edges of the triangular AgNPrs to produce circular Ag nanodisk. Selectivity tests for Ni2+ ions by the triangular AgNPr probe were performed in the presence of other various cations and anions at the optimized conditions (pH 8, 15 °C, and 30 min of reaction time). The probe showed a high linearity between absorption ratio (A475/A750) and concentration in the range of 0 to 30 μM of Ni2+, with a limit of detection of 21.6 nM in aqueous solution. The color and UV–vis absorption spectrum of the triangular AgNPr probe indicated that it is quite stable for two weeks in ambient temperature and pH ranges of 4.0˜10.0. This triangular AgNPr probe was successfully employed for the detection of Ni2+ ions in spiked tap and pond water samples.

Application of bacterial cellulose–silver nanoprism composite for detoxification of endosulfan and inactivation of Escherichia coli cells

This study demonstrates the suitability of a bacterial cellulose–silver nanoprism composite for detoxification of endosulfan and disinfection of water spiked with Escherichia coli cells. Nanoprisms were synthesized using sodium borohydride reduction in combination with hydrogen peroxide-assisted etching. Characterization of nanoparticles using absorption spectroscopy and electron microscopy revealed the presence of silver nanoprisms ranging from 7 to 37 nm. Analysis using inductively coupled plasma atomic emission spectroscopy revealed the successful doping of silver nanoprisms onto bacterial cellulose pellicles through overnight immersion of the polymer in the colloidal solution containing free nanoparticles. The bacterial cellulose–silver nanoprism composite (2.5 mg of Ag0/g of bacterial cellulose) along with Mg0 system removed > 99% of 10 mg L−1 of endosulfan after 45 min of reaction by transforming into its end product, bicyclo-hept-5-ene-2,3-diol. The BC–Ag0 composite exhibited biocidal activity against E. coli (3 × 104 CFU mL−1), and the extent of reduction was ~ 99% after 65 min of contact. The BC–Ag0 composite could be reused successfully for 5–6 cycles of degradation of endosulfan with an efficacy of ~ 86% and 6–7 cycles of disinfection with > 99% antimicrobial activity against E. coli. The leaching of silver was below the permissible limit (0.1 mg L−1). Results obtained from this study suggest that the bacterial cellulose–silver nanoprism composite could be used for remediation of water contaminated with chlorinated pesticides such as endosulfan and infectious bacteria. It can be concluded that impregnation of silver nanoprisms on bacterial cellulose encourages reuse of nanoparticles, reduces environmental risks and makes the process more economical.

UV random laser emission from flexible ZnO-Ag-enriched electrospun cellulose acetate fiber matrix

We report an alternative random laser (RL) architecture based on a flexible and ZnO-enriched cellulose acetate (CA) fiber matrix prepared by electrospinning. The electrospun fibers, mechanically reinforced by polyethylene oxide and impregnated with zinc oxide powder, were applied as an adsorbent surface to incorporate plasmonic centers (silver nanoprisms). The resulting structures – prepared in the absence (CA-ZnO) and in the presence of silver nanoparticles (CA-ZnO-Ag) - were developed to support light excitation, guiding and scattering prototypes of a RL. Both materials were excited by a pulsed (5 Hz, 5 ns) source at 355 nm and their fluorescence emission monitored at 387 nm. The results suggest that the addition of silver nanoprisms to the ZnO- enriched fiber matrix allows large improvement of the RL performance due to the plasmon resonance of the silver nanoprisms, with ~80% reduction in threshold energy. Besides the intensity and spectral analysis, the RL characterization included its spectral and intensity angular dependences. Bending the flexible RL did not affect the spectral characteristics of the device. No degradation was observed in the random laser emission for more than 10,000 shots of the pump laser.

Controlling the Luminescence of Gold Quantum Dots by the Plasmonic Effect of Silver Nanoprisms

Plasmonic nanostructures can be used to control the photoluminescence properties of various emitting materials. In this work, an efficient plasmon-induced energy transfer (quenching) was investigated. The luminescence intensity of gold quantum dots (AuQDs) was controlled by the localized surface plasmon resonance of silver nanoprisms (AgNPrs). The quenching was modulated by the degree of spectral overlap between the photoluminescence band of AuQDs and the dipole plasmon resonance of AgNPrs. Furthermore, an in situ controlled quenching effect of AuQDs using an oxidative etching reaction of AgNPrs by hydrogen peroxide (H2O2) was demonstrated. This technique was further developed for application as a H2O2 sensor. This system was capable of detecting 1 nM H2O2 in an aqueous solution.

Protein-Protected Porous Bimetallic AgPt Nanoparticles with pH-Switchable Peroxidase/Catalase-Mimicking Activity

Bovine serum albumin (BSA)-protected AgPt bimetallic nanoparticles have been synthesized through a galvanic replacement reaction, using a silver nanoprism as a template. Synthesis was performed without the use of synthetic chemical surfactants, using proteins as a surface coating. Structural and compositional characterizations were performed using several spectroscopic and microscopic techniques. The protein-protected AgPt nanoparticles show effective pH-switchable enzyme mimicking (“nanozyme”) activity similar to catalase and peroxidase. The platinum content in the AgPt nanoparticles is playing an important role in determining the enzymatic catalysis rate of the nanoparticles. Because of their porous structure, molecular payloads such as calcein also can be incorporated into the AgPt nanoparticles, which can be released on demand by chemical triggers, such as hydrogen peroxide.