Surface Plasmon Of Ag Nanoparticles Research Articles

An advanced photo-oxidation process for pharmaceuticals using plasmon-assisted Ag-CoFe2O4 photocatalysts

The discharge of amoxicillin (AMX) from pharmaceutical intermediates has adverse effects on aquatic ecosystems. The elimination of AMX requires advanced oxidation processes (AOPs) that utilize high-performance photocatalysts. Furthermore, the design of highly visible light photocatalysts for AOPs demands both cost-effectiveness and efficiency. In this work, a plasmon-assisted visible light photocatalyst of 2D Ag-CoFe2O4 nanohybrids was successfully synthesized and characterized with several analytical tools to degrade AMX in aqueous solutions through advanced AOPs. The results showed that the Ag-CoFe2O4 nanohybrids had excellent photocatalytic activity and stability, which could efficiently reduce the AMX concentration by 99% within 70 min under visible light irradiation. In particular, CoFe2O4 and Ag have an interfacial contact that prevents electron-hole pair recombination more effectively than pure CoFe2O4, which results in electrons in its conduction band (CB) migrating to metallic Ag sites. Thus, charge transfers between the two materials are more efficient, leading to higher photocatalytic oxidation of AMX. Furthermore, the surface plasmon of Ag nanoparticles are excited by their plasmonic resonance, which increases the absorption of visible light. The plasmon-assisted visible light photocatalyst could replace expensive and energy-intensive advanced oxidation processes (AOPs). AOPs pathways associated with AMX have been discussed in detail. The HPLC chromatogram clearly showed AMX was oxidized by four-membered B-lactam ring opening and hydroxylation with •OH. 2D Ag-CoFe2O4 heterostructure was found to be efficient, selective, and cost-effective for the degradation of several pharmaceutical compounds. Additionally, it was found to be eco-friendly and sustainable, making it a viable alternative to AOPs.

Nano Ag-enhanced photoelectric conversion efficiency in all-inorganic, hole-transporting-layer-free CsPbIBr2 perovskite solar cells

All-inorganic, hole-transporting-layer-free CsPbIBr2 perovskite solar cells have great potential for development, but their device performance needs to be further improved. Recently, metal nanostructures have been successfully applied in the field of solar cells to improve their performance. Nano Ag-enhanced power conversion efficiency (PCE) in one CsPbIBr2 perovskite solar cell utilizing localized surface plasmons of Ag nanoparticles (NPs) on the surface has been researched experimentally and by simulation in this paper. The localized surface plasmon resonance of Ag NPs has a near-field enhancement effect, which is expected to improve the light absorption of CsPbIBr2 perovskite photovoltaic devices. In addition, Ag NPs have a forward-scattering effect on the incident light, which can also improve the performance of CsPbIBr2-based perovskite photovoltaic devices. By directly assembling Ag NPs (with a size of about 150 nm) on the surface of fluorine-doped tin oxide it is found when the particle surface coverage is 10%, the CsPbIBr2 perovskite photovoltaic device achieves a best PCE of 2.7%, which is 9.76% higher than that of the control group. Without changing any existing structure in the ready-made solar cell, this facile and efficient method has huge applications. To the best of our knowledge, this paper is the first report on nano Ag-enhanced photoelectric conversion efficiency in this kind of CsPbIBr2 perovskite solar cell.

Localized surface plasmon enhanced electroluminescence of n-ZnCdO/MgO/p-GaN via Ag nanoparticle decoration

Herein, a n-ZnCdO/MgO dual-layer structure was prepared on p-GaN/c-Al2O3 substrate by pulsed laser deposition method. Then, a layer of Ag nanoparticles, obtained by annealing Ag films with different thicknesses in vacuum, were introduced onto the MgO film to form localized surface plasmon. n-ZnCdO/p-GaN heterojunction diodes were constructed by evaporating Ni/Au electrodes on the p-GaN surface and sintering In pellets on the n-ZnCdO surface. By using 6 nm and 20 nm Ag films, whose extinction spectra match to emission peak of p-GaN and n-ZnCdO respectively, electroluminescence of p-GaN and n-ZnCdO have been observably enhanced. The enhanced emissions are mainly depended on resonant coupling between electron-hole pairs in emission layers and surface plasmon of Ag nanoparticles. These results show that the heterojunction diodes can achieve the enhanced dual-mode emission by adjusting the thickness of the Ag film when the MgO blocking layer is located between n-ZnCdO and p-GaN. This work of realizing multi-color luminescence can provide an experimental method for the design of white light devices.

Multi-photon Near-infrared Quantum Cutting Enhancement By Surface Plasmon of Ag Nanoparticles Under Multi-excitation

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A simple route for spray deposition of ZnO thin films embedded with Ag nanoparticles: influence of Ag concentration on the structural, morphological, optical, and photoluminescence properties

Ag nanoparticles (NPs) were embedded in the spray-deposited ZnO thin films by simply adding AgNO3 to the stating solution. The Ag concentration was varied by adding 0, 2, 4, 6, and 10 wt% of AgNO3 to the precursor. The X-ray diffraction (XRD) pattern of the prepared films indicates the presence of both the Ag NPs with cubic structure and the ZnO thin films with hexagonal wurtzite structure. According to the field emission scanning electron microscopy (FESEM) of the surface and cross-section images, the Ag NPs are almost spherical with the average diameter of 65 nm to 99 nm depending on the Ag concentration. The ZnO thin films embedded with Ag NPs exhibit absorption peak around 500 nm, which is related to the Ag NPs surface plasmon (SP). There are two absorption edges in the transmittance spectra of the embedded films, which correspond to the bandgap of ZnO (~ 3.26 eV) and SP of Ag NPs. The photoluminescence (PL) spectra reveal that as the Ag concentration increases, the 395 nm emission related to the Zn vacancies reduces, whereas the yellow emission (570 nm) results from the coupling of ZnO excitons and Ag NPs SP increases.

Tuning of metal oxides photocatalytic performance using Ag nanoparticles integration

Water contamination is increasingly an important issue in developing and under developed countries. The main cause of water contaminations are industrial dyes and toxic chemicals. Hence many technologies are being developed to de-contaminate the toxic materials. The photocatalytic de-contamination of dyes is an effective and simple technology to purify water. Among various photocatalysts, the transition metal based oxides (TiO2, NiO and ZnO) being the state-of art photocatalytic material. But, the metal oxides have large band gap and suffers from the fact that it predominantly absorbs the Ultra Violet region of irradiation. But, any viable photocatalytic technology demands absorption in the visible light region, so as to utilize the cost-free sun light. Herein, we tune and utilize the metal oxides through the integration of Ag metal nanoparticles. The synthesized materials were completely analyzed by PXRD, HRTEM, UV, XPS and BET instruments. All TiO2/Ag, NiO/Ag and ZnO/Ag nanocomposites were subjected to photocatalytic degradation using visible light. The nanocomposites acted as photocatalyst and degrade the colorful methyl orange and colorless toxic 4-chlorophenol. Among the aforementioned three samples, TiO2/Ag exhibited best performance than ZnO/Ag and NiO/Ag. We attributed the enhancement of photocatalytic activity due to Plasmons assistance and nanoscale regime of photocatalyst. In summary, we tuned the metal oxide photocatalytic performance using the Ag nanoparticle surface Plasmon resonance.

Optimizing the performance of ZnO/Au/MgZnO/SiO2 sandwich structured UV photodetectors by surface plasmons in Ag nanoparticles

Optimizing the performance of ZnO/Au/MgZnO/SiO2 sandwich structured UV photodetectors by surface plasmons in Ag nanoparticles

Thermal annealing induced strong photoluminescence enhancement in Ag-TiO2 plasmonic nanocomposite thin films

Thin films of Ag-TiO2 plasmonic nanocomposites were fabricated on silica glass substrates by a combined approach using thermal evaporation and RF magnetron sputtering. The optical and plasmonic response of Ag-TiO2 nanocomposites were tuned with the help of thermal annealing by varying the annealing temperature from 400 °C to 600 °C. The optical absorption spectra revealed the transformation of Ag nanolayer into Ag nanoparticles upon annealing. The band gap of Ag-TiO2 nanocomposite thin films varied from 3.09 eV to 2.53 eV due to annealing. AFM studies revealed growth of nanostructures in the Ag-TiO2 nanocomposites with increase in annealing temperature. The average nanoparticle size varied from 27 nm to 230 nm upon annealing. XRD results confirmed the appearance of Ag nanoparticles along with nanostructured anatase TiO2. The photoluminescence spectra of Ag-TiO2 nanocomposites revealed significant enhancement in intensity of UV and defect emissions upon annealing at 600 °C. The observed enhancement originated from the changes in the plasmonic properties of Ag nanostructures in the nanocomposite upon annealing. The observed significant enhancement in the UV emission arises due to the resonant coupling of surface plasmons of Ag nanoparticles with the band edge emission from TiO2 which significantly improved the number of electrons in the conduction band of TiO2. The PL enhancement in the visible region is ascribed to increased creation of shallow traps in TiO2 due to the presence of Ag nanoparticles. This work provides a simple route to strong enhancement in PL intensity of nanostructured TiO2 thin film which is very promising for applications in nanophotonics.

Time-resolved photoluminescence study of tris(8-hydroxyquinolinato) aluminium with surface plasmon resonance of Ag nanoparticles

Surface plasmon resonance (SPR) of Ag nanoparticles (NPs), and its emission enhancement properties are investigated by time-resolved photoluminescence spectroscopy using tris(8-hydroxyquinolinato)aluminium (Alq3), which is generally applied in organic light-emitting diode, as the emitter. 5-nm-thick Ag island-films were fabricated, and annealed at various temperatures to vary the size of the Ag NPs. The peak position of the SPR band in the absorption spectra of Ag NPs blue-shifts with increasing annealing temperature, that is, the SPR frequency is controlled by the NP size. Comparison of the photoluminescence (PL) spectra of Alq3 with and without Ag NPs annealed at 150 °C indicates 1.2-fold enhancement of PL for Alq3 with Ag NPs compared to the reference Alq3. From the temperature dependence of the PL intensity and lifetime of Alq3 with Ag NPs, we evaluated the degree of enhancement of the radiative recombination rate in the presence of the localized surface plasmon of Ag NPs, in comparison with the competitive non-radiative quenching process.

Plasmonically enhanced lasing by different size silver nanoparticles-silver film hybrid structure

Abstract We reported on the enhanced lasing in organic dyes based on plasmonic hybrid structure of Ag nanoparticles (NPs)-Ag film, the diameters of Ag NPs ranged from 20 nm to 100 nm. The lowest lasing threshold was achieved by the optimal size Ag NPs-Ag film hybrid structure, which was reduced by 5.2 times than that of the neat gain medium. Comparing to the separate Ag NPs or Ag film, the hybrid structure presented the more intense local electric field due to the plasmonics coupling between the localized surface plasmons of Ag NPs and the surface plasmon polariton of Ag film, and the stronger scattering due to the reinjection of the leaking photons by external feedback of Ag film. The effects of different sizes Ag NPs-Ag film hybrid structures on lasing were investigated. It found that when the Ag NPs in hybrid structure is small (diameter≤40 nm), the enhanced localized electric field plays a major role on enhanced lasing; with the increase of Ag NPs size, the enhanced electric field and scattering have comparable contribution on enhancing lasing; for the larger size Ag NPs-Ag film (diameter≥80 nm), the scattering effect is the dominant mechanism for random lasing. Then the lowest threshold was dominated by the balance of enhanced localized electric field and scattering effect. Our results could provide us a unique idea to effectively enhance the lasing of organic dyes, and realize the lower pumped threshold and stronger lasing.

Enhanced photoluminescence of CsPbBr3@Ag hybrid perovskite quantum dots

CsPbBr3@Ag hybrid nanocrystals are synthesized, where photoluminescence was significantly enhanced by localized surface plasmons of Ag nanoparticles.

SERS-active ZnO/Ag hybrid WGM microcavity for ultrasensitive dopamine detection

Dopamine (DA) is a potential neuro modulator in the brain which influences a variety of motivated behaviors and plays a key role in life science. A hybrid ZnO/Ag microcavity based on Whispering Gallery Mode (WGM) effect has been developed for ultrasensitive detection of dopamine. Utilizing this effect of structural cavity mode, a Raman signal of R6G (5 × 10−3 M) detected by this designed surface-enhanced Raman spectroscopy (SERS)-active substrate was enhanced more than 10-fold compared with that of ZnO film/Ag substrate. Also, this hybrid microcavity substrate manifests high SERS sensitivity to rhodamine 6 G and detection limit as low as 10−12 M to DA. The Localized Surface Plasmons of Ag nanoparticles and WGM-enhanced light-matter interaction mainly contribute to the high SERS sensitivity and help to achieve a lower detection limit. This designed SERS-active substrate based on the WGM effect has the potential for detecting neurotransmitters in life science.

Synthesis, structure and optical data storage properties of silver nanoparticles modified with azobenzene thiols

Silver nanoparticles modified with photoresponsive azobenzene thiol ligands are prepared and the interaction between them has been investigated through photoisomerization behaviour by UV–vis spectroscopy. Upon irradiation with UV light at 365 nm, an increase of the absorbance centered at 445 nm corresponding to the n–π* transition band of cis azobenzene isomers is observed for azobenzene solution without Ag and a decrease of the absorbance centered at 445 nm is observed for azobenzene solution with Ag, showing strong interaction of azo chromophores with surface plasmons of Ag nanoparticles, in particular when the absorption bands are overlapped with each other. The enhanced light-responsivity has been confirmed by two-photon induced optical data storage experiments. An image can be recorded on the photoactive film doped with 7 wt% silver nanoparticles modified with azobenzene thiol ligands under writing power of 25 mW, but is failed to be recorded in the azobenzene film without Ag even under the same recording condition.

Enhanced optical output power by the silver localized surface plasmon coupling through side facets of micro-hole patterned InGaN/GaN light-emitting diodes.

Light extraction efficiency of GaN-based light emitting diodes were significantly enhanced using silver nanostructures incorporated in periodic micro-hole patterned multi quantum wells (MQWs). Our results show an enhancement of 60% in the wall-plug efficiency at an injection current of 100 mA when Ag nano-particles were deposited on side facet of MQWs passivated with SiO2. This improvement can be attributed to an increase in the spontaneous emission rate through resonance coupling between localized surface plasmons in Ag nano-particles and the excitons in MQWs.

Enhancing the Surface-State Emission in Trap-Rich CdS Nanocrystals by Silver Nanoparticles

It is well known that surface plasmon resonance (SPR) can selectively enhance the photoluminescence (PL) from nearby chromophores with a single emission peak at an appropriate distance. Here, we combine white light-emitting CdS quantum dot nanocrystals containing band-edge and surface-state emissions simultaneously with Ag nanoparticles and study the interaction between them. It is found that the surface-state emission is always enhanced while the band-edge emission quenched regardless of the SPR wavelength of Ag nanoparticles. This phenomenon reveals that the SPR of Ag nanoparticles is not enhancing the emission from a wavelength-matched state. We propose that the surface plasmon of Ag nanoparticles is first excited by the energy of the band-edge emission and then the excited energetic electrons transfer to the surface-state of CdS. Through this energy transfer process, the surface-state emission is enhanced and band-edge emission quenched. This investigation can not only deliver understanding of the complicated interaction between metallic nanoparticles and nearby multi-emission-peak contained chromophores, but it also has potential applications in tuning the color temperature of white light-emitting materials.

Improvement of the efficiency and power output of solar cells using nanoparticles and annealing

Silver nanoparticles have been deposited on crystalline Si solar cell surfaces using direct-current (DC) magnetron sputtering. The influence of localized surface plasmons in Ag nanoparticles (NPs) on the performance of annealed solar cells has been investigated. We find that the localized surface plasmons can improve the thermal stability of annealed solar cells. When the cell with 8% Ag nanoparticle coverage is annealed at 600°C for 10min, approximately 40% increase in short-circuit current (Isc) and approximately 50% increase in maximum power (Pm) are observed.

Localized surface plasmon of Ag nanoparticles affected by annealing and its coupling with the excitons of Rhodamine 6G

Clean and uniformly distributed silver nanoparticles (AgNPs) are deposited on glass substrates using a vacuum evaporation process. The localized surface plasmon resonance (LSPR) of these AgNPs is successfully tuned from 420 to 780 nm by changing the evaporation time from 20 to 180 s. Further, it is found that the LSPR can be shifted to shorter wavelength in the range of 410 to 478 nm by annealing in flowing nitrogen at 200 °C for 10 min. The blueshift is correlated with the changes in microscopic features of the AgNPs, as revealed by SEM and AFM images. Rhodamine 6G (R6G) was chosen as the probe molecule to explore its coupling with AgNPs before and after annealing. Analysis of extinction spectra suggests that strong coupling takes place when the LSPR is close to the absorption of R6G.

Surface plasmon-enhanced Ag/CuS nanocomposites for cancer treatment.

Photothermal therapy (PTT) for cancer treatment is the use of heat between 41 and 45 °C to damage cancer cells. As a new type of transducer agent for PTT of cancer, CuS nanoparticles have several advantages. The most favorable features are the low cost, simple, and easy preparation and small size for targeting. However, the CuS nanoparticle PTT efficacy needs to be improved for practical applications. In this study, the CuS nano-PTT efficiency is enhanced via the local field enhancement from Ag nanoparticle surface plasmon coupling. The results show that absorbance of CuS nanoparticles in Ag/CuS nanocomposites is enhanced about four times by Ag nanoparticle surface plasmon coupling. Consequently, the PTT efficacy is enhanced and a power of 0.6 W/cm2 with a 980-nm laser is sufficient for Ag/CuS nano-PTT activation for cancer treatment in vitro observations.

RESEARCH ON OPTICAL ABSORPTION CHARACTERISTICS OFAgNANOPARTICLES

In this work, Ag nanoparticles were deposited on quartz glass substrates by magnetron sputtering method, and the morphology was characterized by SEM. Ag nanoparticle surface plasmon resonance characteristics were observed by transmittance measurement. The experimental results demonstrated an increase in particle size that was correlated to an increase in sputtering time and a plasmon resonance absorption peak redshift. This phenomenon was partially explained by Mie scattering model. The differences between our theoretical analysis and experimental results show that both the shape of and the spacing between nanoparticles are key parameters affecting plasmon resonance peak location.

Stable surface plasmon enhanced ZnO homojunction light-emitting devices

Ag nanoparticle surface plasmon enhanced ZnO homojunction light-emitting devices (LEDs) have been constructed. It is found that the Ag nanoparticles can increase the emission of the devices greatly, and the Ag nanoparticle decorated LEDs degrade little after placing in ambient air for three months, revealing their good stability.