Surface Plasmon Resonance Effect Research Articles

Ultraviolet–Visible-near infrared induced photocatalytic H2 evolution over S-scheme Cu2-xSe/ZnSe heterojunction with surface plasma effects

Localized surface plasmon resonance (LSPR) effect plays a crucial role in the field of solar energy utilization. In this work, we successfully prepared a Cu2-xSe/ZnSe S-scheme heterojunction with a broad-spectrum response using the hot-injection and low-temperature water bath method. Importantly, we demonstrated that the photothermal effect induced by the LSPR of nonstoichiometric Cu2-xSe can significantly improve the slow kinetics of water splitting, resulting in an apparent activation energy reduction from 50.1 to 28.7 kJ·mol−1. This improvement is responsible for achieving the highest photocatalytic H2 evolution rate of 63.6 mmol·g−1·h−1 over 2.7 % Cu2-xSe/ZnSe under the wavelength ranged from 200 to 2500 nm, which is 3.4 and 5.6 times higher than that of ZnSe and Cu2-xSe, respectively. Furthermore, the composite exhibits a remarkable H2 production rate of 0.108 mmol·g−1·h−1 under near-infrared spectroscopy (800<λ<2500 nm), while ZnSe shows limited capability in H2 releasing. Additionally, Cu2-xSe/ZnSe demonstrates distinct photocurrent response when λ > 800 nm. The enhanced performance in H2 evolution can be attributed to the synergistic effect of LSPR-induced light absorption and S-scheme heterojunction, which not only expands the light absorption range to the near-infrared region but also facilitates hot electron injection, charge carrier separation and transfer, leading to a faster surface reaction kinetics. This study provides an effective approach for designing a broad-spectrum light responsive non-precious metal-based photothermal-assisted photocatalytic system.

Constructing plasmonic bi-enhanced chrysanthemum-like Bi/BiOClBr microspheres for efficient photocatalytic decontamination of organic pollutants

Exploring cost-effective and highly active photocatalysts is crucial for achieving the thorough breakdown of pollutants and addressing the inherent drawbacks of current photocatalytic technologies. In this research, a chrysanthemum-like Bi/BiOClBr photocatalyst was obtained for the first time using a straightforward solvothermal means. Various analytical methods were utilized to comprehensively analyze the characteristics of the composite materials. The exceptional photocatalytic effectiveness of Bi/BiOClBr was demonstrated by its efficient removal of pollutants such as rhodamine (RhB), tetracycline (TC) and ofloxacin (OFX). The presence of BiOCl and BiOBr heterostructures facilitated the movement of photogenerated carriers. Moreover, by incorporating metallic Bi into the composite, which manifests a surface plasmon resonance (SPR) effect, we not only notably augmented the composite's ability to absorb visible light but also functioned as an “electron trap,” thereby enhancing the efficiency of separating and transferring photogenerated electrons and holes. This work offered innovative perspectives in the development and fabrication of noble metal-free, decorated semiconductor photocatalysts with outstanding activity and reusability.

Synergistic Enhancement of Electron Dynamics and Optical Properties in Zeolitic Imidazolate Framework-8-Derived Zinc Oxide via Surface Plasmon Resonance Effects of Silver Nanoparticles under UV Irradiation.

This study investigates the surface plasmon resonance (SPR)-induced UV photoresponse of zinc oxide (ZnO) derived from zeolitic imidazolate framework-8 (ZIF-8) to assess the influence of silver nanoparticles (Ag NPs) on the photoresponse behavior of metal-organic framework (MOF)-derived ZnO. The initial synthesis involved a thermal treatment in air to convert ZIF-8 into ZnO. We noted enhanced optical absorption both in the UV and visible spectra with the deposition of Ag NPs onto the ZIF-8-derived ZnO. Additionally, the presence of Ag NPs in the ZnO resulted in a substantial increase in current, even without any light exposure. This increase is attributed to the transfer of electrons from the Ag NPs to the ZnO. Photocurrent measurements under UV illumination revealed that the photocurrent with Ag NPs was significantly higher-by two orders of magnitude-compared with that without Ag NPs. This demonstrates that SPR-induced absorption markedly boosted the photocurrent, although the current rise and decay time constants remained comparable to those observed with ZnO alone. Although Ag NPs contribute electrons to ZnO, creating a "pre-doping" effect that heightens baseline conductivity (even in the absence of light), this does not necessarily alter the recombination dynamics of the photogenerated carriers, as indicated by the similar rise and decay time constants. The electron transfer from Ag to ZnO increases the density of charge carriers but does not significantly influence their recombination.

Light-driven green synthesis of tea polyphenols-derived temperature-resistant and environmentally friendly filter loss reducer on MIL-100(Fe)–NH2(20) photocatalyst

Currently, most syntheses of filter loss reducers usually require harsh synthesis conditions with high energy consumption, increasing the cost and deteriorating worldwide unsustainable resource crisis. Thus, it is urgent to explore an effective green synthetic strategy for further developing filter loss reducers. In this work, the amino-modified MIL-100(Fe)–NH2(20) sphere acted as photocatalyst for the photoinduced green synthesis and possessed hierarchical mesoporous, exposed active sites, remarkable light harvesting, robust photogenerated e- − h+ pairs separation and excellent photocatalytic activity. Then, tea polyphenol (TP), acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were polymerized to form a temperature-resistant and environmentally friendly filter loss reducer (SPS) successfully through photopolymerization under Xenon lamp irradiation, and the evaluation results demonstrated that the SPS exhibited excellent rheological and loss-reducing properties, even under the high temperature and high salt conditions. During this photocatalysis, the excitation of electrons on MIL-100(Fe)–NH2(20) occurs, and resulted e- ∼ h+ pairs as free radicals were transferred to TP and vinyl monomers. After the generation of active-species-free radical cations (R•) and selective oxidation or propagation and termination, the full green synthesis cycle can be completed. Notably, the localized surface plasmon resonance (LSPR) effect and photothermal transition of MIL-100(Fe)–NH2(20) could provide sufficient temperature at the local reaction sites, enabling the polymerization with mild conditions. This study opens up new insights into the application of MOF photocatalysis in oilfield chemistry.

Examining the dual effect of copper nanoparticles and nitrogen doping on Cu@N-TiO2

Abstract The study of six compositions of Cu@N-TiO2 with different amounts of copper and nitrogen synthesized using a sol–gel method is reported. X-ray diffraction patterns and Raman spectra indicated the formation of a single anatase TiO2 phase in all materials without evidence of secondary phases including copper or nitrogen. Electron microscopy images showed a homogeneous distribution of the copper particles around a TiO2 matrix, just as that the insertion of nitrogen did not have a significant effect on the morphology of the particles. X-ray photoelectron spectroscopy analysis confirmed that nitrogen was inserted in the atomic arrangement of titanium dioxide, while copper was presented mainly as metallic element on the TiO2 surface. Characterization of the optical properties and photoactivity test confirm that band gap strongly depends on the copper and nitrogen content phenomenon attributed to the combined presence of modifiers over the TiO2 surface and the promotion of a plasmonic effect, which displaced the absorption UV bands to higher wavelengths with respect to un-doped TiO2. The catalytic test performed using rhodamine-B as probe molecule, confirm that TiCuN2 and TiCuN3 samples exhibit the best decomposition percentages of 38 and 36 % respectively. Such results confirm the surface plasmon resonance effect associated to Cu particles on the TiO2 as main cause in the increase in current along synthesized samples and the use of cyclic voltammetry technique to identify these effects between 0.0 and 1.5 V.

Ag nanoparticle-mediated LSPR effect and electron transfer for enhanced oxidative degradation process of g-C3N5 nanoflowers

The design of photocatalytic system with broad-spectrum response to sunlight and rapid electron transfer is critical for efficient destruction of diverse contaminants in various environmental situations. Herein, self-assembled supramolecular strategy was employed to anchor Ag nanoparticles on the nanoflower-like g-C3N5 surface to construct Schottky-type catalyst (ACN-1) for efficient degradation of organic contaminants. The localized surface plasmon resonance (LSPR) effect significantly improves photocatalytic activity of materials by boosting rapid transfer of interlayer energy and photogenerated electrons and extending the absorption edge of catalysts into near-infrared light region. In actual water samples, ACN-1 entirely eliminated tetracycline (k = 1.0787 min−1) within 40 min and maintained high degradation rate (more than 80 %) under various water quality parameters. Furthermore, ACN-1 demonstrated remarkable suitability to microcystin-LR (98.9 %, k = 0.08098 min−1), sulfamethoxazole (81.2 %, k = 0.02984 min−1), and methylene blue (91.4 %, k = 0.04072 min−1). Quenching experiments and ESR tests showed that main active species in system were 1O2, •O2−, and h+. Finally, five photodegradation pathways and 26 intermediates of TC were elucidated by combining ESR signals, LC-MS and Fukui index. After photodegradation treatment, the toxicity of solution was drastically reduced and the mineralization reached 62.48 %. This study provides new insights into the design and interaction mechanisms of novel g-C3N5-based catalysts and effectively contributes to remediation strategies for emerging pollutants in water.

Tunable chalcogenide solid-core anti-resonant fiber polarization filter based on SPR effect

Based on surface plasmon resonance (SPR), we proposed a tunable chalcogenide solid-core anti-resonant fiber (SC-ARF) polarization filter. The purpose of introducing the SPR, which is excited by coating the inner wall of the cladding tubes with a gold film, is to achieve a discrepancy between the confinement loss of two polarized fundamental modes (FMs). The full-vector finite element method (FV-FEM) evaluates the impact of fiber core radius, cladding tube radius, cladding tube wall thickness, and gold film thickness on the polarization filter characteristics. The results show that when the thickness of the gold film is 30 nm and the fiber length is 4 mm, the filter bandwidth can simultaneously cover the S + C + L optical communication band and reach 248 nm, and the extinction ratio (ER) value reaches -377.46 dB. Moreover, we also confirmed the tuning effect of the gold-coated cladding tube wall thickness on the resonance wavelength. The proposed fiber polarization filter has potential application value in optical fiber communication and transmission.

Regulating the Transfer of Photogenerated Carriers for Photocatalytic Hydrogen Evolution Coupled with Furfural Synthesis.

How to simultaneously utilize photogenerated electrons and holes still remains a critical challenge in the field of artificial photosynthesis, especially in the process of photocatalytic hydrogen (H2) evolution coupled with biomass oxidation to value-added chemicals. Herein, a series-parallel photocatalyst (Cu NPs/CdS/In2O3) that can intrinsically regulate the transfer of photogenerated carriers is ingeniously designed for photocatalytic H2 evolution synergized with furfural alcohol (FFA) selective oxidation to furfural (FF). Accordingly, the desired H2 and FF evolution rates with near 100% selectivity toward FF are achieved on Cu NPs/CdS/In2O3 in a sealed atmospheric system. Experimental and theoretical analyses confirm that the localized surface plasmon resonance (LSPR) effect induced by Cu NPs accelerates the reduction of protons (H+) to H2 efficiently, while the photogenerated holes from In2O3 preferentially activate the α-C-H bond of FFA adsorbed on Lewis acid sites to generate FF. This work provides a reference for regulating the transfer of photogenerated carriers for H2 evolution coupled with FF synthesis.

A novel D-shaped photonic crystal fiber refractive index sensor based on surface plasmon resonance effect

A novel D-shaped photonic crystal fiber refractive index sensor based on surface plasmon resonance effect

Mott–Schottky heterostructural TiO2@Ag@AgBr nanohybrids for efficient photocatalytic degradation of Cr (VI) and enhanced on-site SERS detection

In the study, a novel ternary composite TiO2@Ag@AgBr was successfully prepared by surface modification of complete Ag layer and AgBr particles for photocatalytic degradation of representative heavy metal ions Cr (VI) and on-site Surface-enhanced Raman spectroscopy (SERS) detection of the Cr (VI) reduction process. The Mott–Schottky heterojunction contained structure exhibited remarkable photocatalytic ability for heavy metal ions Cr (VI) by tuning the ratio of Ag and AgBr, which could reduce Cr (VI) ions within 30 min and the reaction rate constant is 0.12 min−1. The remarkable photo-reduction performance is attributed to synergistic effect among the various components: the AgBr decorated on the surface of TiO2@Ag could significantly enhance the absorption of visible light and generate numerous photoexcited electrons and holes. Furthermore, the complete Ag layer was constructed on the TiO2 microspheres surface to form heterojunctions in the photocatalytic system by in-situ deposition of AgNO3. Mott–Schottky junctions formed between AgBr/Ag and Ag/TiO2 interface which could extend the charge transfer pathway and facilitate separation of photoexcited electrons and holes. The plasmonic metal layer of nano Ag could generate significant surface plasmon resonance (SPR) effect which not only enhanced the absorption of visible light but also exhibited remarkable SERS effect for probe molecules. And an amazing detection limit of 1 × 10–10 M could be obtained when using crystal violet (CV) as probe molecules. In addition, the SERS substrates exhibited significant linear relationship between concentration and SERS signal intensity which ensures the accuracy of quantitative analysis and monitoring photoreduction process. The substrates have good cycling stability, enabling it to be reused for SERS detection many times. Thus, the excellent photocatalytic and SERS performance of Mott–Schottky hetero-structural TiO2@Ag@AgBr substrates shows great potential toward rapidly photocatalytic removal Cr (VI) ions and SERS on-site detection reduction process of Cr (VI) in waste water, which is of great significance to environmental protection and ecological restoration.

Near-infrared-II responsive ovalbumin functionalized gold-genipin nanosystem cascading photo-immunotherapy of cancer

Synergistic cancer therapies have attracted wide attention owing to their multi-mode tumor inhibition properties. Especially, photo-responsive photoimmunotherapy demonstrates an emerging cancer treatment paradigm that significantly improved treatment efficiency. Herein, near-infrared-II responsive ovalbumin functionalized Gold-Genipin nanosystem (Au–G–OVA NRs) was designed for immunotherapy and deep photothermal therapy of breast cancer. A facile synthesis method was employed to prepare the homogeneous Au nanorods (Au NRs) with good dispersion. The nanovaccine was developed further by the chemical cross-linking of Au–NRs, genipin and ovalbumin. The Au–G–OVA NRs outstanding aqueous solubility, and biocompatibility against normal and cancer cells. The designed NRs possessed enhanced localized surface plasmon resonance (LSPR) effect, which extended the NIR absorption in the second window, enabling promising photothermal properties. Moreover, genipin coating provided complimentary red fluorescent and prepared Au–G–OVA NRs showed significant intracellular encapsulation for efficient photoimmunotherapy outcomes. The designed nanosystem possessed deep photothermal therapy of breast cancer and 90% 4T1 cells were ablated by Au–G–OVA NRs (80 μg ml−1 concentration) after 1064 nm laser irradiation. In addition, Au–G–OVA NRs demonstrated outstanding vaccination phenomena by facilitating OVA delivery, antigen uptake, maturation of bone marrow dendritic cells, and cytokine IFN-γ secretion for tumor immunosurveillance. The aforementioned advantages permit the utilization of fluorescence imaging-guided photo-immunotherapy for cancers, demonstrating a straightforward approach for developing nanovaccines tailored to precise tumor treatment.

Rapid photocatalytic dye degradation, enhanced antibacterial and antifungal activities of silver stacked zinc oxide garnished on carbon nanotubes

A composite of Zinc oxide loaded with 5-weight % silver decorated on carbon nanotubes (Ag-loaded ZnO: CNT) was synthesized using a simple refluxed chemical method. The influence of deviation in the weight % of carbon nanotube loading on photocatalytic dye degradation (methylene blue and rose bengal) and antibiotic (antimicrobial and antifungal) performance was investigated in this study. The light capture ability of Ag-loaded ZnO:CNT in the visible region was higher in photocatalytic activity than that of Ag-loaded ZnO and ZnO:CNT. The bandgap of the Ag-loaded ZnO: CNT was tuned owing to the surface plasmon resonance effect. The photocatalytic degradation investigations were optimized by varying the wt% in CNTs, pH of dye solution, concentration of the dye solution, and amount of catalytic dose. Around 100% photocatalytic efficiency in 2 min against MB dye was observed for Ag doped ZnO with 10 wt% CNT composite at pH 9, at a rate constant 1.48 min−1. Bipolaris sorokiniana fungus was first time tested against a composite material, which demonstrated optimum fungal inhibition efficiency of 48%. They were also tested against the bacterial strains Staphylococcus aureus, Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium, which showed promising antibacterial activity compared to commercially available drugs. The composite of Ag doped ZnO with 5 wt% CNT has shown competitive zone inhibition efficacy of 21.66 ± 0.57, 15.66 ± 0.57, 13.66 ± 0.57 against bacterial strains Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium which were tested for the first time against Ag-loaded ZnO:CNT.

Development of Plasmonic Attapulgite/Co(Ti)Ox Nanocomposite Using Spent Batteries toward Photothermal Reduction of CO2

The rapid development of the battery industry has brought about a large amount of waste battery pollution. How to realize the high-value utilization of waste batteries is an urgent problem to be solved. Herein, cobalt and titanium compounds (LTCO) were firstly recovered from spent lithium-ion batteries (LIBs) using the carbon thermal reduction approach, and plasmonic attapulgite/Co(Ti)Ox (H-ATP/Co(Ti)Ox) nanocomposites were prepared by the microwave hydrothermal technique. H-ATP had a large specific surface area and enough active sites to capture CO2 molecules. The biochar not only reduced the spinel phase of waste LIBs into metal oxides including Co3O4 and TiO2 but also increased the separation and transmission of the carriers, thereby accelerating the adsorption and reduction of CO2. In addition, H-ATP/Co(Ti)Ox exhibited a localized surface plasmon resonance effect (LSPR) in the visible to near-infrared region and released high-energy hot electrons, enhancing the surface temperature of the catalyst and further improving the catalytic reduction of CO2 with a high CO yield of 14.7 μmol·g−1·h−1. The current work demonstrates the potential for CO2 reduction by taking advantage of natural mineral and spent batteries.

A one-pot hydrothermal synthesis of Bi/Bi2O2CO3/Bi2WO6 catalyst with enhanced photocatalytic activity to tetracycline

BackgroundThe abuse and irrational discharge of tetracycline (TC) have threatened the surroundings of human beings. Semiconductor photocatalytic oxidation technology is an emerging green environmental remediation technology, which can be widely applied in wastewater treatment. MethodsThis work is the first attempt to prepare Z-scheme heterojunction Bi/Bi2O2CO3/Bi2WO6 ternary material through one-step hydrothermal synthesis method. Significant findingsAbout 95.5 % tetracycline (10 mg·L−1) have been degraded by Bi/Bi2O2CO3/Bi2WO6 ternary material after 120 min of simulated sunlight exposure. The degradation efficiency of TC was 2.04 and 3.01 times than those of Bi2WO6 and Bi2O2CO3, respectively. Radical trapping experiments and ESR analysis showed that h+, ·O2−, and ·OH played a joint role in the degradation of tetracycline. Based on liquid chromatography-mass spectrometry analysis, energy band analysis and theoretical calculations, the degradation mechanisms were identified. The excellence photocatalytic activity is mainly attributed to two aspects: (1) The generation of Z-scheme heterojunctions provided channels for carrier transfer, accelerated interface charge separation and suppressed the rapid recombination of photo generated carriers and holes; (2) The surface plasmon resonance effect of metallic Bi intensifies photon absorption and boost photocatalytic activity. This work offers a viable method for improving the photocatalytic activity of semiconductors made of bismuth on antibiotics.

Facile synthesis of Ag/AgCl/PAF-54 heterojunction photocatalysts for TC degradation

Photocatalysis plays an increasingly important role in the field of water treatment. Among the catalysts, Ag nanoparticles (NPs), a type of noble metal NP, show extraordinary potential for photocatalysis. Nevertheless, the aggregation caused by high surface energy limits their applications. The simple synthesis of Ag NPs with uniform size remains a challenge. In this work, a nitrogen-rich porous organic polymer (POP) with reduction ability, porous aromatic framework (PAF)-54, was chosen as the carrier for the in-situ synthesis of Ag NPs. By virtue of the reducing framework of PAF-54 and the formation of the AgCl/PAF-54 heterojunction, the in-situ reduction of Ag(I) was realized, and thus Ag NPs with the particle size of 20-25 nm were uniformly distributed on PAF-54, which exhibit a strong localized surface plasmon resonance (LSPR) effect. Furthermore, the Ag/AgCl/PAF-54 heterojunction effectively suppresses the recombination of photogenerated electrons and holes, leading to the enhanced photocatalytic ability of the composite material. Even with a small catalyst dosage, rapid tetracycline (TC) degradation can be achieved, and the degradation rate of TC reached 94.8% in 30 min. This study offers a facilitated approach for fabricating Ag-based POP composites with superior photocatalytic properties.

Construction of Ultrathin BiVO4‐Au‐Cu2O Nanosheets with Multiple Charge Transfer Paths for Effective Visible‐Light‐Driven Photocatalytic Degradation of Tetracycline

AbstractIn this study, unique BiVO4‐Au‐Cu2O nanosheets (NSs) are well designed and multiple charge transfer paths are consequently constructed. The X‐ray photoelectron spectroscopy measurement during a light off‐on‐off cycle and redox capability tests of the photo‐generated charge carriers confirmed the formation of Z‐scheme heterojunction, which can facilitate the charge carrier separation and transfer and maintain the original strong redox potentials of the respective component in the heterojunction. The ultrathin 2D structure of the BiVO4 NSs provided sufficient surface area for the photocatalytic reaction. The local surface plasmon resonance (LSPR) effect of the electron mediator, Au NPs, enhanced the light absorption and promoted the excitation of hot electrons. The multiple charge transfer paths effectively promoted the separation and transfer of the charge carrier. The synergism of the abovementioned properties endowed the BiVO4‐Au‐Cu2O NSs with satisfactory photocatalytic activity in the degradation of tetracycline (Tc) with a removal rate of ≈80% within 30 min under visible light irradiation. The degradation products during the photocatalysis are confirmed by using ultra‐high performance liquid chromatography‐mass spectrometry and the plausible degradation pathways of Tc are consequently proposed. This work paves a strategy for developing highly efficient visible‐light‐driven photocatalysts with multiple charge transfer paths for removing organic contaminants in water.

Lamellar copper molybdate as a novel photocatalyst for the degradation of Rhodamine B

Water containing organic pollutants poses increasingly severe challenges to the clean water resources that humans rely on for survival. Photocatalysis is one of the technologies for removing organic pollutants from wastewater, which is green and has no secondary pollution. Here layered HCu1.5MoO5 photocatalyst is synthesized by wet chemistry. It is assembled from multiple stacked thin nanosheets with a thickness of ∼12.5 nm. The thin-layer structure of two-dimensional photocatalysts considerably reduces the migration distance of photo-generated charge carriers, thereby promoting efficient charge separation. In addition, it exhibits near-ultraviolet light response with the remarkable local surface plasmon resonance (LSPR) effect in the visible light region. The specific surface area and mesoporous structure of HCu1.5MoO5 are particularly advantageous for the mass transfer process of photocatalytic degradation. These characteristics enable it to effectively degrade Rhodamine B, achieving a degradation rate of 78.4 % after 120 min. The work provides a new perspective for the development of layered photocatalysts for photocatalytic degradation.

Plasmonic Near-Infrared-Response S-Scheme ZnO/CuInS2 Photocatalyst for H2O2 Production Coupled with Glycerin Oxidation.

Solar fuel synthesis is intriguing because solar energy is abundant and this method compensates for its intermittency. However, most photocatalysts can only absorb UV-to-visible light, while near-infrared (NIR) light remains unexploited. Surprisingly, the charge transfer between ZnO and CuInS2 quantum dots (QDs) can transform a NIR-inactive ZnO into a NIR-active composite. This strong response is attributed to the increased concentration of free charge carriers in the p-type semiconductor at the interface after the charge migration between ZnO and CuInS2, enhancing the localized surface plasmon resonance (LSPR) effect and the NIR response of CuInS2. As a paradigm, this ZnO/CuInS2 heterojunction is used for H2O2 production coupled with glycerin oxidation and demonstrates supreme performance, corroborating the importance of NIR response and efficient charge transfer. Mechanistic studies through contact potential difference (CPD), Hall effect test, and finite element method (FEM) calculation allow for the direct correlation between the NIR response and charge transfer. This approach bypasses the general light response issues, thereby stepping forward to the ambitious goal of harnessing the entire solar spectrum.

Improved photoelectrochemical performance of TiO2-in-MIL-101(Cr)@CDs@AgNPs and application for the detection of ultralow level AβO

TiO2 was successfully synthesized within the internal pores of MIL-101(Cr), leading to the formation of a TiO2-in-MIL-101(Cr) composite. This heterojunction structure significantly improved the photogenerated electron-hole separation within the metal-organic framework (MOF) composite. Subsequently, carbon dots (CDs) and silver nanoparticles (AgNPs) were introduced to further modify the TiO2-in-MIL-101(Cr), resulting in a multimodified MIL-101(Cr) composite. The integration of CDs enhanced the light absorption capabilities of the composite, thereby boosting the photocurrent. Meanwhile, AgNPs not only enhanced the absorption of visible light through the local surface plasmon resonance effect (LSPR) but also facilitated efficient electron transport. This multimodal modification strategy led to a remarkable enhancement in the photoelectrochemical (PEC) performance of MIL-101(Cr), with the photocurrent density (J) increasing by approximately a factor of 19. To further expand the functionality of this composite, AβO capture DNA (cDNA) and CuS-binding aptamer were grafted onto the TiO2-in-MIL-101(Cr)@CDs@AgNPs, creating a sandwich-like structure. Based on this multimodified MIL-101(Cr) composite, an "on-off-on" type PEC biosensor was constructed. The p-type semiconductor CuS served as a signal amplifier, capturing photogenerated electrons and effectively reducing the photocurrent. When cDNA hybridized with AβO, the Apt-CuS moiety detached from the MIL-101(Cr) composite, leading to the restoration of the photocurrent. The PEC biosensor for the detection of AβO exhibited optimal performance at a pH of 7.00, an incubation temperature of 37 °C, and an incubation time of 45 min. Under these conditions, the biosensor demonstrated a wide detection range of 5 fM to 1 μM, with an ultralow detection limit of 4.36 fM. This method exhibits high sensitivity, robust anti-interference capabilities, and holds great promise for applications in tracing the detection of AβO in human serum.

Remarkable improvement in photocatalytic activity of NiO nanoparticles through Ag doping: A kinetics-mechanism & recyclability

Metal oxides are recognized as exemplary materials for photocatalytic dye degradation attributed to their unique characteristics such as tunable electronic structure, prolonged stability, and cost-effectiveness. However, the wide band gap inherent to most of these materials often limits their light absorption to the ultraviolet (UV) region. Consequently, the doping of noble metal nanoparticles into the metal oxide nanostructures has been proposed to significantly improve their light-harvesting ability. This enhancement is primarily ascribed to the localized surface plasmon resonance (LSPR) effect associated with noble metal nanoparticles, which facilitates more effective utilization of light. Thus, in this study, we synthesized silver-doped nickel oxide (Ag:NiO) with varying Ag concentrations (0, 1, 2, 4, 6 wt%) to evaluate their photocatalytic performance. The X-ray diffraction (XRD) spectra revealed that NiO possesses a cubic crystalline structure, and a peak shift to a higher angle was noted for Ag doping, indicative of compressive strain. Further analyses of morphological, vibrational, and absorption properties were conducted through the acquisition of scanning electron microscopy (SEM) images, Raman spectra and UV–Vis absorption spectra, respectively. The photocatalytic degradation of methylene blue (MB) and rhodamine B (RhB) dyes was assessed, revealing that NiO with 4.wt.% Ag doping exhibited enhanced photocatalytic activity, achieving 99% degradation of MB and 90% degradation of RhB. Notably, Ag doping significantly enhances the light absorption capabilities and modifies the electronic structure of the NiO, thereby improving its performance in photocatalytic dye degradation.