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Hybrid Silver Nanocubes for Improved Plasmon-Enhanced Singlet Oxygen Production and Inactivation of Bacteria
摘要： Plasmonic nanoparticles can strongly interact with adjacent photosensitizer molecules, resulting in significant alteration of their singlet oxygen (1O2) production. In this work, we report the next generation of metal-enhanced 1O2 nanoplatforms exploiting the lightning rod effect, or plasmon hot spots, in anisotropic (non-spherical) metal nanoparticles. We describe the synthesis of Rose Bengal decorated silica-coated silver nanocubes (Ag@SiO2-RB NCs) with silica shell thicknesses ranging from 5 to 50 nm based on an optimized protocol yielding highly homogeneous Ag NCs. Steady-state and time-resolve 1O2 measurements demonstrate not only the silica shell thickness dependence on the metal-enhanced 1O2 production phenomenon, but also the superiority of this next generation of nanoplatforms. A maximum enhancement of 1O2 of approximately 12-fold is observed with a 10 nm silica-shell, which is amongst the largest 1O2 production metal enhancement factor ever reported for a colloidal suspension of nanoparticles. Finally, the Ag@SiO2-RB NCs were benchmarked against Ag@SiO2-RB nanospheres previously reported by our group, and the superior 1O2 production of Ag@SiO2-RB NCs resulted in improved antimicrobial activities in photodynamic inactivation experiments using both gram-positive and -negative bacteria model strains.
关键词： Plasmonic nanoparticles,photodynamic inactivation,singlet oxygen,Rose Bengal,silver nanocubes,bacteria
更新于2025-09-04 15:30:14
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Towards understanding the enhancement of antibacterial activity in manganese doped ZnO nanoparticles
摘要： In this work we focus on enhancing the antibacterial activity of ZnO nanoparticles by Mn doping, synthesized using a wet-chemical method. The as-obtained precursor powders were deeply investigated by thermal analyses correlated with the evolved gas analysis (TG-DTA-FT-IR) and by in situ high-temperature XRD to elucidate the thermally induced processes and to understand the manganese doped ZnO nanoparticles formation. The hexagonal wurtzite-type structure and the morphological characteristics of the thermally treated samples have been investigated by X-ray diffraction, and HRTEM. An average particle size ranging between 10 to 29 nm and a polyhedral and spherical morphology with a tendency to form aggregates were evidenced by TEM images. Optical absorption measurements reveal that the band gap of ZnO decreased from 3.19 to 2.99 eV, which confirmed the existence of Zn-O-Mn interaction. The incorporation of the Mn ions into the ZnO lattice has been studied by EPR spectroscopy and also, the generation of reactive oxygen species (ROS) has been evidenced by using the EPR coupled with the spin trapping probe technique. Here, we report that in addition to altering the crystallite size, morphology and optical absorption characteristics of ZnO, the introduction of Mn dopant also improves the antibacterial efficiency against pathogenic microorganisms, namely Escherichia coli and Bacillus cereus.
关键词： Mn doping,antibacterial activity,ZnO nanoparticles,reactive oxygen species,wet-chemical synthesis
更新于2025-09-04 15:30:14
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Antioxidant and Photocatalytic Activity of Aqueous Leaf Extract Mediated Green Synthesis of Silver Nanoparticles Using <i>Passiflora edulis f. flavicarpa</i>
摘要： The purpose of this study is to minimize the negative impacts of synthetic procedures and to develop environmentally benign procedures for the synthesis of metallic nanoparticles. In the present study, Passiflora edulis f. flavicarpa (P. edulis) aqueous leaf extract mediated green synthesis of silver nanoparticles are described. The synthesized silver nanoparticles were characterized by UV-Vis Spectroscopy, Fluorescence Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) Transmission Electron Microscopy (TEM) and Cyclic Voltammetry (CV). The silver nanoparticles (AgNPs) showed antibacterial activities against both gram positive (staphylococcus) and gram negative (Escherichia coli) bacteria. The efficacy of the synthesized silver nanoparticles (AgNPs) was demonstrated as catalyst in the photocatalytic degradation of Methyl Orange (MO) and Methylene Blue (MB) dyes which were measured spectrophotometrically. The study revealed that biosynthesized silver nanoparticles using Passiflora. edulis f. flavicarpa, plant extract was found to be very effective as antioxidant agent.
关键词： Photocatalytic Activity,Green Synthesis,Silver Nanoparticles,Passiflora edulis f. flavicarpa,Antioxidant
更新于2025-09-04 15:30:14
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Magnetodielectric effect in a metamaterial consisting of xerogel with embedded ε-Fe2O3 iron oxide nanoparticles
摘要： The ε-Fe2O3 iron oxide is a fairly rare polymorphic modification, which only exists in the form of nanoparticles embedded, as a rule, into a silica gel matrix. This magnetically ordered iron oxide, which exhibits a significant room-temperature coercivity, is a ferroelectric; therefore, the magnetoelectric and magnetodielectric properties of this material evoke keen interest. In this work, we investigate the magnetodielectric (MD) effect in a metamaterial consisting of xerogel SiO2 with embedded ε-Fe2O3 nanoparticles 9 nm in size on average in a concentration of 20 mass.%. This bulk material exhibits the MD effect in a wide temperature range. The temperature behavior of the permittivity is related to the magnetic state of the ε-Fe2O3 oxide, which undergoes the magnetic transition from the magnetically hard to magnetically soft phase in the temperature range of 80–150 K, indicating the interplay of the ε-Fe2O3 magnetic and charge subsystems.
关键词： ε-Fe2O3,magnetodielectric effect,xerogel,multiferroics,nanoparticles
更新于2025-09-04 15:30:14
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Preparation of C60 Nanowhiskers/NiS2 Nanocomposites and Photocatalytic Degradation of Organic Dyes
摘要： [C60]Fullerene nanowhiskers/NiS2 nanocomposites were prepared by a reaction of NiS2 nanoparticles and C60 nanowhiskers. The C60 nanowhiskers (FNWs) were synthesized by a liquid-liquid interfacial precipitation method using solvent solutions, such as benzene and toluene saturated with C60 powder and isopropyl alcohol. The NiS2 nanoparticles were synthesized by a reaction of NiCl2·H2O and Na2S2O3·5H2O in deionized water under microwave irradiation. The C60 nanowhiskers/NiS2 nanocomposites were calcined in an electric furnace at 700 °C for 2 h. The C60 nanowhiskers/NiS2 nanocomposites were characterized by X-ray diffraction and UV-visible spectrophotometry. The C60 nanowhiskers/NiS2 nanocomposites were evaluated as a photocatalyst by UV-visible spectrophotometry in the degradation of organic dyes, such as methylene blue and brilliant green, under ultraviolet light at 365 nm.
关键词： [C60]Fullerene nanowhiskers,Brilliant green,NiS2 nanoparticles,Photocatalytic degradation,Methylene blue
更新于2025-09-04 15:30:14
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Synthesis and Characterization of Glucuronic Acid Capped CdO and CdS Nanoparticles
摘要： Cadmium oxide and cadmium sulphide nanoparticles have been prepared with variety of stabilizers for different purposes and glucuronic acid is used for capping CdS and CdS nanoparticles. These nanoparticles were prepared by using cadmium acetate with thioacetamide for CdS and cadmium chloride and the strong base for CdO nanoparticles. The as obtained CdO and CdS nanoparticles were characterized by a combination of microscopy and spectroscopic techniques for their morphology, size and crystallinity. The glucuronic acid-capped CdS and CdO nanoparticles showed blue shifts in their absorption band edges and with emission maxima red shifted from the band edge. The particles were obtained with good crystallinity and spherical in shape with relatively narrow size distribution.
关键词： Cadmium sulphide,Cadmium oxide,Nanoparticles,Thioacetamide,Glucuronic acid
更新于2025-09-04 15:30:14
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Fabrication of Silver-coated Gold Nanoparticles to Simultaneously Detect Multi-class Insecticide Residues in Peach with SERS Technique
摘要： Fast sampling and multicomponent detections are important in the analysis of pesticide residues detection. In this work, surface-enhanced Raman scattering (SERS) method based on silver-coated gold nanoparticles (Au@Ag NPs) was used to simultaneously detect multi-class pesticide residues such as thiacloprid (carbamate), profenofos (organophosphate) and oxamyl (neonicotinoid) in standard solution and peach fruit. The Au@Ag NPs with 26 nm Au core size and 6 nm Ag shell thickness exhibited significant Raman enhancement, especially by the creation of hot spots through NPs aggregation induced by the connection between Au@Ag NPs and target molecules. The findings demonstrated that the characteristic wavenumber of the pesticides (thiacloprid, profenofos, and oxamyl) could be precisely identified using the SERS method. Compared with earlier studies, the current approach was rapid, inexpensive and without lengthy sample pretreatment. Moreover, the results revealed that the limit of detection (LOD) was 0.1 mg/kg for thiacloprid obtained in the peach extract with determination coefficient (R2) of 0.986. Additionally, LOD for both profenofos and oxamyl was 0.01 mg/kg with a determination coefficient (R2) of 0.985 and 0.988, respectively. Good recovery percentage (78.6 to 162.0 %) showed the high SERS activity with better accuracy for the detection of the thiacloprid, profenofos, and oxamyl in peach. The results of this study could offer a promising SERS platform for simultaneous detection of other contaminants such as thiacloprid, profenofos and oxamyl in multifaceted food matrices.
关键词： oxamyl,substrate,fruit,SERS,thiacloprid,simultaneous detection,profenofos,core-shell nanoparticles
更新于2025-09-04 15:30:14
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Excitation-independent hollow orange-fluorescent carbon nanoparticles for pH sensing in aqueous solution and living cells
摘要： We report an ingenious strategy for fabrication of hollow orange fluorescent carbon nanoparticles (HFCNs) and demonstrate their applications for pH biosensing and fingerprint detection. HFCNs have been synthesized using 5-amino salicylic acid as carbon source via one-step hydrothermal treatment without further surface passivation or modification. The as-prepared HFCNs possess excellent hollow structure and bright orange fluorescence. The HFCNs display a remarkable emission enhancement in the orange fluorescence region when the pH is increased from 3.0 to 10.0. The pKa value of HFCNs is found to be 5.97 and a good linearity is shown in the pH range of 5.25–6.75, which makes HFCNs an effective intracellular pH imaging agent for acidic microenvironments. The confocal fluorescent microscopic images of HFCNs-stained latent fingerprint are achieved successfully, suggesting that they have great promise for practical criminal investigations as a simple, fast, and accurate tool.
关键词： Orange fluorescence,Hollow,pH sensing,Carbon nanoparticles
更新于2025-09-04 15:30:14
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Ionic Radii and Concentration Dependency of RE <sup>3+</sup> (Eu <sup>3+</sup> , Nd <sup>3+</sup> , Pr <sup>3+</sup> and La <sup>3+</sup> ) Doped Cerium Oxide Nanoparticles for Enhanced Multi-Enzyme Mimetic and Hydroxyl Radical Scavenging Activity
摘要： The anti-oxidant activity of cerium oxide nanoparticles (CNPs) depends on the concentration of oxygen vacancies and Ce3+ active sites. In the present work, we report the impact of 5 mol% tri-valent rare earth doped (RE3+ = Eu3+, Nd3+, Pr3+ and La3+) CNPs on the oxidation state modulation and anti-oxidant property with respect to ionic radii. An increase in lattice parameter, strain and oxygen vacancy concentration was observed as a function of ionic radii. Among the various dopants in CNP, La3+ with higher ionic radii having smaller crystallite size (7.9 nm) and higher vacancy displayed better peroxidase, oxidase and hydroxyl radical (HO?) scavenging activity. The kinetic parameters for the peroxidase and oxidase activity was found to be superior with Km = 0.217 mM and 0.261 mM, respectively, for 5 mol% La3+ doped CNPs. In order to divulge the role of dopants concentration on structural properties, we also explored using 10 and 20 mol% La3+ doping in CNP. Due to smaller crystallite size (6.7 nm) and higher defect level (3.12 x 1021 cm-3), 20% La3+ doping showed superior peroxidase and oxidase activity as shown by the low Km values. CNPs exhibit both peroxidase and oxidase activity in a concentration dependent manner. Moreover, CNPs exhibit a concentration dependent peroxidase and oxidase activity that can be selectively activated for various theranostic applications. Thus, our results demonstrate the crucial role of ionic radii and concentration of RE3+ dopants on the defect formation in cerium oxide nanoparticles for improved anti-oxidant properties of ceria.
关键词： ionic radii,RE3+ doping,oxygen vacancies,peroxidase activity,oxidase activity,hydroxyl radical scavenging,cerium oxide nanoparticles,anti-oxidant properties
更新于2025-09-04 15:30:14
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Direct Observation of Curved Surface Enhanced Disordering in Ag <sub/>2</sub> S Nanoparticles
摘要： Surface induced order-disorder phase transition has been widely studied on flat bulk surfaces, while such a transition is poorly understood on curved surfaces in nanoscale. Here, we report a direct observation of the dynamic behaviors of surface-initiated disordering in Ag2S nanoparticles using atomic resolution in-situ transmission electron microscopy. It was found that the disordering behavior is different from the traditional model that the disordered layer follows a logarithmical thickness dependence with temperature. In particular, the disordering is largely enhanced at higher temperature when the radius of the residual order phase is getting smaller. Moreover, the correlation length of disordered phase was found to be several times larger than the typical value for bulk surfaces. This significantly enhanced disordering in nanoparticles could be attributed to the extra driving force provided by the decreasing of order-disorder interface area.
关键词： nanoscale,Ag2S nanoparticles,in-situ TEM,phase transition,surface-initiated disordering
更新于2025-09-04 15:30:14