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Pure gold saturable absorber for generating Q-switching pulses at 2?μm in Thulium-doped fiber laser cavity
摘要： We experimentally demonstrate Q-switched Thulium-doped fiber laser operating at 1949.19 nm using pure gold saturable absorber (Au-SA) as a Q-switcher. The Au-SA was fabricated by depositing gold particles molecules using electron beam evaporation on the surface of a polyvinyl alcohol (PVA) film. Subsequently, stable Q-switched pulses were obtained within the 1552 nm pump power range from 343.1 to 467.3 mW, with repetition rate tuned from 11.7 kHz to 21.95 kHz. At 467.3 mW pump power, the TDFL produced pulses train with the pulse width of 2.6 μs and the maximum pulse energy of 89.8 nJ. These results propose that pure gold could be a promising saturable absorber for pulse generation in 2 μm wavelength region.
关键词： Thulium-doped fiber laser,Q-switching,Pure gold saturable absorber
更新于2025-11-28 14:24:03
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Surface plasmon resonance of naked gold nanoparticles for photodynamic inactivation of Escherichia coli
摘要： Although antimicrobial photothermal inactivation of naked gold nanostructures using powerful pulsed lasers has been previously studied, there are little reports about their photodynamic antimicrobial properties under the irradiation of low-power density continuous wave lasers. Therefore, this paper attempts to fill this gap. In this paper, we studied the effects of a 40-mW/cm2 continuous Nd:Yag laser at 532 nm and naked gold nanoparticles on inactivation of Escherichia coli ATCC25922. According to our results, 60 min illumination using the Nd:Yag laser caused a 0.15log reduction of the bacterial viability. Also, the employed gold nanoparticles with an average size of 15 nm were toxic to E. coli ATCC 25922 in the concentrations above 0.5 μg/ml. In addition, synergistic effects of 0.5 μg/ml gold nanoparticles and the light illumination led to a 2.43log reduction of the viability after a 60-min exposure and did not show any considerable temperature change on the media. The obtained results were justified based on the possible interaction mechanisms of low-power density laser lights and naked gold nanoparticles. The paper is proposed as a prelude for future research about localized inactivation of resistant pathogens with minimum side effects on neighbor tissues.
关键词： Photodynamic inactivation,Gold nanoparticles,Low-power density laser,Surface plasmon resonance
更新于2025-11-25 10:30:42
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Direct Imaging of Current‐Induced Transformation of a Perovskite/Electrode Interface
摘要： Formamidinium-lead-iodide (FAPbI3) perovskite films are subjected to a long-term action of the constant electrical current in the dark, using planar vacuum-deposited gold electrodes. The current-induced transformation is monitored by the time-of-flight secondary ion mass spectrometry (ToF-SIMS) mapping complemented by microscopic, spectroscopic methods, and X-ray diffraction. The migration of chemical species inside the lateral interelectrode gap is clearly visualized by ToF-SIMS. Those species correspond to both electrode material and perovskite itself, so that the perovskite/electrode interface becomes disrupted. As a result, the interelectrode gap shrinks, which is reflected in the surface images.
关键词： interfaces,dark current,gold electrodes,perovskites,ToF-SIMS mapping
更新于2025-11-25 10:30:42
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Antiangiogenesis-Combined Photothermal Therapy in the Second Near-Infrared Window at Laser Powers Below the Skin Tolerance Threshold
摘要： Photothermal agents with strong light absorption in the second near-infrared (NIR-II) region (1000–1350 nm) are strongly desired for successful photothermal therapy (PTT). In this work, titania-coated Au nanobipyramids (NBP@TiO2) with a strong plasmon resonance in the NIR-II window were synthesized. The NBP@TiO2 nanostructures have a high photothermal conversion efficiency of (93.3 ± 5.2)% under 1064-nm laser irradiation. They are also capable for loading an anticancer drug combretastatin A-4 phosphate (CA4P). In vitro PTT studies reveal that 1064-nm laser irradiation can efficiently ablate human lung cancer A549 cells and enhance the anticancer effect of CA4P. Moreover, the CA4P-loaded NBP@TiO2 nanostructures combined with PTT induce a synergistic antiangiogenesis effect. In vivo studies show that such CA4P-loaded NBP@TiO2 nanostructures under mild 1064-nm laser irradiation at an optical power density of 0.4 W cm?2, which is lower than the skin tolerance threshold value, exhibit a superior antitumor effect. This work presents not only the development of the NBP@TiO2 nanostructures as a novel photothermal agent responsive in the NIR-II window but also a unique combined chemo-photothermal therapy strategy for cancer therapy.
关键词： Antiangiogenesis therapy,Gold nanobipyramids,Plasmon resonance,Core@shell nanostructures,Photothermal therapy
更新于2025-11-21 11:24:58
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Gold-tagged Polymeric Nanoparticles with Spatially Controlled Composition for Enhanced Detectability in Biological Environments
摘要： Organic nanoparticles offer the advantage of high biocompatibility for biomedical applications but suffer frequently from poor visibility in biological environments. While fluorescent-labeling is convenient and allows for fast and extensive histological analysis, fluorescence imaging and quantitative analysis are limited by low resolution and significantly hindered by tissue auto-fluorescence. Labeling of polymeric nanoparticles with an additional gold tag would allow for high resolution imaging via transmission electron microscopy (TEM) and for quantification of particles by inductively coupled plasma optical emission spectrometry (ICP-OES). However, spatially uncontrolled gold-tagging can cause significant fluorescence quenching. To overcome this restraint, 2.2 nm gold nanoparticles were introduced at the interface between the hydrophobic fluorophore-loaded core and the hydrophilic shell of polymeric nanoparticles. Due to the small size of gold labels and the spatially controlled stratified composition of hybrid nanoparticles, fluorescence quenching by gold tags was minimized to 15.1%, allowing for concomitant detection of both labels via optical microscopy after enhancement of the gold tags. Multilayered hybrid nanoparticles exhibited outstanding detectability by transmission electron microscopy, even without additional sample staining. Furthermore, they were capable of producing remarkable image contrast inside cells after gold or silver enhancement. The interfacial gold layer increased the hydrodynamic particle size only marginally from 71.8 to 89.5 nm and had no negative impact on biocompatibility in vitro. The gold content (0.75% m/m) is sufficiently high for future quantification in tissues after systemic administration. With their clean-cut structure and superior detectability, multilayered hybrid nanoparticles constitute an outstanding blueprint and a precious tool for the development of nanomedicines.
关键词： gold,polymeric nanoparticles,hybrid,TEM,PLGA,contrast agent
更新于2025-11-21 11:24:58
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Multipole Radiations from Large Gold Nanospheres Excited by Evanescent Wave
摘要： We proposed the use of the evanescent wave generated in a total internal reflection configuration to excite large gold nanospheres and investigated the radiations of the high-order plasmon modes supported in gold nanospheres. It was revealed that the evanescent wave excitation is equivalent to the excitation by using both the incident and reflected light, offering us the opportunity to control the orientation of the electric field used to excite nanoparticles. In addition, it was found that the scattering light intensity is greatly enhanced and the background noise is considerably suppressed, making it possible to detect the radiations from high-order plasmon modes. Moreover, the influence of the mirror images on the scattering induced by a metal substrate is eliminated as compared with the surface plasmon polariton excitation. By exciting a gold nanosphere with s-polarized light and detecting the scattering light with a p-polarized analyzer, we were able to reveal the radiation from the electric quadrupole mode of the gold nanosphere in both the spatial and the frequency domains. Our findings are important for characterizing the radiations from the high-order modes of large nanoparticles and useful for designing nanoscale photonic devices.
关键词： scattering,plasmon mode,electric dipole,radiation pattern,gold nanosphere,evanescent wave,electric octupole,electric quadrupole
更新于2025-11-21 11:24:58
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Femtosecond Spectroscopy of Au Hot-Electron Injection into TiO2: Evidence for Au/TiO2 Plasmon Photocatalysis by Bactericidal Au Ions and Related Phenomena
摘要： In the present work, we provide evidence for visible light irradiation of the Au/TiO2 nanoparticles’ surface plasmon resonance band (SPR) leading to electron injection from the Au nanoparticles to the conduction band of TiO2. The Au/TiO2 SPR band is shown to greatly enhance the light absorption of TiO2 in the visible region. Evidence is presented for the light absorption by the Au/TiO2 plasmon bands leading to the dissolution of Au nanoparticles. This dissolution occurs concomitantly with the injection of the hot electrons generated by the Au plasmon into the conduction band of TiO2. The electron injection from the Au nanoparticles into TiO2 was followed by femtosecond spectroscopy. The formation of Au ions was further confirmed by the spectral shift of the transient absorption spectra of Au/TiO2. The spectral changes of the SPR band of Au/TiO2 nanoparticles induced by visible light were detected by spectrophotometer, and the morphological transformation of Au/TiO2 was revealed by electron microscopy techniques as well. Subsequently, the fate of the Au ions was sorted out during the growth and biofilm formation for some selected Gram-negative bacteria. This study compares the bactericidal mechanism of Au ions and Ag ions, which were found to be substantially different depending on the selected cell used as a probe.
关键词： electron injection,antibacterial effects,genes expression,DNA repair,quorum sensing,plasmon photocatalysis,biofilms,gold nanoparticles,porins
更新于2025-11-21 11:20:42
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Differential photothermal and photodynamic performance behaviors of gold nanorods, nanoshells and nanocages under identical energy conditions
摘要： Various gold (Au) nanostructures have shown promising near infrared (NIR) light-activated phototherapeutic effects; however, their reported photothermal or photodynamic performance behavior is usually inconsistent or even conflicted, dramatically limiting the improvement of phototherapeutic Au nanostructures. The potential reason for this uncertainty is mainly because the photoactivities of Au nanostructures are not evaluated under identical energy conditions. Herein, three Au nanostructures, Au nanorods (NRs), nanoshells (NSs), and nanocages (NCs), were prepared to provide the same localized surface plasmon resonance (LSPR) peaks at 808 nm. All these Au nanostructures (at the same optical density) could fully exert their photoactivities under the identical and optimal energy condition of 808 nm laser irradiation. It was found that these Au nanostructures could induce similar levels of temperature elevation but different levels of reactive oxygen species (ROS) production, where Au NCs exhibited the highest ROS production, followed by Au NSs and NRs. In vitro and in vivo phototherapeutic assessments further supported that Au NCs could cause the most severe cell death and tumor growth regression. This means that the identical incident energy has different contribution to photothermal and photodynamic performance of Au nanostructures, and the corner angle structures of Au NCs compared with NSs and NCs could more efficiently convert the photon energy into photodynamic property. Taken all together, Au NCs hold great potential for phototherapy due to their efficient energy utilization capability.
关键词： reactive oxygen species,photodynamic therapy,gold nanostructures,photothermal therapy,cancer treatment
更新于2025-11-21 11:08:12
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Improved in vivo targeting of BCL-2 phenotypic conversion through hollow gold nanoshell delivery
摘要： Although new cancer therapeutics are discovered at a rapid pace, lack of effective means of delivery and cancer chemoresistance thwart many of the promising therapeutics. We demonstrate a method that confronts both of these issues with the light-activated delivery of a Bcl-2 functional converting peptide, NuBCP-9, using hollow gold nanoshells. This approach has shown not only to increase the efficacy of the peptide 30-fold in vitro but also has shown to reduce paclitaxel resistant H460 lung xenograft tumor growth by 56.4%.
关键词： Bcl-2,Resistant cancer,Apoptosis,Hollow gold nanoshells,NuBCP,Peptide delivery
更新于2025-11-21 11:08:12
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Highly sensitive and selective label-free detection of dopamine in human serum based on nitrogen-doped graphene quantum dots decorated on Au nanoparticles: Mechanistic insights through microscopic and spectroscopic studies
摘要： A rapid, facile and label-free sensing strategy is developed for the detection of dopamine (DA) in the real samples by exploiting nitrogen-doped graphene quantum dots (N-GQDs) decorated on Au nanoparticles (Au@N-GQD). The as-grown Au@N-GQD exhibits strong blue fluorescence at room temperature and the fluorescence intensity is drastically quenched in presence of DA in neutral medium. The mechanistic insight into the DA sensing by Au@N-GQDs is explored here by careful monitoring of the evolution of the interaction of Au NPs and N-GQDs with DA under different conditions through electron microscopic and spectroscopic studies. The highly sensitive and selective detection of DA over a wide range is attributed to the unique core-shell structure formation with Au@N-GQD hybrids. The quenching mechanism involves the ground state complex formation as well as electron transfer from N-GQDs. The presence of Au NPs in Au@N-GQD hybrids accelerates the quenching process (~14 fold higher than bare N-GQDs) by the formation of stable dopamine-o-quinone (DQ) in this present detection scheme. The fluorescence quenching follows the linear Stern-Volmer plot in the range 0-100 μM, establishing its efficacy as a fluorescence-based DA sensor with a limit of detection (LOD) 590 nM, which is ~27 fold lower than the lowest abnormal concentration of DA in serum (16 μM). This sensing scheme is also successively applied to trace DA in Brahmaputra river water sample with LOD 480 nM including its satisfactory recovery (95-112%). Our studies reveal a novel sensing pathway for DA through the core-shell structure formation and it is highly promising for the design of efficient biological and environmental sensor.
关键词： Dopamine,Fluorescence quenching,Nitrogen-doped graphene quantum dots,Colorimetric sensing,Core-shell structure,Gold nanoparticles
更新于2025-11-21 11:01:37