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TEM images of Au@SiO2@Au MNs and corresponding nanorattles with various sizes. (A) and (B): 22/37/55; (C) and (D): 22/49/67; (E) and (F): 22/72/90. Scale bars represent 50 nm.
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Localized electromagnetic fields generated by interparticle plasmon coupling suffer greatly from the nonreproducibility because they are extremely sensitive to the nanoparticle aggregation status and the incident polarization. Here, we synthesize gold nanorattles that exhibit inherent aggregation-insensitive hotspots due to the intraparticle core-s...
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Citations
... [22,23] The SiO 2 core was then decomposed and removed by alkaline etching of the SiO 2 @PdAu core-shell particles with NaOH solution. [24] Subsequently, the obtained PdAu HSs were drop-casted on the surface of a glass substrate and calcinated in air to produce PdO-Au HSs. Finally, the PdO-PdAu HSs were obtained by reduction of PdO-Au HSs in NaBH 4 solution for certain degree via controlling the reaction time. ...
... Synthesis of PdAu HSs, PdO-Au HSs, and PdO-PdAu HSs: Firstly, SiO 2 @PdAu core-shell NPs were synthesized as reported in our previous works. [22,24,32] Specifically, gold-seeded silica colloidal spheres and a certain amount of H 2 PdCl 4 stock solution and HAuCl 4 stock solution were added into 24 mL water at room temperature under vigorous stirring. After that, l-ascorbic acid solution (20 mm, a mild reducing agent) was added dropwisely, via a syringe controlled by a stepper motor. ...
Designing ultrafast H2 sensors is of particular importance for practical applications of hydrogen energy but still quite challenging. Herein, PdO decorated PdAu ternary hollow shells (PdO‐PdAu HSs) exhibiting an ultrafast response of ≈0.9 s to 1% H2 in air at room temperature are presented. PdO‐PdAu HSs are fabricated by calcinating PdAu bimetallic HSs in air to form PdO‐Au binary HSs, which are then partially reduced by NaBH4 solution, forming PdO‐PdAu HSs. This ternary hybrid material takes advantage of multiple aspects to synergistically accelerate the sensing speed. The HS morphology promises high gas accessibility and high surface area for H2 adsorption, and decoration of Au and PdO alters the electronic state of Pd and reduces the energy barrier for hydrogen diffusing from the surface site of Pd into the subsurface site. The content of Au and PdO in the ternary HSs can be simply tuned, which offers the possibility to optimize their promotion effects to reach the best performance. The proposed fabrication strategy sheds light on the rational design of ultrafast Pd‐based H2 sensors by controlling the sensor structure and engineering the electronic state of active species.
... In the final stage, the center of the SPR peak was gradually located at 635 nm, which means that the structure of Au NPCs tends to be stable. The change in the SPR peak of Au NPC during the synthesis is due to the location of the SPR peak, depending on the size, shape and surrounding medium [29][30][31]. The shift of the SPR peak reflects the change in particle size of the Au NPCs, which is consistent with the results measured by DLS. ...
In general, the preparation of Au nanoparticle clusters (NPCs) is more challenging than that of nanoparticles. The traditional two-step method for preparing Au NPCs is time-consuming and highly sensitive to the reaction conditions. Here, we report a simple and feasible method for the rapid preparation of Au NPCs (~ 30 min), in which Au (Ⅲ) is reduced to Au (0) by trisodium citrate, and assembled into nanoparticle cluster in the presence of a trace amount of cysteine. The surface plasmon resonance peak of the Au NPCs is tunable ranged from visible to near-IR regions by varying the content of cysteine added. The growth process of Au NPCs was monitored by dynamic light scattering, UV-vis absorption spectroscopy and TEM. Their elemental composition, chemical state and molecular structure of the sample surface were measured by XPS. The proposed synthesis mechanism has guiding significance for the preparation of other nanoparticle clusters. Au NPCs used as SERS substrate has a good enhancement effect because of its unique morphology.
... For example, polarization properties of metallic nanocubes [89][90][91], arrays of silver NP rows [92], gold nanoassemblies [93], metallic gratings structures [94], half-shells [95] etc. were studied in literature. A frequently-studied SERS-active system from the point of view of polarization and angular characteristics are arrays of elongated NPs appearing under different names in literature such as NRs [96][97][98][99], nanowires [43,60,[100][101][102][103], nanoantennas [104,105], nanorattles [106,107], nanobones [108] or NP-nanowire systems [109][110][111] where the ∼ cos ϑ trends were often observed (Figures 13-15). Published results indicate that the optical response for light polarized parallel/perpendicular to the long axis of the nanoobjects (related to excitation of longitudinal plasmon modes (LM) or transverse plasmon modes (TM), respectively) is indeed different. ...
... For example, polarization properties of metallic nanocubes [89][90][91], arrays of silver NP rows [92], gold nanoassemblies [93], metallic gratings structures [94], half-shells [95] etc. were studied in literature. A frequently-studied SERS-active system from the point of view of polarization and angular characteristics are arrays of elongated NPs appearing under different names in literature such as NRs [96][97][98][99], nanowires [43,60,[100][101][102][103], nanoantennas [104,105], nanorattles [106,107], nanobones [108] or NP-nanowire systems [109][110][111] where the ~cos trends were often observed (Figures 13-15). ...
A sometimes overlooked degree of freedom in the design of many spectroscopic (mainly Raman) experiments involve the choice of experimental geometry and polarization arrangement used. Although these aspects usually play a rather minor role, their neglect may result in a misinterpretation of the experimental results. It is well known that polarization- and/or angular- resolved spectroscopic experiments allow one to classify the symmetry of the vibrations involved or the molecular orientation with respect to a smooth surface. However, very low detection limits in surface-enhancing spectroscopic techniques are often accompanied by a complete or partial loss of this detailed information. In this review, we will try to elucidate the extent to which this approach can be generalized for molecules adsorbed on plasmonic nanostructures. We will provide a detailed summary of the state-of-the-art experimental findings for a range of plasmonic platforms used in the last ~ 15 years. Possible implications on the design of plasmon-based molecular sensors for maximum signal enhancement will also be discussed.
Continuously advancing technologies is crucial to tackling modern challenges such as efficient energy transfer, directing catalytic behavior, and better understanding of microscopic phenomena. At the heart of many of these problems is nanoscale chemistry. In previous decades, the scientific community has made significant progress in nanoscale structures and technologies, especially relating to their interactions with light. Plasmonic nanostructures have been extensively studied over the past decades because of their fascinating properties and vast technological applications. They can confine light into intense local electromagnetic fields, which has been exploited in the fields of spectroscopy, energy harvesting, optoelectronics, chemical sensing, and biomedicine. Recently, however, plasmonic nanostructures have shown great potential to trigger chemical transformations of proximal molecular species via hot carrier and thermally driven processes. In this review, we discuss the basic concepts governing nanoscale light–matter interactions, the immediate phenomena induced by them, and how we can use nanoscale light–matter interactions to our advantage with surface-enhanced spectroscopy techniques and chemical reactions in confined plasmonic environments.
Carcinoembryonic antigen (CEA) is a cancer-related tumor marker, and it is important to develop a sensitive CEA detection technique. In this paper, a SERS-aptamer sensor for carcinoembryonic antigen (CEA) was based on thiol aptamer and phenylboronic acid. CEA thiol aptamer (Aptamer-SH) modified silver nanorod array chip was used as the SERS capture substrate. 4-Mercaptophenylboronic acid (4-MPBA) modified Ag NPs was used as SERS tags (Ag@4-MPBA). The affinity of the aptamer with CEA was used to ensure the selectivity of the sensor, while 4-MPBA could be recognized with glycoproteins and reduce the cost. The results showed that the SERS intensity and the logarithm of CEA concentrationa had a good linear relationship in the range of 1 pg/mL-100 ng/mL, with a correlation coefficient (R2) of 0.9907. The limit of detection (LOD) was 0.447 pg/mL (S/N=3); the recovery of the standard addition test for CEA in serum was between 97.25% and 102.67%, and the RSD ≤ 2.52% (n=3). The sensor has the advantages of high sensitivity, wide linear range, and stability. It provides a possible method for the detection of CEA in serum.
Developing a simple strategy to fabricate high performance hydrogen sensors with long-term stability remains quite challenging. Here, we report the H2 sensing performance of Pd decorated PdO hollow shells (Pd/PdO HSs). In this novel system, the catalyst nanoparticles (Pd NPs) and semiconductor support (PdO) are interconvertible, which is different from traditional hydrogen sensing systems such as Pd/TiO2 and Pd/ZnO. This Pd/PdO system exhibits multiple unique properties. Firstly, well-distributed Pd NPs with controllable density can be decorated on PdO support through a one-step NaBH4 treatment during which PdO is partially reduced into Pd. Secondly, the decorated Pd NPs are physically inlaid in the PdO support, which not only prevents the agglomeration or detachment of Pd NPs but also enhances the electron transfer between Pd NPs and PdO. Thirdly, Pd/PdO HSs can be reoxidized into PdO HSs once their sensing performance degrades, which makes Pd/PdO HSs repeatably manipulated under the initial reduction process, leading to the reactivation of the sensing performance. With all these advantages, Pd/PdO HSs demonstrate a detection limit lower than 1 ppm, response/recovery time to 1% H2 of 5 s/32 s at room temperature, and a repeatable reactivation ability. The strategy presented here is convenient, time-saving and with no need to pre-functionalize the PdO surface for the decoration of catalyst NPs. Moreover, the unique reactivation ability of Pd/PdO system opens a new strategy towards extending the life time of H2 sensors.
In this paper, Pd hollow shells (HSs) are chemically prepared by depositing Pd on the surface of silica cores followed by a silica core etching process. The as-prepared Pd HSs are assembled on the interdigital electrode and used as hydrogen sensors. Upon exposure to H2, the gap size between HSs repeatedly decreases or increases in accordance with the volume expansion or shrink of the Pd HSs, resulting in a detectable resistance variation of the sensor. The sensing performances of Pd HSs are characterized and optimized. It is found the presence of polyvinylpyrrolidone during the Pd deposition process helps to generate robust and smooth Pd HSs, which is crucial to stable and repeatable hydrogen detection. In the meanwhile, in contrast to previous reports that focus on decreasing the feature size of Pd structures to achieve a faster and more sensitive response, we show herein increasing the particle size can improve the sensing performance of Pd HSs. In our experiment, Pd HSs with the largest particle size show the lowest limit of detection. We conclude that Pd HSs with larger particle size can generate more considerable volume expansion, which leads to more efficient tuning of the sensor’s electrical property at low H2 concentration.
Plasmonic metal nanostructures with complex morphologies provide an important route to tunable optical responses and local electric field enhancement at the nanoscale for a variety of applications including sensing, imaging, and catalysis. Here we report a high-concentration synthesis of gold core-cage nanoparticles with a tethered and structurally aligned octahedral core and examine their plasmonic and catalytic properties. The obtained nanostructures exhibit a double band extinction in the visible-near infrared range and a large area electric field enhancement due to the unique structural features, as demonstrated using finite difference time domain (FDTD) simulations and confirmed experimentally using surface enhanced Raman scattering (SERS) tests. In addition, the obtained structures had a photoelectrochemical response useful for catalyzing the CO2 electroreduction reaction. Our work demonstrates the next generation of complex plasmonic nanostructures attainable via bottom-up synthesis and offers a variety of potential applications ranging from sensing to catalysis.
