Abstract:Due to the competitive growth on the crystal face of seed, it is always difficult to control the morphology of the formation of nanoparticles precisely by a seed-mediated growth method.
“…Indeed, all the spectra exhibit a strong and broad absorption related to the plasmonic properties of the silver component (Figure 5); however, in the presence of PVP, absorption was observed for a wavelength of 433 nm while it was observed at 455 nm without using PVP. Moreover, an additional sharp peak appeared at about 343 nm for this last sample series, in good agreement with a plate silver structure [31].…”
Section: Phase and Microstructure Analysis Of The Engineered Fe 3 O 4 -Ag Nanocompositessupporting
The formation of silver nanopetal-Fe3O4 poly-nanocrystals assemblies and the use of the resulting hetero-nanostructures as active substrates for Surface Enhanced Raman Spectroscopy (SERS) application are here reported. In practice, about 180 nm sized polyol-made Fe3O4 spheres, constituted by 10 nm sized crystals, were functionalized by (3-aminopropyl)triethoxysilane (APTES) to become positively charged, which can then electrostatically interact with negatively charged silver seeds. Silver petals were formed by seed-mediated growth in presence of Ag+ cations and self-assembly, using L-ascorbic acid (L-AA) and polyvinyl pyrrolidone (PVP) as mid-reducing and stabilizing agents, respectively. The resulting plasmonic structure provides a rough surface with plenty of hot spots able to locally enhance significantly any applied electrical field. Additionally, they exhibited a high enough saturation magnetization with Ms = 9.7 emu g−1 to be reversibly collected by an external magnetic field, which shortened the detection time. The plasmonic property makes the engineered Fe3O4-Ag architectures particularly valuable for magnetically assisted ultra-sensitive SERS sensing. This was unambiguously established through the successful detection, in water, of traces, (down to 10−10 M) of Rhodamine 6G (R6G), at room temperature.
“…Indeed, all the spectra exhibit a strong and broad absorption related to the plasmonic properties of the silver component (Figure 5); however, in the presence of PVP, absorption was observed for a wavelength of 433 nm while it was observed at 455 nm without using PVP. Moreover, an additional sharp peak appeared at about 343 nm for this last sample series, in good agreement with a plate silver structure [31].…”
Section: Phase and Microstructure Analysis Of The Engineered Fe 3 O 4 -Ag Nanocompositessupporting
The formation of silver nanopetal-Fe3O4 poly-nanocrystals assemblies and the use of the resulting hetero-nanostructures as active substrates for Surface Enhanced Raman Spectroscopy (SERS) application are here reported. In practice, about 180 nm sized polyol-made Fe3O4 spheres, constituted by 10 nm sized crystals, were functionalized by (3-aminopropyl)triethoxysilane (APTES) to become positively charged, which can then electrostatically interact with negatively charged silver seeds. Silver petals were formed by seed-mediated growth in presence of Ag+ cations and self-assembly, using L-ascorbic acid (L-AA) and polyvinyl pyrrolidone (PVP) as mid-reducing and stabilizing agents, respectively. The resulting plasmonic structure provides a rough surface with plenty of hot spots able to locally enhance significantly any applied electrical field. Additionally, they exhibited a high enough saturation magnetization with Ms = 9.7 emu g−1 to be reversibly collected by an external magnetic field, which shortened the detection time. The plasmonic property makes the engineered Fe3O4-Ag architectures particularly valuable for magnetically assisted ultra-sensitive SERS sensing. This was unambiguously established through the successful detection, in water, of traces, (down to 10−10 M) of Rhodamine 6G (R6G), at room temperature.
“…It implies that the formed nanoparticles are polydisperse in the seed solution. Related researches exhibited that Br − can strongly bond to Ag + to form AgBr that inhibits the growth of silver seeds [29, 32]. According to our experimental results, it explains that CTAB has two main functions in the formation of silver seeds, i.e., bonding to silver to form AgBr to decrease the reduction rate of Ag + and showing its selective adsorption in the presence of TSC to induce the orientation growth of silver seeds.Fig.…”
Section: Resultssupporting
confidence: 60%
“…Furthermore, the aging time of the seed collosol has a big influence on the selective adsorption behavior derived from the new seeds in our case. As a result, the morphology and particle size of the formed nanoparticles can be controlled through the following ways: (1) by changing in the aging time of the silver seeds prepared by adding both TSC and CTAB and (2) by adjusting the addition of TSC and CTAB in the procedure of silver seeds [29].…”
Section: Resultsmentioning
confidence: 99%
“…In the theoretical calculation, it can be confirmed that precipitation reaction between Ag + and Br − is dominant in the system, indicating that most of Ag + reacts with Br − instead of citrate [29]. It can slow down the reducing procedure and thus reduce the concentration of free Ag + .…”
Contrast to the polydisperse nanorods formed by common seed-mediated growth method without the presence of cetyltrimethylammonium bromide (CTAB) in seed solution, we successfully obtained silver nanoparticles with different morphologies in the same reaction system by addition of CTAB in the seed solution. In this work, an appropriate amount of CTAB was added into the solution to prepare silver seed crystals. The results show that the aging time of silver seeds have a great influence on the sizes and morphologies of silver nanoparticles and thus the shape-controllable silver nanoparticles can be easily achieved by simply changing the seed aging time. The results also support that the selective adsorption ability or adsorption behavior of TSC can be adjusted by adding CTAB in the preparation procedure of silver seeds. We suggest that different aging times generate different effects on the competitive adsorption between CTAB and citrate to induce the orientation growth of silver seeds. As a result, silver nanospheres, nanorods, and triangular nanoplates can be easily prepared in the same system. In addition, we overcome the time limitation about the use of the seeds by adding CTAB into seed solution and make the synthesis of silver or other metal nanoparticles with different morphologies more easily and more efficiently.
Electronic supplementary material
The online version of this article (10.1186/s11671-019-2898-x) contains supplementary material, which is available to authorized users.
“…[3,4] The LSPR in T-SNPs can be tuned from the visible to the near IR spectrum depending on the initial synthesis parameters, [5] and the final T-SNPs' morphology including their edges length, thickness, tip shape, and equilateral triangle aspect ratio. [5][6][7][8][9][10][11][12] It has been reported [6,7] that the optical properties shown by T-SNPs open the possibility to use this nanostructured material in several fields. For instance, understanding the parameters for the correct formation of T-SNPs will open a novel branch of study in the field of surface-enhanced Raman spectroscopy (SERS) and plasmonic antennas due to their unique chemical and physical properties when combined with advanced nanostructures like graphene.…”
Triangular silver nanoplates (T‐SNPs) are synthesized via a facile, low‐cost photochemical process. It is proved that both the pH and the concentration of trisodium citrate (TSC) are the key factors to describe the mechanism for the photochemical growth and modulation of the extinction band along the formation of T‐SNPs. A precise photoreduction growth mechanism of T‐SNPs is proposed and confirmed by X‐ray photoelectron spectroscopy (XPS) considering the face block theory and the localized surface plasmon resonance (LSPR) in T‐SNPs revealing the optimal conditions for their growth to be at a neutral pH of 7, a concentration between 1.0 and 2.0 mm of TSC preferentially monodentate, and using a 520 nm excitation energy. These results exhibit important implications for the behavior of T‐SNPs in a wide variety of plasmonic applications that can be further moved to controlled surface‐enhanced biomedical applications.
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