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Fabrication and evolution of multilayer silver nanofilms for surface-enhanced Raman scattering sensing of arsenate.

Hao J, Han MJ, Xu Z, Li J, Meng X - Nanoscale Res Lett (2011)

Bottom Line: The SERS spectra of arsenate showed that characteristic SERS bands of arsenate appear at approximately 780 and 420 cm-1, and the former possesses higher SERS intensity.By comparing the peak heights of the approximately 780 cm-1 band of the SERS spectra, the optimal Ag/GL substrate has been obtained for the most sensitive SERS sensing of arsenate.Using this optimal substrate, the limit of detection (LOD) of arsenate was determined to be approximately 5 μg·l-1.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA. xmeng@stevens.edu.

ABSTRACT
Surface-enhanced Raman scattering (SERS) has recently been investigated extensively for chemical and biomolecular sensing. Multilayer silver (Ag) nanofilms deposited on glass slides by a simple electroless deposition process have been fabricated as active substrates (Ag/GL substrates) for arsenate SERS sensing. The nanostructures and layer characteristics of the multilayer Ag films could be tuned by varying the concentrations of reactants (AgNO3/BuNH2) and reaction time. A Ag nanoparticles (AgNPs) double-layer was formed by directly reducing Ag+ ions on the glass surfaces, while a top layer (3rd-layer) of Ag dendrites was deposited on the double-layer by self-assembling AgNPs or AgNPs aggregates which had already formed in the suspension. The SERS spectra of arsenate showed that characteristic SERS bands of arsenate appear at approximately 780 and 420 cm-1, and the former possesses higher SERS intensity. By comparing the peak heights of the approximately 780 cm-1 band of the SERS spectra, the optimal Ag/GL substrate has been obtained for the most sensitive SERS sensing of arsenate. Using this optimal substrate, the limit of detection (LOD) of arsenate was determined to be approximately 5 μg·l-1.

No MeSH data available.


Related in: MedlinePlus

SEM images of AgNPs multilayer films of the substrates: (a) Ag/GL-1/0.5-25, (b) Ag/GL-5/2.5-18, and (c) Ag/GL-10/5-6. The top panels present the low magnification (large area) images, and the bottom panels are high magnification (high resolution) images indicating the nanostructures of Ag double-layer films. The insets in (b) and (c) show the high-resolution images of the corresponding Ag dendrites.
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Figure 6: SEM images of AgNPs multilayer films of the substrates: (a) Ag/GL-1/0.5-25, (b) Ag/GL-5/2.5-18, and (c) Ag/GL-10/5-6. The top panels present the low magnification (large area) images, and the bottom panels are high magnification (high resolution) images indicating the nanostructures of Ag double-layer films. The insets in (b) and (c) show the high-resolution images of the corresponding Ag dendrites.

Mentions: Comparing the results in Table 2, it is found that each optimum reaction time is equal to or near to the time needed to reach each valley λmax (2nd turning point in Figure 3A). It has been demonstrated that at the 2nd turning points, the 3rd-layer Ag dendrites had formed but still at the early stages for the two high concentrations of AgNO3/BuNH2 solutions. These observations imply that the 3rd-layer Ag dendrites may play a significant role in the arsenate SERS enhancements. Figure 6 presents the SEM images of the three optimized Ag/GL substrates (Ag/GL-1/0.5-25, Ag/GL-5/2.5-18, and Ag/GL-10/5-6) in both low magnification (large area) and high magnification (high resolution). The large area SEM images show that some Ag dendrites with 1-5 μm size appeared; larger area images (data not shown) show the Ag dendrites were distributed uniformly on the double-layer films of Ag/GL-5/2.5-18 and Ag/GL-10/5-6 substrates, while only few Ag dendrites were observed on the double-layer film of the Ag/GL-1/0.5-25 substrate. The high-resolution SEM images indicate that there is not much difference in AgNPs properties and microstructures among the three double-layer films except that the AgNPs look a little more irregular in the Ag/GL-5/2.5-18 substrate. The Ag dendrites consist of small AgNPs of 20-50 nm. The previous study also indicated that Ag dendrites are very SERS-active [19,22,44,45]. Therefore, the two Ag/GL substrates with Ag dendrites on them exhibited much higher SERS effects than that without Ag dendrites. For a given concentration of reactants, after the optimum reaction time, some AgNPs in the Ag dendrites agglomerated together to form big solid Ag masses (images not shown), leading to the decreasing SERS magnitude.


Fabrication and evolution of multilayer silver nanofilms for surface-enhanced Raman scattering sensing of arsenate.

Hao J, Han MJ, Xu Z, Li J, Meng X - Nanoscale Res Lett (2011)

SEM images of AgNPs multilayer films of the substrates: (a) Ag/GL-1/0.5-25, (b) Ag/GL-5/2.5-18, and (c) Ag/GL-10/5-6. The top panels present the low magnification (large area) images, and the bottom panels are high magnification (high resolution) images indicating the nanostructures of Ag double-layer films. The insets in (b) and (c) show the high-resolution images of the corresponding Ag dendrites.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211326&req=5

Figure 6: SEM images of AgNPs multilayer films of the substrates: (a) Ag/GL-1/0.5-25, (b) Ag/GL-5/2.5-18, and (c) Ag/GL-10/5-6. The top panels present the low magnification (large area) images, and the bottom panels are high magnification (high resolution) images indicating the nanostructures of Ag double-layer films. The insets in (b) and (c) show the high-resolution images of the corresponding Ag dendrites.
Mentions: Comparing the results in Table 2, it is found that each optimum reaction time is equal to or near to the time needed to reach each valley λmax (2nd turning point in Figure 3A). It has been demonstrated that at the 2nd turning points, the 3rd-layer Ag dendrites had formed but still at the early stages for the two high concentrations of AgNO3/BuNH2 solutions. These observations imply that the 3rd-layer Ag dendrites may play a significant role in the arsenate SERS enhancements. Figure 6 presents the SEM images of the three optimized Ag/GL substrates (Ag/GL-1/0.5-25, Ag/GL-5/2.5-18, and Ag/GL-10/5-6) in both low magnification (large area) and high magnification (high resolution). The large area SEM images show that some Ag dendrites with 1-5 μm size appeared; larger area images (data not shown) show the Ag dendrites were distributed uniformly on the double-layer films of Ag/GL-5/2.5-18 and Ag/GL-10/5-6 substrates, while only few Ag dendrites were observed on the double-layer film of the Ag/GL-1/0.5-25 substrate. The high-resolution SEM images indicate that there is not much difference in AgNPs properties and microstructures among the three double-layer films except that the AgNPs look a little more irregular in the Ag/GL-5/2.5-18 substrate. The Ag dendrites consist of small AgNPs of 20-50 nm. The previous study also indicated that Ag dendrites are very SERS-active [19,22,44,45]. Therefore, the two Ag/GL substrates with Ag dendrites on them exhibited much higher SERS effects than that without Ag dendrites. For a given concentration of reactants, after the optimum reaction time, some AgNPs in the Ag dendrites agglomerated together to form big solid Ag masses (images not shown), leading to the decreasing SERS magnitude.

Bottom Line: The SERS spectra of arsenate showed that characteristic SERS bands of arsenate appear at approximately 780 and 420 cm-1, and the former possesses higher SERS intensity.By comparing the peak heights of the approximately 780 cm-1 band of the SERS spectra, the optimal Ag/GL substrate has been obtained for the most sensitive SERS sensing of arsenate.Using this optimal substrate, the limit of detection (LOD) of arsenate was determined to be approximately 5 μg·l-1.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA. xmeng@stevens.edu.

ABSTRACT
Surface-enhanced Raman scattering (SERS) has recently been investigated extensively for chemical and biomolecular sensing. Multilayer silver (Ag) nanofilms deposited on glass slides by a simple electroless deposition process have been fabricated as active substrates (Ag/GL substrates) for arsenate SERS sensing. The nanostructures and layer characteristics of the multilayer Ag films could be tuned by varying the concentrations of reactants (AgNO3/BuNH2) and reaction time. A Ag nanoparticles (AgNPs) double-layer was formed by directly reducing Ag+ ions on the glass surfaces, while a top layer (3rd-layer) of Ag dendrites was deposited on the double-layer by self-assembling AgNPs or AgNPs aggregates which had already formed in the suspension. The SERS spectra of arsenate showed that characteristic SERS bands of arsenate appear at approximately 780 and 420 cm-1, and the former possesses higher SERS intensity. By comparing the peak heights of the approximately 780 cm-1 band of the SERS spectra, the optimal Ag/GL substrate has been obtained for the most sensitive SERS sensing of arsenate. Using this optimal substrate, the limit of detection (LOD) of arsenate was determined to be approximately 5 μg·l-1.

No MeSH data available.


Related in: MedlinePlus