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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

UV-Vis absorption spectra of the AgNPs films prepared in AgNO3/BuNH2 ethanolic solutions at different reaction time. The reactants concentrations: (A) 1/0.5 mM, (B) 5/2.5 mM, and (C) 10/5 mM. The background spectra have been subtracted for all the UV-Vis absorption spectra.
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Figure 2: UV-Vis absorption spectra of the AgNPs films prepared in AgNO3/BuNH2 ethanolic solutions at different reaction time. The reactants concentrations: (A) 1/0.5 mM, (B) 5/2.5 mM, and (C) 10/5 mM. The background spectra have been subtracted for all the UV-Vis absorption spectra.

Mentions: The Ag nanofilms were found to exhibit strong plasmon absorption. Figure 2 shows the UV-Vis absorption spectra of the Ag films prepared at different reaction times for three different concentrations of reactants. It was found that the bandwidth of the plasmon resonance peak varied with the reaction time, especially for the 1/0.5 mM AgNO3/BuNH2 reaction solution. The plots of maximum absorption wavelength (λmax) and the absorbance at λmax against the reaction time are shown in Figure 3A,B, respectively. Figure 3A shows that λmax of the Ag films increased (shifted to longer wavelength) with the reaction time at the initial reaction stage, indicating that the size of AgNPs was increasing during this period [24,40]. It is interesting that when a maximum (1st turning point) was reached within 2-5 h, the λmax started to descend till a valley occurred (2nd turning point) followed by another increase. By comparison with the SEM images, we noticed that the 1st turning point was right around the reaction time when the 2nd-layer AgNPs started to appear. The formation of the 2nd-layer AgNPs and their growth in the direction normal to the substrate surface might lead to decrease in their diameter-to-height (a/b) ratio, and consequently a decrease in λmax [41]. The second rise in λmax was probably related to the formation of the 3rd-layer Ag dendrites. Since only few Ag dendrites were observed on the film prepared in the 1/0.5 mM AgNO3/BuNH2 solution, the second increase in λmax for these samples appeared to be much slower than others.


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)

UV-Vis absorption spectra of the AgNPs films prepared in AgNO3/BuNH2 ethanolic solutions at different reaction time. The reactants concentrations: (A) 1/0.5 mM, (B) 5/2.5 mM, and (C) 10/5 mM. The background spectra have been subtracted for all the UV-Vis absorption spectra.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: UV-Vis absorption spectra of the AgNPs films prepared in AgNO3/BuNH2 ethanolic solutions at different reaction time. The reactants concentrations: (A) 1/0.5 mM, (B) 5/2.5 mM, and (C) 10/5 mM. The background spectra have been subtracted for all the UV-Vis absorption spectra.
Mentions: The Ag nanofilms were found to exhibit strong plasmon absorption. Figure 2 shows the UV-Vis absorption spectra of the Ag films prepared at different reaction times for three different concentrations of reactants. It was found that the bandwidth of the plasmon resonance peak varied with the reaction time, especially for the 1/0.5 mM AgNO3/BuNH2 reaction solution. The plots of maximum absorption wavelength (λmax) and the absorbance at λmax against the reaction time are shown in Figure 3A,B, respectively. Figure 3A shows that λmax of the Ag films increased (shifted to longer wavelength) with the reaction time at the initial reaction stage, indicating that the size of AgNPs was increasing during this period [24,40]. It is interesting that when a maximum (1st turning point) was reached within 2-5 h, the λmax started to descend till a valley occurred (2nd turning point) followed by another increase. By comparison with the SEM images, we noticed that the 1st turning point was right around the reaction time when the 2nd-layer AgNPs started to appear. The formation of the 2nd-layer AgNPs and their growth in the direction normal to the substrate surface might lead to decrease in their diameter-to-height (a/b) ratio, and consequently a decrease in λmax [41]. The second rise in λmax was probably related to the formation of the 3rd-layer Ag dendrites. Since only few Ag dendrites were observed on the film prepared in the 1/0.5 mM AgNO3/BuNH2 solution, the second increase in λmax for these samples appeared to be much slower than others.

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