Probing the surface composition effect of silver-gold alloy in SERS efficiency

Shweta Pawar; Banda Ravi Teja; Ravikiran Nagarjuna; Ramakrishnan Ganesan; Amit Nag

doi:10.1016/j.colsurfa.2019.123638

Probing the surface composition effect of silver-gold alloy in SERS efficiency

Shweta Pawar
, Banda Ravi Teja
, Ravikiran Nagarjuna
, Ramakrishnan Ganesan
, Amit Nag

Birla Institute of Technology and Science Pilani

Research output: Contribution to journal › Article › peer-review

26 Scopus citations

Abstract

Ag-Au alloy microflower substrates with tunable surface compositions are prepared through simple thermolysis of metal-alkyl ammonium halide precursors for probing the role of surface composition in SERS. The bulk and surface composition of the microflowers are characterized using ED-XRF and XPS analyses, respectively. For alloys, the ED-XRF studies show that the bulk compositions are in tune with the feed ratio, while the surface compositions are found to be rich in silver, as revealed by XPS studies. Efficiency studies on these substrates using the analyte molecule Rhodamine 6 G (R6 G) evidence 30 fold enhancements in SERS spectra with 90:10 Ag-Au alloy microflowers as opposed to the pure Ag ones. Raman mapping studies performed on individual microflowers clearly show increase in the density of hot spots, in addition to the enhancement, with increase in concentration of gold in the alloys. It is critically observed that, the surface needs to be rich in Ag in the alloy substrates for obtaining maximum SERS enhancement. The optimized Ag-Au alloy substrate also finds applicability for mercury sensing in water via quantitative loss of SERS enhancement of R6 G.

Original language	English
Article number	123638
Journal	Colloids and Surfaces A: Physicochemical and Engineering Aspects
Volume	578
DOIs	https://doi.org/10.1016/j.colsurfa.2019.123638
State	Published - 5 Oct 2019
Externally published	Yes

Bibliographical note

Publisher Copyright:
© 2019

Funding

S.P. thanks DST- inspire (IF150605) scheme for providing senior research fellowship. A.N. thanks the DST-SERB (SB/FT/CS-129/2013) for financial support. R.G. thanks the DST-SERB, India, for the financial aid (SERB/F/4864/2013-14). Authors gratefully acknowledge the support from Department of Science and Technology, India for the FIST grant SR/FST/CSI-240/2012 . Central Analytical Facility of BITS Pilani Hyderabad Campus is gratefully acknowledged for SEM, XRD and ED-XRF analyses.

Funders	Funder number
DST-SERB	SERB/F/4864/2013-14, SB/FT/CS-129/2013
FIST
Department of Science and Technology, Ministry of Science and Technology, India	IF150605, SR/FST/CSI-240/2012

Keywords

Alloy microflower
Gold
Mercury sensing
SERS
Silver
Surface composition

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10.1016/j.colsurfa.2019.123638

Cite this

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title = "Probing the surface composition effect of silver-gold alloy in SERS efficiency",

abstract = "Ag-Au alloy microflower substrates with tunable surface compositions are prepared through simple thermolysis of metal-alkyl ammonium halide precursors for probing the role of surface composition in SERS. The bulk and surface composition of the microflowers are characterized using ED-XRF and XPS analyses, respectively. For alloys, the ED-XRF studies show that the bulk compositions are in tune with the feed ratio, while the surface compositions are found to be rich in silver, as revealed by XPS studies. Efficiency studies on these substrates using the analyte molecule Rhodamine 6 G (R6 G) evidence 30 fold enhancements in SERS spectra with 90:10 Ag-Au alloy microflowers as opposed to the pure Ag ones. Raman mapping studies performed on individual microflowers clearly show increase in the density of hot spots, in addition to the enhancement, with increase in concentration of gold in the alloys. It is critically observed that, the surface needs to be rich in Ag in the alloy substrates for obtaining maximum SERS enhancement. The optimized Ag-Au alloy substrate also finds applicability for mercury sensing in water via quantitative loss of SERS enhancement of R6 G.",

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AU - Nag, Amit

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N2 - Ag-Au alloy microflower substrates with tunable surface compositions are prepared through simple thermolysis of metal-alkyl ammonium halide precursors for probing the role of surface composition in SERS. The bulk and surface composition of the microflowers are characterized using ED-XRF and XPS analyses, respectively. For alloys, the ED-XRF studies show that the bulk compositions are in tune with the feed ratio, while the surface compositions are found to be rich in silver, as revealed by XPS studies. Efficiency studies on these substrates using the analyte molecule Rhodamine 6 G (R6 G) evidence 30 fold enhancements in SERS spectra with 90:10 Ag-Au alloy microflowers as opposed to the pure Ag ones. Raman mapping studies performed on individual microflowers clearly show increase in the density of hot spots, in addition to the enhancement, with increase in concentration of gold in the alloys. It is critically observed that, the surface needs to be rich in Ag in the alloy substrates for obtaining maximum SERS enhancement. The optimized Ag-Au alloy substrate also finds applicability for mercury sensing in water via quantitative loss of SERS enhancement of R6 G.

AB - Ag-Au alloy microflower substrates with tunable surface compositions are prepared through simple thermolysis of metal-alkyl ammonium halide precursors for probing the role of surface composition in SERS. The bulk and surface composition of the microflowers are characterized using ED-XRF and XPS analyses, respectively. For alloys, the ED-XRF studies show that the bulk compositions are in tune with the feed ratio, while the surface compositions are found to be rich in silver, as revealed by XPS studies. Efficiency studies on these substrates using the analyte molecule Rhodamine 6 G (R6 G) evidence 30 fold enhancements in SERS spectra with 90:10 Ag-Au alloy microflowers as opposed to the pure Ag ones. Raman mapping studies performed on individual microflowers clearly show increase in the density of hot spots, in addition to the enhancement, with increase in concentration of gold in the alloys. It is critically observed that, the surface needs to be rich in Ag in the alloy substrates for obtaining maximum SERS enhancement. The optimized Ag-Au alloy substrate also finds applicability for mercury sensing in water via quantitative loss of SERS enhancement of R6 G.

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Probing the surface composition effect of silver-gold alloy in SERS efficiency

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Keywords

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