One-Shot SERRS Detection of Iron and Acidity in Aqueous Systems
Irene Calderón González1, Robbert Schuett2, Gerwin Chilla2
1Department of Physical and Inorganic Chemistry, Universitat Rovira i Virgili, 43007 Tarragona, Spain.
ACS Applied Materials & Interfaces
|January 14, 2026
Summary
This study introduces a novel optical sensor platform for simultaneous Fe(II) ion detection and pH monitoring in water. The surface-enhanced resonance Raman scattering (SERRS) sensor overcomes pH interference for reliable metal ion analysis.
Area of Science:
- Analytical Chemistry
- Materials Science
- Spectroscopy
Background:
- Optical ion sensing is promising for portable analysis but suffers from pH interference.
- Metal-ligand interactions crucial for sensing are sensitive to pH fluctuations.
- Accurate in situ monitoring of metal ions like Fe(II) is vital for environmental and biological applications.
Purpose of the Study:
- To develop a multiprobe surface-enhanced resonance Raman scattering (SERRS) platform for simultaneous Fe(II) quantification and in situ pH readout.
- To overcome pH-dependent interferences in optical ion sensing.
- To enable robust and reliable metal ion analysis in aqueous media.
Main Methods:
- Fabrication of polystyrene beads coated with silver nanoparticles.
- Functionalization with phenanthroline (Phen) for Fe(II) detection and 4-mercaptobenzoic acid (MBA) for pH sensing.
- Utilizing resonant excitation at 532 nm for SERRS analysis.
Main Results:
- Achieved Fe(II) detection down to 30 ppb with high selectivity.
- Demonstrated simultaneous and independent quantification of Fe(II) and pH.
- The MBA probe effectively decoupled pH effects, preventing false Fe(II) readings at alkaline pH.
Conclusions:
- The developed dual-sensing SERRS platform offers a robust solution to pH interference in optical ion sensing.
- This strategy enables accurate, time-resolved monitoring of metal ions in complex aqueous systems.
- Paves the way for portable, reliable in situ analysis of metal ions in environmental and biological samples.
Related Concept Videos
01:17Precipitation and Co-precipitation
4.0K
Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...
4.0K
01:19Precipitation Titration: Endpoint Detection Methods
4.9K
In argentometric precipitation titrations, endpoints can be detected visually by the Mohr, Volhard, and Fajans methods. In the Mohr method, adding a soluble chromate indicator gives an initial yellow color to the analyte solution. As the titrant is added, the first excess of silver ions forms a red silver chromate precipitate, marking the endpoint. The solution pH should be maintained at about 8 by adding solid CaCO3.
In the Volhard method, a standard excess of AgNO3 is first added to the...
In the Volhard method, a standard excess of AgNO3 is first added to the...
4.9K
01:18Effects of EDTA on End-Point Detection Methods
614
Different methods, such as visual observance of metal-ion indicators, spectroscopic techniques, and potentiometric methods, can determine the endpoint of an EDTA titration.
In the visual method, metal-ion indicators (metallochromic dyes), which have distinct colors in their free and complex forms, are added to the mixture to signal the titration's end point. They form stable complexes with metal ions, but these complexes are weaker than the corresponding metal–EDTA complexes. As a...
In the visual method, metal-ion indicators (metallochromic dyes), which have distinct colors in their free and complex forms, are added to the mixture to signal the titration's end point. They form stable complexes with metal ions, but these complexes are weaker than the corresponding metal–EDTA complexes. As a...
614
01:18Titration of Polyprotic Base with a Strong Acid
4.4K
The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
4.4K
02:39Indicators
57.9K
Certain organic substances change color in dilute solution when the hydronium ion concentration reaches a particular value. For example, phenolphthalein is a colorless substance in any aqueous solution with a hydronium ion concentration greater than 5.0 × 10−9 M (pH < 8.3). In more basic solutions where the hydronium ion concentration is less than 5.0 × 10−9 M (pH > 8.3), it is red or pink. Substances such as phenolphthalein, which can be used to determine the pH of a solution, are...
57.9K
01:16Titration in Nonaqueous Solvents
1.3K
Most acid-base titrations are performed in an aqueous medium. In aqueous titrations, water competes with weaker acids or bases for proton donation or acceptance, leading to ambiguous endpoints in the titration curve. Water also affects the partial ionization of weak acids or bases. For example, water accepts a proton from acetic acid to form hydronium and acetate ions. The hydronium ion formed is a stronger acid than acetic acid, and the acetate ion is a stronger base than water. As a result,...
1.3K