Selective Colorimetric Detection of Hexavalent Chromium Using Gold Nanoparticles
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Solution Overview
Problem
Current methods for detecting hexavalent chromium (Cr6+) ions are complex, costly, and require expert analysis, often reducing Cr6+ to Cr3+ for total chromium analysis, leading to incorrect diagnosis and interference from other metal ions, while existing sensors detect both Cr3+ and Cr6+ ions, lacking specificity.
Innovation Solution
A selective colorimetric detection sensor using size-controlled label-free gold nanoparticles with diameters between 20 to 80 nm, specifically reacting with Cr6+ ions by adjusting the molar ratio of chloroauric acid and sodium citrate, and purifying the nanoparticles to prevent interference from other metal ions, allowing for precise detection of Cr6+ ions without ligand binding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional analysis methods (AAS, ICP-MS, electrochemical analyzer) are used for chromium ion detection, then measurement precision and sensitivity are improved, but device complexity and operational difficulty increase significantly
Solution Approach 1:
The patent replaces complex mechanical and electrical analysis systems (AAS, ICP-MS, electrochemical analyzers) with a simple colorimetric detection system based on gold nanoparticle aggregation. The detection mechanism uses optical properties (color change) instead of complex instrumentation, enabling precise Cr6+ detection through visual or simple spectral measurement without requiring sophisticated equipment
Solution Approach 2:
The patent utilizes color change of gold nanoparticles as the detection signal. When Cr6+ ions interact with gold nanoparticles, they induce aggregation that causes a visible color change from red to blue. This colorimetric response provides a simple, intuitive, and precise detection method that eliminates the need for complex apparatus while maintaining measurement accuracy
2Measurement precision
If total chromium analysis is performed by reducing Cr6+ to Cr3+, then measurement precision is improved, but loss of information occurs regarding the oxidation state
Solution Approach 1:
The patent applies local quality by designing gold nanoparticles with specific size characteristics (20-80 nm) that are selectively responsive to Cr6+ ions. The nanoparticles are engineered to interact specifically with hexavalent chromium through localized surface plasmon resonance, enabling detection of Cr6+ in its oxidation state without reduction, thus preserving oxidation state information while maintaining measurement precision
3Ease of operation
If existing gold nanoparticle sensors are used for chromium detection, then ease of operation is improved, but measurement precision deteriorates due to interference from other metal ions
Solution Approach 1:
The patent employs parameter changes by carefully controlling the size of gold nanoparticles (20-80 nm) and their surface properties. This size control, achieved through adjusted synthesis conditions, creates a selective interaction with Cr6+ ions that distinguishes them from other metal ions. The specific size range optimizes the localized surface plasmon resonance frequency to match Cr6+ interaction, enabling easy operation while maintaining high measurement precision through selective response
4Measurement precision
If ligand-modified gold nanoparticles are used for chromium detection, then measurement precision is improved, but device complexity increases due to ligand binding requirements
Solution Approach 1:
The patent applies the taking out principle by removing the ligand modification step from the gold nanoparticle synthesis process. Instead of attaching organic ligands to the nanoparticle surface, the invention uses bare gold nanoparticles where the metal surface itself interacts with Cr6+ ions. This extraction of the ligand component simplifies the sensor structure while maintaining measurement precision through direct nanoparticle-ion interaction mediated by localized surface plasmon resonance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables rapid, precise, and cost-effective detection of Cr6+ ions with high selectivity, reducing the need for complex apparatuses and expert analysis, and provides reliable on-site measurements, avoiding interference from other metal ions.
Implementation Method 1
The assembling and aggregation reactions of gold nanoparticles (AuNPs) result from the localized surface plasmon resonance (LSPR) of nanoparticles
Implementation Method 2
if nanoparticles are modified, the color is changed due to the surface plasmon resonance phenomenon when the nanoparticles are bound to specific molecules
Data Source
AI summary
Disclosed are a selective colorimetric detection sensor and a colorimetric detection method for C6+ ions using size controlled label-free gold nanoparticles, which may be useful for the detection of toxic materials such as heavy metal ions in the environmental sector and the industry. Selective colorimetric sensor solution used therein is selectively reacted with only Cr6+ ions in trivalent chromium ions (Cr3+) and hexavalent chromium ions (Cr6+), and there is no interference effect resulting from other metal ions, and it is possible to very rapidly and precisely detect Cr6+ ions compared to the related art.