Au25 Nanocluster Charge State Control via Photooxidation
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Solution Overview
Problem
Current methods for controlling the charge state of Au nanoparticles are limited in their ability to rationally design active sites for electrochemical reactions, such as CO2 reduction, O2 reduction, and CO oxidation, as they lack precise control over the charge state-dependent catalytic activity.
Innovation Solution
A method involving the combination of Au nanoclusters with electron accepting molecules and excess counter ions, followed by exposure to light to manipulate the charge state, creating Au+ nanoclusters that can be deposited onto a catalyst support, thereby controlling the charge state and enhancing catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to control charge state of Au nanoparticles, then general catalytic activity is maintained, but precise control over charge state-dependent catalytic activity is lost
Solution Approach 1:
The patent applies parameter changes by systematically varying the charge state (q) of Au25 nanoclusters through controlled oxidation processes. By adjusting oxidation conditions and using different counterions (TOA+, NBu4+), the method achieves precise control over charge states (q=−1, 0, +1), which directly controls catalytic activity for different reactions (CO2 reduction, O2 reduction, CO oxidation).
Solution Approach 2:
The patent uses counterions (tetraoctylammonium TOA+ and tetrabutylammonium NBu4+) as intermediaries to stabilize specific charge states of Au25 nanoclusters. These counterions act as mediators that enable precise charge state control while maintaining cluster stability, resolving the contradiction between precision and complexity by providing a straightforward chemical control mechanism.
2Productivity
If Au nanoclusters with specific charge states are used, then catalytic activity for specific reactions is enhanced, but the complexity of controlling and maintaining charge state increases
Solution Approach 1:
The patent applies preliminary action by pre-synthesizing Au25 nanoclusters with specific charge states (q=−1, 0, +1) before catalytic applications. The oxidation process is performed in advance to generate the desired charge state, and counterions are pre-added to stabilize these states. This preliminary preparation simplifies the overall process by eliminating the need for complex in-situ charge state control during catalysis.
Solution Approach 2:
The method uses parameter changes in oxidation程度 and counterion concentration to control the final charge state of the nanoclusters. By systematically varying these parameters during synthesis, the patent achieves high catalytic activity for specific reactions (e.g., CO oxidation with Au25+, CO2 reduction with Au25−) while maintaining a relatively simple procedural framework.
3Reliability
If atomically precise Au nanoclusters are used, then charge state-dependent optical and reactivity properties emerge, but the difficulty of isolating and characterizing specific charge states increases
Solution Approach 1:
The patent utilizes color changes and optical absorbance spectra as indicators of charge state. Au25 nanoclusters in different charge states (q=−1, 0, +1) exhibit distinct optical absorbance spectra, which serve as reliable indicators for identifying and characterizing the charge state. This optical fingerprinting method simplifies detection and characterization compared to other techniques.
Solution Approach 2:
The patent employs feedback through optical spectroscopy to monitor and confirm the charge state of Au25 nanoclusters during and after synthesis. By measuring the optical absorbance spectra and comparing them to reference spectra for known charge states, the method provides immediate feedback on the success of charge state control, facilitating reliable isolation and characterization.
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 effectively controls the charge state of Au nanoparticles, leading to improved reactivity in CO2 reduction, O2 reduction, and CO oxidation reactions, with positively charged Au+ nanoclusters showing enhanced oxidation reactions and negatively charged Au− clusters showing enhanced reduction reactions.
Implementation Method 1
exposing the nanocluster, electron acceptor and counter ion mixture to light creating Au+ nanoclusters
Implementation Method 2
combining at least one Au nanocluster with at least one electron accepting molecule in the presence of an excess amount of counter ion; and exposing the nanocluster, electron acceptor and counter ion mixture to light creating Au+ nanoclusters
Implementation Method 3
Au25− and Au250 were converted to Au25+ by illuminating an O2 saturated solution containing a negative counter-ion with visible light
Data Source
AI summary
Methods for manipulating charge states of Au nanoparticles and uses for the corresponding nanoparticles are described. A preferred embodiment comprises the following steps: 1) combining at least one Au nanocluster with at least one electron accepting molecule in the presence of an excess amount of counter ion; and 2) exposing the nanocluster, electron acceptor and counter ion mixture to light creating Au+ nanoclusters. In one or more embodiments, an additional step of depositing the Au+ nanoclusters onto a catalyst support is performed.