Silver Nanoparticle Dispersions With Synergistic Co-Dispersants
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Solution Overview
Problem
Existing methods for preparing silver nanoparticles result in large particle sizes and require excessive amounts of dispersants, leading to aggregation and potential toxicity issues, especially in concentrated systems.
Innovation Solution
A method involving a combination of a reducing dispersant, such as Arabic gum, and a non-reactive co-dispersant, like sodium alginate, is used to form a stable, concentrated dispersion of silver nanoparticles by reducing the ionic strength and maintaining uniformity, with the silver nanoparticles being less than 25 nm in size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If polymeric dispersants are used in large excess to prevent particle aggregation, then particle stability is improved, but the amount of residual dispersant causes processing problems and potential adverse effects
Solution Approach 1:
The patent introduces a non-reducing dispersant as an intermediary substance that works synergistically with the reducing dispersant. This non-reducing dispersant provides protective colloid action without undergoing structural change, thereby maintaining stability while avoiding the harmful residual effects associated with excessive reducing dispersant usage. The non-reducing dispersant acts as a mediator that enables reduced dispersant dosage while maintaining particle stability.
Solution Approach 2:
The patent employs a composite dispersant system combining both reducing and non-reducing dispersants. This composite approach leverages the reducing properties of one component and the protective colloid properties of the other, achieving effective particle stabilization at lower total dispersant concentrations and eliminating the need for excessive dispersant addition.
2Ease of manufacture
If polysaccharide dispersants are used to reduce silver ions, then silver nanoparticle formation is achieved, but the structural change in the polysaccharide diminishes dispersing efficiency
Solution Approach 1:
The patent segments the dispersant function into two separate components: a reducing dispersant that performs the reduction function and a non-reducing dispersant that performs the protective colloid function. This segmentation allows each component to perform its specific function optimally without the structural change issue affecting overall dispersing efficiency.
Solution Approach 2:
The non-reducing dispersant serves as an intermediary that maintains dispersing efficiency without undergoing structural change. It compensates for the diminished efficiency of the reducing dispersant by providing stable protective colloid action, thereby maintaining overall dispersing efficiency throughout the nanoparticle formation process.
3Ease of manufacture
If conventional methods are used to prepare silver nanoparticles, then particle formation is achieved, but large particle sizes result in toxicity issues
Solution Approach 1:
The patent changes the chemical parameters of the reaction system by introducing a non-reducing dispersant that alters the reduction kinetics and particle growth dynamics. This parameter change enables control over nanoparticle size, producing smaller particles (less than 25 nm) that reduce toxicity while maintaining ease of manufacture.
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 produces highly stable, uniform silver nanoparticles with reduced dispersant usage, minimizing aggregation and toxicity, suitable for applications like antimicrobial and drug delivery.
Implementation Method 1
a reducing dispersant and a non-reactive co-dispersant are used to form a stable, concentrated dispersion of silver nanoparticles by reducing the ionic strength
Implementation Method 2
Their outstanding 'colloid protective' capacity is primarily due to their large molecules, which are more effective in screening the interparticles attractive forces (primarily Van der Waals)
Implementation Method 3
mixing the slurry with a basic solution to form an alkaline basic slurry, and heating the alkaline basic slurry to yield highly uniform silver nanoparticles
Data Source
AI summary
Methods for preparing highly stable concentrated dispersions of silver nanoparticles and described herein. Contemplated methods comprise combining a selected polysaccharidic dispersant with a selected non-reacting dispersant to yield concentrated silver dispersions with enhanced stability and lowered undesirable residual organics. Contemplated methods further comprise selecting an appropriate source of silver ions to reduce the ionic strength of the reaction medium and final silver dispersions.