AgNP Deposition Research Articles

In situ polydopamine-assisted deposition of silver nanoparticles on a two dimensional support as an inexpensive and highly efficient SERS substrate

Versatile substrates were modified with polydopamine followed by in situ AgNP deposition to fabricate a cheap, flexible and disposable SERS substrate.

Fouling-Resistant Behavior of Silver Nanoparticle-Modified Surfaces against the Bioadhesion of Microalgae

Unwanted adhesion of microalgae on submerged surfaces is a ubiquitous problem across many maritime operations. We explored the strategy of developing a silver nanoparticle (AgNP) coating for antifouling applications in marine and freshwater environments. In situ growth of AgNPs was achieved by a polydopamine (PDA)-based method. A range of most used industrial materials, including glass, polystyrene, stainless steel, paint surface, and even cobblestone, were employed, on which AgNP coatings were built and characterized. We described the fouling-resistant behavior of these AgNP-modified surfaces against two typical fouling organisms: a marine microalga Dunaliella tertiolecta and a freshwater green alga community. The PDA-mediated AgNP deposition strategy was demonstrated applicable for all the above materials; the resulting AgNP coatings showed a significant surface inhibitory effect against the adhesion of microalgae by above 85% in both seawater and freshwater environments. We observed that contact killing was the predominant antifouling mechanism of AgNP-modified surfaces, and the viability of the microalgae cells in bulk media would not be affected. In addition, silver loss from PDA-mediated AgNPs was relatively slow; it could allow the coating to persist for long-term usage. This study showed the potential of preparing environmentally friendly surfaces that can effectively manage biofouling through the direct deposition of AgNP coatings.

Influence of pH and ionic strength on the deposition of silver nanoparticles on microfiltration membranes

In this study, we investigated the influence of pH and ionic strength on the deposition of silver nanoparticles (AgNPs) on cellulous acetate microfiltration membranes. Results indicated that flux and total silver concentration in the permeate increased with increasing pH. AgNPs and membrane zeta potential measurements suggest the increased flux and particle breakthrough with increasing pH were a result of more repulsive particle–particle and particle–membrane interactions. The greater repulsive interactions under these conditions resulted in less AgNP deposition, greater particle breakthrough, and higher water flux. Increasing ionic strength, on the other hand, increased deposition and reduced total silver in the permeate, at least at pH 4. This lower silver concentration observed in the permeate presumably was a result of the screening of repulsive electrostatic particle–particle and particle–membrane interactions and the resulting steric exclusion caused by membrane fouling. At higher pH values (7.6 and 10), however, no difference in flux decline was observed at different ionic strengths and significant breakthrough of silver occurred. These results at higher pH values suggest that sodium chloride facilitated the dissolution of AgNPs and the formation of AgCl, AgCl2− and AgCl32− on the particle surface, which enabled soluble silver complexes and AgNPs to penetrate the membrane.

Relative Importance of the Humic and Fulvic Fractions of Natural Organic Matter in the Aggregation and Deposition of Silver Nanoparticles

As engineered nanoparticles (NPs) are increasingly used, their entry into the environment has become an important topic for water sustainability. Recent investigations point to the critical role of natural organic matter (NOM) in altering the persistence of NPs by complexing with their surfaces. The NP-NOM complex, in turn, is the new entity that may potentially influence subsequent fate of NPs. To understand the relative impact of humic (HA) and fulvic fraction of NOM on the stability and mobility of silver nanoparticles (AgNPs), a combination of dynamic light scattering and quartz crystal microgravimetry with dissipation monitoring was used. In the absence of unbound NOM, (1) surface modification on either AgNP or silica substrate by different NOM fractions could lead to substantial changes in the extent and kinetics of AgNP aggregation and deposition, and (2) HA has a greater capability to enhance the transport of AgNPs by reducing their aggregation and deposition. With unbound NOM, HA seems to compete more successfully for binding sites on the substrate under electrostatically favorable conditions and formed a steric layer to prevent subsequent deposition of AgNPs. These findings highlighted the importance of NOM fraction in the overall environmental partitioning of AgNPs.

RETRACTED ARTICLE: Controlling the properties of silver nanoparticles deposited on surfaces using supercritical carbon dioxide for surface-enhanced Raman spectroscopy

Silver nanoparticles (AgNPs) have been deposited on silicon and glass surfaces via a supercritical carbon dioxide (sc-CO2) synthesis route for application in surface-enhanced Raman spectroscopy (SERS). Arrhenius plots revealed that nucleation and growth processes in this system depend on both temperature and surface chemistry. Results also demonstrated that temperature and surface chemistry could be varied to control nanoparticle properties, such as the mean nanoparticle size, density, and surface coverage, providing two useful variables for manipulating the properties of AgNPs deposited on surfaces in this system. These data also provide scientific insight into the underlying mechanisms governing heterogeneous AgNP deposition on a substrate in a sc-CO2 system in addition to engineering insight into the variables that can be used to manipulate AgNP characteristics. The mean particle size could be tuned over the range 20–200 nm, the interparticle distance could be tuned over the range 70 nm–1 μm, and the surface coverage could be tuned over the range 0.035–0.58. Products were analyzed by scanning electron microscopy with image analysis, transmission electron microscopy, X-ray diffraction, and SERS. The silver nanoparticle-coated substrates were successfully applied in SERS, detecting the model analyte Rhodamine 6G at a concentration of 1 μM, a three orders of magnitude improvement over SERS surfaces previously fabricated in sc-CO2 systems. Such surfaces can find use in trace concentration analyte detection in biomedical, chemical, and environmental applications.

Multiple depositions of Ag nanoparticles on chemically modified agarose films for surface-enhanced Raman spectroscopy

A facile and cost-effective approach for the preparation of a surface-enhanced Raman spectroscopy (SERS) substrate through constructing silver nanoparticle/3-aminopropyltriethoxysilane/agarose films (Ag NPs/APTES/Agar film) on various solid supports is described. The SERS performance of the substrate was systematically investigated, revealing a maximum SERS intensity with four layers of the Ag NP deposition. The enhancement factor of the developed substrate was calculated as 1.5 × 10(7) using rhodamine 6G (R6G) as the probe molecule, and the reproducibility of the SERS signals was established. A high throughput screening platform was designed, manufactured and implemented which utilised the ability to cast agarose to assemble arrays. Quantitative analysis of 4-aminobenzoic acid (4-ABA) and 4-aminothiophenol (4-ATP) was achieved over a ∼0.5 nM-0.1 μM range.