Tuning of Ag Nanoparticle Properties in Cellulose Nanocrystals/Ag Nanoparticle Hybrid Suspensions by H2O2 Redox Post-Treatment: The Role of the H2O2/AgNP Ratio

Abstract

Hybrid nanoparticles involving 10-nm silver nanoparticles (AgNPs) nucleated on unmodified rod-like cellulose nanocrystals (CNCs) were prepared by chemical reduction. H2O2 used as a post-treatment induced a size-shape transition following a redox mechanism, passing from 10-nm spherical AgNPs to 300-nm triangular or prismatic NPs (AgNPrisms), where CNCs are the only stabilizers for AgNPs and AgNPrisms. We investigated the role of the H2O2/AgNP mass ratio (α) on AgNPs. At α values above 0.20, the large amount of H2O2 led to extensive oxidation that produced numerous nucleation points for AgNPrisms on CNCs. On the contrary, for α below 0.20, primary AgNPs are only partially oxidized, releasing a reduced amount of Ag+ ions and thus preventing the formation of AgNPrisms and reforming spherical AgNPs. While XRD and EXAFS reveal that the AgNP fcc crystal structure is unaffected by the H2O2 treatment, the XANES spectra proved that the AgNP–AgNPrism transition is always associated with an increase in the metallic Ag fraction (Ag0). In contrast, the formation of new 15-nm spherical AgNPs keeps the initial Ag0/Ag+ ratio unmodified. For the first time, we introduce a complete guide map for the fully-controlled preparation of aqueous dispersed AgNPs using CNC as a template.

Impact of Physico-Chemical Properties of Cellulose Nanocrystal/Silver Nanoparticle Hybrid Suspensions on Their Biocidal and Toxicological Effects

“…As shown in STEM images ( Figure 2 ), the H 2 O 2 redox action turned the primary ~10 nm AgNPs nucleated on CNC surfaces into bigger AgNPrisms. Our group recently investigated variations of morphological and physico-chemical properties of AgNP as a function of the H 2 O 2 /AgNP mass ratio [ 56 ]. In the present work, we briefly summarized the main characteristics of the CNC/AgNP hybrid suspensions where an H 2 O 2 redox post-treatment was performed.…”

“…To produce well-dispersed CNC/AgNP hybrid suspensions at various AgNP contents, an experimental procedure proposed in our previous study was used [ 56 ]. Briefly, a volume of 10 mL of CNC aqueous suspension (2 g/L) was dialyzed against water for 3 days and then mixed with various amounts of AgNO 3 aqueous solution (50 mM, from 15 to 700 μL) and with 500 μL of freshly-prepared NaBH 4 aqueous solution (100 mM) to reduce Ag + ions and to synthesize AgNPs.…”

Multimorphological Remoldable Silver Nanomaterials from Multimode and Multianalyte Colorimetric Sensing to Molecular Information Technology

“…The core-level spectrum of O 1s (Figure H) also confirmed the presence of different oxygen-containing functional groups of the citrate, including CO (530.98 eV), – O (532.48 eV), and O–CO (535.48 eV). In addition, the Ag 3d core-level spectrum (Figure I) can be decomposed into Ag 3d 5/2 (367.88 eV) and Ag 3d 3/2 (373.88 eV), which can be attributed to metallic Ag. ,− , …”

“…NaBH 4 reduces Ag + to generate Ag nanomaterials, while H 2 O 2 can cause unstable Ag nanomaterials to oxidize and dissolve to form defective Ag nanomaterials. These defective Ag nanomaterials may continue to grow as seeds, resulting in M-AgN. − M-AgN with four morphologies (NDs, NPs, NTs, and NRs) and tunable plasmonic absorption can be used for multimode and multianalyte colorimetric sensing (Scheme B) and molecular information technology (including parallel batch logic computing, dual-function molecular encryption, and steganography, Scheme C,D). Interestingly, multiple analytes (Cr 3+ , Hg 2+ , and Ni 2+ ) can interact with M-AgN to controllably reshape their four morphologies (including number, proportion, and the dimensions, Scheme E), resulting in multimode colorimetric responses (including changes in color, absorption, and wavelength shift), thus achieving selective and sensitive detection of multiple metal ions (Scheme B).…”

CNC/AgNP hybrids as safer-by-design biocides in paints

“…The synthesis method of this system was carried following the experimental protocol proposed in another work of our group. 37,39 A volume of 500 mL of CNC suspension (15 g/L) was dialyzed against water for 3 days and then mixed with 25 mL of AgNO 3 aqueous solution (1 M). Then, 40 mL of freshly-prepared NaBH 4 aqueous solution (1 M) were gently added to the CNC/AgNO 3 aqueous suspension under stirring to reduce Ag + ions and synthetize AgNPs (NaBH 4 /AgNO 3 molar ratio of 2).…”