Carbon–SiO₂ Hybrid Nanoparticles with Enhanced Radical Stabilization and Biocide Activity

Abstract

Nanocarbon and nanosilica are widely-used nanomaterials of significant industrial interest. Herein, a library of {carbon–SiO2} hybrid nanoparticles, with controlled nanocarbon content and sp3/sp2 profile, was engineered by a flame spray pyrolysis (FSP) process in one step. Their structure–function relationship was evaluated by studying their radical-generation and radical-stabilization activities, using electron paramagnetic resonance spectroscopy in tandem with their biocide activity toward marine bacteria Aliivibrio fischeri. The surface properties of the C–SiO2 hybrids were studied by Raman spectroscopy and surface-charge analysis by zeta potential measurements. Raman spectroscopy indicates that the FSP process, as designed and used herein, allows the progressive incorporation of nanocarbon moieties into the SiO2 nanostructure, which may lead to distortion of the siloxane matrix. Concurrently, the C–SiO2 hybrids’ surface charge profile reveals a trend correlated with the acute biocide activity toward Aliiv. fischeri. Interestingly, we find no correlation between the stable radical population and the nanohybrids’ biocide activity. Within this context, we discuss the role of surface charge, radical properties, and SiO2 lattice distortions by the nanocarbon, all of them parametrized via FSP process protocols. Thus, the present study’s findings provide critical insight into the structure–biocide activity relationship of carbon–SiO2 hybrid nanoparticles. Technology-wise, the present work exemplifies a scalable FSP process for the industrial production of applied nanomaterials, such as C–SiO2 nanostructures.

Carbon-Coated TiO2 Nanoparticles for Noble-Metal-Free Photocatalytic H2 Production from H2O

“…More specifically, the G band at ∼1580 cm –1 is attributed to stretching of the sp 2 -bonded carbon atoms in graphitic-type structures, while the D band is correlated to sp 3 carbon atoms due to defects or disorder, presented in graphitic structures . The intensity ratio I D / I G can serve as a metric of the graphitization degree of the nanocarbon layers . The I D / I G ratios listed in Table show a nonmonotonous trend.…”

Flame Spray Pyrolysis Synthesis of Vo-Rich Nano-SrTiO3-x

“…A library of four SrTiO 3-x (for convenience, these are codenamed STO) perovskites was prepared in an enclosed single-nozzle FSP reactor using two different Anoxic-FSP configurations (see Figure 1 A,B). The A-FSP reactor set-up uses CH 4 to control the anoxic-combustion environments, as exemplified in our recent works [ 16 , 26 , 27 ]. This CH 4 is additional to the classically used CH 4 in the pilot-flame of FSP [ 28 ].…”

“…The two A-FSP configurations in Figure 1 A,B are codenamed Radial- and Axial-A-FSP; these define the way in which CH 4 is introduced, respectively. In all cases, the FSP-nozzle was enclosed by a cylindrical metal chamber consisting of two concentric tubes, a sinter metal tube (outer tube) and a perforated metal tube (inner tube) to isolate the flame from the surrounding atmosphere, as has been described in detail in previous works [ 16 , 26 , 27 , 29 ]. The so-produced materials (listed in Table 1 ) are codenamed STO-R and STO-A for Radial- and Axial-A-FSP, respectively.…”

“…Herein, the specific aims of the present works were: (i) to develop FSP protocols for controlled Vo-engineering in nanosized SrTiO 3-x , employing an advanced FSP approach in which the combustion stoichiometry was controlled by the FSP-design and operating conditions [ 16 , 20 , 26 , 27 ]; (ii) to study the structural and spectroscopic properties of the so-produced SrTiO 3-x ; (iii) to extend and highlight the versatility of A-FSP as a technique capable of producing large quantities of elaborated nanostructures.…”

Engineering of Oxygen-Deficient Nano-CeO2–x with Tunable Biocidal and Antioxidant Activity

“…In our recent work, we proposed the A-FSP technology to engineer carbon-SiO 2 nanocomposites. As shown, control of the type and amount of carbon by A-FSP allowed tuning of the properties of the SiO 2 matrix. Our detailed study revealed structure–function relationships with a focus on the biocidal activity of the C-SiO 2 composites.…”