Cluster-cluster interaction in nanodiamond hydrosols by small-angle scattering

Transparent Colloids of Detonation Nanodiamond: Physical, Chemical and Biological Properties

Aqueous suspensions (colloids) containing detonation nano-diamond (DND) feature in most applications of DND and are an indispensable stage of its production; therefore, the interaction of DND with water is actively studied. However, insufficient attention has been paid to the unique physico-chemical and biological properties of transparent colloids with low DND content (≤0.1%), which are the subject of this review. Thus, such colloids possess giant dielectric permittivity which shows peculiar temperature dependence, as well as quasi-periodic fluctuations during slow evaporation or dilution. In these colloids, DND interacts with water and air to form cottonwool-like fibers comprising living micro-organisms (fungi and bacteria) and DND particles, with elevated nitrogen content due to fixation of atmospheric N2. Prolonged contact between these solutions and air lead to the formation of ammonium nitrate, sometimes forming macroscopic crystals. The latter was also formed during prolonged oxidation of fungi in aqueous DND colloids. The possible mechanism of N2 fixation is discussed, which can be attributable to the high reactivity of DND.

Improving PFSA Membranes Using Sulfonated Nanodiamonds

Aquivion®-type perfluorosulfonic acid membranes with a polytetrafluoroethylene backbone and short side chains with sulfonic acid groups at the ends have great prospects for operating in hydrogen fuel cells. To improve the conducting properties of membranes, various types of nanofillers can be used. We prepared compositional Aquivion®-type membranes with embedded detonation nanodiamond particles. Nanodiamonds were chemically modified with sulfonic acid groups to increase the entire amount of ionogenic groups involved in the proton conductivity mechanism in compositional membranes. We demonstrated the rise of proton conductivity at 0.5-2 wt.% of sulfonated nanodiamonds in membranes, which was accompanied by good mechanical properties. The basic structural elements, conducting channels in membranes, were not destroyed in the presence of nanodiamonds, as follows from small-angle neutron scattering data. The prepared compositional membranes can be used in hydrogen fuel cells to achieve improved performance.

Template-Directed Polymerization Strategy for Producing rGO/UHMWPE Composite Aerogels with Tunable Properties

In this paper, we suggest a previously unknown template-directed polymerization strategy for producing graphene/polymer aerogels with elevated mechanical properties, preservation of the nanoscale pore structure, an extraordinary crystallite structure, as well as tunable electrical and hydrophobic properties. The suggested approach is studied using the reduced graphene oxide (rGO)/ultrahigh molecular weight polyethylene (UHMWPE) system as an example. We also develop a novel method of ethylene polymerization with formation of UHMWPE directly on the surface of rGO sheets prestructured as the aerogel template. At a UHMWPE content smaller than 20 wt %, composite materials demonstrate completely reversible deformation and good conductivity. An ultrahigh polymer content (more than 80 wt %) results in materials with pronounced plasticity, improved hydrophobic properties, and a Young's modulus that is more than 200 times larger than that of pure rGO aerogel. Variation of the polymer content makes it possible to tune the electro-conductive properties of the aerogel in the range from 4.8 × 10^-6 to 4.9 × 10^-1 S/m and adjust its hydrophobic properties. The developed approach would make it possible to create composite materials with highly developed nanostructural morphology and advanced properties controlled by the thickness of the polymer layer on the surface of graphene sheets.