Introducing fluorocarbon vapor in the air above an aqueous dispersion of clusters of nanodiamonds induces their disaggregation, a prerequisite for most of their biomedical uses. Furthermore, the fluorocarbon gas promotes the adsorption of nanodiamonds at the gas/water interface. As an example of the benefits that can be gained from our findings relative to the implementation of nanomaterials for practical uses, we investigated the role that a fluorocarbon gas may play in the generation of microbubbles, which are currently actively investigated in ultrasound-mediated diagnosis and therapy. Remarkably, the fluorocarbon gas enables the production of microbubbles shelled only with nanodiamonds, in the absence of any other surfactant, which could not be achieved without the fluorocarbon being present. This demonstrates that a supernatant gas can decisively affect the adsorption of nanoparticles from an aqueous phase to an air/water interface, likely through physical adsorption at the nanodiamond surface. The investigations involved solid-state NMR and FTIR, microbubble generation experiments with acoustic attenuation monitoring, and bubble profile analysis tensiometry on spontaneously adsorbed Gibbs films. Perspectives include control of aggregation of nanodiamonds and their retrieval from aqueous dispersions, and applications in multimodal diagnostic imaging, bioimaging and therapeutic cell tracking. It is proposed that the disaggregating potency of fluorocarbons can be applied to other nanomaterials, providing a simple and effective means of alleviating aggregation.

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Ligand-targeted microbubbles are focusing interest for molecular imaging and delivery of chemotherapeutics. Lipid–peptide conjugates (lipopeptides) that feature alternating serine–glycine (SG) n segments rather than classical poly(oxyethylene) linkers between the lipid polar head and a targeting ligand were proposed for the liposome-mediated, selective delivery of anticancer drugs. Here, we report the synthesis of perfluoroalkylated lipopeptides (F-lipopeptides) bearing two hydrophobic chains (C n F2 n +1, n = 6, 7, 8, 1–3) grafted through a lysine moiety on a hydrophilic chain composed of a lysine–serine–serine (KSS) sequence followed by 5 SG sequences. These F-lipopeptides are precursors of targeting lipopeptide conjugates. A hydrocarbon counterpart with a C10H21 chain (4) was synthesized for comparison. The capacity for the F-lipopeptides to spontaneously adsorb at the air/water interface and form monolayers when combined with dipalmitoylphosphatidylcholine (DPPC) was investigated. The F-lipopeptides 1–3 demonstrated a markedly enhanced tendency to form monolayers at the air/water interface, with equilibrium surface pressures reaching ≈7–10 mN m−1 versus less than 1 mN m−1 only for their hydrocarbon analog 4. The F-lipopeptides penetrate in the DPPC monolayers in both liquid expanded (LE) and liquid condensed (LC) phases without interfacial film destabilization. By contrast, 4 provokes delipidation of the interfacial film. The incorporation of the F-lipopeptides 1–3 in microbubbles with a shell of DPPC and dipalmitoylphosphatidylethanolamine-PEG2000 decreased their mean diameter and increased their stability, the best results being obtained for the C8F17-bearing lipopeptide 3. By contrast, the hydrocarbon lipopeptide led to microbubbles with a larger mean diameter and a significantly lower stability.