# Size-dependent reactivity of diamond nanoparticles.
> ダイヤモンドナノ粒子の水素表面修飾によるサイズ依存的反応性と分散安定化


## Abstract

Diamond nanoparticles of approximately 4 nm diameter are promising candidates for drug delivery and fluorescence monitoring due to their photostability, but aggregate formation limits their practical use. This study presents a method in which aggregated nanodiamond powder is annealed in hydrogen gas, breaking down large aggregates exceeding 100 nm into their constituent ~4 nm core particles. Subsequent high-power ultrasonication and high-speed centrifugation yield a monodisperse colloidal suspension exhibiting long-term stability across a broad pH range and a strongly positive zeta potential above 60 mV. Notably, the pronounced shift in zeta potential following hydrogen gas exposure indicates that the surfaces of ~4 nm nanoparticles react with molecular hydrogen at relatively low temperatures, a reactivity absent in larger 20 nm diamond particles and bulk diamond surfaces, confirming a size-dependent interaction with H2.

### Mechanism

Annealing in hydrogen gas causes ~4 nm nanodiamond surfaces to react with molecular H2 at low temperatures, substantially altering surface charge (zeta potential) and preventing aggregation. This reactivity is size-dependent and is not observed in particles of 20 nm or larger.

## Bibliographic

- **Authors**: Williams OA, Hees J, Dieker C, Jäger W, Kirste L, Nebel CE
- **Journal**: ACS Nano
- **Year**: 2010 (2010-08-24)
- **PMID**: [20731457](https://pubmed.ncbi.nlm.nih.gov/20731457/)
- **DOI**: [10.1021/nn100748k](https://doi.org/10.1021/nn100748k)
- **Study type**: other
- **Delivery route**: not specified
- **Effect reported**: not assessed

## Delivery context

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)

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> **Cite as**: H2 Papers — PMID 20731457. https://h2-papers.org/en/papers/20731457
> **Source**: PubMed PMID [20731457](https://pubmed.ncbi.nlm.nih.gov/20731457/)