Search

Nanodiamonds containing negatively charged nitrogen-vacancy (NV−) centers are versatile room-temperature quantum sensors in a growing field of research. Yet, knowledge regarding the NV− formation mechanism in very small particles is still limited. This study focuses on the formation of the smallest NV−-containing diamonds, 5 nm detonation nanodiamonds (DNDs). As a reliable method to quantify NV− centers in nanodiamonds, half-field signals in electron paramagnetic resonance (EPR) spectroscopy are recorded. By comparing the NV− concentration with a series of nanodiamonds from high-pressure high-temperature (HPHT) synthesis (10−100 nm), it is shown that the formation process in 5 nm DNDs is unique in several aspects. NV− centers in DNDs are already formed at the stage of electron irradiation, without the need for high-temperature annealing, an effect related to the very small particle size. Also, the NV− concentration (in atomic ratio) in 5 nm DNDs surpasses that of 20 nm-sized nanodiamonds, which contradicts the observation that the NV− concentration generally increases with particle size. This can be explained by the 10 times higher concentration of substitutional nitrogen atoms in the studied DNDs ([NS ≈ 1000 ppm]) compared to the HPHT nanodiamonds ([NS ≈ 100 ppm]). Upon electron irradiation at a fluence of 1.5 × 10^19 e−/cm2, DNDs show a 12.5-fold increment in the NV− concentration with no sign of saturation reaching 1 out of about 80 DNDs containing an NV− center. These findings can be of interest for the creation of defects in other very small semiconductor nanoparticles beyond NV-nanodiamonds as quantum sensors., The Journal of Physical Chemistry C, 126 (11), ISSN:1932-7455, ISSN:1932-7447

Detonation nanodiamonds (DNDs) are a class of very small and spherical diamond nanocrystals. They are used in polymer reinforcement materials or as drug delivery systems in the field of nanomedicine. Synthesized by detonation, only the final deaggregation step down to the single-digit nanometer size (, Nanoscale Advances, 4 (10), ISSN:2516-0230

Detonation nanodiamonds (DNDs) with sizes below 10 nm have attracted attention as single photon emitters with potential in many research fields from life sciences to quantum technologies. However, while nitrogen-vacancy (NV) color centers are found in nanodiamonds directly after the detonation synthesis without the need for irradiation or annealing, silicon-vacancy (SiV) color centers are not present in these pristine samples. Herein, SiV centers are created in DNDs by an annealing treatment up to 1100 °C in high vacuum. As silicon is not added, the precursor of the SiV centers must be pristine silicon impurities inside the nanodiamond lattice. A sharp emission line at the wavelength of 737 nm with a linewidth of 7.7 nm is observed in DNDs that are electron irradiated before annealing. This wavelength is consistent with the characteristic emission line of SiV centers and its linewidth is comparable with that in larger nanodiamonds created by chemical vapor deposition and subsequent milling. The average lifetime (0.4 ± 0.04 ns) of the fluorescence, which is in the range of reported lifetimes in nanodiamonds, also support that the observed emission peak are due to SiV centers in DNDs., Physica Status Solidi A, 218 (19), ISSN:1862-6300, ISSN:1862-6319, ISSN:0031-8965, ISSN:1521-396X

Fluorescent nanodiamonds (FNDs) have been attracting much attention as promising therapeutic agents and probes for bioimaging and nanosensing. For their biological applications, several hydrophilizing methods to enhance FND colloidal stability have been developed to suppress their aggregation and the nonspecific adsorption to biomolecules in complex biomedical environments. However, these methods involve several complicated synthetic and purification steps, which prohibit the use of FNDs for bioapplications by biologists. In this study, we describe a simple one-pot FND hydrophilization method that comprises coating of the surface of the nanoparticles with COOH-terminated hyperbranched polyglycerol (HPG-COOH). HPG-COOH-coated FNDs (FND-HPG-COOHs) were found to exhibit excellent dispersibility under physiological conditions despite the thinness of the 5 nm HPG-COOH layer. Biotinylated FND-HPG-COOHs specifically captured avidin molecules in the absence of nonspecific protein adsorption. Moreover, we demonstrated that FND-HPG-COOHs conjugated with antibodies can be used to selectively target integrins in fixed HeLa cells. In addition, intracellular temperature changes were measured via optically detected magnetic resonance using FND-HPG-COOHs conjugated with mitochondrial localization signal peptides. Our one-pot synthetic method will encourage the broad use of FNDs among molecular and cellular biologists and pave the way for extensive biological and biomedical applications of FNDs.

Background Nanodiamonds (NDs) provide a unique multitasking system for drug delivery and fluorescent imaging in biological environments. Owing to their quantum properties, NDs are expected to be employed as multifunctional probes in the future for the accurate visualization of biophysical parameters such as temperature and magnetic fields. However, the use of NDs for the selective targeting of the biomolecules of interest within a complicated biological system remains a challenge. One of the most promising solutions is the appropriate surface design of NDs based on organic chemistry and biochemistry. The engineered NDs have high biocompatibility and dispersibility in a biological environment and hence undergo cellular uptake through specific pathways. Scope of review This review focuses on the selective targeting of NDs for biomedical and biophysical applications from the viewpoint of ND surface functionalizations and modifications. These pretreatments make possible the specific targeting of biomolecules of interest on or in a cell by NDs via a designed biochemical route. Major conclusions The surface of NDs is covalently or noncovalently modified with silica, polymers, or biomolecules to reshape them, control their size, and enhance the colloidal stability and biomolecular selectivity toward the biomolecules of interest. Electroporation, chemical treatment, injection, or endocytosis are the methods generally adopted to introduce NDs into living cells. The pathway, efficiency, and the cell viability depend on the selected method. General significance In the biomedical field, the surface modification facilitates specific delivery of a drug, leading to a higher therapeutic efficacy. In biophysical applications, the surface modification paves the way for the accurate measurement of physical parameters to gain a better understanding of various cell functions.