Water Adsorption Property of Hierarchically Nanoporous Detonation Nanodiamonds

Powders of Diamond Nanoparticles as a Promising Material for Reflectors of Very Cold and Cold Neutrons

More than 15 years ago, the study of nanodiamond (ND) powders as a material for designing reflectors of very cold neutrons (VCNs) and cold neutrons (CNs) began. Such reflectors can significantly increase the efficiency of using such neutrons and expand the scope of their application for solving applied and fundamental problems. This review considers the principle of operation of VCN and CN reflectors based on ND powders and their advantages. Information is presented on the performed experimental and theoretical studies of the effect of the size, structure, and composition of NDs on the efficiency of reflectors. Methods of chemical and mechanical treatments of powders in order to modify their chemical composition and structure are discussed. The aim is to avoid, or at least to decrease, the neutron inelastic scatterers and absorbers (mainly hydrogen atoms but also metallic impurities and nitrogen) as well as to enhance coherent elastic scattering (to destroy ND clusters and sp2 carbon shells on the ND surface that result from the preparation of NDs). Issues requiring further study are identified. They include deeper purification of NDs from impurities that can be activated in high radiation fluxes, the stability of NDs in high radiation fluxes, and upscaling methods for producing larger quantities of ND powders. Possible ways of solving these problems are proposed.

Room-Temperature Oxygen Dissociative Chemisorption on Carbon Surface-Experimental Evidence

Oxygen interaction with the carbon surface is one of the most important topics of study in the field of material chemistry. In this work, experimental evidence for molecular oxygen dissociative chemisorption on a carbon surface at room temperature is shown for the first time. It was determined that the process occurs only on the bare carbon surface, and the quantitative description of the phenomena is possible using the Temkin model, which explains an almost linear decrease in the calorimetric heat of adsorption. The results provided by in situ infrared studies show that surface carbonyl oxides appear as intermediates of final functionality, i.e., carbonyl structures. Examining the thermal stability of surface structures shows that all surface species decompose at temperatures below 500 °C, leaving a pristine carbon surface.

Complex Dispersion of Detonation Nanodiamond Revealed by Machine Learning Assisted Cryo-TEM and Coarse-Grained Molecular Dynamics Simulations

Understanding the polydispersity of nanoparticles is crucial for establishing the efficacy and safety of their role as drug delivery carriers in biomedical applications. Detonation nanodiamonds (DNDs), 3-5 nm diamond nanoparticles synthesized through detonation process, have attracted great interest for drug delivery due to their colloidal stability in water and their biocompatibility. More recent studies have challenged the consensus that DNDs are monodispersed after their fabrication, with their aggregate formation poorly understood. Here, we present a novel characterization method of combining machine learning with direct cryo-transmission electron microscopy imaging to characterize the unique colloidal behavior of DNDs. Together with small-angle X-ray scattering and mesoscale simulations we show and explain the clear differences in the aggregation behavior between positively and negatively charged DNDs. Our new method can be applied to other complex particle systems, which builds essential knowledge for the safe implementation of nanoparticles in drug delivery.

Sorption and Magnetic Properties of Oxalato-Based Trimetallic Open Framework Stabilized by Charge-Assisted Hydrogen Bonds

We report a new structure of {[Co(bpy)₂(ox)][{Cu₂(bpy)₂(ox)}Fe(ox)₃]}_n·8.5nH₂O NCU-1 presenting a rare ladder topology among oxalate-based coordination polymers with anionic chains composed of alternately arranged [Cu₂(bpy)₂(ox)]²⁺ and [Fe(ox)₃]³⁻ moieties. Along the a axis, they are separated by Co(III) units to give porous material with voids of 963.7 ų (16.9% of cell volume). The stability of this structure is assured by a network of stacking interactions and charge-assisted C-H…O hydrogen bonds formed between adjacent chains, adjacent cobalt(III) units, and alternately arranged cobalt(III) and chain motifs. The soaking experiment with acetonitrile and bromobenzene showed that water molecules (8.5 water molecules dispersed over 15 positions) are bonded tightly, despite partial occupancy. Water adsorption experiments are described by a D’arcy and Watt model being the sum of Langmuir and Dubinin–Serpinski isotherms. The amount of primary adsorption sites calculated from this model is equal 8.2 mol H₂O/mol, being very close to the value obtained from the XRD experiments and indicates that water was adsorbed mainly on the primary sites. The antiferromagnetic properties could be only approximately described with the simple Cu^II-ox-Cu^II dimer using H = −J·S₁·S₂, thus, considering non-trivial topology of the whole Cu-Fe chain, we developed our own general approach, based on the semiclassical model (SC) and molecular field (MF) model, to describe precisely the magnetic superexchange interactions in NCU-1. We established that Cu(II)-Cu(II) coupling dominates over multiple Cu(II)-Fe(III) interactions, with J_CuCu = −275(29) and J_CuFe = −3.8(1.6) cm⁻¹ and discussed the obtained values against the literature data.

Pore-Mouth Structure of Highly Agglomerated Detonation Nanodiamonds

Detonation nanodiamond aggregates contain water that is removed by thermal treatments in vacuo, leaving available pores for the adsorption of target molecules. A hard hydrogel of detonation nanodiamonds was thermally treated at 423 K for 2 h, 10 h, and 52 h in vacuo to determine the intensive water adsorption sites and clarify the hygroscopic nature of nanodiamonds. Nanodiamond aggregates heated for long periods in vacuo agglomerate due to the removal of structural water molecules through the shrinkage and/or collapse of the pores. The agglomerated nanodiamond structure that results from long heating periods decreases the nitrogen adsorption but increases the water adsorption by 40%. Nanodiamonds heated for long times possess ultramicropores <0.4 nm in diameter in which only water molecules can be adsorbed, and the characteristic mouth-shaped mesopores adsorb 60% more water than nitrogen. The pore mouth controls the adsorption in the mesopores. Long-term dehydration partially distorts the pore mouth, decreasing the nitrogen adsorption. Furthermore, the nitrogen adsorbed at the pore mouth suppresses additional nitrogen adsorption. Consequently, the mesopores are not fully accessible to nitrogen molecules because the pore entrances are blocked by polar groups. Thus, mildly oxidized detonation nanodiamond particles can show a unique molecular sieving behavior.

Simulating facet-dependent aggregation and assembly of distributions of polyhedral nanoparticles

Coarse-grained molecular dynamics simulations of diamond nanoparticles were performed to investigate the effects of size polydispersity on three polyhedral shapes chosen to span a diverse space of surface interactions. It was found that the resulting self-assembly was size dependent as the simulations were quenched, with the largest nanoparticles providing a clustered scaffold for subsequent smaller nanoparticle assembly. Additionally, facet-facet interactions were dominated by the {111} surface and the resulting aggregate was dominated by meso-sized porosity for monodisperse systems, broadening to larger diameters for polydisperse systems.

Ultrafast and simultaneous removal of anionic and cationic dyes by nanodiamond/UiO-66 hybrid nanocomposite

In this research, UiO-66 and its composite nanoparticles with thermally oxidized nanodiamond (OND) were synthesized via a simple solvothermal method and utilized as solid adsorbent for the removal of anionic methyl red (MR) dye and cationic malachite green (MG) dye from contaminated water. The synthesized adsorbents were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), N₂ adsorption-desorption, and zeta potential analyzer. The influences of various factors such as initial concentrations of the dyes, adsorption process time, solution pH, solution temperature and ionic strength on adsorption behavior of MR dye onto OND-UiO hybrid nanoparticle were investigated. The adsorption of MR onto OND-UiO hybrid nanoparticle could be well described by Langmuir isotherm model. Meanwhile, pseudo-second order kinetic model was found to be suitable for illustration of adsorption kinetics of MR onto OND-UiO. Thermodynamic investigation suggested that the adsorption process was spontaneous and endothermic, and controlled by an entropy change instead of enthalpy effect. The experimental adsorption results indicated that OND-UiO hybrid nanoparticle could simultaneously adsorb 59% of MR and 43% of MG from the mixture of both dyes in only 2 min showing synergistic effect compared with single UiO-66 and OND nanoparticles in terms of adsorption rate and removal capacity of anionic dyes. The appropriate removal efficiency, rapid adsorption kinetic, high water stability, and good reusability make OND-UiO hybrid nanoparticle attractive candidate for simultaneously removal of both anionic MR and cationic MG dyes from wastewater.

Dynamic self-assembly of detonation nanodiamond in water

Nanodiamonds are increasingly used in many areas of science and technology, yet, their colloidal properties remain poorly understood. Here we use direct imaging as well as light and X-ray scattering reveal that purified detonation nanodiamond (DND) particles in an aqueous environment exhibit a self-assembled lace-like network, even without additional surface modification. Such behaviour is previously unknown and contradicts the current consensus that DND exists as mono-dispersed single particles. With the aid of mesoscale simulations, we show that the lace network is likely the result of competition between a short-ranged electrostatic attraction between faceted particles and a longer-ranged repulsion arising from the interaction between the surface functional groups and the surrounding water molecules which prevents complete flocculation. Our findings have significant implications for applications of DND where control of the aggregation behaviour is critical to performance.

Fabrication of detonation nanodiamond@sodium alginate hydrogel beads and their performance in sunlight-triggered water release

Agricultural water use accounts for around 70% of total water use in the world. Enhancing agricultural water use efficiency is a key way to cope with water shortage. Here, sunlight-responsive hydrogel beads consisting of sodium alginate (SA) matrix and detonation nanodiamond (DND) were fabricated by an ion gelation technique, which has potential applications in controlled water release. The interaction between the DND and SA matrix was investigated by Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD). UV-vis diffuse reflectance spectra verified DND can absorb solar energy in the UV, visible and even near-infrared regions. DND dispersed in the hydrogel matrix can absorb sunlight and generate heat, increasing the temperature of the matrix and resulting in slow release of water from the elastic beads. In addition, the effects of DND content and pH were systematically studied to evaluate their water adsorption properties. The swelling kinetics of DND@SA hydrogel beads in distilled water could be fitted well with a pseudo-second-order kinetic model. Six consecutive cycles of water release-reswelling indicated that their easy regeneration and reusability. The novel and eco-friendly hydrogel beads should be applicable to on-demand, sequential, and long-term release of water via light exposure.

Unusual hygroscopic nature of nanodiamonds in comparison with well-known porous materials

Nanodiamond aggregates have interparticle pores of 4.5 nm on average, exhibiting porous nature involved in their water storage. This work studies the hygroscopic nature of porous nanodiamond aggregates by water absorption based on liquid water droplets. Nanodiamond aggregates show hydrophobicity from the water vapor adsorption. Surprisingly, porous nanodiamond aggregates quickly absorb water droplets at the bulk scale. The volume of absorbed liquid water is comparable to that of the water-absorbing clay Montmorillonite and higher than those of zeolites ZSM-5 and molecular sieve 5A. This hygroscopic nature of nanodiamonds is ascribed to the micro- and mesoporous structure of their aggregates and the special core-shell structure of each nanodiamond particle (wrapped by graphene-like carbon). The absorption rate of liquid water in the porous nanodiamonds is influenced by the surface wettability, while the hygroscopic capacity depends mainly on the hierarchical porosity.

Predicting the impact of structural diversity on the performance of nanodiamond drug carriers

Diamond nanoparticles (nanodiamonds) are unique among carbon nanomaterials, and are quickly establishing a niché in the biomedical application domain. Nanodiamonds are non-toxic, amenable to economically viable mass production, and can be interfaced with a variety of functional moieties. However, developmental challenges arise due to the chemical complexity and structural diversity inherent in nanodiamond samples. Nanodiamonds present a narrow, but significant, distribution of sizes, a dizzying array of possible shapes, and a complicated surface containing aliphatic and aromatic carbon. In the past these facts have been cast as hindrances, stalling development until perfectly monodispersed samples could be achieved. Current research has moved in a different direction, exploring ways that the polydispersivity of nanodiamond samples can be used as a new degree of engineering freedom, and understanding the impact our limited synthetic control really has upon structure/property relationships. In this review a series of computational and statistical studies will be summarised and reviewed, to characterise the relationship between chemical complexity, structural diversity and the reactive performance of nanodiamond drug carriers.

Novel biocatalytic systems for maintaining the nucleotide balance based on adenylate kinase immobilized on carbon nanostructures

In this study graphene oxide (GO), carbon quantum dots (CQD) and carbon nanoonions (CNO) have been characterized and applied for the first time as a matrix for recombinant adenylate kinase (AK, EC 2.7.4.3) immobilization. AK is an enzyme fulfilling a key role in metabolic processes. This phosphotransferase catalyzes the interconversion of adenine nucleotides (ATP, ADP and AMP) and thereby participates in nucleotide homeostasis, monitors a cellular energy charge as well as acts as a component of purinergic signaling system. The AK activity in all obtained biocatalytic systems was higher as compared to the free enzyme. We have found that the immobilization on carbon nanostructures increased both activity and stability of AK. Moreover, the biocatalytic systems consisting of AK immobilized on carbon nanostructures can be easily and efficiently lyophilized without risk of desorption or decrease in the catalytic activity of the investigated enzyme. The positive action of AK-GO biocatalytic system in maintaining the nucleotide balance in in vitro cell culture was proved.