Efficient and Scalable Production of 2D Material Dispersions using Hexahydroxytriphenylene as a Versatile Exfoliant and Dispersant

Thin‐layer 2D materials have been attracting enormous interest, and various processes have been investigated to obtain these materials efficiently. In view of their practical applications, the most desirable source for the preparation of these thin‐layer materials is the pristine bulk materials with stacked layers, such as pristine graphite. There are many options in terms of conditions for the exfoliation of thin‐layer materials, and these include wet and dry processes, with or without additives, and the kind of solvent. In this context, we found that the versatile exfoliant hexahydroxytriphenylene works efficiently for the exfoliation of typical 2D materials such as graphene, MoS₂, and hexagonal boron nitride (h‐BN) by both wet and dry processes by using sonication and ball milling, respectively, in aqueous and organic solvents. As for graphene, stable dispersions with relatively high concentrations (up to 0.28 mg mL^?1) in water and tetrahydrofuran were obtained from graphite in the presence of hexahydroxytriphenylene by a wet process with the use of bath sonication and by a dry process involving ball milling. Especially, most of the graphite was exfoliated and dispersed as thin‐layer graphene in both aqueous and organic solvents through ball milling, even on a large scale (47–86 % yield). In addition, the exfoliant was easily removed from the precipitated composite by heat treatment without disturbing the graphene structure. Bulk MoS₂ and h‐BN were also exfoliated by both wet and dry processes. Similar to graphene, dispersions of MoS₂ and h‐BN of high concentrations in water and DMF were produced in high yields through ball milling.     

Surface Chemistry and Catalytic Reactivity of Borocarbonitride in Oxidative Dehydrogenation of Propane

Borocarbonitride (BCN) materials are newly developed oxidative dehydrogenation catalysts that can efficiently convert alkanes to alkenes. However, BCN materials tend to form bulky B₂O₃ due to over-oxidation at the high reaction temperature, resulting in significant deactivation. Here, we report a series of super stable BCN nanosheets for the oxidative dehydrogenation of propane (ODHP) reaction. The catalytic performance of the BCN nanosheets can be easily regulated by changing the guanine dosage. The control experiment and structural characterization indicate that the introduction of a suitable amount of carbon could prevent the formation of excessive B₂O₃ from BCN materials and maintain the 2D skeleton at a high temperature of 520 °C. The best-performing catalyst BCN exhibits 81.9 % selectivity towards olefins with a stable propane conversion of 35.8 %, and the propene productivity reaches 16.2 mmol h⁻¹ g⁻¹, which is much better than hexagonal BN (h-BN) catalysts. Density functional theory calculation results show that the presence of dispersed rather than aggregated carbon atoms can significantly affect the electronic microenvironment of h-BN, thereby boosting the catalytic activity of BCN.     

Structural analysis of boron compounds using 11B-3QMAS solid state NMR

The structural analysis of three boron compounds, boron carbide (B₄C), silicon tetraboride (SiB₄) and hexagonal-boron nitride (h-BN), were performed using 2D ¹¹B-triple quantum MAS (3QMAS) solid state NMR capable of averaging the second-order quadrupolar interaction of ¹¹B that cause line broadening, splitting and low frequency shift of the central transition (−1/2, 1/2). The coordination number around the boron atom and structural symmetry of each boron compound is discussed by means of the isotropic chemical shift Δσ and the quadrupolar coupling constant C_Q calculated from 3QMAS spectra. Δσ of SiB₄ is quite larger than that of B₄C, which is thought to be caused by its structural distortion and distribution. Δσ of h-BN was found to be higher frequency shift obviously than that of B₄C and SiB₄ because of the difference of the boron coordination number, three-coordinated in h-BN and six-coordinated in B₄C and SiB₄. h-BN has very large C_Q compared to other two boron compounds since the h-BN forming a two-dimensional network has less structural symmetry than B₄C and SiB₄.     

Exploring two-dimensional graphene and boron-nitride as potential nanocarriers for cytarabine and clofarabine anti-cancer drugs

Development in two-dimensional (2D) drug-delivery materials have quickly translated into biological and pharmacological fields. In this present work, pristine graphene (PG) and hexagonal boron nitride (h-BN) sheets are explored as a drug carrier for cytarabine (CYT) and clofarabine (CLF) anti-cancer drugs using density functional theory (DFT). The obtained geometrical, energetic and electronic properties revealed that the PG sheet is more reactive and it adsorbs CYT and CLF anti-cancer drugs better than the h-BN sheet. The adsorption energies of CYT and CLF on PG sheet is -24.293 and -23.308 kcal/mol respectively, this is due to the delocalized electrons present in the PG sheet. The flow of electron direction between anti-cancer drugs and 2D sheet are calculated by ΔN, ΔE_A(B), and ΔE_B(A) parameters and Natural bond orbital analysis (NBO). The electronic and optical properties are calculated to understand the chemical reactivity and stability of the complex systems. The obtained results exhibit that the PG sheet retains significant therapeutic potential as a drug delivery vehicle for a drug molecule to treat cancer therapy.     

Physicochemical and Biochemical Profiling of Diphenyl Diselenide

The objective of the present study was to evaluate the physicochemical and biochemical profiling of diphenyl diselenide (PhSe)₂, a selenoorganic compound with biological activity. Experimental protocols were established for chemical stability in isotonic phosphate buffer (PBS) pH 7.4 and in simulated gastric and intestinal fluids, biological stability (bovine serum albumin (BSA) and plasma), solubility in PBS pH 7.4, distribution coefficient (Log D) in octanol/PBS, and determination of free (PhSe)₂ concentrations in BSA and plasma by using liquid chromatography with ultraviolet detection and tandem mass spectrometry. (PhSe)₂ was found to be chemically stable and not susceptible to degradation in plasma. The aqueous solubility was 0.98?±?0.072 μM and the Log D in octanol/PBS system was found to be 3.13. The percentage of unbound fractions of (PhSe)₂ obtained by equilibrium dialysis from BSA and plasma incubated with 100 μM (PhSe)₂ were 0.69?±?0.12 and 0.44?±?0.09 %, respectively. The findings indicated that (PhSe)₂ presents chemical and biological stability. Though, the compound showed low aqueous solubility, high Log D value and high binding to plasmatic protein. These data contribute to the knowledge of the toxicokinetic properties of (PhSe)₂ and further explain its low bioavailability in experimental models.     

Degradation of Structurally Defined Graphene Nanoribbons by Myeloperoxidase and the Photo-Fenton Reaction

As an emerging member of the graphene family, structurally defined graphene nanoribbons (GNRs) have shown promising applications in various fields. The evaluation of the degradability of GNRs is particularly important for assessing the persistence level and risk of these materials in living organisms and the environment. However, there is a void in the study of the degradation of GNRs. Here, we report the degradation behavior of GNRs in the presence of human myeloperoxidase (hMPO) or treated with the photo-Fenton (PF) reaction. With the assistance of potassium hydroxide or imidazole, which facilitates the dispersion of GNRs in the aqueous solution, GNRs underwent only partial degradation after 25-hour incubation with hMPO, while, the PF reaction degraded GNRs almost completely after 120 hours. These results indicate that structurally precise GNRs can be efficiently degraded under suitable conditions, providing more opportunities for future applications in different fields.     

Visible Light Induced Water Cleavage in CdS Dispersions Loaded with Pt and RuO2, Hole Scavenging by RuO2

Illumination of aqueous CdS dispersions loaded with Pt and RuO₂ by visible light produces hydrogen and oxygen in stoichiometric proportion. No degradation of the photocatalyst is noted after 60 h of irradiation time. The RuO₂ deposit on the particle surface greatly accelerates the transfer of holes from the semiconductor valence band to the aqueous solution thus inhibiting photocorrosion.     

Degradation kinetics of fluvoxamine in buffer solutions: In silico ADMET profiling and identification of degradation products by LC-MS/ESI

The kinetics of hydrolysis of fluvoxamine maleate (FLV) has been investigated over the pH range 1.0–12.0 at 40, 60 and 80 °C. FLV degradation follows pseudo-first-order kinetics which is consistent with the kinetics of drugs that are not readily dissolved in aqueous medium. The hydrolytic degradation rate constant (k_obs) range from 0.92 (pH 6.0) to 13.8 × 10⁻⁴ min⁻¹ (pH 1.0). The k_obs represents the sum of six different degradation rate constants; the k_H has been found to be higher than k_OH. The FLV exhibits a typical rate- pH profile with a flat bottom over the pH range 3.0–6.0 which indicates its maximum stability at pH 6.0. Ten FLV degradants have been predicted by Zeneth software and among them four degradation products (D1, D2, D3 and D4) have been identified in degraded samples. The in-silico pharmacokinetics and toxicity of degradation products have been determined using Swiss ADME and admetSAR software. The toxicity profile reveals that D2 is both AMES toxic and carcinogenic while the rest of the products are non-AMES toxic and non-carcinogenic. All of the degradation products are high in causing fish toxicity thus their presence in pharmaceutical waste is alarming for environmental safety.     

Poly(3,4‐ethylenedioxythiophene):GlycosAminoGlycan Aqueous Dispersions: Toward Electrically Conductive Bioactive Materials for Neural Interfaces

There is an actual need of advanced materials for the emerging field of bioelectronics. One commonly used material is the conducting polymer poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) due to its general use in organic electronics. However, depending on the application in bioelectronics, PEDOT:PSS is not fully biocompatible due to the high acidity of the residual sulfonate protons of PSS. In this paper, the synthesis and biocompatibility properties of new poly(3,4‐ethylenedioxythiophene):GlycosAminoGlycan (PEDOT:GAG) aqueous dispersions and its resulting films are shown. Thus, negatively charged GAGs as an alternative to PSS are presented. Three different commercially available GAGs, hyaluronic acid, heparin, and chondroitin sulfate are used. Indeed, PEDOT:GAGs dispersions are prepared through an oxidative chemical polymerization in water. Biocompatibility assays of the PEDOT:GAGs coatings are performed using SH‐SY5Y and CCF‐STTG1 cell lines and with ATP and Ca²⁺. Results show full biocompatibility and a pronounced anti‐inflammatory effect. This last characteristic becomes crucial if implanted in the body. These materials can be used for in vivo applications, as transistor or electrode for electrical recording and for all the possible situations when there is contact between electronic circuits and living tissues.

     

The influence of dissolved transition metals on the photocatalytic degradation of phenol with TiO2

The influence of dissolved cupric and ferric ions on the photocatalytic degradation of phenol in aqueous dispersions of titanium dioxide was investigated. At pH 3.5 both ion species enhanced the TiO₂ photocatalytic activity until an optimum metal concentration was reached (1×10^?3 M for Cu²⁺ and 7×10^?6 M for Fe³⁺). Beyond these values the activity was observed to decrease, what was mainly attributed to precipitation of metal derivatives. A mechanism based in the formation of a complex between the metal and the organic compound adsorbed onto the titania surface is proposed to explain the observed positive effect of copper and iron ions addition.     

Fabrication of super-macroporous nanocomposites by deposition of carbon nanotubes onto polymer cryogels

Electrically conducting super-macroporous carbon nanotube/polymer cryogel nanocomposites were fabricated by a novel approach based on deposition of carbon nanotubes (CNTs) onto the inner surface of pre-formed cryogels assisted by cryogenic treatment. Stable aqueous dispersions of multi-walled and single-walled carbon nanotubes were firstly obtained by non-covalent modification of pristine nanotubes with either pyrene containing polydimethylacrylamide or poly(ethylene oxide)₂₆-b-poly(propylene oxide)₄₀-b-poly(ethylene oxide)₂₆ copolymers and, then, exploited for the preparation of nanocomposites. The mechanical and electrical properties of nanocomposite materials were measured and compared to similar materials prepared by established method. The novel approach provided super-macroporous nanocomposites with high electrical conductivity (>10^?2 S/m) at much lower nanotube content (0.12 wt.%).     

Cu3(hexaiminotriphenylene)2: An Electrically Conductive 2D Metal–Organic Framework for Chemiresistive Sensing

The utility of metal–organic frameworks (MOFs) as functional materials in electronic devices has been limited to date by a lack of MOFs that display high electrical conductivity. Here, we report the synthesis of a new electrically conductive 2D MOF, Cu₃(HITP)₂ (HITP=2,3,6,7,10,11‐hexaiminotriphenylene), which displays a bulk conductivity of 0.2 S cm^?1 (pellet, two‐point‐probe). Devices synthesized by simple drop casting of Cu₃(HITP)₂ dispersions function as reversible chemiresistive sensors, capable of detecting sub‐ppm levels of ammonia vapor. Comparison with the isostructural 2D MOF Ni₃(HITP)₂ shows that the copper sites are critical for ammonia sensing, indicating that rational design/synthesis can be used to tune the functional properties of conductive MOFs.     

Chemiluminescence in the ozonation of C60 aqueous dispersions

Two types of chemiluminescence (CL) arising upon ozonation of crystalline, amorphous, and molecular aqueous dispersions of C₆₀ prepared in different ways were discovered and studied. The weak long-wavelength CL-1 (λ_max > 650 nm) is due to thermocatalytic decomposition of ozone on the surface of fullerene micro- and nanoparticles. The bright short-wavelength CL-2 (λ_max = 570 nm) is caused by generation of electronically excited states of the products of C₆₀ oxidation with ozone. CL-1 appears upon ozonation of aqueous dispersions of C₆₀ consisting of surface-hydrated crystalline micro- and nanoparticles by low concentrations of ozone. CL-2 is exhibited upon ozonation of nano-sized C₆₀ aqueous dispersions and colloid solutions, which contain C₆₀ molecules surrounded by a strong aqueous shell and their associates, by higher concentrations of ozone. Owing to shielding by the hydration shell, C₆₀ fullerene in aqueous dispersions is much less reactive towards ozone and forms oxidation products of different composition as compared with C₆₀ in organic solvents.     

Degradation of ofloxacin by UVA-LED/TiO<Subscript>2</Subscript> nanotube arrays photocatalytic fuel cells

The degradation of ofloxacin (OFX) at low concentration in aqueous solution by UVA-LED/TiO₂ nanotube arrays photocatalytic fuel cells (UVA-LED/TiO₂ NTs PFCs) was investigated. TiO₂ nanotube arrays (TiO₂ NTs) photoanode prepared by anodization-constituted anatase–rutile bicrystalline framework. The results indicated that the degradation efficiency of OFX by UVA-LED/TiO₂ NTs PFC was significantly enhanced by 14.3% compared with UVA-LED/TiO₂ NTs photocatalysis. The pH affected the degradation efficiency markedly; the highest degradation efficiency (95.0%) and the pseudo-first-order reaction rate constant k value (0.049 min^?1) were achieved in neutral condition (pH 7.0). The degradation efficiency increased with the increasing concentration of dissolved oxygen (DO) in the UVA-LED/TiO₂ NTs PFC. The main reactive species of OFX degradation are positive holes (h⁺) and superoxide ion radicals (O ₂ ^·? ) in a DO sufficient condition. Furthermore, the possible pathways of OFX degradation were proposed.     

Existence of the Sugar–Bisulfite Adducts and Its Inhibiting Effect on Degradation of Monosaccharide in Acid System

Degradation of fermentable monosaccharides is one of the primary concerns for acid prehydrolysis of lignocellulosic biomass. Recently, in our research on degradation of pure monosaccharides in aqueous SO₂ solution by gas chromatography (GC) analysis, we found that detected yield was not actual yield of each monosaccharide due to the existence of sugar–bisulfite adducts, and a new method was developed by ourselves which led to accurate detection of recovery yield of each monosaccharide in aqueous SO₂ solution by GC analysis. By the use of this method, degradation of each monosaccharide in aqueous SO₂ was investigated and results showed that sugar–bisulfite adducts have different inhibiting effect on degradation of each monosaccharide in aqueous SO₂ because of their different stability. In addition, NMR testing also demonstrated possible existence of reaction between conjugated based HSO₃ ^? and aldehyde group of sugars in acid system.     

The stability of graphene and boron nitride for III-nitride epitaxy and post-growth exfoliation

A challenging approach, but one providing a key solution to material growth, remote epitaxy (RE)—a novel concept related to van der Waals epitaxy (vdWE)—requires the stability of a two-dimensional (2-D) material. However, when graphene, a representative 2-D material, is present on substrates that have a nitrogen atom, graphene loss occurs. Although this phenomenon has remained a hurdle for over a decade, restricting the advantages of applying graphene in the growth of III-nitride materials, few previous studies have been conducted. Here, we report the stability of graphene on substrates containing oxygen or nitrogen atoms. Graphene has been observed on highly decomposed Al₂O₃; however, graphene loss occurred on decomposed AlN at temperatures over 1300 °C. To overcome graphene loss, we investigated 2-D hexagonal boron nitride (h-BN) as an alternative. Unlike graphene on AlN, it was confirmed that h-BN on AlN was intact after the same high-temperature process. Moreover, the overgrown AlN layers on both h-BN/AlN and h-BN/Al₂O₃ could be successfully exfoliated, which indicates that 2-D h-BN survived after AlN growth and underlines its availability for the vdWE/RE of III-nitrides with further mechanical transfer. By enhancing the stability of the 2-D material on the substrate, our study provides insights into the realization of a novel epitaxy concept.

A challenging approach, but one providing a key solution to material growth, remote epitaxy (RE)—a novel concept related to van der Waals epitaxy (vdWE)—requires the stability of a two-dimensional (2-D) material.     

13C NMR spectra of 1-stearoyl-2-linoleyl-sn-glycero-3-phosphorylcholine and 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine in CDCl3 solution and in sonicated dispersions in 2H2O

Two mixed-acid lecithins: 1-stearoyl-2-linoleyl-sn-glycero-3-phosphorylcholine (SLL) and 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (SAL) have been synthesized by phospholipase A₂ digestion of 1,2-distearoyl-sn-glycero-3-phosphorylcholine (DSL), followed by reacylation of the lysolecithin with the desired fatty acid anhydride. ¹³C (25.2 MHz) NMR spectra of SLL and SAL in CDCl₃ solution and in sonicated dispersions in ²H₂O have been obtained. Complete spectral assignments are reported for the two molecules in both systems. ¹³C nuclear spin-lattice relaxation times (T₁) of SLL and SAL in sonicated aqueous dispersions have also been measured. Relaxation rate profiles as a function of the chain segment position are in general agreement with those recently obtained from ²H NMR for similar systems.     

The Photocatalytic Degradation of Imazapyr

The degradation of imazapyr, an imidazolinone herbicide, in aqueous solution has been investigated with TiO₂ slurry as photocatalyst at 30°C under UV radiation. The depletion of imazapyr concentration in an aqueous suspension followed 1^st order kinetic behavior. The influence of pH and the charge densities of imazapyr geometries were calculated at the semi-empirical AM1 level, and the effect of temperature was investigated. The addition of electron acceptors such as potassium persulfate and hydrogen peroxide showed that the rate constant doubled at least. At higher persulfate concentrations the herbicide degradation was more efficient in direct photolysis than TiO₂-photocatalysis. The degradation rate constant increased by 38% upon variation of the temperature between 20.0 and 50.0°C and displayed non-Arrhenius behavior.     

Use of Gemini surfactants to stabilize TiO2 P25 colloidal dispersions

Photocatalytically active TiO₂ P25 nanoparticles, widely used for practical applications, were investigated. The nominal size of TiO₂ P25 nanoparticles is 21 nm, but they easily agglomerate in aqueous media, depending on pH and ionic strength. TiO₂ P25 aqueous dispersions were stabilized by alkanediyl-α,ω-bis-N-dodecyl-N, N′-dimethyl-ammonium bromide, cationic Gemini surfactant. The optimal conditions required to obtain stable dispersions, without formation of large agglomerates, were experienced. The stabilization of TiO₂ P25 nanoparticles by cationic Gemini surfactant was investigated in some details. Different amounts of Gemini surfactant were used, at concentrations between 1.0 and 250 × 10⁻⁶ mol L⁻¹, well below the critical micelle concentration. Dynamic light scattering and zeta potential analyses estimated the particle size and the dispersions stability. When the proper amount of Gemini surfactant was used, the resulting nanoparticles were still poly-disperse, but large agglomerates disappeared and were remarkably redispersible.