Experimental All of the chemicals used – potassium permanganate (KMnO4), potassium hydroxide (KOH), hydrochloric acid (HCl), boric acid (H3BO3), urea (CO(NH2)2), and melamine (C3H3N6) – were supplied by Sigma-Aldrich Company, Ltd. (St. Louis, MO, USA). The natural minerals tungstenite (WS2) and molybdenite (MoS2) were obtained from US Research Nanomaterials, Inc. (Houston, TX, USA) and from Rokospol Ltd. (Uherský Brod, Czech Republic), respectively. Preparation of bulk h-BN and h-BCN The bulk h-BN was prepared from boric acid and urea by the modified method reported by Nag et al. [33]. This chemical method allows for the control of the number of layers through the composition of the starting feedstock because the number

of BN layers decreases with increasing urea content in the reaction mixture. The boric acid and urea, in a molar ratio of 1:3, were dissolved in 100 ml of water and heated at 70°C until the full evaporation of water occurred. The selleck chemical dried crystal powder was heated at 950°C for 5 h under a nitrogen atmosphere. To synthesize the h-BCN bulk compound [34], boric acid was mixed with melamine in the ratio of 1:2 in an agate mortar. The mixture was then heated in a beaker at 200°C for 1 h and subsequently at 300°C for an additional 2 h. The obtained precursor was heated under a nitrogen atmosphere

at 1,300°C for 5 h. Preparation of bulk g-C3N4 The g-C3N4 was prepared by direct heating of 5 g melamine powder and was put into an alumina crucible with a cover [35]. The sample was heated at 580°C for 2 h with a heat MK-2206 rate of 10°C/min. After heating, a yellow powder of bulk g-C3N4 was obtained. Exfoliated samples in a hydrophobic environment Exfoliated MoS2, WS2, h-BN, h-BCN, and g-C3N4 were prepared in a large quantity from synthesized bulk samples

CYTH4 by using a high-intensity cavitation field in a pressurized ultrasound reactor (UIP2000 hd, 20 kHz, 2,000 W, Hielscher Ultrasonics, GmbH, Teltow, Germany). A portion of 0.75 to 1 g of the bulk sample was suspended in 120 ml of appropriate aprotic solvent (N-methyl-2-pyrrolidone, N,N-dimethylformamide, or dimethyl sulfoxide) and exposed to an intense cavitation field in a pressurized batch ultrasonic reactor for 20 min. The pressure of 6 bar was set in the reactor by means of an air compressor [29]. The exfoliation led to the formation of stable suspensions in the hydrophobic (organophilic) solvents. Exfoliated samples in a hydrophilic environment The exfoliated IAGs stabilized in an aqueous solution were prepared through high-intensity ultrasound in a solution of KMnO4 in an alkaline environment. Generally, 1 g of IAG was mixed with 120 ml of an aqueous solution of 1.5 g KMnO4 and 24 g KOH in an ultrasonic reactor. The reactor was sealed and pressurized to 6 bar, and the reaction mixture was sonicated for 10 min. After irradiation, a suspension of IAG and MnO2 in a dark green solution of K2MnO4 was obtained.