The bifunctionalization of graphene oxide (GO) has attracted attention as a promising tool for broadening applications, despite its many challenges, especially regarding site-specific reactions. Herein, we obtained mono-and bifunctionalized GO containing thiol and imidazole groups that were anchored on the carboxylic acid sites of GO via amidation reactions. We varied the bifunctionalization methodology and showed that consecutive addition of the reagents (containing imidazole and thiol groups) led to materials with higher degrees of functionalization, in contrast to their simultaneous addition. The functionalized materials were evaluated as nanocatalysts in the neutralization reaction of a toxic organophosphate. Also, it was evidenced that the effect of the mono-and bifunctionalized materials on the catalytic outcomes gives insight toward neighboring effects. All catalysts were effective in the reaction studied with the monofunctionalized materials (containing thiol or imidazole groups) showing similar activity. Among the bifunctionalized materials (with both thiol and imidazole moieties), the one with the lower degree of functionalization showed the best performance. This was attributed to a combination of mechanisms, strongly dependent on the neighboring groups: attraction on the GO surface, nucleophilic catalysis by thiol/imidazole groups, and bifunctional intramolecular catalysis, for example, by thiol and imidazole groups, assisting potential nucleophilic hydroxyl groups. Oddly, the bifunctionalized materials with the higher degree of functionalization did not show the most prominent activity; they were actually similar to the monofunctionalized ones. This can be attributed to the inhibition or hindering of some of the proposed mechanisms due to steric effects or a nonideal positioning of the groups. A lot remains to be clarified in this field, but one thing is clear: a higher degree of functionalization should not always be pursued because the application of the material is what should guide what characteristics should be determined. Several other applications should be impacted by neighboring effects, which are directly influenced by the functionalization procedure.

Organophosphorus compounds play an important role in the modern chemical industry and have a broad range of applications as flame retardants, agrochemicals and chemical warfare. Unfortunately, they still present a...

Chemical security has been a hot topic over several years, especially involving organophosphates (OP), which are related to organophosphorus chemical warfare and pesticides. The main challenges are to develop efficient ways to destroy stockpiles of these materials and also to monitor their presence in the field or food. A promising approach in this sense is the targeted design of catalysts that can react with OP and degrade them. Herein, we present a summary of some recent advances towards OP detoxification and monitoring that involves four different approaches: (i) How? Understanding the mechanism: thorough mechanistic elucidation and design of an ideal catalytic scaffold; (ii) Nanocatalysts and sensors: rational functionalization of carbon nanomaterials leading to nanocatalysts as powder and thin films. A surface-enhanced Raman scattering (SERS) sensor for OP was also obtained combining the functionalized material with silver nanoparticles; (iii) Catalysts from waste: reuse of rice husk waste as well as waste derived from the cheap gum arabic for developing biocatalysts that have high added-value and are environmentally friendly; (iv) A simple sensor: a simple, cheap and compact homemade colorimeter that can be used as a colorimetric sensor for detecting quantitatively various compounds, including pesticides.

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Two dimensional (2D) carbon nanomaterials such as few graphite layers or graphene are extensively studied due to their unique properties suitable to be exploiting in a wide range of technological applications. Recently, the growth of high quality graphene monolayers using insects and waste as carbon precursors was reported in the literature. This methodology opened a new way to convert the waste carbon into a high-value-added product. In the present work coconut coir dust, an agroindustrial biomass, was used as biotemplate for preparing carbonaceous materials. Carbon structures were synthesized through pyrolysis under nitrogen atmosphere (100mL/min) at 500, 1000, and 1500°C during 2 hours. Starting materials were coconut coir dust in natura and coconut coir dust hydrothermally treated. The samples were characterized by X-ray diffraction, Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Raman spectra showed the D band for all samples, related to the presence of defects in sp2 carbon structure and G band, indicative of graphite crystallites. It was also observed that the sample carbonized at 1500°C from coconut coir dust treated by hydrothermal method showed G’ band at 2685cm-1 associated with the stacking order along the c-axis. X-ray diffraction analysis showed a broad peak around 2θ= 22° related to the presence of amorphous carbon. By increasing the pyrolysis temperature changes in XRD diffractograms were observed and the sample which was pyrolysed at 1500°C from coconut coir dust hydrothermally treated showed peaks at 2θ= 26.5°, 43° e 45° assigned to (002), (100) (101) graphite plans, respectively. Scanning electron microscopy images showed the presence of overlapping sheets and plates. Transmission Electron Microscopy (TEM) images of coconut coir dust in natura unveiled the formation of amorphous sheet. Coconut coir dust in natura and treated by the hydrothermal method pyrolysed at 1500°C, lead to the formation of some graphitic domains and few graphene layers.