Efficient chlorine atom functionalization at nanodiamond surfaces by electron beam irradiation

Abstract

Surface functionality of nanodiamonds is of crucial importance for their desired chemical, optical and electromagnetic properties. Chlorinated surfaces are expected to enable an easy further modification of diamond surfaces via various substitution reactions for targeted molecule grafting, particularly interesting for biochemical applications. Previously reported chlorination approaches of diamonds required troublesome handling of hazardous chemicals, such as chlorine gas, and long chlorination time or high temperature. Here, we describe a radiation chemistry approach using electron beam irradiation for efficient surface chlorination of nanodiamonds (with averaged diameter of ca. 30 nm) at ambient temperature. Nanodiamonds with hydrogenated and graphitized surfaces were used for chlorination in CCl4, CHCl3 and CH2Cl2 at increasing radiation doses. A comprehensive set of measurements, including XPS, ATR-FTIR and in-source thermal desorption mass spectrometry (IS-TD-MS) was applied to characterize the chlorinated products. Density functional theory (DFT) calculations were performed to assist the discussion of reaction mechanisms. It is confirmed that remarkable covalently chlorine-covered surfaces bearing adequate stability against air and water were achieved for hydrogenated nanodiamonds in CCl4 by applying doses ≥500 kGy.