Expression of concern: Fe3O4/PEG-SO3H as a heterogeneous and magnetically-recyclable nanocatalyst for the oxidation of sulfides to sulfones or sulfoxides

Expression of concern for ‘Fe 3 O 4 /PEG-SO 3 H as a heterogeneous and magnetically-recyclable nanocatalyst for the oxidation of sulfides to sulfones or sulfoxides’ by Saeideh Mirfakhraei et al. , New J. Chem. , 2018, 42 , 1757–1761, https://doi.org/10.1039/C7NJ02513K.