Solvent free mechanical grinding assisted synthesis of reduced graphene oxide and its composites with porphyrins for fabricating UV–vis photodetectors

Reduced graphene oxide (rGO) is one of the most demanding carbon based materials for energy conversion and optoelectronics. However, its synthesis from graphene oxide (GO) is still challenging and requires high-energy consumption with longer reaction time. Herein, a solvent free mechanical grinding (MG) method was realized for synthesizing rGO from GO by mechanical grinding for 30 minutes (MG-0.5H) and one hour (MG-1H). The formation of rGO was confirmed spectroscopically with substantial oxygen reduction in MG-1H, restoration of sp² conjugation, and the C/O ratio of approximately 5.59. Furthermore, we prepared its composites with hemin (Hm) and protoporphyrin IX (P IX) using an ex-situ (E) MG method, along with conventional solvent assisted in-situ (I) method and named as rGO-HmE, rGO-P(IX)E, GO-HmI, rGO-P(IX)I. These materials were subjected to a facile technique for fabricating photodetectors that exhibit detectivity of 1.43 × 10¹³, 2.68 × 10¹³, 9.98 × 10¹³, and 4.91 × 10¹³ Jones respectively. Such high detectivity is due to π-π interaction and electron transfer between rGO and the porphyrins and hence the materials do not require supporting materials such as electron and hole transport layer to enhance the efficacy of the photodetectors. Therefore, it can be stated that the mechanical grinding method serve as a greener alternative with low-cost, low-energy consumption, short reaction time for the synthesis of superior optoelectronic material and its composites.