Supplementary Material The variation in the conductivity is observed in Cu2O nanostructure due to the adsorption of H2S gas molecules as discussed in the main article. Moreover, the other adsorption sites of S atom in H2S gas molecule adsorbed on Cu atom in N substituted Cu2O nanostructure is found to be the most favourable site among other positions. Furthermore, DFT calculations are performed for positions E1, G1 and I1. Figure S1 refers the DOS spectrum and the adsorption of S atom in H2S gas molecule adsorbed on Cu atom in N substituted Cu2O nanostructure and it is mentioned as position E1. Figure S2 depicts the DOS spectrum and the adsorption of S atom in H2S molecule adsorbed on Cu atom in Ni substituted Cu2O nanostructure, which is denoted by position G1. Figure S3 refers the DOS spectrum and the adsorption of S atom in H2S gas adsorbed on Cu atom in Zn substituted Cu2O nanostructure and it is represented by position I1. Table S1 shows the adsorbed energy, Mulliken population, HOMO-LUMO gap and average energy gap variation. From the observations, it is revealed that the most prominent adsorption site is when S atom in H2S gas molecule gets adsorbed on Cu atom in N substituted Cu2O nanostructure owing to large variation in energy gap. However, the other positions G1 and I1 do not show much variation in energy gap. Thus, the adsorption properties of Cu2O nanostructure can be fine-tuned with the incorporation of N atom in Cu2O nanostructures. Fig. S1 DOS spectrum and H2S adsorbed on position ‘E1’ Fig. S2 DOS spectrum and H2S adsorbed on position ‘G1’ Fig. S3 DOS spectrum and H2S adsorbed on position ‘I1’ Table S1 Adsorbed energy, Mulliken population, energy gap and average energy gap variation of Cu2O nanostructures H2S adsorbed on Cu2O nanostructures Ead (eV) Q (e) EHOMO EFL (eV) ELUMO Eg (eV) Ega % N substituted Cu2O - - -7.61 -4.485 -1.36 6.25 - E1 0.85 0.445 -7.55 -6.11 -4.67 2.88 117.01 Ni substituted Cu2O - - -7.9 -6.43 -4.96 2.94 - G1 0.1 0.403 -8.1 -6.095 -4.09 4.01 26.68 Zn substituted Cu2O - - -8.91 -6.8 -4.69 4.22 - I1 0.07 0.447 -8.94 -6.465 -3.99 4.95 14.75