Inks containing metal precursors nanoparticles

A printing formulation comprising a

• (i) non-aqueous medium,
• (ii) an oxidation-resistant copper precursor being a copper formate or a copper acetate, and
• (iii) amino methyl propanol (AMP) as a complexing agent,
• wherein said copper formate or copper acetate and said amino methyl propanol form a copper complex that is dissolved in the non-aqueous medium, and
• wherein a ratio of number of copper atoms of the copper formate or the copper acetate to number of the hydroxy groups of the AMP in the copper complex is 1 and a ratio of the number of copper atoms of the copper formate or the copper acetate to the number of amine groups of the AMP in the copper complex is 1.