Substrates, systems, and methods for array synthesis and biomolecular analysis

A method of attaching a coupling molecule to a substrate, comprising:

• obtaining a substrate comprising a plurality of carboxylic acid groups for linking to a coupling molecule;
• contacting said substrate with a carboxylic acid activating compound formulation comprising a carbodiimide precursor selected from the group consisting of:
• 1-(3-(diethylamino)-propyl)-4-(2-methoxyphenyl)-1,4-dihydro-5H-tetrazole-5-thione, 4,5-dihydro-4-(hydroxymethyl)-1-phenyl-1H-tetrazole-5-thione, 1-(3-(dimethylamino) propyl)-4-ethyl-1,4-dihydro-5H-tetrazole-5-thione, 1,4-Bis (2,2-dimethyl-1,3-dioxolan-4-ylmethyl)-1,4-dihydro-5H-tetrazole-5-thione, 4-cyclohexyl-1H-tetrazole-5(4H)-thione, and 1-phenyl-4-(piperidinomethyl)-tetrazole-5(4H)-thione, wherein said carbodiimide precursor converts to a carbodiimide upon exposure to electromagnetic radiation at a defined wavelength;
• selectively exposing said carboxylic acid activating compound formulation to the electromagnetic radiation, thereby generating said carbodiimide and activating the carboxylic acid groups to form carbonyl groups on said substrate at a selectively exposed area;
• contacting said substrate with a coupling formulation comprising a coupling molecule and a solvent;
• coupling the coupling molecule to at least one of said plurality of carbonyl groups at said selectively exposed area.