gap size (nm) SERS enhancement EF_em 0.484957310542059 22164187.5915551 0.611096201766277 10795188.5026527 0.708152642062856 6773846.89123133 0.802989834763038 4625046.45789259 0.911941713518224 3288936.08961891 1.011849965788 1673596.71048014 2.02457720573351 143213.513292899 4.05090972037894 35383.389762406 6.03581882506599 15159.5149495199 8.10533158043495 5041.32205160307 9.99407794385446 3027.83790644066