the NaCl concentration and pH value were adjusted before Several minutes later, SERS spectra were recorded. Fig. 9 shows the SERS spectrum of TNT vapor together with the spectrum of TNT solution as reference. As illustrated three discernable Raman peaks at 1006, 1238 and 1390 cm1 could be used as a ‘‘fingerprint’’ for the detection of TNT vapor, which is
similar to TNT solution