A method for detecting for the presence of H.sub.2S or HS.sup.− anion in a system, comprising contacting a sample from the system with a compound, or a protonate or salt thereof, having a structure represented by:

##STR00001## wherein Y represents an aromatic group or a substituted aromatic group; n is 1 or 2; R is independently H, alkyl, substituted alkyl, a polyether moiety, carboxyl, substituted carboxyl, carbamate, substituted carbonate, carbonyloxy, alkoxy, substituted alkoxy, haloalkyl, halogen, nitro, amino, amido, aryloxy, cyano, hydroxyl, or sulfonyl; R.sup.1 is H, substituted lower alkyl, lower alkyl, substituted aralkyl or aralkyl; R.sup.2 is selected from H, acyl, substituted aralkyl, aralkyl, phosphonyl, —SO.sub.2R.sup.3; —C(O)R.sup.5; —C(O)OR.sup.7 or —C(O)NR.sup.9R.sup.10; R.sup.3; R.sup.5; R.sup.7; R.sup.9 and R.sup.10 are each independently selected from H, substituted lower alkyl, lower alkyl, substituted aralkyl, aralkyl, substituted aryl or aryl.

A method for detecting for the presence of H.sub.2S or HS.sup.− anion in a system, comprising contacting a sample from the system with a compound, or a protonate or salt thereof, having a structure represented by: ##STR00001## wherein Y represents an aromatic group or a substituted aromatic group; n is 1 or 2; R is independently H, alkyl, substituted alkyl, a polyether moiety, carboxyl, substituted carboxyl, carbamate, substituted carbonate, carbonyloxy, alkoxy, substituted alkoxy, haloalkyl, halogen, nitro, amino, amido, aryloxy, cyano, hydroxyl, or sulfonyl; R.sup.1 is H, substituted lower alkyl, lower alkyl, substituted aralkyl or aralkyl; R.sup.2 is selected from H, acyl, substituted aralkyl, aralkyl, phosphonyl, —SO.sub.2R.sup.3; —C(O)R.sup.5; —C(O)OR.sup.7 or —C(O)NR.sup.9R.sup.10; R.sup.3; R.sup.5; R.sup.7; R.sup.9 and R.sup.10 are each independently selected from H, substituted lower alkyl, lower alkyl, substituted aralkyl, aralkyl, substituted aryl or aryl.

A method for detecting for the presence of H.sub.2S or HS.sup.− anion in a system, comprising contacting a sample from the system with a compound, or a protonate or salt thereof, having a structure represented by:

##STR00001## wherein Y represents an aromatic group or a substituted aromatic group; n is 1 or 2; R is independently H, alkyl, substituted alkyl, a polyether moiety, carboxyl, substituted carboxyl, carbamate, substituted carbonate, carbonyloxy, alkoxy, substituted alkoxy, haloalkyl, halogen, nitro, amino, amido, aryloxy, cyano, hydroxyl, or sulfonyl; R.sup.1 is H, substituted lower alkyl, lower alkyl, substituted aralkyl or aralkyl; R.sup.2 is selected from H, acyl, substituted aralkyl, aralkyl, phosphonyl, —SO.sub.2R.sup.3; —C(O)R.sup.5; —C(O)OR.sup.7 or —C(O)NR.sup.9R.sup.10; R.sup.3; R.sup.5; R.sup.7; R.sup.9 and R.sup.10 are each independently selected from H, substituted lower alkyl, lower alkyl, substituted aralkyl, aralkyl, substituted aryl or aryl.

A device that includes a polymeric layer, wherein the polymeric layer comprises (A) a polymer and, incorporated within the polymeric layer, (B) a compound, or a protonate or salt thereof, wherein the compound, or a protonate or salt thereof, has a structure that includes at least one moiety configured for reversible, non-covalent binding of the anionic sulfide species.

A method for preparing hydrophobic gold nanoparticles includes adding 1,2-dichlorobenzene as a solvent to gold precursor and using oleylamine and oleic acid with volume ratio of 7.5:2.5 to 5:5 as surfactants. The size of the prepared gold nanoparticles can be controlled over a broad range and may be utilized in various fields such as bio-imaging, photonic crystallization, sensors, organic catalysts, surface enhanced raman spectrum, electronic devices, etc. Further, a method for colorimetric detection of a strong acid uses hydrophilic nanoparticles that are phase transited from the prepared hydrophobic gold nanoparticles. Up to 5 ppm of low content hydrochloric acid can be detected utilizing phase transited hydrophilic nanoparticles in the colorimetric detection method, and the gold nanoparticles that were used in the detection of strong acid can be reused without loss of activity through neutralization with bases.