A　squaraine-based　compound　(USQ-1)　was　designed　and　synthesized　as　a　new　colorimetric　probe　for　thiols,　with　a　sensing　mechanism　based　on　the　nucleophilic　attack　of　a　thiol　at　the　electron-deficient　central　squaraine　ring　of　USQ-1　in　the　presence　of　cetyltrimethylammonium　bromide　(CTAB).　The　interaction　between　surfactants　and　USQ-1　have　been　investigated,　and　the　influence　of　type　and　amount　of　surfactants　were　also　examined.　Notably,　USQ-1　exhibited　a　rapid　response　to　thiols　without　the　interference　from　other　amino　acids　and　bioanalytes　in　physiological　conditions,　and　the　linear　range　of　the　method　was　0.15-8.5　mu　M　with　a　detection　limit　of　1.0　x　10(-8)　M　for　glutathione.　The　whole　recognition　process　was　accompanied　by　a　visual　color　change　from　green　to　yellow　which　allowed　a　naked-eye　observation.　More　interestingly,　through　time　controlled　experiments,　the　sensing　system　may　be　used　to　discriminate　cysteine　from　glutathione　and　homocysteine.　(C)　2013　Elsevier　B.V.　All　rights　reserved.