Glutathione　(GSH)　plays　key　roles　in　biological　systems　and　serves　many　cellular　functions.　Since　biothiols　all　incorporate　thiol,　carboxylic　and　amino　groups,　discriminative　detection　of　GSH　over　cysteine　(Cys)　and　homocysteine　(Hcy)　is　still　challenging.　We　herein　report　a　dual-mode　nanosensor　with　both　colorimetric　and　fluorometric　readout　based　on　carbon　quantum　dots　and　gold　nanoparticles　for　discriminative　detection　of　GSH　over　Cys/Hcy.　The　proposed　sensing　system　consists　of　AuNPs　and　fluorescent　carbon　quantum　dots　(CQDs),　where　CQDs　function　as　fluorometric　reporter,　and　AuNPs　serve　a　dual　function　as　colorimetric　reporter　and　fluorescence　quencher.　The　mechanism　of　the　nanosensor　is　based　on　two　distance-dependent　phenomenons,　color　change　of　AuNPs　and　FRET.　Through　controlling　the　surface　properties　of　as-prepared　nanoparticles,　the　addition　of　CQDs　into　AuNPs　colloid　solution　might　induce　the　aggregation　of　AuNPs　and　CQDs,　leading　to　AuNPs　color　changing　from　red　to　blue　and　CQDs　fluorescence　quench.　However,　the　presence　of　GSH　can　protect　AuNPs　from　being　aggregated　and　enlarge　the　inter-particle　distance,　which　subsequently　produces　color　change　and　fluorescent　signal　recovery.　The　nanosensor　described　in　this　report　reflects　on　its　simplicity　and　flexibility,　where　no　further　surface　functionalization　is　required　for　the　as-prepared　nanoparticles,　leading　to　less　laborious　and　more　cost-effective　synthesis.　The　proposed　dual-mode　nanosensor　demonstrated　highly　selectivity　toward　GSH,　and　allows　the　detection　of　GSH　as　low　as　50.　nM.　More　importantly,　the　nanosensor　could　not　only　function　in　aqueous　solution　for　GSH　detection　with　high　sensitivity　but　also　exhibit　sensitive　responses　toward　GSH　in　complicated　biological　environments,　demonstrating　its　potential　in　bioanalysis　and　biodection,　which　might　be　significant　in　disease　diagnosis　in　the　future.　©　2014　Elsevier　B.V.