Quantum dots-based ratiometric fluorescence probe for mercuric ions in biological fluids

Preparation of graphene quantum dots based core-satellite hybrid spheres and their use as the ratiometric fluorescence probe for visual determination of mercury(II) ions

“…The CdTe QDs embedded silica (CdTe@SiO 2 ) nanoparticles were prepared by a modified St€ ober method [15,18]. Typically, 30 mL of ethanol and 5 mL of red-emitting CdTe QDs solution were mixed in a 100 mL flask and stirred for 5 min at room temperature.…”

“…The particle size can be calculated to be 3.44 nm in virtue of the reported expression [50], which is consistent with the results of the TEM image. CdTe@SiO 2 nanospheres have been synthesized through a typical St€ ober method with some modification [15,18]. Specifically, CdTe QDs were initially conjugated to an amine-containing silane agent APTS, and then APTS and a silica alkoxide precursor TEOS were allowed to hydrolyze and co-condense in the ethanol/NH 3 H 2 O mixture, which resulted in CdTe@SiO 2 nanospheres.…”

“…These CdS@CS@CdTe nanospheres have been empolyed as the visual fluorescence probe for the detection of trace Hg 2þ . Some other Cd chalcogenide QDsbased hybrid nanospheres have been hybridized by embedding the red-emitting CdTe QDs [9,15e17] or CdTe/CdS QDs [18] into silica nanoparticles and covalently linking the green-emitting one onto the silica surface. Following the "on-off" or "on-off-on" detection mode, these dual-emission hybrid probes with desired intensity ratios have been demonstrated to be promising for the visual detection of 5-fluorouracil [9], trinitrotoluene [15], cysteine/ homocysteine [16], Cu 2þ [17], and Hg 2þ [18].…”

“…Some other Cd chalcogenide QDsbased hybrid nanospheres have been hybridized by embedding the red-emitting CdTe QDs [9,15e17] or CdTe/CdS QDs [18] into silica nanoparticles and covalently linking the green-emitting one onto the silica surface. Following the "on-off" or "on-off-on" detection mode, these dual-emission hybrid probes with desired intensity ratios have been demonstrated to be promising for the visual detection of 5-fluorouracil [9], trinitrotoluene [15], cysteine/ homocysteine [16], Cu 2þ [17], and Hg 2þ [18]. Although these traditional QDs have great potential for the ratiometric fluorescence probes fabrication, certain limitations may restrict their practical use because those Cd-based QDs that are highly toxic to both cell and live animals due to their inherent chemical composition, size, shape, and surface [19e23].…”

Analytical strategies based on quantum dots for heavy metal ions detection

“…75 The red-emitting larger-sized CdTe/CdS QDs embedded in silica nanoparticles were insensitive to Hg 2þ , while the green-emitting smaller sized ones were covalently conjugated onto the silica nanoparticles surface and sensitive to Hg 2þ . The addition of Hg 2þ can only quench green fluorescence in the dual-emission QDs nanocomposites, which trigger the change of fluorescence intensity ratio of two different emission wavelengths and hence induces the evolution of fluorescence color of the probe solution with variation of Hg 2þ concentration.…”