Ratiometric quantum dot-rhodamine B sensing compound and device made from the compound

A sensor, comprising:

• a support matrix;
• and
• a sensing agent embedded in the support matrix, the sensing agent comprising:
• a quantum dot;
• and
• a dye moiety coupled to the quantum dot,
• wherein the sensing agent is capable of sensing at least one analyte chosen from hydrogen sulfide by FRET modulation between the quantum dot and the dye moiety, and wherein the sensing agent has the formula
• QDX2—R2—S—S—R1—X1—Y)n
• wherein:
• QD is the quantum dot,
• Y is the dye moiety,
• wherein the dye moiety is a rhodamine group selected from one of:
• where the dotted bond shows the position of attachment to the coupling moiety;
• R1 and R2 organic bridging groups that will, in combination with the associated linkages X1 and X2 and disulfide bond (—S—S—), provide a distance between the dye and the QD that is from about 0.1 nm to about 10 nm, and
• X1 and X2 are linkages that respectively function to attach the R1 group to the dye and R2 group to the quantum dot;
• n is the number of coupling-dye groups attached to the QD;
• wherein R1 and R2 are alkyl bridges and X1 and X2 are amide linkages;
• and
• wherein the sensor has a detection limit for bisulfide, in water, of less than 2 μM at a sensor concentration of 3.4×10−9 M as determined by the boot strap method, where the conjugated dye:QD ratio is 1.3:1.