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The severe background fluorescence and scattering light of real biological samples or environmental samples largely reduce the sensitivity and accuracy of fluorescence resonance energy transfer sensors based on fluorescent quantum dots (QDs). To solve this problem, we designed a novel target sequence DNA biosensor based on phosphorescent resonance energy transfer (PRET). This sensor relied on Mn-doped ZnS (Mn-ZnS) room-temperature phosphorescence (RTP) QDs/poly-(diallyldimethylammonium chloride) (PDADMAC) nanocomposite (QDs + ) as the energy donor and the single-strand DNA-ROX as the energy receptor. Thereby, an RTP biosensor was built and used to quantitatively detect target sequence DNA. This biosensor had a detection limit of 0.16nM and a linear range of 0.5-20nM for target sequence DNA. The dependence on RTP of QDs effectively avoided the interference from background fluorescence and scattering light in biological samples. Moreover, this sensor did not need sample pretreatment. Thus, this sensor compared with FRET is more feasible for quantitative detection of target sequence DNA in biological samples. Interestingly, the QDs + nanocomposite prolonged the phosphorescence lifetime of Mn-ZnS QDs by 2.6 times to 4.94ms, which was 5-6 magnitude-order larger than that of fluorescent QDs. Thus, this sensor largely improves the optical properties of QDs and permits chemical reactions at a long enough time scale., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A QDs-DNA nano-probe was made by combining Mn-doped ZnS room-temperature phosphorescence (RTP) quantum dots (QDs) and DNA. Then an RTP sensor for quantitative detection of genetically-modified mark sequence cauliflower mosaic virus 35S promoter (Ca MV 35S) DNA was built on basis of phosphorescent resonance energy transfer (PRET). The underlying principles were that a QDs-DNA water-soluble nano-probe was built by connecting single-strand DNA to the surfaces of QDs via a ligand exchange method. This probe had good RTP performance and could well identify Ca MV 35S. Thereby, the simple, rapid and efficient detection of genetically-modified organisms was realized. With the increase of target DNA sequence, the phosphorescent intensity of QDs was gradually reduced due to the energy transfer between QDs and the organic quencher BHQ 2 . This sensor had a detection limit of 4.03nM and a detection range of 12-300nM. Moreover, this sensor had high selectivity. This sensor could effectively detect the target DNA compared with mismatched and random sequences. Thus, this method is very promising for biological analysis., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A selective system was developed to detect heparin in aqueous solutions by using MPA(3-Mercaptopropionic Acid)-capped Mn-doped ZnS quantum dots (QDs)/polybrene (hexadimethrine bromide) hybrids as a sensitive room temperature phosphorescence (RTP) nanosensor. In this system, the RTP intensity of QDs was remarkably enhanced via electrostatic self-assembly after the addition of polybrene. The addition of heparin into the system was competitively bound to polybrene and enable to deprive it from the surface of QDs, as a result, the RTP intensity of Mn-doped ZnS QDs/polybrene hybrids was reduced with the increased of heparin concentration. Based on this effect, a selective system was proposed to detect heparin. Under the optimal conditions, the change of RTP intensity was proportional to the heparin concentration from 0.05 to 1.4 U mL(-1) (about 0.38-10.76 μg mL(-1)) and the limit of detection (LOD) was 0.021 U mL(-1) (about 0.16 μg mL(-1)). This proposed nanosensor is simple and relatively free of interference from coexisting substances, which can be applied to detect heparin in heparin injection and human serum. In addition, a new pathway was also provided based on the assembly of QDs with other cationic homopolymers for further design of biosensors and detection of biomolecules., (Copyright © 2015. Published by Elsevier B.V.)

MPA-capped Mn-doped ZnS QDs/DXR nanohybrids (MPA: 3-mercaptopropionic acid; QDs: quantum dots; DXR: cetyltrimethyl ammonium bromide) were constructed via photoinduced electron transfer (PIET) and then used as a room-temperature phosphorescence (RTP) probe for detection of DNA. DXR as a quencher will quench the RTP of Mn-doped ZnS QDs via PIET, thereby forming Mn-doped ZnS QDs/DXR nanohybrids and storing RTP. With the addition of DNA, it will be inserted into DXR and thus DXR will be competitively desorbed from the surface of Mn-doped ZnS QDs, thereby releasing the RTP of Mn-doped ZnS QDs. Based on this, a new method for DNA detection was built. The sensor for DNA has a detection limit of 0.039 mg L(-1) and a linear range from 0.1 to 14 mg L(-1). The present QDs-based RTP method does not need deoxidants or other inducers as required by conventional RTP detection methods, and avoids interference from autofluorescence and the scattering light of the matrix that are encountered in spectrofluorometry. Therefore, this method can be used to detect the DNA content in body fluid., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Quantum dots (QDs) nanohybrids are an effective route to obtain new property of materials, and are very significant for developing specific materials and improving the performance of existing QDs materials. The objectives of this work are to prepare MPA-capped Mn-doped ZnS QDs/CTAB nanohybrids (MPA: 3-mercaptopropionic acid; CTAB: cetyltrimethyl ammonium bromide) through electrostatic self-assembly, to investigate the formation mechanism and the Room-Temperature Phosphorescenee (RTP) changes, and to explore the possibility of their application in detection of rutin. As a result, MPA-capped Mn-doped ZnS QDs/CTAB nanohybrids greatly improve the rutin detection ability of QDs and provide an important method for developing more convenient and effective rutin detection sensor. The sensor for rutin gave a detection limit of 0.037 mg L(-1) and two linear ranges from 0.05 to 0.5 mg L(-1) and from 0.5 to 5 mg L(-1), and thus can be expanded to selective detection of other substances. Since the present QDs-based RTP method does not need deoxidants or other inducers as conventional RTP detection methods, and avoids interference from autofluorescence and the scattering light of the matrix that are encountered in spectrofluorometry, this method can be used to detect the content of rutin in body fluid., (© 2013 Published by Elsevier B.V.)