Room-temperature Phosphorescence Sensor Research Articles

Development of a new phosphorescence sensor based on surface molecularly imprinted Mn-doped ZnS quantum dots for detection of melamine in milk products

This paper presents a novel room temperature phosphorescence sensor (IMIPs-ZnS QDs RTP sensor) based on inorganic surface molecularly imprinted polymers and Mn-doped ZnS quantum dots (QDs) for the rapid detection of trace melamine (MEL) in commercial milk products. The surface of Mn-ZnS QDs was modified with 3-(mercaptopropyl) trimethoxy silane (MPTS). Then, MEL, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were used as a template/target molecule, functional monomer, and cross-linker, respectively. IMIPs-ZnS QDs RTP sensor was characterized using spectrofluorimeter, UV–Vis spectrophotometer, FT-IR, transmission electron microscope (TEM), and X-ray photoelectron spectrometer (XPS).Detection time and linear range for IMIPs-ZnS QDs RTP sensor were 30 min and 4.0–79.2 µM with a correlation coefficient value of 0.9946, respectively. Furthermore, LOD and LOQ values were calculated using Stern-Volmer equation as 0.29 and 0.97 µM, respectively. Thus, IMIPs-ZnS QDs RTP sensor was successfully applied for the detection of MEL residue in milk samples. Recovery values were in the range of 88.62–90.22 % with relatively high precision values (0.57–0.92 % RSD). Our findings indicate that the developed IMIPs-ZnS QDs RTP sensor exhibits high sensitivity and selectivity towards the MEL in milk sample containing potentially relatively high number of interfering compounds.

A room-temperature phosphorescence sensor for the detection of alkaline phosphatase activity based on Mn-doped ZnS quantum dots

A convenient and efficient biosensor for detection of alkaline phosphatase (ALP) activity was built with Mn-ZnS quantum dots (QDs) as the phosphorescent probe and adenosine 5′-monophosphate (AMP) as the substrate. Eu3+, which could coordinate with surface carboxyl group of Mn-ZnS QDs, was added into Mn-ZnS QDs to form Mn-ZnS QDs/Eu3+ nanocomposites, which quenched the RTP of Mn-ZnS QDs through photoinduced electron-transfer (PIET). After ALP and AMP were added into the system, under the hydrolytic catalysis of ALP, AMP was rapidly converted into adenosine and phosphate ions. The higher affinity of phosphate ions to Eu3+ than QDs resulted in the formation of a more stable composite, and subsequently, Eu3+ was desorbed from the surfaces of Mn-ZnS QDs, which restored the RTP of Mn-ZnS QDs. Under the optimal conditions, the RTP intensity of the Mn-ZnS QDs (ΔRTP) was well linearly related to the logarithm of the ALP activity, with a detection range of 0.15－18 U L−1 and a detection limit of 0.065 U L−1. This phosphorescent sensor avoided interference from autofluorescent and scattering light in real biological samples and was highly sensitive to ALP.

A phosphorescent sensor for detection of Micrococcal nuclease base on phosphorescent resonance energy transfer between quantum dots and DNA-ROX

To solve interference from background fluorescence and scattering light of real biological samples, we developed a room-temperature phosphorescence (RTP) sensor to detect Micrococcal nuclease (MNase). The sensor was based on the phosphorescent resonance energy transfer (PRET) between 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs) and single-marked oligonucleotide (DNA-ROX). Specifically, the poly-(diallyldimethylammonium chloride) (PDAD)-modified QDs (PDAD-QDs) were prepared as the energy donor, and the DNA-ROX was chosen as the energy receptor. The DNA-ROX could be adsorbed to the surface of the PDAD-QDs through electrostatic interaction, which induced PRET and quenched the RTP of PDAD-QDs. The MNase could efficiently degrade the DNA-ROX into small DNA segments, which were less prone to electrostatic interaction with PDAD-QDs, and thus the PRET efficiency decreased. The RTP intensity of PDAD-QDs was gradually enhanced with the increment of MNase concentration. Under the optimal conditions, the change of RTP intensity was proportional to the logarithm of MNase concentration in the range from 2×10−3 to 8.0×10−2UmL−1, with a high correlation coefficient of 0.993 and a detection limit of 6×10−4UmL−1. This proposed RTP sensor can avoid interferences from the background fluorescence or scattering light of the matrix that are encountered in spectrofluorometry. Thus, this biosensor can be applied to detect MNase in culture media.

A DNA probe based on phosphorescent resonance energy transfer for detection of transgenic 35S promoter DNA

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 BHQ2. 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.

Phosphorescence detection of 2-mercaptobenzothiazole in environmental water samples by Mn-doped ZnS quantum dots

A room-temperature phosphorescence sensor was constructed based on MPA-capped Mn-doped ZnS QDs for the detection of MBT in water samples.

L-cysteine capped ZnS:Mn quantum dots for room-temperature detection of dopamine with high sensitivity and selectivity

Dopamine (DA) is one of the most important catecholamine neurotransmitters of the human central nervous system, and is involved in many behavioral responses and brain functions. Below normal DA levels in biological fluids can lead to different neurodegenerative conditions. For excess DA levels, a failure in energy metabolism is indicated. In this study, a facile room-temperature phosphorescence sensor is developed to detect DA based on l-cysteine capped Mn doped ZnS quantum dots (l-cys ZnS:Mn QDs). The QDs display a prominent orange emission band peaking at ~598nm, which is strongly quenched upon addition of DA in alkaline medium. The sensor exhibits a linear working range of ~0.15–3.00μM, and a limit of detection of ~7.80nM. These results are explained in terms of a pH-dependent electron transfer process, in which the oxidized dopamine quinone functions as an efficient electron acceptor. The QDs-based sensor shows a high selectivity to DA over common interfering biomolecules (including some amino acids, ascorbic acid, chloride and glucose). The sensor has been successfully applied for the detection of DA in urine samples, yielding recoveries as high as 93%. Our findings indicate that our developed sensor exhibits high sensitivity and reproducibility to determine DA even in biological fluids where DA is at low levels, e.g., in the central nervous system, which is the usual clinical profile of a neurodegenerative disorder associated to the Parkinson's disease.

Glutathione-capped Mn-doped ZnS quantum dots as a room-temperature phosphorescence sensor for the detection of Pb2 + ions

The room-temperature phosphorescence (RTP) of glutathione-capped Mn-doped ZnS quantum dots (GSH-Mn-ZnS QDs) was effectively quenched by the addition of Pb2+. A simple and sensitive RTP sensor for Pb2+ detection based on the quenching effect was developed. Under the optimal conditions, good linear correlations were obtained for Pb2+ over a concentration range from 1.0 to 100μg·L−1, and the detection limit was 0.45μg·L−1. The established method has been successfully applied for the determination of Pb2+ in real water samples without complicated sample pretreatment with the recoveries in the range of 95.4%–104.0%.

Room-Temperature Phosphorescence Turn-on Detection of DNA Based on Riboflavin-Modulated Manganese Doped Zinc Sulfide Quantum Dots.

A sensitive phosphorescent sensor based on riboflavin (RF)-modulated mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs) was developed and utilized as room-temperature phosphorescence (RTP) sensor for DNA detection. The RTP of the MPA-capped Mn-doped ZnS QDs was stored via photoinduced electron transfer by RF, and formed an electrochemically nonactive QDs/RF nanohybrids through electrostatic attraction. In the presence of DNA, RF could bind with DNA, which has a double helical structure, via electrostatic interaction and intercalation. RF can be removed from the surface of the QDs, thus releasing the RTP of the QDs. On the basis of this principle, an RTP sensor for DNA detection was developed. Under optimal conditions, the detection limit for DNA was 15μgmL(-1), the relative standard deviation was 1.9%, and the method recovery ranged from 97% to 103%. The proposed method was applied to biological fluids, in which satisfactory results were obtained.

L-Cysteine capped Mn-doped ZnS quantum dots as a room temperature phosphorescence sensor for in-vitro binding assay of idarubicin and DNA.

L-cysteine capped Mn doped ZnS quantum dots/ Idarubicin (IDA) nanohybrids were used as novel room temperature phosphorescence (RTP) sensor to detect double stranded deoxyribonucleic acid (ds-DNA)/drug interaction. IDA, anthracycline derivative anticancer drug, was adsorbed on the surface of the QDs as an electron acceptor to quench the RTP emission. The RTP intensity of QDs was quenched quickly upon addition of quencher and the reaction reached equilibrium within 2 min. The quenching mechanism of phosphorescence of Mn-doped ZnS QDs by IDA is a combined dynamic and static quenching. The static and dynamic quenching constants were found as 1.1×10(5) M(-1) and 8.7×10(4) M(-1), respectively. The addition of ds-DNA caused formation of ds-DNA/IDA complex and recovered the RTP signal of Mn-doped ZnS QDs, which allowed qualitative analysis. Under optimal conditions, RTP intensity of QDs/IDA nanohybrids increased linearly with the concentration of ds-DNA from 1.2 to 6.0 µM. This method is simple, low cost and avoids from interferences.

Phosphorescent quantum dots/ethidium bromide nanohybrids based on photoinduced electron transfer for DNA detection

Mercaptopropionic acid-capped Mn-doped ZnS quantum dots/ethidium bromide (EB) nanohybrids were constructed for photoinduced electron transfer (PIET) and then used as a room-temperature phosphorescence (RTP) probe for DNA detection. EB could quench the RTP of Mn-doped ZnS QDs by PIET, thereby forming Mn-doped ZnS QDs/EB nanohybrids and storing RTP. Meanwhile, EB could be inserted into DNA and EB could be competitively desorbed from the surface of Mn-doped ZnS QDs by DNA, thereby releasing the RTP of Mn-doped ZnS QDs. Based on this mechanism, a RTP sensor for DNA detection was developed. Under optimal conditions, the detection limit for DNA was 0.045mgL−1, the relative standard deviation was 1.7%, and the method linear ranged from 0.2 to 20mgL−1. The proposed method was applied to biological fluids, in which satisfactory results were obtained.

Label-free room-temperature phosphorescence turn-on detection of tiopronin based on Cu2+-modulated homocysteine-capped manganese doped zinc sulfide quantum dots

A label-free turn-on room-temperature phosphorescence (RTP) sensor for tiopronin based on Cu2+-modulated homocysteine (Hcy)-capped Mn-doped ZnS quantum dots (QDs) was described in this paper. The RTP of Hcy-capped Mn-doped ZnS QDs can be effectively quenched by Cu2+ due to the binding of Cu2+ to the Hcy on the surface of the QDs and the electron transfer generated from the photoexcited QDs to Cu2+. The high affinity of tiopronin to Cu2+ enables the dissociation of the ion from the surface of the QDs, thereby forming a stable complex with tiopronin in the solution, and recovering the RTP of the QDs. The Cu2+-induced RTP quenching and subsequent tiopronin-induced RTP recovery for MPA-capped ZnS QDs provide a solid basis for the present RTP sensor based on QDs for the detection of tiopronin. The detection limit for tiopronin is 0.18ngmL−1, the relative standard deviations is 1.9%, and the recovery of urine and serum samples with tiopronin addition range from 96% to 106% under optimal conditions. The proposed method was successfully applied to biological fluids and obtained satisfactory results.

Highly selective manganese-doped zinc sulfide quantum dots based label free phosphorescent sensor for phosphopeptides in presence of zirconium (IV)

We report a room-temperature phosphorescence (RTP) sensor for phosphopeptides based on zirconium (IV)-modulated mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs). This sensor incorporates the advantages of the well-known Zr4+-phosphopeptide affinity pair and the RTP properties of doped QDs. The RTP of Mn-doped ZnS QDs capped with MPA can be effectively quenched by Zr4+. The high affinity of phosphopeptides to Zr4+ enables the dissociation of the ion from the surface of MPA-capped ZnS QDs, thereby forming a stable complex with phosphopeptides in the solution, and recovering the RTP of the QDs. The Zr4+-induced RTP quenching and subsequent phosphopeptide-induced RTP recovery for MPA-capped ZnS QDs provide a solid basis for the present RTP sensor based on QDs for the detection of phosphopeptides. The detection limit for phosphopeptides is 0.9ngmL−1, the relative standard deviations is 2.5%, and the recovery of urine and serum samples with phosphopeptides addition rangs from 96% to 105% at optimal conditions. The proposed method was successfully applied to biological fluids and obtained satisfactory results.

Melamine-modulated mercaptopropionic acid-capped manganese doped zinc sulfide quantum dots as a room-temperature phosphorescence sensor for detecting clenbuterol in biological fluids

A turn-off room-temperature phosphorescence (RTP) sensor for clenbuterol (CB) based on melamine (MA)-modulated mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs) was described in this paper. Due to the hydrogen-bonding interaction between CB and MA, introduction of CB into the solution of MPA-capped Mn-doped QDs in the presence of MA could increase the surface defects of the QDs and lead to their reaction aggregation. So that the MA-induced RTP could be enhanced and subsequent CB-induced RTP quenching could be observed. This phenomenon could build a solid base for us to develop a QDs-based turn-off RTP sensor for detecting CB. Under the optimal conditions, the detection limit for CB was 3.2ngmL−1, the relative standard deviations was 2.9% while the recovery of the method was in the range of 97–104%. The coexisting substances which includes 2000-fold excesses of Na+ and K+, 1500-fold excesses of lysine, cysteine, ascorbic acid, uric acid, Vitamin B1, Vitamin B2, Mn2+, Mg2+, Ca2+, Zn2+ and Al3+, 500-fold excesses Cu2+ and Ag+ did not affect the determination of CB. The proposed method was successfully applied to biological fluids with satisfactory results.

Room-temperature phosphorescence sensor based on manganese doped zinc sulfide quantum dots for detection of urea

In this work, a simple scheme was proposed to prepare a urea-sensing system, which was composed of water-soluble Mn-doped ZnS phosphorescent QDs and urease. It allows for effective and quantitative detection of urea. The phosphorescence properties of MPA-capped Mn-doped ZnS QDs were explored to develop an RTP method for facile, rapid, cost-effective and selective detection of urea. This method does not need any deoxidant or other inducers and detects urea in biological fluids without being interfered from autofluorescence or the scattering light of the matrix. The new RTP sensor for urea detection has a detection limit of 0.014mM and two linear ranges from 0 to 10mM and from 10 to 60mM. The precision for 11 replicate detections of 0.1mM urea was 4.7%. The recoveries on spiked urine samples are 95–103%. It was successfully applied to the determination of urine without any complicated sample pretreatment.

Determination of trace gastrin and diagnosis of human diseases using CdTe quantum dots labelled gastrin antibodies as phosphorescence sensors

CdTe quantum dots (CdTe-QDs) can emit strong and stable room temperature phosphorescence (RTP) via the perturbation effect of a Pb(2+) ion on the surface of a nitrocellulose membrane (NCM). CdTe-QDs-Ab(GAS), the product of CdTe-QDs labelled gastrin antibodies (Ab(GAS)), can not only maintain good RTP characteristics, but can also be used as a RTP sensor and carry out highly specific immunoreactions with gastrin (GAS) to form GAS-Ab(GAS)-CdTe-QDs causing the ΔI(p) of the system to sharply enhance. Thus, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of GAS was established based on the linear relativity between the ΔI(p) of the system and the content of GAS. The limit of quantification (LOQ) of this method was 0.43 fg spot(-1) with the corresponding concentration being 1.1 × 10(-12) g mL(-1) and sampling quantity being 0.40 per spot(-1). This highly specific, accurate, selective and sensitive RTP sensor has been applied to the determination of GAS in biological samples and the diagnosis of diseases, and the results agreed well with those obtained by radioimmunometric assay (RIA). Meanwhile, the mechanism of SSRTPIA for the determination of GAS using CdTe-QDs-Ab(GAS) as the RTP sensor was discussed.

Conjugation of Glucose Oxidase onto Mn-Doped ZnS Quantum Dots for Phosphorescent Sensing of Glucose in Biological Fluids

Integrating various enzymes with nanomaterials provides various nanohybrids with new possibilities in biosensor applications. Furthermore, the enzymatic activity and stability are also improved due to the large surface area of nanomaterials. Here we report the conjugation of glucose oxidase (GOD) onto phosphorescent Mn-doped ZnS quantum dots (QDs) using 1-ethyl-3-(3-dimethylaminopropy)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) as coupling reagents for glucose biosensing based on the effective quenching of the room temperature phosphorescence (RTP) of Mn-doped ZnS QDs by the H(2)O(2) generated from GOD-catalyzed oxidation of glucose. The obtained bioconjugate not only provided improved enzymatic performance with Michaelis-Menten constant of 0.70 mM but also favored biological applications because the phosphorescent detection mode avoided the interference from autofluorescence and scattering light from the biological matrix. In addition, the GOD-conjugated Mn-doped ZnS QDs showed better thermal stability in the temperature range of 20-80 degrees C. The GOD-Mn-doped ZnS QDs based RTP sensor for glucose gave a detection limit of 3 microM and two linear ranges from 10 microM to 0.1 mM and from 0.1 to 1 mM. The developed biosensor was successfully applied to the determination of glucose in real serum samples without the need for any complicated sample pretreatments.

Self‐Assembly of Mn‐Doped ZnS Quantum Dots/Octa(3‐aminopropyl)octasilsequioxane Octahydrochloride Nanohybrids for Optosensing DNA

Simple plan! Nanohybrids have been built from capped Mn-doped ZnS quantum dots and octa(3-aminopropyl)octasilsequioxane octahydrochloride (OA-POSS) by means of electrostatic self-assembly for the development of a novel room-temperature phosphorescence sensor for DNA sensing in biological fluids (see graphic).

Fluorescence and room temperature phosphorescence of 6-bromo-2-naphthol in β-cyclodextrin solution and its selective molecular recognition for cyclohexane

The room temperature phosphorescence (RTP) and fluorescence behavior of 6-bromo-2-naphthol (BN) in water and β-cyclodextrin (β-CD) aerated aqueous solution was investigated. The study of fluorescence behavior at different pH values indicated that three kinds of species of BN (protonated, uncharged and anionic species) formed 1:1 inclusion complexes with β-CD, and RTP and fluorescence emission depended on the pH of the solution. The inclusion complex constants were 430±25 l mol −1 (pH 1.80), 840±25 l mol −1 (pH 5.80), 1850±75 l mol −1 (pH 11.50), respectively. Experimental results elucidated that RTP of the BN/β-CD/cyclohexane solution came from the protonated and uncharged species of BN, but not from the anionic species, though the inclusion constant of the anionic species of BN with β-CD was larger than that of the other two species of BN Selective molecular recognition of BN/β-CD as an RTP sensor for 28 small organic molecules was studied, it was shown that BN/β-CD could be develop as a new RTP sensor with high selectivity molecular recognition ability for cyclohexane.