Selective Detection Of Dopamine Research Articles

Design and synthesis of fluorescent reagents for selective detection of dopamine

I report the development of (E)-2,2′-(5-(2-(4-(dicyanomethylene)-6-methyl-4H-pyran-2-yl)vinyl)-2-hydroxy benzylazanediyl)diacetic acid Fe(II) complex (1-Fe2+), a fluorescent reagent that can be used to detect dopamine. 1-Fe2+ was constructed using the cyanopyranyl group as the fluorophore and an Fe2+ complex both as the ligand exchange site and fluorescence quenching moiety. In contrast to the weak fluorescence emission of 1-Fe2+ in the absence of dopamine, a much stronger fluorescence emission was observed following the addition of dopamine owing to the release of Fe2+ from compound 1, which indicates significant fluorescence enhancement and the binding of Fe2+ to dopamine. The fluorescence intensities of the reagent were plotted as a function of the dopamine concentration and a good linear relationship was observed. The reaction of 1-Fe2+ with dopamine was not affected by the presence of foreign substances, thereby allowing for the highly selective detection of dopamine. The experimental results clearly showed that 1-Fe2+ is a good dopamine indicator, and it can be widely employed in dopamine detection protocols.

Selective detection of dopamine based on Cu2O@Pt core-shell nanoparticles modified electrode in the presence of ascorbic acid and uric acid

The Cu2O@Pt nanoparticles were prepared by a two-step method, using Vulcan XC-72 carbon as support (donated as Cu2O@Pt/C). Transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy were used to characterize the resulting Cu2O@Pt core-shell nanoparticles. The chemically modified electrode based on Cu2O@Pt/C nanocomposites was employed to eliminate the interference from ascorbic acid and uric acid for the sensitive and selective determination of dopamine. The electrochemical results indicate that the Cu2O@Pt/C nanocomposites show better electrocatalytic activity for the oxidation of dopamine than Pt/C nanocomposites with a linear range from 10 nM to 1027.16 μM, a detection limit of 3 nM (S/N = 3) and sensitivity of 638.0 μA mM−1 cm−2. Moreover, the sensor exhibits excellent long-time stability, good reproducibility and can be applied for practical application.

Facile fabrication of cobalt oxide nanograin-decorated reduced graphene oxide composite as ultrasensitive platform for dopamine detection

A sensitive and selective detection of dopamine (DA) by a sensor based on cobalt oxide (Co3O4) nanograin-decorated reduced graphene oxide (rGO) composite modified glassy carbon electrode (GCE) is reported. The rGO-Co3O4 nanograin composites are synthesized by a facile hydrothermal route and optimized by varying the contents of rGO (5.7, 7.4, 9.1 and 10.7wt%, denoted as C1, C2, C3 and C4 respectively). The crystallinity of the composite is examined by X-ray diffraction (XRD). Raman spectrum revealed the successful reduction of graphene oxide (GO) into rGO. The surface morphology through field emission scanning electron microscopy (FESEM) revealed that the granular-shaped Co3O4 are decorated on rGO matrix with an average particle size of∼35nm. For electrochemical oxidation of DA, glassy carbon electrode (GCE) is modified with nanocomposites. Cyclic voltammetric results show that C3 modified GCE exhibit enhanced electrocatalytic performance in terms of oxidation potential and peak current in comparison to those of bare GCE, Co3O4 nanograins, C1, C2 and C4 modified GCE. The choronoamperometric studies indicate that C3 modified GCE exhibit a low detection limit of (S/N=3) 0.277μM in the linear range of 1–30μM. In addition, C3 demonstrates good selectivity towards the detection of DA in the presence of a 100-fold higher concentration of ascorbic acid, glucose and uric acid as the interfering species. The electrochemical sensing studies suggest that 3D rGO-Co3O4 nanograins endow excellent catalytic activity, high selectivity and sensitivity towards DA.

An electrochemical aptasensor for sensitive and selective detection of dopamine based on signal amplification of electrochemical-chemical redox cycling

This paper presented an electrochemical aptasensor for dopamine detection with high sensitivity and selectivity. The electrochemical signal was amplified by electrochemical-chemical redox cycling with tris(2-carboxyethyl)phosphine (TCEP) as the reducing reagent. Specifically, dopamine captured by the aptamer-covered gold nanoparticles-modified carbon glass electrode was cycled by TCEP after its electrochemical oxidization, enabling an increase in the anodic current. Because of the high specificity and strong binding affinity of aptamer to dopamine, the sensor is fairly selective in not responding to common interferences. The results of chronoamperometry indicated that this aptasensor allowed for the detection of dopamine in a linear concentration range of 5nM to 0.5μM. The detection limit was estimated to be 1.8nM. Additionally, the aptasensor was successfully applied to determine dopamine spiked in the serum sample and gave recoveries ranging from 94.6 to 107.2%. This work would also be valuable for development of new types of electrochemical sensors for determination of other electroactive substances by marrying specific receptors and effective reducing or oxidizing reagents.

Preparation of copper (I) oxide nanohexagon decorated reduced graphene oxide nanocomposite and its application in electrochemical sensing of dopamine

An electrochemical sensor using copper (I) oxide nanostructure decorated reduced graphene oxide (rGO) nanocomposite has been proposed for selective detection of dopamine. The rGO–Cu2O nanocomposite was synthesized by in-situ chemical reduction method and was characterized using Transmission Electron Microscope (TEM), Energy Dispersive X-ray (EDX) analysis, X-ray Diffraction (XRD) patterns, Fourier Transform Infrared (FTIR), UV–vis and Raman Spectroscopy, respectively. From Cyclic Voltammetric (CV) studies, it was inferred that rGO–Cu2O/GCE exhibits excellent electrocatalytic activity toward dopamine, which is attributed to the enhanced conductivity as well as the synergistic effect of the nanocomposite. The sensing was carried out using Differential Pulse Voltammetry (DPV) wherefrom a Limit of Detection (LOD) of 50 nM with a linear range from 10 µM to 900 µM was estimated. The effect of potential interfering agents such as Uric Acid (UA), Ascorbic Acid (AA), glucose, K+, Na+, Cl−, and SO4− ions toward sensing were investigated. The performance of the sensor toward the estimation of dopamine in human blood and urine samples were analyzed. The facile method for the preparation of a nanocomposite in conjunction with the low detection limit and the wide linear range for dopamine sensing is the advantage of this present study.

An electrochemical sensor for selective detection of dopamine based on nickel tetrasulfonated phthalocyanine functionalized nitrogen-doped graphene nanocomposites

A novel electrochemical sensing platform based on nitrogen-doped graphene (N-G)/nickel tetrasulfonated phthalocyanine (NiTsPc) nanocomposites has been developed for selective determination of dopamine (DA). NiTsPc was immobilized on N-G matrix via π-π interaction, while N-G provided a compatible microenvironment for NiTsPc to enhance electron transfer and to retain its electrocatalytic activity as well. The N-G/NiTsPc nanocomposite was characterized by using transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The proposed modified electrode presented superior catalytic efficiency for DA in the presence of ascorbic acid (AA) and uric acid (UA) owing to the synergistic effect of N-G and NiTsPc. The sensors also exhibited a wide linear range from 1×10−7 to 2×10−4M and a limit of detection as low as 100nM with high sensitivity of 88.9μAmM−1.

Selective Detection of Dopamine in the Presence of Uric Acid Using NiO Nanoparticles Decorated on Graphene Nanosheets Modified Screen‐printed Electrodes

AbstractA convenient, low cost, and sensitive electrochemical method, based on a disposable graphene nanosheets (GR) and NiO nanoparticles modified carbon screen printed electrode (NiO/GR/SPE), is described for the simultaneous determination of dopamine (DA) and uric acid (UA). The modified electrode exhibited good electrocatalytic properties toward the oxidation of DA and UA. A peak potential difference of 150 mV between DA and UA was large enough to determine DA and UA individually and simultaneously. The anodic peak currents of DA were found to be linear in the concentration range of 1.0–500.0 μM with the detection limit of 3.14×10−7 M.

Clay Composite Modified Electrodes II: Voltammetric Method for Simultaneous Detection of Dopamine and Serotonin

Dopamine (DA) and serotonin (SN) are important catecholamine neurotransmitters in the central nervous system that play key roles in muscle stimulation and transmission of signals. DA release in the brain plays a key role in the regulations of pleasure and pain while SN helps to relay messages from one area of the brain to another. Abnormal DA levels are associated with serious diseases such as Schizophrenia and Parkinson’s. Imbalance in SN levels affects the muscles and cardiovascular system. Thus developing methods for detection of DA and SN in the presence of interfering species is an important area of research. Electrochemical methods for DA and SN detection have been developed since there is increasing demand for more reliable and rapid methods. Excess levels of interfering species such as ascorbic acid (AA) and uric acid (UA) co-exist in biological samples. These pose problems for DA and SN detection during electrochemical measurements since they all oxidize around the same potential region. Several types of electrode modifications have been reported for selective detection of DA and SN, but each one has its own advantages and limitations. The use of clay-composite modified electrodes have not been exploited. This work aims to employ clay composite modified glassy carbon electrodes for selective detection of DA and SN. The goal is to use clay composites to exclude AA and UA while enhancing DA and SN detection. Clay film serves as the polymeric membrane as clays are able to form membrane-like films. Clays are naturally occurring and much more stable than synthetic membranes. Clay film on an electrode surface provides important functions such as charge-exclusion and catalysis of electrochemical reactions. The clay composite was prepared by incorporating methylene blue and xanthate into clay interlayers by simply mixing them with clay suspension and sonicating. Several voltammetric experiments were undertaken to investigate the behavior of DA, SN, AA, and UA at the bare electrode (BE), clay modified electrode (CME), glycerol-clay modified electrode (GCME), glycerol-methylene blue-clay modified electrode (GMBCME), glycerol-xanthate-clay modified electrode (GXTCME), and glycerol-methylene blue-xanthate-clay modified electrode (GMBXTCME). Voltammetric techniques used were Cyclic Voltammetry (CV), Square-Wave Voltammetry (SWV), and Differential-Pulse Voltammetry (DPV). Experiments were performed at the physiological pH of 7.4. Glycerol was added to prevent cracks in films. At GCME, calibration curves by CV show linear range of 0.0010 – 0.25 and 0.0010 – 0.10 mM for DA and SN, respectively. The DA and SN oxidation peak potentials are around 0.26 and 0.27 V versus Ag/AgCl, respectively. For a mixture of DA and SN, the CV shows an oxidation peak around 0.43 V (due to SN) with a small hump around 0.28 V (due to DA). The hump is more pronounced at the GCME than at the BE, indicating catalytic effect by the clay on DA. For a mixture of DA, SN, AA, and UA, one broad oxidation peak is observed. Oxidation currents for both AA and UA at GCME are much lower than those at BE. This is evidenced by the fact that at pH of 7.4, AA and UA exist in their anionic form while DA and SN exist in the cationic form. Most clay layer surfaces are negatively charged so readily attract the cationic DA/SN into the interlayers and repel the anionic AA/UA. This enhances DA/SN detection while diminishing AA/UA detection. Only clay does not efficiently exclude AA/UA, hence the incorporation of methylene blue and xanthate. At GMBCME, both DA and SN exhibit oxidation potential at 0.20 V. However, a mixture of DA and SN exhibits peak potentials at 0.22 (DA) and 0.32 V (SN). Hence, the GMBCME film is able to separate and distinguish between the two peaks. It is also observed that both DA and SN peak potentials shift slightly negative compared to the BE. The DA peak currents increased at GMBCME compared to BE, while those of SN decreased. This confirms the catalytic effect of clay on DA stated above, but little or insignificant catalytic effect on SN. Again, GMBCME is unable to efficiently exclude AA and UA. With the addition of xanthate to form GMBXTCME, no oxidation peaks for AA and UA are seen. This is true for all three voltammetric techniques. This implies that the glycerol-methylene blue-xanthate-clay composite film efficiently discriminates against AA and UA detection. GMBXTCME film stability was also investigated and was observed that all old films exhibited great stability, reproducible results, and efficiently exclude both AA and UA. REFERENCES 1. T. Selvaraju, R. Ramaraj, J. Appl. Electrochem., 33, 759 (2003). 2. J.-M. Zen, P.-J. Chen, Anal. Chem., 69, 5087 (1997).

Graphene coated by polydopamine/multi-walled carbon nanotubes modified electrode for highly selective detection of dopamine and uric acid in the presence of ascorbic acid

Graphene (GR) was easily coated with a reactive biopolymer polydopamine (Pdop), and the Pdop functionalized graphene (Pdop@GR) novel nanomaterial was obtained by dispersing graphene in a dopamine solution and mildly stirring at room temperature. Meanwhile, a new modified electrode based on three-dimensional (3D) Pdop@GR-multiwalled carbon nanotubes (MWCNTs) hybrid nanomaterial has been prepared and applied on the simultaneous electrochemical determination of dopamine (DA) and uric acid (UA). The interference test showed that the coexisted ascorbic acid (AA) had no electrochemical interference toward DA and UA. Under the optimum conditions, the calibration curves for DA and UA were obtained in the range of 7.0–297.0μM and 20.0–320.0μM with detection limits (S/N=3) of 1.0×10−6M and 1.5×10−5M, respectively. Importantly, the proposed method offers promise for rapid, simple, selective and cost-effective analysis of small biomolecules.

Laser Treated Carbon Nanotube Yarn Microelectrodes for Rapid and Sensitive Detection of Dopamine in Vivo.

Carbon nanotube yarn microelectrodes (CNTYMEs) exhibit rapid and selective detection of dopamine with fast-scan cyclic voltammetry (FSCV); however, the sensitivity limits their application in vivo. In this study, we introduce laser treatment as a simple, reliable, and efficient approach to improve the sensitivity of CNTYMEs by three fold while maintaining high temporal resolution. The effect of laser treatment on the microelectrode surface was characterized by scanning electron microscopy, Raman spectroscopy, energy dispersion spectroscopy, and laser confocal microscopy. Laser treatment increases the surface area and oxygen containing functional groups on the surface, which provides more adsorption sites for dopamine than at unmodified CNTYMEs. Moreover, similar to unmodified CNTYMEs, the dopamine signal at laser treated CNTYMEs is not dependent on scan repetition frequency, unlike the current at carbon fiber microelectrodes (CFMEs) which decreases with increasing scan repetition frequency. This frequency independence is caused by the significantly larger surface roughness which would trap dopamine-o-quinone and amplify the dopamine signal. CNTYMEs were applied as an in vivo sensor with FSCV for the first time and laser treated CNTYMEs maintained high dopamine sensitivity compared to CFMEs with an increased scan repetition frequency of 50 Hz, which is five-fold faster than the conventional frequency. CNTYMEs with laser treatment are advantageous because of their easy fabrication, high reproducibility, fast electron transfer kinetics, high sensitivity, and rapid in vivo measurement of dopamine and could be a potential alternative to CFMEs in the future.

Preparation of electro-reduced graphene oxide supported walnut shape nickel nanostructures, and their application to selective detection of dopamine

A selective and sensitive method is reported for the detection of dopamine (DA) by using electro-reduced graphene oxide (er-GO) supported walnut shape nickel nanocomposite (er-GO-Ni) modified glassy carbon electrode. The surface morphological characterizations reveal that the Ni nanoparticles were homogeneously distributed on the er-GO nanosheets. Subsequently the electrochemical study shows an excellent selectivity, reproducibility, low detection limit (10 ± 0.03 nM), high sensitivity (23.3 nA·μM−1), and reasonably wide linear range (0.05–50 μM) for the detection of DA at +0.1 V vs SCE. The selectivity for DA over ascorbic acid and uric acid is attributed to the charge-based discrimination of the modified electrode. An excellent correspondence of calculated and reported rate constant for the DA oxidation is also obtained by hydrodynamic experiments using a rotating disk electrode.

Graphene quantum dots as effective probes for label-free fluorescence detection of dopamine

A label-free fluorescence based method using graphene quantum dots (GQDs) as effective probes was developed for sensitive and selective detection of dopamine (DA). The initial strong blue fluorescence of the GQDs in aqueous solution was effectively quenched upon addition of DA. The quenching mechanism may involve transfer of electrons from the photoexcited GQDs to dopamine–quinine, which was produced via the oxidization of DA by ambient O2 in alkaline solution. The quenching efficiency was linearly proportional to the concentration of DA within the range of 0.25–50μM with a low detection limit down of 0.09μM. The proposed sensing system is simple and low-cost with facile experimental operations, and has a high selectivity for DA over a number of possible interfering species. Additionally, this method was successfully applied to the determination of DA in biological samples with satisfactory recoveries (98.8–106.4%).

Molecularly imprinted silica films prepared by electroassisted deposition for the selective detection of dopamine

Dopamine (DA) can be detected by electrochemical oxidation in conventional electrodes. However, the presence of other oxidizable species (interferents) usually present in physiological fluids at high concentrations (like ascorbic acid) makes very difficult its electrochemical detection. In the present work, glassy carbon electrodes have been modified with molecularly imprinted silica (MIS) films prepared by electroassisted deposition of sol–gel precursors. The production of MIS films was performed by adding the template molecule (DA) to the precursor sol. The molecular impression of silica was assessed showing a high coherency allowing a filtering capacity in the molecular scale. The MIS-modified electrodes present a high selectivity for the detection of DA in neutral or acidic solutions. The MIS-modified electrodes allow the amperometric determination of dopamine in solutions containing ascorbic acid with molar ratios lower than 1:50,000.

Selective detection of dopamine in the presence of ascorbic acid via fluorescence quenching of InP/ZnS quantum dots.

Dopamine is a neurotransmitter of the catecholamine family and has many important roles, especially in human brain. Several diseases of the nervous system, such as Parkinson’s disease, attention deficit hyperactivity disorder, restless legs syndrome, are believed to be related to deficiency of dopamine. Several studies have been performed to detect dopamine by using electrochemical analysis. In this study, quantum dots (QDs) were used as sensing media for the detection of dopamine. The surface of the QDs was modified with l-cysteine by coupling reaction to increase the selectivity of dopamine. The fluorescence of cysteine-capped indium phosphide/zinc sulfide QDs was quenched by dopamine with various concentrations in the presence of ascorbic acid. This method shows good selectivity for dopamine detection, and the detection limit was 5 nM.

Electrochemical Co-Reduction Synthesis of AuPt Bimetallic Nanoparticles-Graphene Nanocomposites for Selective Detection of Dopamine in the Presence of Ascorbic Acid and Uric Acid.

In this paper, AuPt bimetallic nanoparticles-graphene nanocomposites were obtained by electrochemical co-reduction of graphene oxide (GO), HAuCl4 and H2PtCl6. The as-prepared AuPt bimetallic nanoparticles-graphene nanocomposites were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and other electrochemical methods. The morphology and composition of the nanocomposite could be easily controlled by adjusting the HAuCl4/H2PtCl6 concentration ratio. The electrochemical experiments showed that when the concentration ratio of HAuCl4/H2PtCl6 was 1:1, the obtained AuPt bimetallic nanoparticles-graphene nanocomposite (denoted as Au1Pt1NPs-GR) possessed the highest electrocatalytic activity toward dopamine (DA). As such, Au1Pt1NPs-GR nanocomposites were used to detect DA in the presence of ascorbic acid (AA) and uric acid (UA) using the differential pulse voltammetry (DPV) technique and on the modified electrode, there were three separate DPV oxidation peaks with the peak potential separations of 177 mV, 130 mV and 307 mV for DA and AA, DA and UA, AA and UA, respectively. The linear range of the constructed DA sensor was from 1.6 μM to 39.7 μM with a detection limit of 0.1 μM (S/N = 3). The obtained DA sensor with good stability, high reproducibility and excellent selectivity made it possible to detect DA in human urine samples.

Cerium Oxide Nanoparticles Decorated Graphene Nanosheets for Selective Detection of Dopamine.

The fabrication of a novel amperometric biosensor based on selective determination of dopamine (DA) using nafion coated cerium oxide nanoparticles (NPs) decorated graphene nanosheets (CeO2-HEG-nafion) as a transducer candidate is reported. Graphene was synthesized by hydrogen exfoliation technique. Decoration of CeO2NPs over graphene nanosheets was done by chemical reduction method. The electrochemical impedance spectroscopy (EIS) study shows the enhanced electron transfer kinetics of the composite compared to HEG modified and bare glassy carbon electrode (GCE). The response of the composite towards dopamine displays a lower oxidation potential of 0.23 V and a high oxidation current. The sensor exhibits linearity from 10 µM to 780 µM with a detection limit of 1 µM. In the presence of nafion, it shows excellent selectivity for coexisting interference species like Ascorbic acid (AA) and Uric acid (UA). The excellent performance of the biosensor can be attributed to large active surface area, enhanced electron transfer kinetics and high catalytic activity of the composite.

A surface acoustic wave sensor functionalized with a polypyrrole molecularly imprinted polymer for selective dopamine detection.

A surface acoustic wave sensor operating at 104 MHz and functionalized with a polypyrrole molecularly imprinted polymer has been designed for selective detection of dopamine (DA). Optimization of pyrrole/DA ratio, polymerization and immersion times permitted to obtain a highly selective sensor, which has a sensitivity of 0.55°/mM (≈ 550 Hz/mM) and a detection limit of ≈ 10 nM. Morphology and related roughness parameters of molecularly imprinted polymer surfaces, before and after extraction of DA, as well as that of the non imprinted polymer were characterized by atomic force microscopy. The developed chemosensor selectively recognized dopamine over the structurally similar compound 4-hydroxyphenethylamine (referred as tyramine), or ascorbic acid,which co-exists with DA in body fluids at a much higher concentration. Selectivity tests were also carried out with dihydroxybenzene, for which an unexpected phase variation of order of 75% of the DA one was observed. Quantum chemical calculations, based on the density functional theory, were carried out to determine the nature of interactions between each analyte and the PPy matrix and the DA imprinted PPy polypyrrole sensing layer in order to account for the important phase variation observed during dihydroxybenzene injection.

Highly Sensitive and Selective Detection of Dopamine at Poly(chromotrope 2B)-Modified Glassy Carbon Electrode in the Presence of Uric Acid and Ascorbic Acid

A highly sensitive and selective electrochemical method based on a poly(chromotrope 2B)-modified anodized glassy carbon electrode (PCHAGCE) was developed for the determination of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). The PCHAGCE sensor exhibited excellent electron-mediating behavior towards the oxidation of DA in 0.1M phosphate buffer solution (PBS) (pH7.0). It was found that the electrocatalytic activity was significantly dependent on the charge status and molecular structure of the target molecules. Differential pulse voltammetry (DPV) measurements revealed oxidation signals for DA, UA, and AA that were well-resolved into three distinct peaks with AA–DA, DA–UA, and AA–UA peak potential separations (ΔEp) of 172, 132, and 304mV, respectively. A detection limit of 0.04±0.001μM (S/N=3) and a quantification limit (S/N=10) of 0.149±0.03μM were obtained for DA sensing in a linear range of 1 to 40μM in PBS (pH7.0) with a very high sensitivity of 1.522±0.032μA·μM−1. The DA concentrations in human urine samples were also successfully determined with recoveries of 94.0–98.0%. This approach provides a simple, easy, sensitive, and selective method to detect DA in the presence of AA and UA.

Simultaneous Detection of Ascorbic Acid, Dopamine and Uric Acid Using Carboxyl-C60 Modified Electrodes

In this paper, a gold electrode is modified with Carboxyl-C60 for the selective detection of dopamine (DA) in the presence of high concentration ascorbic acid (UA). And we also investigated the effects of electrical and catalytic mechanism of the modified electrodes. The electrochemical behavior of the carboxyl-C60 modified electrode was characterized by cyclic voltammetry (CV) and differential pulse voltametry (DPV), which showed good performance toward individual detection of DA and UA and even their simultaneous detection in the presence of 5.0 μM UA.

Highly sensitive and selective detection of dopamine using one-pot synthesized highly photoluminescent silicon nanoparticles.

A simple and highly efficient method for dopamine (DA) detection using water-soluble silicon nanoparticles (SiNPs) was reported. The SiNPs with a high quantum yield of 23.6% were synthesized by using a one-pot microwave-assisted method. The fluorescence quenching capability of a variety of molecules on the synthesized SiNPs has been tested; only DA molecules were found to be able to quench the fluorescence of these SiNPs effectively. Therefore, such a quenching effect can be used to selectively detect DA. All other molecules tested have little interference with the dopamine detection, including ascorbic acid, which commonly exists in cells and can possibly affect the dopamine detection. The ratio of the fluorescence intensity difference between the quenched and unquenched cases versus the fluorescence intensity without quenching (ΔI/I) was observed to be linearly proportional to the DA analyte concentration in the range from 0.005 to 10.0 μM, with a detection limit of 0.3 nM (S/N = 3). To the best of our knowledge, this is the lowest limit for DA detection reported so far. The mechanism of fluorescence quenching is attributed to the energy transfer from the SiNPs to the oxidized dopamine molecules through Förster resonance energy transfer. The reported method of SiNP synthesis is very simple and cheap, making the above sensitive and selective DA detection approach using SiNPs practical for many applications.