BSA–AuNPs@Tb–AMP metal–organic frameworks for ratiometric fluorescence detection of DPA and Hg2+

An easy and effective strategy for synthesizing a ratiometric fluorescent nanosensor has been demonstrated in this work. Novel fluorescent BSA–AuNPs@Tb–AMP (BSA, bovine serum albumin; AMP, adenosine 5′‐monophosphate; AuNPs, Au nanoparticles) metal–organic framework (MOF) nanostructures were synthesized by encapsulating BSA–AuNPs into Tb–AMP MOFs for the detection of 2,6‐pyridinedicarboxylic acid (DPA) and Hg²⁺. DPA could strongly co‐ordinate with Tb³⁺ to replace water molecules from the Tb³⁺ center and accordingly enhanced the fluorescence of Tb–AMP MOFs. The fluorescence of BSA–AuNPs at 405 nm remained constant. While the fluorescence of BSA–AuNPs at 635 nm was quenched after Hg²⁺ was added, the fluorescence of Tb–AMP MOFs remained constant. Accordingly, a ratiometric fluorescence nanosensor was constructed for detection of DPA and Hg²⁺. The ratiometric nanosensor exhibited good selectivity to DPA over other substances. The F₅₄₅/F₄₀₅ linearly increased with increase of DPA concentration in the range of 50 nM to 10 μM with a detection limit as low as 17.4 nM. F₆₃₅/F₄₀₅ increased linearly with increase of Hg²⁺ concentration ranging from 50 nM to 1 μM with a detection limit as low as 20.9 nM. Additionally, the nanosensor could be successfully applied for the determination of DPA and Hg²⁺ in running water.     

Carbon dots-modified paper-based chemiluminescence device for rapid determination of mercury (II) in cosmetics

Here, a simple and portable paper-based analytical device (PAD) based on the inherent capability of carbon quantum dots (CQDs) to serve as a great emitter for the bis(2,4,6-trichlorophenyl)oxalate (TCPO)–hydrogen peroxide (H₂O₂) chemiluminescence (CL) reaction is introduced for the detection of harmful mercury ions (Hg²⁺). The energy is transferred from the unstable reaction intermediate (1,2-dioxetanedione) to CQDs, as acceptors, and an intensive orange-red CL emission is generated at ~600 nm, which is equal to the fluorescence emission wavelength of CQDs. The analytical applicability of this system was examined for the determination of Hg²⁺. It was observed that Hg²⁺ could significantly quench the produced emission, which can be attributed to the formation of a stable and nonluminescent Hg²⁺–CQDs complex. Accordingly, a simple and rapid PAD was established for monitoring Hg²⁺, with a limit of detection of 0.04 μg ml⁻¹. No interfering effect on the signal was found from other examined cations, indicating the acceptable specificity of the method. The designed assay was appropriately utilized to detect Hg²⁺ ions in cosmetic samples with high efficiency. It was characterized by its low cost, ease of use, and was facile but accurate and high selective for the detection of Hg²⁺ ions. In addition, the portability of this probe makes it suitable for on-site screening purposes.     

Nitrogen-rich silicon quantum dots: facile synthesis and application as a fluorescent ‘on–off–on’ probe for sensitive detection of Hg2+ and cyanide ions

The sensitive and reliable detection of Hg²⁺ and CN⁻ as harsh environmental contaminants are of great importance. In view of this, a novel ‘on–off–on’ fluorescent probe based on nitrogen-rich silicon quantum dots (NR-SiQDs) has been designed for sensitive detection of Hg²⁺ and CN⁻ ions in aqueous medium. NR-SiQDs were synthesized using a facile, one-step, and environment friendly procedure in the presence of 3-aminopropyl trimethoxysilane (APTMS) and ascorbic acid (AA) as precursors, with l -asparagine as a nitrogen source for surface modification. The NR-SiQDs exhibited strong fluorescence emission at 450 nm with 42.34% quantum yield, satisfactory salt tolerance, and superior photostability and pH stability. The fluorescence emission was effectively quenched using Hg²⁺ (turn-off) due to the formation of a nonfluorescent stable NR-SiQDs/Hg²⁺ complex, whereas after the addition of cyanide ions (CN⁻), Hg²⁺ ions could be leached from the surface of the NR-SiQDs and the fluorescence emission intensity of the quenched NR-SiQDs fully recovered (turn-on) due to the formation of highly stable [Hg(CN)₄]²⁻ species. After optimizing the response conditions, the obtained limits of detection were found to be 53 nM and 0.46 μM for Hg²⁺ and CN⁻, respectively. Finally, the NR-SiQD-based fluorescence probe was utilized to detect Hg²⁺ and CN⁻ ions in water samples and satisfactory results were obtained, suggesting its potential application for environmental monitoring.     

Resonance scattering spectral detection of ultratrace Hg(II) using herring sperm DNA modified nanogold probe as catalyst

Herring sperm DNA (hsDNA) was used to modify 10 nm nanogold to obtain a resonance scattering (RS) probe (AuhsDNA) for detection of Hg²⁺. In the presence of salt, Hg²⁺ interacts with AuhsDNA to form stable Hg²⁺–hsDNA complexes, and releases nanogold particles to form larger nanogold clusters that can be removed by membrane filtration. The excess AuhsDNA in the filtrate solution exhibits a catalytic effect on the reaction between hydroxylamine (NH₂OH) and Cu(II). The excess AuhsDNA decreased with the addition of Hg²⁺, which led the RS intensity at 602 nm to decrease. The decreased RS intensity (Δl_{602 nm}) had a linear response to Hg²⁺ concentration in the range of 0.4–400 nM, with a detection limit of 0.2 nM Hg²⁺. This RS method was applied for the detection of Hg²⁺ in water samples, with sensitivity, selectivity and simplicity. Copyright © 2009 John Wiley & Sons, Ltd.     

Differential action of Hg2+ and Cd2+ on the phycobilisomes and chlorophyll a fluorescence,and photosystem II dependent electron transport in the cyanobacterium Anabaena flos-aquae

The effect of equimolar concentrations of Hg²⁺ and Cd²⁺ on the whole cell absorption spectra, absorption spectra of the extracted phycocyanin (PC) and fluorescence emission spectra of phycobilisomes (PBS) was investigated in the cells of Anabaena flos-aquae. The PC component of the PBS was found to be extremely sensitive to the Hg²⁺ rather than the Cd²⁺ ions. Further, the results showed that Hg²⁺ and Cd²⁺ induced decrease in the rate of Hill activity (H₂O - DCPIP) was partially restored by the electron donor NH₂OH, not by the diphenyl carbazide. Similarly, chlorophyll a fluorescence emission in the presence of metals showed that addition of NH₂OH could effectively reverse the metal induced alterations in the fluorescence emission intensity. These results, together, suggested that Hg²⁺ and Cd²⁺ caused damage to the photosystems (PS) II reaction center. However, a relatively higher stimulation of the chlorophyll a emission at 695 nm with a red shift of 4.0 nm in the presence of Hg²⁺, and Cd²⁺ induced preferential decrease in the emission intensity at 676 nm as compared with the peak at 695 nm were indicative of the differential action of Hg²⁺ and Cd²⁺ on the PS II.     

Preparation and application of solvent‐modulated self‐doped N–S multicolour fluorescence carbon quantum dots

In this paper, two types of carbon quantum dot (CQDs) were prepared using biocompatible l ‐methionine as the carbon source and urea as the nitrogen source and a one‐step hydrothermal treatment. By changing the reaction solvents (deionized (DI) water and dimethylformamide (DMF)), the maximum emission of the resulting CQDs shifted from blue to red light. Specifically, the emission wavelength of the CQDs moved from 433 nm to 625 nm following embedding of a new functional group (–CONH–) on the surface of the CQDs. Photoluminescence quantum yields of the CQDs with blue and red emission reached 64% and 61%, respectively. The R‐CQDs were used to detect metal ions and a linear relationship was demonstrated between ln(F/F₀) and Fe³⁺ concentration in the range 0–0.5 mmol/L with a detection limit of 0.067 μM. Therefore these R‐CQDs have great potential as fluorescent probes for Fe³⁺ detection. We expect that the excellent water‐soluble, biocompatible and optical properties of the CQDs developed in this work mean that they will be widely used to detect biological cells.     

A highly sensitive and reversible chemosensor for Hg2+ detection based on porphyrin‐thymine conjugates

In this study, we demonstrated a highly sensitive, selective, and reversible chemosensor for Hg²⁺ determination. This chemosensor was synthesized by direct condensation of thymin‐1‐ylacetic acid with zinc tetraaminoporphyrin, which has a porphyrin core as the fluorophore and four thymine (T) moieties as the specific interaction sites for Hg²⁺. The probe (4T‐ZnP) exhibited split Soret bands with a small peak at 408 nm and a strong band at 429 nm in a dimethylformamide/H₂O (7/3, v/v) mixed solvent as well as a strong emission band at 614 nm. Upon the addition of Hg²⁺, the probe displayed strong fluorescence quenching due to the formation of T‐Hg²⁺‐T complexes. With the aid of the fluorescence spectrometer, the chemosensor in the dimethylformamide/H₂O (7/3, v/v) mixed solvent (0.3 μM) exhibited a detection limit of 6.7 nM. Interferences from other common cations, such as Co²⁺, K⁺, Sn²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Na⁺, Ca²⁺, Mg²⁺, Pb²⁺, and Cd²⁺, associated with Hg²⁺ analysis were effectively inhibited. Copyright © 2015 John Wiley & Sons, Ltd.     

Ratiometric fluorescent detection of Cu2+ based on dual‐emission ZIF‐8@rhodamine‐B nanocomposites

Zeolitic imidazolate framework‐8 (ZIF‐8) loading rhodamine‐B (ZIF‐8@rhodamine‐B) nanocomposites was proposed and used as ratiometric fluorescent sensor to detect copper(II) ion (Cu²⁺). Scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray powder diffraction, nitrogen adsorption/desorption isotherms and fluorescence emission spectroscopy were employed to characterize the ZIF‐8@rhodamine‐B nanocomposites. The results showed the rhodamine‐B was successfully assembled on ZIF‐8 based on the π‐π interaction and the hydrogen bond between the nitrogen atom of ZIF‐8 and –COOH of rhodamine‐B. The as‐obtained ZIF‐8@rhodamine‐B nanocomposites were octahedron with size about 150–200 nm, had good water dispersion, and exhibited the characteristic fluorescence emission of ZIF‐8 at 335 nm and rhodamine‐B at 575 nm. The Cu²⁺ could quench fluorescence of ZIF‐8 rather than rhodamine‐B. The ZIF‐8 not only acted as the template to assemble rhodamine‐B, but also was employed as the signal fluorescence together with the fluorescence of rhodamine‐B as the reference to construct a novel ratiometric fluorescent sensor to detect Cu²⁺. The resulted ZIF‐8@rhodamine‐B nanocomposite fluorescence probe showed good linear range (68.4 nM to 125 μM) with a low detection limit (22.8 nM) for Cu²⁺ combined with good sensitivity and selectivity. The work also provides a better way to design ratiometric fluorescent sensors from ZIF‐8 and other fluorescent molecules.     

A sensitive assay of mercury using fluorescence correlation spectroscopy of gold nanoparticles

We described a new and sensitive method for the determination of mercury ions (Hg²⁺) on the basis of fluorescence correlation spectroscopy (FCS) and recognition of oligonucleotides. In this assay, 30‐nm gold nanoparticles (GNPs) were modified with oligonucleotides containing thymine bases (T) as fluorescent probes, and the principle of this assay was based on the specific binding of Hg²⁺ by two DNA thymine bases. When two GNPs labelled with different oligonucleotides were mixed with a sample containing Hg²⁺, the T‐Hg²⁺‐T binding reaction should cause GNPs to form dimers (or oligomers), which would lead to a significant increase in the characteristic diffusion time of GNPs in the detection volume. The FCS method is a single molecule detection method and can sensitively detect the change in the characteristic diffusion time of GNPs before and after binding reactions. The quantitative analysis was performed according to the relation between the change in the characteristic diffusion time of GNPs and the concentration of Hg²⁺. Under optimal conditions, the linear range of this method was from 0.3 nM to 100 nM, and the detection limit was 0.14 nM for Hg²⁺. This new method was successfully applied for direct determination of Hg²⁺ levels in water and cosmetics samples. Copyright © 2014 John Wiley & Sons, Ltd.     

An integrated system of pyrene and rhodamine-6G for selective colorimetric and fluorometric sensing of mercury(II)

A pyrene and rhodamine-6G functionalized simple chemosensor L is studied toward sensing of metal ions in solution extensively. L shows selective color change from colorless to pink in the presence of Hg²⁺ in acetonitrile and the UV-Vis study shows peak at 525 nm with a ε value of 5.2 × 10⁴ M⁻¹ cm⁻¹ due to selective ring opening of rhodamine spirolactam moiety. The selective sensing of Hg²⁺ by L in the presence of other metal ions and reversible nature of “OFF-ON-OFF” functionality of L by Hg²⁺ and EDTA, respectively, are also established. The fluorescence study of L in the presence of Hg²⁺ shows emission at 550 nm when excited at 525 nm (ring opened rhodamine wavelength) or 340 nm (pyrene wavelength) in dry CH₃CN. Thus L acts as a selective colorimetric and fluorometric probe (dual probe) for the Hg²⁺ in solution. Metal ion sensing ability of L is also carried out in water as well as in aqueous Hepes buffer. These studies suggest that the fluorescence output of L in presence of Hg²⁺ in aqueous environment is apparently due to the generation of acid upon addition of Hg²⁺ salt in water.     

Hg2+‐selective ratiometric and colorimetric probe based on dansyl–rhodamine and its staining function in cell imaging

A new ratiometric probe composed of a dansyl–rhodamine dyad for the detection of Hg²⁺ via fluorescence resonance energy transfer was designed and synthesized. Rhodamine, dansyl chloride, and hydrazide were selected as the acceptor, donor, and reaction site, respectively. It displayed high selectivity and sensitivity to Hg²⁺ with obvious colour change and fluorescence change due to Hg²⁺‐assisted hydrolysis of rhodamine hydrazide. A good linear relationship ranging from 0 to 16 μM and 0–28 μM for the Hg²⁺ concentration was found based on absorbance and fluorescence assay, respectively. Detection limits of absorbance and fluorescence for Hg²⁺ were calculated to be 1.22 μM and 9.10 μM, respectively.     

Naphthalimide-based fluorescent probe for Hg2+ detection and imaging in living cells and zebrafish

A simple naphthalimide-based fluorescent probe was designed and synthesized for the determination of mercury ion (Hg²⁺). The probe showed a noticeable fluorescence quenching response for Hg²⁺. When added with Hg²⁺, the fluorescence intensity of the probe at 560 nm was remarkably decreased with the color changed from yellow to colorless under ultraviolet (UV) light. The probe had a notable selectivity and sensitivity for Hg²⁺ and displayed an excellent sensing performance when detecting Hg²⁺ at low concentration (19.5 nM). The binding phenomenon between the probe and Hg²⁺ was identified by Job's method and high-resolution mass spectrometry (HRMS). Moreover, the probe was not only utilized to identify Hg²⁺ in real samples with satisfactory results (92.00%–110.00%) but also was successfully used for bioimaging in cells and zebrafish. The recognition mechanism has been verified by transmission electron microscopy (TEM) for the first time. All the results showed that the probe could be used as a potent useful tool for detection of Hg²⁺.     

Prevention by Ce3+ of DNA destruction caused by Hg2+ in fish intestine

The interactions between Hg²⁺, Ce³⁺, and the mixuure of Ce³⁺ and Hg²⁺, and DNA from fish intestine in vitro were investigated by using absorption spectrum and fluorescence emission spectrum. The ultraviolet absorption spectra indicated that the addition of Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ to DNA generated an obviously hypochromic effect. Meanwhile, the peak of DNA at 205.2 nm blue-shifted and at 258.2 nm red-shifted. The size of the hypochromic effect and the peak shift of DNA by metal ion treatments was Hg²⁺>Hg²⁺+Ce³⁺>Ce³⁺. The fluorescence emission spectra showed that with the addition of Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ the emission peak at about 416.2 nm of DNA did not obviously change, but the intensity reduced gradually and the sequence was Hg²⁺>Hg²⁺+Ce²⁺>Ce³⁺. Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ had 1.12, 0.19, and 0.41 binding sites to DNA, respectively; the fluorescence quenching of DNA caused by the metal ions all attributed to static quenching. The binding constants (K _A ) of binding siees were 8.98×10⁴ L/mol and 1.02×10⁴ L/mol, 5.12×10⁴ L/mol and 1.10×10³ L/mol, 6.66×10⁴ L/mol and 2.36×10³ L/mol, respectively. The results showed that Ce³⁺ could relieve the destruction of Hg²⁺ on the DNA structure.     

Synthesis of a water-stable CsPbBr3 perovskite for selective detection of mercury ion in water

By using the method of low-temperature crystallization, CsPbBr₃ perovskite nanocrystals (PNCs) coated with trifluoroacetyl lysine (Tfa-Lys) and oleamine (Olam) were synthesized in aqueous solution. The structure of the CsPbBr₃ PNCs was characterized by many methods, such as ultraviolet (UV)-visible absorption spectrophotometer, fluorescence spectrophotometer, transmission electron microscopy (TEM), and X-ray diffraction (XRD) pattern. The fluorescence emission of the CsPbBr₃ PNCs is stable in water for about 1 day at room temperature. It was also found that the fluorescence of the PNCs could be obviously and selectively quenched after the addition of mercury ion (Hg²⁺), allowing a visual detection of Hg²⁺ by the naked eye under UV light illumination. The fluorescence quenching rate (I₀/I) has a good linear relationship with the addition of Hg²⁺ in the concentration range 0.075 to 1.5 mg/L, with a correlation coefficient (R²) of 0.997, and limit of detection of 0.046 mg/L. The fluorescence quenching mechanism of the PNCs was determined by the fluorescence lifetime and X-ray photoelectron spectroscopy (XPS) of the PNCs. Overall, the synthesis method for CsPbBr₃ PNCs is simple and rapid, and the as-prepared PNCs are stable in water that could be conveniently used for selective detection of Hg²⁺ in the water environment.     

Silver nanoclusters stabilized with denatured fish sperm DNA and the application on trace mercury ions detection

In this study, fluorescent silver nanoclusters (Ag NCs) were synthesized using denatured fish sperm DNA as the template. In contrast to other methods, this method did not use artificial DNA as the template. After their reaction with denatured fish sperm DNA, Ag⁺ ions were reduced by NaBH₄ to form Ag NCs. The Ag NCs showed a strong fluorescence emission at 650 nm when excited at 585 nm. The fluorescence intensity increased fourfold at pH 3.78, controlled with Britton–Robinson buffer solution. The fluorescence of the Ag NCs was quenched in the presence of trace mercury ions (Hg²⁺) in a weakly acidic medium and nitrogen atmosphere. The extent of the fluorescence quenching of Ag NCs strongly depends on the Hg²⁺ ion concentration over a linear range from 2.0 nmol L^?1 to 3.0 μmol L^?1. The detection limit (3σ/k) for Hg²⁺ was 0.7 nmol L^?1. Thus, a sensitive and rapid method was developed for the detection of Hg²⁺ ions.     

Fluorescence detection of single nucleotide polymorphisms using a universal molecular beacon

We present a simple and novel assay—employing a universal molecular beacon (MB) in the presence of Hg²⁺—for the detection of single nucleotide polymorphisms (SNPs) based on Hg²⁺–DNA complexes inducing a conformational change in the MB. The MB (T₇-MB) contains a 19-mer loop and a stem of a pair of seven thymidine (T) bases, a carboxyfluorescein (FAM) unit at the 5′-end, and a 4-([4-(dimethylamino)phenyl]azo)benzoic acid (DABCYL) unit at the 3′-end. Upon formation of Hg²⁺–T₇-MB complexes through T–Hg²⁺–T bonding, the conformation of T₇-MB changes from a random coil to a folded structure, leading to a decreased distance between the FAM and DABCYL units and, hence, increased efficiency of fluorescence resonance energy transfer (FRET) between the FAM and DABCYL units, resulting in decreased fluorescence intensity of the MB. In the presence of complementary DNA, double-stranded DNA complexes form (instead of the Hg²⁺–T₇-MB complexes), with FRET between the FAM and DABCYL units occurring to a lesser extent than in the folded structure. Under the optimal conditions (20 nM T₇-MB, 20 mM NaCl, 1.0 μM Hg²⁺, 5.0 mM phosphate buffer solution, pH 7.4), the linear plot of the fluorescence intensity against the concentration of perfectly matched DNA was linear over the range 2–30 nM (R² = 0.991), with a limit of detection of 0.5 nM at a signal-to-noise ratio of 3. This new probe provides higher selectivity toward DNA than that exhibited by conventional MBs.     

Water‐soluble polymeric chemosensor for selective detection of Hg2+ in aqueous solution using rhodamine‐based modified poly(acrylamide–acrylic acid)

We report the fabrication of a novel easily available turn‐on fluorescent water‐soluble polymeric chemosensor for Hg²⁺ ions that was simply prepared by micellar free radical polymerization of a water‐insoluble organic rhodamine‐based Hg²⁺‐recognizing monomer (GR6GH), with hydrophilic monomers acrylamide (AM) and acrylic acid (AA). The chemical structure of the polymeric sensor was characterized by FT‐IR and ¹H NMR spectroscopy. The apparent viscosity average molecular weight M_η of poly(acrylamide–acrylic acid) [poly(AM–NaAA)] and the water‐soluble polymeric chemosensor poly(AM–NaAA–GR6GH) were 1.76 × 10⁶ and 6.84 × 10⁴ g/mol, respectively. Because of its amphiphilic property, the water‐soluble polymeric chemosensor can be used as a chemosensor in aqueous media. Upon addition of Hg²⁺ ions to an aqueous solution of poly(AM–NaAA–GR6GH), fluorescence enhancements were observed instantly. Moreover, other metal ions did not induce obvious changes to the fluorescence spectra. This approach may provide an easily measurable and inherently sensitive method for Hg²⁺ ion detection in environmental and biological applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Calix[4]arene based molecular sensors with pyrene as fluoregenic unit: Effect of solvent in ion selectivity and colorimetric detection of fluoride

Fluorescent molecular sensors having excimer emission property have been designed and synthesised incorporating calix[4]arene derivatives in cone and 1,3-alternate conformation as ionophore and two pyrene moieties at close proximity as fluorophore. They exhibit strong excimer emission around 515 nm, which is used to monitor interaction of metal ions with the ionophores. Ion-binding study of these fluoroionophore has been investigated in acetonitrile-chloroform and THF-H₂O with a wide range of cations and anions and the recognition process is monitored by luminescence, UV-Vis and ¹H NMR (for F⁻) spectral changes. The present study demonstrated profound influence of solvent in ion selectivity, in acetonitrile-chloroform they formed complexes with Hg²⁺, Pb²⁺, Cu²⁺ and Ni²⁺, whereas in THF-H₂O they exhibit selectivity only for Cu²⁺. In the case of anions, selectivity for only F⁻ with color change is observed. Composition of the complexes formed was determined from mass spectrometry and the binding constants were determined from fluorescence titration data. The reasons for formation of excimer emission, quenching of it in presence of certain metal ions, role of solvent in selectivity and energy/electron transfer process involved in the ion-recognition event have been discussed on the basis of experimental data.     

A rhodamine‐triazole fluorescent chemodosimeter for Cu2+ detection and its application in bioimaging

A rhodamine‐based fluorescent chemodosimeter rhodamine hydrazide‐triazole (RHT) tethered with a triazole moiety was developed for Cu²⁺ detection. In aqueous medium, the RHT probe exhibited high selectivity and sensitivity toward Cu²⁺ among other metal ions. The addition of Cu²⁺ triggered a fluorescence emission of RHT by 384‐fold (Φ = 0.33) based on a ring‐opening process and a subsequent hydrolysis reaction. Moreover, RHT also showed a selective colorimetric response toward Cu²⁺ from colorless solution to pink, readily observed with the naked eye. The limit of detection of RHT for Cu²⁺ was calculated to be 1 nM (0.06 ppb). RHT was successfully demonstrated to detect Cu²⁺ in Chang liver cells by confocal fluorescence microscopy.     

Phenothiazine–rhodamine‐based colorimetric and fluorogenic ‘turn‐on' sensor for Zn2+ and bioimaging studies in live cells

A phenothiazine–rhodamine (PTRH) fluorescent dyad was synthesized and its ability to selectively sense Zn²⁺ ions in solution and in in vitro cell lines was tested using various techniques. When compared with other competing metal ions, the PTRH probe showed the high selectivity for Zn²⁺ ions that was supported by electronic and emission spectral analyses. The emission band at 528 nm for the PTRH probe indicated the ring closed form of PTRH, as for Zn²⁺ ion binding to PTRH, the λ_em get shift to 608 nm was accompanied by a pale yellow to pink colour (under visible light) and green to pinkish red fluorescence emission (under UV light) due to ring opening of the spirolactam moiety in the PTRH ligand. Spectral overlap of the donor emission band and the absorption band of the ring opened form of the acceptor moiety contributed towards the fluorescence resonance energy transfer ON mechanism for Zn²⁺ ion detection. The PTRH sensor had the lowest detection limit for Zn²⁺, found to be 2.89 × 10^?8 M. The sensor also demonstrated good sensing application with minimum toxicity for in vitro analyses using HeLa cells.