A fluorescent chemosensor for Hg2+ based on naphthalimide derivative by fluorescence enhancement in aqueous solution

Novel coumarin-based ratiometric bifunctional fluorescent probe mimicking a set-reset memorized device

A novel coumarin-based fluorescent sensor CHE, incorporating 2-hydrazinylbenzothiazole and coumarin aldehyde, has been developed that demonstrated a preferential detection of Hg2+ and Ag+ in presence of interferences. Compared to previously prevalent intensity-based fluorescent probes, CHE exhibited a ratiometric fluorescence response to Hg2+ and Ag+, and further accurately differentiated Hg2+ and Ag + using the differential extractive ability of EDTA when interacting with ion-CHE complexes. Sensing mechanism was investigated and elucidated. The chemosensor CHE was successfully applied to detect Hg2+ and Ag+ in six distinct samples with satisfactory results. Additionally, combinatorial logic circuits were constructed utilizing three distinct logic gates (NOT, OR, and INH) based on the sensor's differential output signals in response to Hg2+/Ag+ and other cations. Interestingly, utilizing the reversible and reproducible switching behavior of the EDTA interaction with Hg2+, a conceptual 'Write-Read-Erase-Read' memory function with multi-write capability was proposed, offering a novel perspective for molecular-based memory systems.

Clarity improvement of the discoloration boundary and detection of Hg2+ ions by using a polystyrene nanoparticle-modified paper-based microdevice

Distance-based microfluidic paper-based analytical devices (μPADs) can be used to calculate the analyte content by reading the length of the discolored area in the channel. A blurred discoloration boundary is difficult to distinguish, resulting in reading errors. In this study, we constructed a μPAD modified with carboxyl-containing polystyrene nanoparticles (PS-μPAD) to improve the discoloration-boundary clarity. The filling of the pores of the fibers with the deposited polystyrene nanoparticles (PS NPs) caused a decrease in the paper porosity, resulting in a flow delay. Meanwhile, the carboxyl groups carried by PS NPs were able to form hydrogen bonds with hydroxyl-containing compounds FLPI, a Hg²⁺ probe, and the two factors acted synergistically to fix the FLPI to react in situ, raising the discoloration-boundary clarity. Compared with the unmodified μPAD, the detection of Hg²⁺ ions using the PS-μPAD still had a good linear relationship. Importantly, the color-depth difference inside and outside the discoloration boundary improved by about four times and showed excellent reproducibility in different populations. The method was simple and easy to expand, thereby providing an idea for more widespread application of distance-based μPADs.

Naphthalimide-Piperazine Derivatives as Multifunctional "On" and "Off" Fluorescent Switches for pH, Hg2+ and Cu2+ Ions

Novel 1,8-naphthalimide-based fluorescent probes NI-1 and NI-2 were designed and screened for use as chemosensors for detection of heavy metal ions. Two moieties, methylpyridine (NI-1) and hydroxyphenyl (NI-2), were attached via piperazine at the C-4 position of the napthalimide core resulting in a notable effect on their spectroscopic properties. NI-1 and NI-2 are pH sensitive and show an increase in fluorescence intensity at around 525 nm (switch "on") in the acidic environment, with pK_a values at 4.98 and 2.91, respectively. Amongst heavy metal ions only Cu²⁺ and Hg²⁺ had a significant effect on the spectroscopic properties. The fluorescence of NI-1 is quenched in the presence of either Cu²⁺ or Hg²⁺ which is attributed to the formation of 1:1 metal-ligand complexes with binding constants of 3.6 × 10⁵ and 3.9 × 10⁴, respectively. The NI-1 chemosensor can be used for the quantification of Cu²⁺ ions in sub-micromolar quantities, with a linear range from 250 nM to 4.0 μM and a detection limit of 1.5 × 10^-8 M. The linear range for the determination of Hg²⁺ is from 2 μM to 10 μM, with a detection limit of 8.8 × 10^-8 M. Conversely, NI-2 behaves like a typical photoinduced electron transfer (PET) sensor for Hg²⁺ ions. Here, the formation of a complex with Hg²⁺ (binding constant 8.3 × 10³) turns the green fluorescence of NI-2 into the "on" state. NI-2 showed remarkable selectivity towards Hg²⁺ ions, allowing for determination of Hg²⁺ concentration over a linear range of 1.3 μM to 25 μM and a limit of detection of 4.1 × 10^-7 M.

Fluorescent, colourimetric, and ratiometric probes based on diverse fluorophore motifs for mercuric(II) ion (Hg2+) sensing: highlights from 2011 to 2019

Though it has not been shown to deliver any biological importance, mercuric(II) ion (Hg²⁺) is a deleterious cation which poses grievous effects to the human body and/or the ecosystem, hence, the need for its sensitive and selective monitoring in both environmental and biological systems. Over the years, there has been a great deal of work in the use of fluorescent, colourimetric, and/or ratiometric probes for Hg²⁺ recognition. Essentially, the purpose of this review article is to give an overview of the advances made in the constructions of such probes based on the works reported in the period from 2011 to 2019. Discussion in this review work has been tailored to the kinds of fluorophore scaffolds used for the constructions of the probes reported. Selected examples of probes under each fluorophore subcategory were discussed with mentions of the typically determined parameters in an analytical sensing operation, including modulation in fluorescence intensity, optimal pH, detection limit, and association constant. The environmental and biological application ends of the probes were also touched where necessary. Important generalisations and conclusions were given at the end of the review. This review article highlights 196 references.

A novel water-soluble naked-eye probe with a large Stokes shift for selective optical sensing of Hg2+ and its application in water samples and living cells

A water-soluble and colorimetric fluorescent probe with a large Stokes shift (139 nm) for rapidly detecting Hg2+, namely Hcy-mP, was synthesized by using an indole derivative and 2,4-dihydroxybenzaldehyde as starting materials. This probe demonstrates good selectivity for Hg2+ over other metal ions including Ag+, Pb2+, Cd2+, Cr3+, Zn2+, Fe3+, Co2+, Ni2+, Cu2+, K+, Na+, Mg2+, and Ca2+ in aqueous solution. With the increase in concentration of Hg2+, the color of the solution changed from pale yellow to pink and the fluorescence intensity decreased slightly. When 5-equivalents of EDTA were added to the solution with Hg2+, the fluorescence intensity of this probe was restored. The probe has been applied to the detection of Hg2+ in real water samples. Moreover, this probe was confirmed to have low cytotoxicity and excellent cell membrane permeability. The effect of Hcy-mP-Hg2+ towards living cells by confocal fluorescence was also investigated.

Highly sensitive and selective determination of Hg(II) based on microfluidic chip with on-line fluorescent derivatization

In this study, a convenient, sensitive, rapid and simple method was developed on microfluidic chip which was integrated with on-line complexing and laser-induced fluorescence detection. A rhodamine derivative (RD) was developed as a fluorescent chemosensor for Hg(II). It exhibited high selective recognition toward Hg(II) over other examined metal ions in water samples. Under the optimized conditions, the response was linearly proportional to the concentration of Hg(II) in the range of 0-70 μM with a detection limit of 0.031 μM. Satisfactory repeatability and reproducibility were achieved, with a relative standard deviation (RSD) of 6.62%. The established method was successfully applied for the determination of Hg(II) in environmental water samples (surface water, tap water, and waste water). Recoveries obtained for the determination of Hg(II) in spiking samples ranged from 85% to 103%.

A New Reactive 1,8-Naphthalimide Derivative for Highly Selective and Sensitive Detection of Hg2

A 1,8-naphthalimide derivative with a reactive aliphatic hydroxyl was designed and synthesized as a fluorescent probe. Its structure was characterized by IR, ¹H NMR, ¹³C NMR, LC-MS and HPLC. The probe showed high selectivity and sensitivity to Hg²⁺ over other metal ions such as Pb²⁺, Na⁺, K⁺, Cd²⁺, Cr³⁺, Zn²⁺, Cu²⁺, Ni²⁺, Ca²⁺, Fe³⁺, Fe²⁺, Co²⁺, Mn²⁺ and Mg²⁺ in MeCN/H₂O (15/85, v/v). The increase in fluorescence intensity was linearly proportional to the concentration of Hg²⁺ in the range of 18-40 μM with a detection limit of 1.38 × 10^-7 mol/L. The probe could work in a pH span of 4.3-9.0 and respond to Hg²⁺ quickly with strong anti-interference ability. Job's plot suggested a 1:2 complex of the probe and Hg²⁺.

Fluorimetric detection of Sn(2+) ion in aqueous medium using Salicylaldehyde based nanoparticles and application to natural samples analysis

The fluorescent 2-[(E)-(2-phenylhydrazinylidene)methyl]phenol nanoparticles (PHPNPs) were prepared by a simple reprecipitation method. The prepared PHPNPs examined by Dynamic Light Scattering show narrower particle size distribution having an average particle size of 93.3nm. The Scanning Electron Microphotograph shows distinct spherical shaped morphology of nanoparticles. The blue shift in UV-absorption and fluorescence spectra of PHPNPs with respect to corresponding spectra of PHP in acetone solution indicates H- aggregates and Aggregation Induced Enhanced Emission (AIEE) for nanoparticles. The nanoparticles show selective tendency towards the recognition of Sn(2+) ions by enhancing the fluorescence intensity preference to Cu(2+), Fe(3+), Fe(2+), Ni(2+), NH4(+), Ca(2+), Pb(2+), Hg(2+) and Zn(2+) ions, which actually seem to quench the fluorescence of nanoparticles. The studies on Langmuir adsorption plot, fluorescence lifetime of PHPNPs, DLS-Zeta sizer, UV-visible and fluorescence titration with and without Sn(2+) helped to propose a suitable mechanism of fluorescence enhancement of nanoparticles by Sn(2+) and their binding ability during complexation. The fluorescence enhancement effect of PHPNPs induced by Sn(2+) is further used to develop an analytical method for detection of Sn(2+) from aqueous medium in environmental samples.

A rhodamine-based chemosensor with diphenylselenium for highly selective fluorescence turn-on detection of Hg2+in vitro and in vivo

A rhodamine-B based chemosensor with diphenylselenium, RhoSe, has been developed for highly selective fluorescent turn-on detection of Hg²⁺.

Highly Hg2+-sensitive and selective fluorescent sensors in aqueous solution and sensors-encapsulated polymeric membrane

The sensors in solutions and sensors encapsulated polymeric membranes exhibited high sensitivity and selectivity for Hg²⁺ detection, with detection limits of 0.2–49 ppb.

Fluorescence staining of salicylaldehyde azine, and applications in the determination of potassium tert-butoxide

Salicylaldehyde azine (1), with an aggregation-induced emission (AIE) function, was synthesized from salicylaldehyde and characterized by nuclear magnetic resonance, high resolution mass spectrometry, and X-ray single crystal diffraction.

1,8-Naphthalimide derivative-based turn-off fluorescent probe for the detection of picrate in organic aqueous media

The synthesis of a simple fluorescent naphthalimide-based receptor N-allyl-4-iminodi(N-butylacetamide)-1,8-naphthalimide 3 was carried out as a selective picrate (Pic–) anion probe, and the detecting behavior of this probe was studied by fluorescence spectroscopy. In DMF solution, the interaction of compound 3 with different anions, including Pic–, F–, Cl–, Br–, I–, OH–, Ac–, NO3 –, ClO4 –, SCN–, SO3 2–, SO4 2–, H2PO4 –, and HPO4 2–, revealed significant fluorescence quenching only with the Pic– anion. By adding the picrate anions, green-yellow fluorescence emission quenches, which is easily observed by naked eyes under a 365 nm UV light irradiation. This phenomenon is essential for producing a highly selective and sensitive fluorescent probe for picrate anions. The probe can be applied to the quantification of Pic– with a linear range covering from 4.97 × 10–6 to 6.82 × 10–5 m and a detection limit of 5.8 × 10–7 m. Most importantly, probe 3 has a high selectivity for picrate over competitive anions and picrate-containing analytes, which meet the selective requirements for practical application. Thus, the present results would be inspiring findings in the future design of reaction-based fluorescent turn-off probes for the environmentally relevant picrate probe.

A naphthalimide based PET probe with Fe3+ selective detection ability: theoretical and experimental study

A naphthalimide based Fe³⁺ selective fluorescence ‘turn-on’ probe that operates based on a PET mechanism has been synthesized, and its application in the detection of Fe³⁺ ions in aqueous samples and in live cells is explored.