First generation poly(propyleneimine) dendrimers functionalised with 1,8-naphthalimide units as fluorescence sensors for metal cations and protons

New Water-Soluble Poly(propylene imine) Dendrimer Modified with 4-Sulfo-1,8-naphthalimide Units: Sensing Properties and Logic Gates Mimicking

A new water-soluble poly(propylene imine) dendrimer (PPI) modified with 4-sulfo-1,8-naphthalimid units (SNID) and its related structure monomer analog (SNIM) has been prepared by a simple synthesis. The aqueous solution of the monomer exhibited aggregation-induced emission (AIE) at 395 nm, while the dendrimer emitted at 470 nm due to an excimer formation beside the AIE at 395 nm. Fluorescence emission of the aqueous solution of either SNIM or SNID was significantly affected by traces of different miscible organic solvents, and the limits of detection were found to be less than 0.05% (v/v). Moreover, SNID exhibited the function to execute molecular size-based logic gates where it mimics XNOR and INHIBIT logic gates using water and ethanol as inputs and the AIE/excimer emissions as outputs. Hence, the concomitant execution of both XNOR and INHIBIT enables SNID to mimic digital comparators.

Using a Dendritic Sensor as a Feasible Method for Detection of Copper in Water Samples

Due to the severe dangers of copper on human health, development of identification and measurement copper methods in aquatic environments as well as prevention transfer methods of these substances to water resources have received much attention. Among of this expansion, rapid, simple, safe, sensitive and economically viable detection methods are more considerable. In this paper, the sensor activity of the poly(amidoamine) dendrimer containing eight methoxy groups modified with naphthalimide fluorescent derivative is studied. The sensor potential of dendrimer-naphthalimide fluorescence was evaluated in various solvents with different polarities, and results indicated that the detection of cuprum cations (Cu²⁺) is possible at low concentration. Also, the fluorescence properties of dendrimer-naphthalimide system are measured in the presence of diverse metal cations. In light of above, from the obtaining results, it can be concluded that dendritic sensor can be used as a feasible method to detect of copper in water samples in low concentrations.

Self-Associated 1,8-Naphthalimide as a Selective Fluorescent Chemosensor for Detection of High pH in Aqueous Solutions and Their Hg2+ Contamination

A novel diamino triazine based 1,8-naphthalimide (NI-DAT) has been designed and synthesized. Its photophysical properties have been investigated in different solvents and its sensory capability evaluated. The fluorescence emission of NI-DAT is significantly impacted by the solvent polarity due to its inherent intramolecular charge transfer character. Moreover, the fluorescence emission quenched at higher pH as a result of photo-induced electron transfer (PET) from triazine moiety to 1,8-naphthalimide after cleaving hydrogen bonds in the self-associated dimers. Furthermore, the new chemosensor exhibited a good selectivity and sensitivity towards Hg²⁺ among all the used various cations and anions in the aqueous solution of ethanol (5:1, v/v, pH = 7.2, Tampon buffer). NI-DAT emission at 540 nm was quenched remarkably only by Hg²⁺, even in the presence of other cations or anions as interfering analytes. Job's plot revealed a 2:1 stoichiometric ratio for NI-DAT/Hg²⁺ complex, respectively.

A Urease-Containing Fluorescent Hydrogel for Transient Information Storage

The improper handling of decrypted information can lead to the leakage of confidential data. Thus, there is increasing interest in the development of self-erasing decrypted data. Herein, we report a urease-containing fluorescent hydrogel for multistage information security protection. Information can be input into the fluorescent hydrogel, which is based on the protonated 4-(N,N-dimethylaminoethylene) amino-N-allyl-1,8-naphthalimide (DEAN-H⁺ ) and doped with urease, using metal ions, such as Zn²⁺ that coordinate with DEAN. Upon exposure to urea, urease produces NH₃ , which reduces the fluorescence of the hydrogel. In the presence of urea, metal-coordinated hydrogel fluorescence decreases more slowly than the fluorescence of the hydrogel alone, revealing the information. The displayed information is then automatically erased within a few minutes. This work opens up a new insights in designing and fabricating information storage materials.

Synthesis, Photophysical Characterization, and Sensor Activity of New 1,8-Naphthalimide Derivatives

Three new 1,8-naphthalimide derivatives M1-M3 with different substituents at the C-4 position have been synthesized and characterized. Their photophysical properties have been investigated in organic solvents of different polarity, and their fluorescence intensity was found to depend strongly on both the polarity of the solvents and the type of substituent at C-4. For compounds M1 and M2 having a tertiary amino group linked via an ethylene bridge to the chromophore system, high quantum yield was observed only in non-polar media, whereas for compound M3, the quantum efficiency did not depend on the medium polarity. The effect of different metal ions (Ag⁺, Ba²⁺, Cu²⁺, Co²⁺, Mg²⁺, Pb²⁺, Sr²⁺, Fe³⁺, and Sn²⁺) on the fluorescence emission of compounds M1 and M2 was investigated. A significant enhancement has been observed in the presence of Ag⁺, Pb²⁺, Sn²⁺, Co²⁺, Fe³⁺, as this effect is expressed more preferably in the case of M2. Both compounds have shown significant pH dependence, as the fluorescence intensity was low in alkaline medium and has been enhanced more than 20-fold in acidic medium. The metal ions and pH do not affect the fluorescence intensity of M3. Density-functional theory (DFT) and Time-dependent density-functional theory (TDDFT) quantum chemical calculations are employed in deciphering the intimate mechanism of sensor mechanism. The functional properties of M1 and M2 were compared with polyamidoamine (PAMAM) dendrimers of different generations modified with 1,8-naphthalimide.

Impact of Cu(ii) and Zn(ii) ions on the functional properties of new PAMAM metallodendrimers

Two new PAMAM metallodendrimers have been synthesized and characterized and their antimicrobial activity in solution and after deposition on textile fabrics has been described.

A novel Ag⁺ cation sensor based on polyamidoamine dendrimer modified with 1,8-naphthalimide derivatives

In this study, 4-amino-1,8-naphthalimide-conjugated polyamidoamine dendrimer was synthesized and characterized and its potentiality as a cation sensor was investigated. 4-Amino-1,8-naphthalic anhydride reacted with polyamidoamine dendrimer and the product was characterized using FTIR, (1)H NMR, (13)C NMR and melting point analysis method. The synthesized compound was applied to detect various cations in water media and N,N-dimethylformamide (DMF) via monitoring the quenching of the fluorescence intensity. Furthermore, various metal cations including Cu(2+), Ni(2+), Zn(2+), Pb(2+),Ca(2+), Ba(2+), Cd(2+), Hg(2+), Fe(2+), Fe(3+) and Ag(+) were tested. The complexes formed between the synthesized compound and metal cations in solution and their effects on Photoinduced Electron Transfer (PET) process were investigated regarding the potential application of the newly-synthesized dendrimer as a colorimetric and fluorescent sensor for such cations. The results clearly confirmed that the 1,8-naphthalimide groups surrounding the central dendrimer core showed strong green fluorescence emission at 553 nm. This effect considerably decreased with the introduction of all cations, except Ag(+) where the fluorescence quenching effect was remarkable and more dominant. Therefore, it can be concluded that the synthesized dye has the potentiality of being a highly sensitive and selective fluorescence sensor for Ag(+) cation.

Dye chemistry with time-dependent density functional theory

In this perspective, we present an overview of the determination of excited-state properties of "real-life" dyes, and notably of their optical absorption and emission spectra, performed during the last decade with time-dependent density functional theory (TD-DFT). We discuss the results obtained with both vertical and adiabatic (vibronic) approximations, choosing relevant examples for several series of dyes. These examples include reproducing absorption wavelengths of numerous families of coloured molecules, understanding the specific band shape of amino-anthraquinones, optimising the properties of dyes used in solar cells, mimicking the fluorescence wavelengths of fluorescent brighteners and BODIPY dyes, studying optically active biomolecules and photo-induced proton transfer, as well as improving the properties of photochromes.

Surface enhanced Raman spectroscopy as a new spectral technique for quantitative detection of metal ions

Four newly synthesized poly (propylene amine) dendrimers from first and second generation modified with 1,8-naphthalimide units in the dendrimer periphery have been investigated as ligands for the detection of heavy metal ions (Al(3+), Sb(2+), As(2+), Cd(2+) and Pb(2+)) by surface-enhanced Raman spectroscopy. Calibration curves were established for all metal ions between the concentration ranges of 1 x 10(-6) to 5 x 10(-4) M. It has been shown that these dendrimers can be coordinated, especially with different metal ions. Using dendrimer molecules and silver colloids at the same time allowed us to obtain an SERS signal from the abovementioned metal ions at very low concentrations. Principle component analysis (PCA) analysis was also applied to the collected SERS data. Four different PCA models were developed to accomplish the discrimination of five metal ions, which interacted with each of the four dendrimer molecules, separately. A detailed investigation was performed in the present study to provide the basis of a new approach for heavy metal detection.

A novel fluorescent sensor for Cr3+ based on rhodamine-cored poly (amidoamine) dendrimer

A novel poly (amidoamine) (PAMAM) dendrimer, comprising rhodamine B unit in the core and 1-phenyl-3-methyl-5-pyrazolone unit at the periphery, has been synthesized and characterized. The dendrimer shows dramatic increase in its fluorescence intensity in the presence of proton and metal cations, especially in the presence of Cr(3+). The complex formed by dendrimer and Cr(3+) in ethanol solution has also been studied, considering the potential application for Cr(3+) fluorescent sensor. The influence of the unique chemical structure and resulted photoinduced electron transfer, as well as spirolactam ring-opening on the photophysical properties of the product has been investigated.