A Novel Naphthalene-Immobilized Nanoporous SBA-15 as a Highly Selective Optical Sensor for Detection of Fe3+ in Water

Spherical Silica Functionalized by 2-Naphthalene Methanol Luminophores as a Phosphorescence Sensor

Photoluminescence is known to have huge potential for applications in studying biological systems. In that respect, phosphorescent dye molecules open the possibility to study the local slow solvent dynamics close to hard and soft surfaces and interfaces using the triplet state (TSD: triplet state solvation dynamics). However, for that purpose, probe molecules with efficient phosphorescence features are required with a fixed location on the surface. In this article, a potential TSD probe is presented in the form of a nanocomposite: we synthesize spherical silica particles with 2-naphthalene methanol molecules attached to the surface with a predefined surface density. The synthesis procedure is described in detail, and the obtained materials are characterized employing transmission electron microscopy imaging, Raman, and X-ray photoelectron spectroscopy. Finally, TSD experiments are carried out in order to confirm the phosphorescence properties of the obtained materials and the route to develop phosphorescent sensors at silica surfaces based on the presented results is discussed.

Utilizing the interfacial reaction of naphthalenyl thiosemicarbazide-modified carbon dots for the ultrasensitive determination of Fe (III) ions

Since thiosemicarbazide contains numerous nitrogen and sulfur atoms in its structural formula that enhance its strong coordinating abilities with metal ions, it is always selected as the mother molecule for the design of metal-ion sensors. In this report, a thiosemicarbazide derivative (4-naphthalenyl-3-thiosemicarbazide (NTSC)) was synthesized via a single step process and covalently conjugated onto the surfaces of carbon dots (CDs). The modified CDs demonstrated excellent monodispersity, good photostability, and tunable luminescence properties. More importantly, the CDs retained a highly specific Fe³⁺ recognition capacity in contrast to other competing metal ions. Fe³⁺ can efficiently quench the fluorescence of CDs even at fairly low concentration (30μM) with a detection limit as low as 1.68nM. The fluorescence quenching kinetics are likely to involve static quenching, which is caused by specific interactions between NTSC-CDs and Fe³⁺ toward the formation of a ground state complex. Due to their excellent optical performance, low toxicity, and good biocompatibility the NTSC-CDs may be applied to the imaging and monitoring of Fe³⁺ in bacillus subtilis. In effect we successfully fabricated an effective fluorescent nanosensor for both the quantitative detection of Fe³⁺ in aqueous solutions, and its real-time imaging in vivo.

Fluorescence study of 5-nitroisatin Schiff base immobilized on SBA-15 for sensing Fe3+

N’-(5-nitro-2-oxoindolin-3-ylidene) thiophene-2-carbohydrazide (NH) was successfully synthesized as a ligand, then grafted onto the surface of mesoporous silica SBA-15via an aminopropyl bridge. The successful grafting of ligand NH onto the hybrid nanomaterial (SBA-15/APTES-NH) was confirmed by infrared spectroscopy. On excitation at 276 and 370 nm, the ligand NH and the hybrid nanomaterial SBA-15/APTES-NH showed a strong and narrow emission peak centered at 533 nm. By dispersing SBA-15/APTES-NH in an aqueous solution containing metal ions, the resulting solid materials showed a higher binding of NH sensing site to Fe3+ ions as compared to the others with a quench of the emission intensity up to 84%. This result showed that the hybrid nanomaterial is a potential chemosensor that requires development for the detection of metal ions.

Formation of functionalized silica-based nanoparticles and their application for extraction and determination of Hg (II) ion in fish samples

An isonicotinic acid hydrazide (INAH) chemically modified fumed silica, as a novel adsorbent, was designed for the preconcentration and determination of Hg (II) ions in fish samples via the solid phase extraction followed by the hydride generation atomic absorption spectrometry (HG-AAS). In this work, the efficiency of the synthesized adsorbent was investigated to determine its ability for the extraction of the Hg (II) ions from the aqueous solutions. The extraction efficiency was investigated by optimizing of different experimental conditions, such as pH, sample volume, flow rate, adsorbent dosage, and eluent type. Under the optimal conditions, a linear calibration curve for the solid phase extraction method was obtained in the range of between 0.12 and 16.5 μg L^-1. The obtained detection limit and preconcentration factor were 0.018 μg L^-1 and 25, respectively (RSD > 3%). The proposed optimized method was successfully applied to fish samples.

GSH-doped GQDs using citric acid rich-lime oil extract for highly selective and sensitive determination and discrimination of Fe3+ and Fe2+ in the presence of H2O2 by a fluorescence “turn-off” sensor

Synthesis and characterization of graphene quantum dots (GQDs) simultaneously doped with 1% glutathione (GSH-GQDs) by pyrolysis using citric acid rich-lime oil extract as a starting material. The excitation wavelength (λ_max = 337 nm) of the obtained GSH-GQD solution is blue shifted from that of bare GQDs (λ_max = 345 nm), with the same emission wavelength (λ_max = 430 nm) indicating differences in the desired N and S matrices decorating the carbon based nanoparticles, without any background effect of both ionic strength and masking agent. For highly Fe³⁺-sensitive detection under optimum conditions, acetate buffer at pH 4.0 in the presence of 50 μM H₂O₂, the linearity range was 1.0–150 μM (R² = 0.9984), giving its calibration curve: y = 34.934x + 169.61. The LOD and LOQ were found to be 0.10 and 0.34 μM, respectively. The method’s precisions expressed in terms of RSDs for repeatability (n = 3 × 3 for intra-day analysis) were 2.03 and 3.17% and for reproducibility (n = 5 × 3 for inter-day analysis) were 3.11 and 4.55% for Fe²⁺ and Fe³⁺, respectively. The recoveries of the method expressed as the mean percentage (n = 3) were found in the ranges of 100.1–104.1 and 98.08–102.7% for Fe²⁺ and Fe³⁺, respectively. The proposed method was then implemented satisfactorily for trace determination of iron speciation in drinking water.

Synthesis and characterization of graphene quantum dots (GQDs) simultaneously doped with 1% glutathione (GSH-GQDs) by pyrolysis using citric acid rich-lime oil extract as a starting material.

Schiff base derived Fe3+-selective fluorescence turn-off chemsensors based on triphenylamine and indole: synthesis, properties and application in living cells

A Schiff base with an AIE effect could act as a turn-off fluorescent chemosensor for Fe³⁺in living cells.

A Fluorescent Sensor for Al(III) and Colorimetric Sensor for Fe(III) and Fe(II) Based on a Novel 8-Hydroxyquinoline Derivative

A novel 8-hydroxyquinoline-based fluorescent and colorimetric chemosensor was designed, synthesized and fully characterized. The sensor showed high selectivity and sensitivity toward Al(3+) over other tested cations in EtOH/H2O (1:99, v/v) medium. The increase in fluorescence intensity was linearly proportional to the concentration of Al(3+) with a detection limit of 7.38 × 10(-6) M. Moreover, the sensor exhibited an obvious color change from yellow to black in the presence of Fe(2+) and Fe(3+) in EtOH/THF (99:1, v/v) solution. The absorbance changes showed a linear response to iron ions with the detection limits of 4.24 × 10(-7) M and 5.60 × 10(-7) M for Fe(2+) and Fe(3+), respectively. Thus, this chemosensor provides a novel approach for selectively recognition of Al(3+), Fe(3+) and Fe(2+) among environmentally relevant metal ions.

SBA-15 Functionalized with Naphthalene Derivative for Selective Optical Sensing of Cr2O7(2-) in Water

A novel organic-inorganic hybrid optical sensor (NUS) was designed and prepared in two steps: the grafting of 3-(isocyanatopropyl)trimethoxysilane onto the surface of SBA-15, and then the attachment of naphthalene-1-amine. The obtained materials were characterized using low-angle XRD, N2 adsorption-desorption, TGA, FT-IR, and TEM techniques. A fluorescence study revealed that the NUS was a highly selective optical sensor for the detection of Cr2O7(2-) among various anions, including F(-), I(-), Cl(-), Br(-), CO3(2-), HCO3(-), NO3(-), H2PO4(-), CH3COO(-), and NO2(-) with a good linearity between the fluorescence intensity and the concentration of Cr2O7(2-) as well as a detection limit of 1.2 × 10(-7) M in a 100% aqueous medium. Moreover, the applicability of real samples of the sensor is also discussed.