Glutathione-capped Syzygium cumini carbon dot-amalgamated agarose hydrogel film for naked-eye detection of heavy metal ions

Development of a facile and sensitive analytical tool for the detection of heavy metal ions is still a challenging task because of interference from other chemical species. In this work, glutathione (GSH)-capped Syzygium cumini carbon dots (CDs) have been integrated with agarose hydrogel film and used as an amalgamated solid probe for sensing of different metal ions (Pb2+, Fe3+, and Mn2+). The synthesis of a solid sensing platform is based on the electrostatic interactions between GSH-capped Syzygium cumini CDs and agarose hydrogel. The developed hydrogel-based solid probe exhibited good linearities with the concentration ranges of metal ions from 0.005 to 0.075, 0.0075 to 0.1, and 0.0075 to 0.1 mM with detection limits of 1.3, 2.5, and 2.1 μM for Pb2+, Fe3+, and Mn2+ ions, respectively.

Functionalized-AgNPs for Long-Term Stability and Its Applicability in the Detection of Manganese Ions

In this study, silver nanoparticles (AgNPs) were functionalized by various molecules, including sodium borohydride (NaBH4), polyhexamethylene biguanide hydrochloride (PHMB), and Tween 80 to investigate the long-term stabilization of AgNPs in an aqueous dispersion. PHMB-functionalized silver nanoparticles (AgNPs/PHMB) exhibited better stability than others and could be stored at ambient temperature for at least 180 days. In addition to creating stabilization based on the electrostatic repulsion, the use of PHMB helped to increase the degree of stability of the colloidal AgNPs for a long time owing to strong interactions between Ag atoms on AgNPs with nitrogen (N) positions in PHMB molecules. The formed bond led to improving maintenance ability of the electrostatic repulsion layer among independent nanoparticles. The applicability of the as-prepared AgNPs/PHMB was also examined for Mn2+ detection via a colorimetric approach. The calibration curve was found to be linear over the range of 0–100 mM with a correlation coefficient of 0.97. The amine groups of PHMB brought out a cooperative effect to form of ion-templated chelation with Mn2+, which caused the aggregation of AgNPs/PHMB. This suggested that the AgNPs/PHMB could be used as a potential probe in the detection of Mn2+ ions. More importantly, the long-term stability of AgNPs/PHMB paved a great promising path to provide many further solutions for the producer in practical applications.

Glutathione modified Ag nanoparticles as efficient detector for pyrimethanil

This work reports on glutathione modified Ag nanoparticles (GSH-Ag NPs) as a chemosensor for detecting pyrimethanil in an aqueous medium. The GSH-Ag NPs were expediently obtained by reducing AgNO₃ with NaBH₄ and modified with glutathione based on the Ag-S bond. The rapid discrimination for pyrimethanil from other pesticides exhibited the high selectivity of GSH-Ag NPs, then the selectivity was proved by ¹H NMR, FT-IR and computational simulation. Based on the good properties of localized surface plasmon resonance, the selective recognition was transformed to visible optical signal in colorimetric test. Additionally the quantitative detection was achieved with good sensitivity and could be applied to analyze practical samples. The experimental results have shown a good linear relationship with pyrimethanil concentration ranging from 10 μM to 1 mM and a low detection limit of 3.87 μM.

Facile, one-pot, in aqua synthesis of catalytically competent gold nanoparticles using pyrogallol[4]arene as the sole reagent

Rapid and facile synthesis of macrocycle-capped gold nanoparticles employing pyrogallol[4]arenes as a dual-role reducing and stabilizing agent.

Development of a novel tridentate ligand for colorimetric detection of Mn2+ based on AgNPs

A novel tridentate ligand nitrilotris(methylene)tris(1,2,3-triazole)triacetate (NTTTA) has been synthesized by click reaction and followed with ester hydrolysis reaction. The silver nanoparticles (AgNPs) were then modified and stabilized by this ligand, and subsequently been employed for the highly selective and sensitive colorimetric detection of Mn²⁺ in aqueous solution. The presence of Mn²⁺ can cause the aggregation of AgNPs, which leads to the color change of the dispersion from yellow to brown, as well as the decrease and red-shift of the surface plasmon resonance absorption. The detection limit of Mn²⁺ was as approximately 0.5 μM by the naked eyes. UV-vis spectroscopy analysis showed a good linear relationship between the logarithm of the ratios (A₅₅₀/A₃₉₅) and the concentration of Mn²⁺over the range of 0.05 μM-10 μM, and the LOD was calculated to be 12.6 nM (S/N = 3). The present assay showed good simplicity without the need of adjusting the pH value. The feasibility of this technique was evaluated for successful detection of Mn²⁺ in tap water and lake water samples, with good recoveries.

Perylene dye-functionalized silver nanoparticles serving as pH-dependent metal sensor systems

Lysine-functionalized perylene was used to modify nanoparticles. Due to the benefits from a synergetic effect that originated between the perylene and silver nanoparticles, color-based metal sensor systems were established.

Silicon Quantum Dot-Based Fluorescence Turn-On Metal Ion Sensors in Live Cells

Multiple sensor systems are designed by varying aza-crown ether moiety in silicon quantum dots (SiQDs) for detecting individual Mg(2+), Ca(2+), and Mn(2+) metal ions with significant selectivity and sensitivity. The detection limit of Mg(2+), Ca(2+), and Mn(2+) can reach 1.81, 3.15, and 0.47 μM, respectively. Upon excitation of the SiQDs which are coordinated with aza-crown ethers, the photoinduced electron transfer (PET) takes place from aza-crown ether moiety to the valence band of SiQDs core such that the reduced probability of electron-hole recombination may diminish the subsequent fluorescence. The fluorescence suppression caused by such PET effect will be relieved after selective metal ion is added. The charge-electron binding force between the metal ion and aza-crown ether hinders the PET and thereby restores the fluorescence of SiQDs. The design of sensor system is based on the fluorescence "turn-on" of SiQDs while in search of the appropriate metal ion. For practical application, the sensing capabilities of metal ions in the live cells are performed and the confocal image results reveal their promising applicability as an effective and nontoxic metal ion sensor.

Functionalization of silver nanoparticles with 5-sulfoanthranilic acid dithiocarbamate for selective colorimetric detection of Mn2+ and Cd2+ ions

A schematic representation of Mn²⁺ and Cd²⁺ ion-induced aggregation of SAA-DTC-Ag NPs.

Furthering the chemosensing of silver nanoclusters for ion detection

An eco-friendly silver nanocluster chemosensor for Mn²⁺and I⁻ion detection, differentiation and bioimaging was synthesized. The chemosensing mechanisms were elucidated by microscopic characterization and spectral analyses.

A novel AgNPs-based colorimetric sensor for rapid detection of Cu2+ or Mn2+via pH control

The AgNPs-based colorimetric sensor at pH 1.9 or 12.0 can respectively be used for rapid detection of Cu²⁺ or Mn²⁺.

A pyrene based Schiff base probe for selective fluorescence turn-on detection of Hg2+ ions with live cell application

A novel pyrene based free thiol containing a Schiff base derivative PT1 was synthesized and reported as a fluorescence turn-on sensor for Hg²⁺ ions, via CHEF and excimer (PT1-PT1*) formation with live cell imaging.

Calix[4]arene triazole-linked pyrene: click synthesis, assembly on graphene oxide, and highly sensitive carbaryl sensing in serum

Graphene oxide modified with a fluorescent calix[4]arene showed a highly selective recognition for carbaryl.

Sensitive and selective colorimetric detection of Cu(2+) in aqueous medium via aggregation of thiomalic acid functionalized Ag nanoparticles

A simple and effective colorimetric method for determination of Cu(2+) in real samples was developed. In this method, thiomalic acid functionalized silver nanoparticles (TMA-AgNPs) were prepared and changes in solution color, induced by the aggregation of TMA-AgNPs in the presence of Cu(2+), were employed for quantitative analysis. The surface plasmon resonance (SPR) band of our synthesized TMA-AgNPs was located at 392 nm and shifted to a longer wavelength after aggregation due to the interactions between carboxylate and Cu(2+). A band intensity ratio of A455/(A392-A455) was constructed and used to correlate with the concentration of Cu(2+). A linear relationship was found with a linear response up to 50 nM of Cu(2+). Due to the formation of a stable carboxylate Cu(2+) complex, highly sensitive detection of Cu(2+) was achieved with the estimated detection limit approaching 1 nM. Moreover, the formation of the stable complex leads to high selectivity in the detection of Cu(2+), which was verified by examination of 12 other metal ions. In the detection of Cu(2+) in real samples, results indicated that our proposed method is simple, sensitive and selective for application in such measurements.