A supramolecular hydrogel possessing pH-sensitive properties and thermo-reversibility was prepared, and the release behavior of salicylic acid from it is in accordance with the Fickian diffusion control within the given time.

Two new silver(I) complexes, formulated as [Ag2(L1)2](picrate)2 (1), {[Ag2(L2)2(terephthalate)](C2H5OH)3(H2O)}n (2) (L1 = 1,3‐bis(2‐benzimidazyl)benzene, L2 = 1,3‐bis(1‐methylbenzimidazol‐2‐yl)‐2‐thiapropane), were synthesized and characterized by X‐ray crystallography, elemental analysis, infrared, and UV–Vis spectroscopy. The crystal analysis results showed that the complexes exhibited different structures: binuclear for 1 and one‐dimensional polymeric for 2. Their Ag(I) centers displayed different coordination geometric structures: two‐coordinated linear in 1, whereas four‐coordinated distorted tetrahedron in 2. The electrochemical sensing performance of Ag(I) complexes modified carbon paste electrode (CPE‐1 and CPE‐2) toward hydrogen peroxide (H2O2) was evaluated by chronoamperometry in 0.2 M phosphate buffer saline (pH = 6) at −0.2 V. The CPE‐1 was found to have a wide linear response from 1.0 × 10−5 to 4.0 × 10−3 M, lower detection limit of 1.73 μM, excellent anti‐interference ability, and stability. The CPE‐2 does not have recognition properties for H2O2, which may be due to the large steric hindrance around Ag(I) centers that is not easy to combine with H2O2 to form a catalytic transition state. The above studies proved that Ag(I) complexes can be used as effective components of electrode materials for the electrochemical recognition of H2O2.

Two new silver(I) complexes, formulated as [Ag2L12(isophthalate)]·(C2H5OH)5 (1), [Ag2L22(isophthalate)] (2) (L1 = 1,3‐bis[(N‐methyl‐benzimidazole)methylene]‐2‐aniline, L2 = 1,3‐bis[(N‐ethyl‐benzimidazole)methylene]‐2‐aniline), were synthesized by volatilization method and characterized by X‐ray crystallography, elemental analysis, IR and UV/Vis spectroscopy. The crystal analysis showed that although complexes 1 and 2 were both binuclear, their Ag(I) centers exhibited different coordination geometric structures: four‐coordinated distorted tetrahedron in complex 1, whereas three‐coordinated planar triangle in complex 2. The electrochemical sensing performances of carbon paste electrode modified with Ag(I) complexes (CPE‐1 for complex 1 and CPE‐2 for complex 2) toward H2O2 were evaluated by cyclic voltammogram and chronoamperometry in 0.2 M phosphate‐buffered saline (PBS, pH = 6.0) at −0.2 V. The results show that both CPE‐1 and CPE‐2 showed excellent electrocatalytic activity, quick response time (≤5 s) and high selectivity toward H2O2. The linear response range was from 5.0 × 10−7 to 4.0 × 10−3 M. The CPE‐1 exhibits better sensitivity and limit of detection (LOD) than CPE‐2, which is related to the coordination environment of Ag(I) ions. Sensors based on Ag(I) complexes have great application prospects in the field of electrochemical sensing.

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A highly sensitive fluorescence “turn‐on” 1,8‐naphthalimide Schiff base probe: N‐allyl‐4‐(ethylenediamine‐salicylidene)‐1,8‐naphthalimide (HL) for Hg2+ was designed, synthesized and characterized. In addition, the sensing behavior of HL towards various transition metal ions has been investigated in solution (DMF/Tris–HCl buffer, 1:1, vol/vol, pH = 7.2). The HL exhibited high selectivity for Hg2+ over other metal ions with obvious fluorescence enhancement. Moreover, the fluorescence intensity of HL showed good linearity with a correlation coefficient (R2) of 0.99, confirming that HL could be applied to detect the quantification of Hg2+ in a linear fashion from 0.5 to 4 μM and the detection limit reach at 0.16 μM. Meanwhile, the association constant (Ka) between Hg2+ and HL achieves 1.23 × 1012 M−1. Moreover, the fluorescence titration experiment and Job plot analysis indicate the formation of a 2:1 stoichiometric complex of HL with Hg2+. The fluorescence enhancement of HL response to Hg2+ ions could be attributed to the photoinduced electron transfer (PET) mechanism.