Junling Jin

A new turn-on fluorescent sensor based on NBD for highly selective detection of Hg2+ in aqueous media and imaging in live cells

A new and simple fluorescent probe bearing 7-nitrobenz-2-oxa-1,3-diazole and N,N-bis(thiophen-2-ylmethyl)ethane-1,2-diamine was developed as a fluorescent chemosensor with high selectivity and sensitivity toward Hg2+ over other cations tested. The signaling is due to the coordination of S and N atoms of N,N-bis(thiophen-2-ylmethyl)ethane-1,2-diamine to Hg2+. Upon addition of 30 equivalents of Hg2+, a 45-fold increase in fluorescence emission intensity was observed. Moreover, the probe is further successfully used to image Hg2+ in MCF-7 cells.

A simple and reversible fluorescent probe based on NBD for rapid detection of hypochlorite and its application for bioimaging

A simple and reversible fluorescent probe bearing 7-nitrobenz-2-oxa-1,3-diazole and a selenomorpholine fragment was designed and synthesized. The probe showed highly selective, sensitive and fast (<10 s) recognition to hypochlorite in aqueous solutions. The relative results demonstrated that the linear response range of the probe was between 5.0 × 10−8 M and 1.2 × 10−4 M, with a low detection limit of 3.3 nM (S/N = 3). The probe was capable of monitoring hypochlorite reversibly in the presence of glutathione. In addition, the biological applications in living cells have been described.

A novel colorimetric/fluorescence dual-channel sensor based on NBD for the rapid and highly sensitive detection of cysteine and homocysteine in living cells

A novel and simple turn-on fluorescent probe bearing 7-nitrobenz-2-oxa-1,3-diazole and benzaldehyde fragments for the rapid optical sensing of cysteine and homocysteine has been designed and synthesized. The probe has almost no background fluorescence (Φf < 0.0001) in aqueous solutions; however, it displayed fluorescence turn-on response to cysteine and homocysteine and exhibited a large bathochromic-shift (106 nm) in absorption wavelength accompanied by color changes which could be distinguished by the naked-eye. There is a good linearity with cysteine in the range of 0 to 1.37 × 10−4 M, with a detection limit of 98 nM (S/N = 3). In addition, the optical responses of the probe were investigated by density function theory (DFT) calculations. Moreover, it can be used to detect biological thiols in living cells.

A new simple phthalimide-based fluorescent probe for highly selective cysteine and bioimaging for living cells

A new turn-on phthalimide fluorescent probe has designed and synthesized for sensing cysteine (Cys) based on excited state intramolecular proton transfer (ESIPT) process. It is consisted of a 3-hydroxyphthalimide derivative moiety as the fluorophore and an acrylic ester group as a recognition receptor. The acrylic ester acts as an ESIPT blocking agent. Upon addition of cystein, intermolecular nucleophilic attack of cysteine on acrylic ester releases the fluorescent 3-hydroxyphthalimide derivative, thereby enabling the ESIPT process and leading to enhancement of fluorescence. The probe displays high sensitivity, excellent selectivity and with large Stokes shift toward cysteine. The linear interval range of the fluorescence titration ranged from 0 to 1.0×10-5M and detection limit is low (6×10-8M). In addition, the probe could be used for bio-imaging in living cells.

New reduction mechanism of CO dimer by hydrogenation to C2H4 on a Cu(100) surface: theoretical insight into the kinetics of the elementary steps

A systematic DFT study that examines the role of the kinetics of the elementary reaction steps during the course of the reduction of a CO dimer, OCCO*, to C2H4 on Cu(100) is presented for the first time in the present study, and a new mechanism is introduced. Kinetic analysis of the elementary reaction steps has suggested that the further reduction of CO is the key selectivity-determining step for the formation of C2H4 and CH4 on Cu(100) and Cu(111), respectively. The main reaction pathway on Cu(111) proceeds through the reduction of CO to a CHO* intermediate, which may eventually result in CHx species by the breaking of a C–O bond and production of CH4. On Cu(100), OCCO* is first formed by CO dimerization, which is the first step and a more favorable pathway than the further hydrogenation of CO. This explains why only C2 species and not C1 species are observed experimentally on Cu(100). For the formation of C2H4 on Cu(100), the results suggest that the hydrogenation of OCCO* to the OCCHO* intermediate is the most likely reaction path, followed by the formation of intermediate OHCCHO* through further hydrogenation of the OCCHO* intermediate. The formation of OCCO* may be the rate-determining step in the reduction mechanism of the CO dimer. Kinetic analysis of the elementary steps gives a different mechanistic explanation for the selectivity of C2H4 production, which is in contrast to a previous suggested thermodynamic theoretical study on the reduction mechanisms of a CO dimer to C2H4. This present reduction pathway is consistent with the latest experimental results and explains the experimental uncertainty regarding the reaction intermediates. At present, it appears that the mechanism proposed in this study is most agreeable with the present experimental results.

A simple and new fluorescent and colorimetric probe based on NBD–maleimide for detecting thiols in living cells

A simple and new fluorescent and colorimetric probe bearing 7-nitrobenz-2-oxa-1,3-diazole and 4-maleimidophenol fragments for biothiols was designed and synthesized. The probe itself showed almost no background fluorescence (ΦF < 1 × 10−4) and displayed fluorescence turn-on response with selectivity for thiols over other relevant biological species in aqueous solutions. In addition, the probe exhibited 110 nm red-shifted absorption spectra accompanied by color changes which could be obviously distinguished by the naked eye. Furthermore, the probe showed high sensitivity towards thiols with a detection limit of 1.2 × 10−7 M (S/N = 3) and the mechanism regarding the optical responses of the probe to thiols was explained by density function theory (DFT) calculations. Finally, the probe has been successfully used to image thiols in HeLa cells.

A new water-soluble and colorimetric fluorescent probe for highly sensitive detection of organophosphorus pesticides

A new water-soluble fluorescent probe bearing 1,8-naphthalimide dye, a quaternary ammonium salt and a boronate group was developed for the detection of organophosphorus pesticides. The detection assay was composed of the probe, choline oxidase (ChOx) and acetylcholinesterase (AChE), which involved ChOx and AChE catalyze acetylcholine chloride (ACh) to produce H2O2 that increases the fluorescence of the probe. In the presence of pesticides, the activity of AChE was inhibited and the enzyme-generated H2O2 was decreased, which results in a decrease in the fluorescence of the probe. The probe displays sensitive and rapid colorimetric fluorescence towards pesticides. The fluorescence intensity was proportional to the logarithm concentration of acephate, parathion-methyl and trichlorfon over a range of 1.0 × 10−8 to 1.0 × 10−4 g L−1 (R2 = 0.9908), 1.0 × 10−9 to 1.0 × 10−5.5 g L−1 (R2 = 0.9938), 1.0 × 10−8 to 1.0 × 10−4.5 g L−1 (R2 = 0.9932), respectively. The detection limits for acephate, parathion-methyl and trichlorfon were 1.16 × 10−9, 3.36 × 10−10 and 4.72 × 10−9 g L−1 (S/N = 3), respectively. Moreover, this method has been used for the determination of practical samples with satisfactory results, which further demonstrates its value in practical applications.

A new bifunctional fluorescent sensor based on naphthalimide-functionalized silica nanoparticles for detection and adsorption of Cu2+ in aqueous solution

A new bifunctional fluorescent sensor for Cu2+ based on naphthalimide-functionalized silica nanoparticles (NF-SiO2) was designed and synthesized. NF-SiO2 exhibits excellent fluorescence sensitivity and selectivity towards Cu2+ over other metal ions in aqueous media, and it also shows a good adsorption capacity for Cu2+. Moreover, the detection limit of NF-SiO2 for Cu2+ is 1.5 × 10−7 M (S/N = 3) and it can be easily recovered by treatment of a solution of EDTA. These results indicate that this fluorescent sensor may find potential and favorable applications for simple detection and efficient removal of Cu2+ in toxicological and environmental fields.

A new fluorescence and colorimetric sensor for highly selective and sensitive detection of glucose in 100% water

A new naphthalimide derivative containing hexanoic acid and boronate groups was designed and synthesized. The compound displays off/on ratio singles, highly selective and sensitive towards glucose based on a naphthalimide derivative reacting with enzyme generated H2O2 in 100% water. The fluorescence intensity is proportional to the concentration of glucose over a range of 0–120 μM (R2 = 0.9912), with a limit of detection of 0.3 μM (S/N = 3). Moreover, the fluorescent sensor has been used for determination of glucose in serum with satisfactory results, which further demonstrates its value in practical applications.

Theoretical insight into effect of doping of transition metal M (M = Ni, Pd and Pt) on CO2 reduction pathways on Cu(111) and understanding of origin of electrocatalytic activity

The effect of the doped transition metal M (M = Ni, Pd and Pt) on CO2 reduction pathways and the origin of the electrocatalytic activity are investigated systematically by focusing on the CH4 and CH3OH formation pathways based on DFT calculations associated with the computational hydrogen electrode model. Our studies show that the doping of Ni, Pd and Pt can promote CO2 reduction into hydrocarbons and influence the selectivity of reduction pathways, in which the doping of Pt may be able to lead to the strongest catalytic activity. The adsorption behavior between reaction intermediates and surfaces is crucial and the interactions of intermediates with the catalysts should be moderate in order to efficiently catalyze CO2 reduction into CH4 and CH3OH, and avoid OH surface poisoning. The enhanced electrocatalytic activity of transition metal-doped Cu(111) surfaces may be owing to decreased overpotential and moderate electronic interactions between Cu and the doped transition metals. The doped Ni, Pd and Pt atoms can considerably decrease the overpotential and remove surface OH poisoning, in which the doped Pt can simultaneously reduce overpotential for CO formation and further reduction, and most easily remove OH, thus suggesting the best electrocatalytic activity. The moderate electron interaction between Cu and Pt and moderate upshift of the d-band center of Pt also explain why the Pt-doped Cu(111) surface has the best electrocatalytic activity for CO2 reduction. Two possible descriptors can be proposed in order to scale the electrocatalytic activity of Cu-based electrocatalysts for CO2 reduction, in which an ideal Cu-based electrocatalyst should be able to reduce barriers for CO formation and further reduction, and should have moderate electron interactions between Cu and the doped transition metals, and a moderate upshift of d-band center of the doped transition metals. In these ways, CO2 reduction pathways can be facilitated and the yield of hydrocarbons CH4 and CH3OH can be enhanced.