Copper nanoclusters-modified with papaya juice for fluorescence turn-on detection of serum l-histidine Today four files of proofs was sent to m.saksena@elsevier.com Please check the files

Portable smartphone-integrated AuAg nanoclusters electrospun membranes for multivariate fluorescent sensing of Hg2+, Cu2+ and l-histidine in water and food samples

Detection of heavy metals have been pivotal due to their non-biodegradability and food chain accumulation. Herein, a multivariate ratiometric sensor was developed by in situ integrating AuAg nanoclusters (NCs) into electrospun cellulose acetate nanofibrous membranes (AuAg-ENM) for visual detection of Hg²⁺, Cu²⁺ and consecutive sensing of l-histidine (His), which was integrated into a smartphone platform for quantitative on-site detection. AuAg-ENM achieved multivariate detection of Hg²⁺ and Cu²⁺ by fluorescence quenching, and subsequent selective recovery of the Cu²⁺-quenched fluorescence by His, which distinguished Hg²⁺ and Cu²⁺ and fulfilled determination of His simultaneously. Notably, AuAg-ENM achieved selective monitoring of Hg²⁺, Cu²⁺ and His in water, food and serum samples with high accuracy comparable to ICP and HPLC tests. A logic gate circuit was devised to further explain and promote the application of AuAg-ENM detection by smartphone App. This portable AuAg-ENM provides a promising reference for fabricating intelligent visual sensors for multiple detection.

A novel fluorescent probe based on a tripeptide-Cu(II) complex system for detection of histidine and its application on test strips and smartphone

Herein, we reported a novel peptide-based fluorescent probe DSSH for highly selective and sensitive detections of both Cu²⁺ and _l-histidine (_l-His). DSSH exhibited different color changes and fluorescence "on-off" response toward Cu²⁺ with a 2:1 binding stoichiometry, and the limit of detection (LOD) for Cu²⁺ was calculated to be 22.9 nM. The in situ formed DSSH-Cu²⁺ ensemble showed obvious fluorescence "off-on" response to _l-His based on replacement reaction with Cu²⁺, as well as the discernable color changes under 365 nm UV lamp irradiation with "naked eye". The specificity of Cu²⁺/_l-His interactions allowed _l-His to be determined without interference from other amino acids, and the detection limit of DSSH-Cu²⁺ ensemble response to _l-His was determined as 25.7 nM. Notably, DSSH was successfully applied for detecting Cu²⁺ and _l-His in RKO living cells owing to its remarkable fluorescence behavior and low cytotoxicity. Test strips experiments suggested that DSSH can recognize Cu²⁺ and _l-His together by a remarkable fluorescence change. More importantly, smartphone was combined with _l-His solutions of different concentrations and converted into digital values through RGB channels, which was successfully used for semi-quantitative identification of _l-His, and the limit of detection (LOD) was 0.97 μM.

A copper nanoclusters probe for dual detection of microalbumin and creatinine

A fluorescent probe based on glutathione-capped copper nanoclusters (GSH-CuNCs) was developed for the detection of dual targets, human serum albumin (HSA) and creatinine, in human urine. The GSH-CuNCs were synthesized by a one-pot green method using ascorbic acid as a reducing agent. The detection of HSA was in a turn-on mode via electrostatic interaction in a basic condition while the detection of creatinine was in a turn-off mode via non-covalent bonding in an acidic condition. Under optimal conditions, the linear range and detection limit of HSA were 5.0 nM to 150 nM and 1.510 ± 0.041 nM, while those of creatinine were 30 μM to 1000 μM and 13.0 ± 1.0 μM. This easily fabricated nanocluster probe provided a fast response with high sensitivity, and good selectivity. Recoveries from urine samples were in the range of 81.44 ± 0.25 to 109.22 ± 0.57% for HSA and 80.57 ± 0.16 to 109.0 ± 0.10% for creatinine. The urinary analytical results from the fluorescent probe were in good agreement (P > 0.05) to those obtained from immunoturbidimetric and enzymatic methods, signifying the excellent performance of this sensing system.

Determination of l-theanine in tea water using fluorescence-visualized paper-based sensors based on CdTe quantum dots/corn carbon dots and nano-porphyrin with chemometrics

BACKGROUND

The quality of tea is influenced by numerous factors, especially l-theanine, which is one of the important markers used to evaluate the sweetness and freshness of tea. Sensitive, rapid, and accurate detection of l-theanine is therefore useful to identify the grade and quality of tea.

RESULTS

A high-sensitivity, paper-based fluorescent sensor combined with chemometrics was established to detect l-theanine in tea water based on CdTe quantum dots / corn carbon dots and nano tetra pyridel-porphine zinc (ZnTPyP). To verify the reliability of this method, fluorescence spectra and fluorescence-visualized paper-based sensors were compared. The fluorescence spectrum method demonstrated a linear range of 1 to 10 000 nmol L^-1 and a limit of detection (LOD) of 0.19 nmol L^-1 . In the fluorescence-visualized paper-based sensors there was a linear range of 10-1000 nmol L^-1 , and the LOD was 10 nmol L^-1 . Partial least squares discriminant analysis (PLSDA) and partial least squares regression analysis (PLSR) were used successfully to determine l-theanine accurately in tea water with this approach. The accuracy of the PLSDA model was 100% both in the training set and the predicting set, and the correlation coefficient between the actual concentration and the predicted concentration was greater than 0.9997 in the PLSR model.

CONCLUSION

This fluorescence-visualized paper-based sensor, combined with chemometrics, could be applied efficiently to the practical analysis of tea water samples, which provides a new idea to ensure the flavor and quality of tea. © 2020 Society of Chemical Industry.