Search

Upconversion nanoparticles (UCNPs) are widely used as energy donors via a luminescence resonance energy transfer (LRET) technique in biosensing field. To enhance LRET efficiency and afford an improved sensitivity for Cu2+ detection, sandwich structured NaYF4@NaYF4:Er3+/Yb3+@NaYF4 UCNPs have been designed and prepared. For the core-internal shell-external shell structure, luminescence ions (Er3+) are located in the internal shell near the nanoparticle surface, which is close enough to energy acceptors outside. To study the sensing properties, the UCNPs are used as energy donors and rhodamine B hydrazide (RBH) as energy acceptors to construct the nanoprobes. It is found that the sandwich structured nanoparticles gains more intense luminescence than the naked NaYF4:Er3+/Yb3+ UCNPs, which is beneficial to the further improvement of signal sensitivity in biological detection. Moreover, the specificity for detecting Cu2+ is also checked and found that the designed probe is much more sensitive to Cu2+ than the other ions including K+, Na+, Li+, Ca2+, Ba2+, Mg2+, Zn2+ and Sr2+. The experiment on the stability of UCNPs-RBH probe and RBH shows the 980 nm laser produces less photodamage to RBH than that of visible light. Therefore, the UCNPs can be used to construct potential probes for realizing effective detection of Cu2+.

In present work, rhodamine B hydrazide and rhodamine 6G hydrazide were synthesized and the chemiluminescence performance has been investigated. Based on the chemiluminescence of rhodamine 6G hydrazide‑chromium(VI), a selective and sensitive method for the direct detection of chromium(VI) was developed. The chemiluminescence intensity was linearly related to the concentration of chromium(VI) in the range of 2.60 × 10− 8–8.00 × 10− 6 mol/L with a correlation coefficient of r = 0.998 and a detection limit of 1.4 × 10− 8 mol/L (S/N = 3). The results indicated rhodamine 6G hydrazide was an excellent chemiluminescent probe for chromium(VI) without reduction of chromium(VI) to chromium(III). A possible mechanism of CL emission was also suggested.

Rhodamine B hydrazide (RBH) was prepared as a new derivatizing reagent for residual formaldehyde in a drug such as N-butyl-2-cyanoacrylate (NBCA). RBH reacted with formaldehyde rapidly at room temperature, and the resulting derivative can be detected sensitively at 238 nm. After optimizing the derivatization and chromatographic separation conditions, RBH as a pre-column derivatizing reagent has been successfully used for the analysis of formaldehyde in real NBCA samples by high-performance liquid chromatography (HPLC). The detection limit of the method is 0.004 μg/mL for formaldehyde, and the recovery is 94.0%-96.6%. Most notably, compared with the previous HPLC methods, the developed method has the advantages of mild derivatization temperature, short derivatization time and high sensitivity.

A bifunctional colorimetric and fluorescent chemosensor RbCS has been successfully designed and synthesized by simple condensation of 3,5-dichlorosalicylaldehyde and rhodamine B hydrazide. In aqueous media, chemosensor RbCS exhibits remarkably enhanced absorbance intensity and color change from colorless to pink for Cu 2+ , and shows significant “off–on” fluorescence accompanied with color changes from colorless to red upon binding to Hg 2+ . The absorbance and fluorescence signals of RbCS can be restored with addition of EDTA disodium into solutions of RbCS–Cu 2+ and RbCS–Hg 2+ , showing that the binding of chemosensor RbCS and Cu 2+ /Hg 2+ is chemically reversible.

A novel rhodamine-based chemosensor, 3′,6′-bis(diethylamino)-2-((2,7-dimethoxy-9H-fluoren-9-ylidene)amino)spiro[isoindoline-1,9′-xanthen]-3-one (1) for aluminum ion, was designed and synthesized. Compound 1 is an orange colored, weak fluorescent compound which was synthesized via one-step facile reaction of rhodamine B hydrazide with 2,7-dimethoxy-9H-fluoren-9-one in MeOH. When Al3+ salt was added in methanol:water (30:70, v/v) solution then spirolactum ring of 1 was opened. The absorbance and fluorescence of the mixed solution were increased dramatically because of the opening of the lactum ring. Thus, signal transduction occurred via reversible CHEF (chelation-enhanced fluorescence) mechanism in the range 580–584 nm.

A new rhodamine B derivative colorimetric and fluorescent sensor (1) was synthesized by condensation reaction of rhodamine B hydrazide and 2,4-dihydroxybenzaldehyde, which showed reversible and highly selective and sensitive recognition toward Cu2+ over other examined metal ions. Upon addition of Cu2+, sensor 1 exhibits remarkably enhanced absorbance intensity and color change from colorless to pink in DMSO and MeCN aqueous buffer solution or pure MeCN, and shows significant off–on fluorescence accompanied by color changes from colorless to orange in MeCN. The sensor 1 was also successfully applied to the determination of Cu2+ in water samples.

A novel spectrofluorimetric method for the determination of sulfite using rhodamine B hydrazide as fluorogenic reagent in the presence of polyoxyethylene sorbitan monooleate (Tween 80) surfactant micelles is described. The method is based on the mixture of sulfite with rhodamine B hydrazide, a colorless, non-fluorescent substance in Tween 80 surfactant micelles which gives rhodamine B-like fluorescence emission. The fluorescence intensity increase is linearly related to the concentration of sulfite in the range 5–800 ng ml −1 with a detection limit of 1.4 ng ml −1 (3 σ ). The optimal conditions for the detection of sulfite are evaluated and the possible detection mechanism is also discussed. The method has been successfully applied to the determination of total sulfite in wines and compares well with the standard iodimetric method.