Molecular Fluorescence, Phosphorescence, and Chemiluminescence Spectrometry

A Highly Integrated and Diminutive Fluorescence Detector for Point-of-Care Testing: Dual Negative Feedback Light-Emitting Diode (LED) Drive and Photoelectric Processing Circuits Design and Implementation

As an important detection tool in biochemistry, fluorescence detection has wide applications. Quantitative detection can be achieved by detecting fluorescence signals excited by excitation light at a specific wavelength range. Therefore, the key to fluorescence detection is the stable control of the excitation light and the accurate acquisition of weak photoelectric signals. Moreover, to improve portability and instantaneity, devices are developing in miniaturization and integration. As the core of such devices, fluorescence detectors should also have these features. Under this circumstance, we designed a highly integrated and diminutive fluorescence detector and focused on its excitation light driving and photoelectric signal processing. A current–light dual negative feedback light-emitting diode (LED) driving circuit was proposed to obtain constant current and luminance. In addition, a silicon photodiode (PD) was used to receive and convert the fluorescence signal to an electric signal. Then, amplifying, filtering, and analog-to-digital (A/D) converting were applied to make the detection of weak fluorescence signals possible. The test results showed that the designed circuit has wonderful performance, and the detector shows good linearity (R² = 0.9967) and sensitivity (LOD = 0.077 nM) in the detection of fluorescein sodium solution. Finally, a real-time fluorescence polymerase chain reaction (real-time PCR) of Legionella pneumophila was carried out on a homemade platform equipped with this detector, indicating that the detector met the requirements of real-time PCR detection.

Co-metal-organic-frameworks with pure uniform crystal morphology prepared via Co2+ exchange-mediated transformation from Zn-metallogels for luminol catalysed chemiluminescence

Cation exchange-mediated transformation from Zn-metallogels (MOGs), which was a mild facile strategy relative to the demanding hydrothermal method, was employed to develop Co²⁺ metal-organic frameworks (Co-MOFs) at room temperature. The obtained Co-MOFs was of uniform octahedral morphology and possessed high activity to catalyze luminol chemiluminescence without extra oxidants. By adding cysteine, the CL emission of luminol-Co-MOFs system was further enhanced. Based on this phenomenon, Co-MOFs was utilized to build a practical sensing platform for cysteine determination. Under the optimized conditions, the relative CL intensity (ΔI) was proportional to the concentration of cysteine in the range of 2-10μM, and the detection limit was 0.49μM (3S/N). Moreover, the established method was applied to the determination of cysteine in commercially available pharmaceutical injections.

A metal (Co)–organic framework-based chemiluminescence system for selective detection of l-cysteine

A metal (Co)–Organic Framework–luminol chemiluminescence system was successfully established for the determination of l-cysteine.

Fluorescent BINOL-based sensor for thorium recognition and a density functional theory investigation

A novel 1,1'-bi-2-naphthol (BINOL) derivative fluorescence sensor L-1 for the recognition of thorium ion with a fluorescence quench response. This ligand showed high selectivity and sensitivity for thorium ion recognition. Coordination effects were investigated by DFT calculations, and the coordination modes and sites were confirmed. Moreover, the coordination abilities of the L-1 ligand with Th(4+) and UO2(2+) were evaluated.

Chemiluminescence switching on peroxidase-like Fe3O4 nanoparticles for selective detection and simultaneous determination of various pesticides

To achieve selectivity in direct chemiluminescence (CL) detection is very significant and a great challenge as well. Here, we report a novel concept of developing intrinsically selective CL switching at the surface of Fe(3)O(4) nanoparticles for the sensitive detection and simultaneous determination of various pesticides. Fe(3)O(4) nanoparticles have peroxidase-like catalytic activity and catalyze the decomposition of dissolved oxygen to generate superoxide anions, so that the CL intensity of luminol was amplified by at least 20 times. The CL signals can be quenched by the addition of ethanol because ethanol readily reacts with superoxide anions as a radical scavenger. However, the quenching effect can be inhibited through the specific binding of target molecules on Fe(3)O(4) nanoparticles, leading to CL "turn-on" in the presence of ethanol. The novel CL "switching-on" concept demonstrated unique advantages in the detection of pesticide residues. Using the surface coordinative reactions, nonredox pesticide ethoprophos were sensitively detected with a detection limit of 0.1 nM and had a very wide detection range of 0.1 nM to 100 μM. More importantly, the selectivity of CL switching is tunable through the special surface modification of Fe(3)O(4) nanoparticles, and these Fe(3)O(4) nanoparticles with different surface groups can generate unique CL response pattern for the simultaneous determination of various pesticides. Meanwhile, the superparamagnetic properties of Fe(3)O(4) nanoparticles provide a simple magnetic separation approach to attain interference-free measurement for real detection. The very facile and versatile strategy reported here should open a new window to exploration of selective CL molecular switching and application of magnetic nanoparticles for chemo/biodetection.

Transparency-based microplates for fluorescence quantification

Microplates for use in resource-limited laboratories should ideally not require processes that involve substantial large-scale production in order to be viable. We describe and demonstrate here an approach of using a silicone sheet with holes, conveniently cut out precisely using an inexpensive cutting plotter to correspond with regions where liquid is to be dispensed, and attaching it to a transparency to create very thin well arrays. With this, the contact angle hysteresis behavior of liquid could be harnessed to produce taller drop shapes so that the fiber probe used could read in the emitted light more effectively. Experimentation conducted revealed fluorescence measurements that were significantly more sensitive than standard microplates, notwithstanding that smaller volumes of liquid were needed. This was achieved using both the fiber optic and imaging evaluation modes. The two methods investigated, one with a lid placed and one without, showed the latter to produce marginally more sensitive readings as opposed to improved immunity from the environment with the former. These favorable measurement characteristics were found to be achievable with an estimated production cost of AU $0.40 and fabrication times of 3.5 min (96 wells) and 6.5 min (384 wells) per plate.

Luminescence sensors applied to water analysis of organic pollutants--an update

The development of chemical sensors for environmental analysis based on fluorescence, phosphorescence and chemiluminescence signals continues to be a dynamic topic within the sensor field. This review covers the fundamentals of this type of sensors, and an update on recent works devoted to quantifying organic pollutants in environmental waters, focusing on advances since about 2005. Among the wide variety of these contaminants, special attention has been paid polycyclic aromatic hydrocarbons, pesticides, explosives and emerging organic pollutants. The potential of coupling optical sensors with multivariate calibration methods in order to improve the selectivity is also discussed.

Determination of Sudan IV in hot chilli powder with luminol/dissolved oxygen chemiluminescence system

BACKGROUND

A green, simple and sensitive flow injection chemiluminescence (CL) procedure is proposed for the determination of Sudan dyes. The method is based on the finding that Sudan I, II, III and IV markedly enhance the CL intensity of the luminol/dissolved oxygen reaction.

RESULTS

The increment in CL intensity was proportional to the concentration of Sudan I, II, III and IV, giving calibration graphs linear over the ranges 0.007-1, 0.5-30, 1-10 and 0.7-300 ng mL(-1) respectively (R(2) >or= 0.9981), with limits of detection of 0.002, 0.2, 0.3 and 0.2 ng mL(-1) respectively. At a flow rate of 2 mL min(-1), complete determination of Sudan dyes, including sampling and washing, could be accomplished in 40 s, with relative standard deviations of less than 5% (n = 7).

CONCLUSION

The proposed method was successfully applied to the determination of Sudan IV in contaminated hot chilli powder, with recoveries ranging from 89.3 to 108.4%. The possible mechanism of enhancement of the luminol/dissolved oxygen CL reaction by Sudan IV can be attributed to the acceleration of electron transfer. Compared with other procedures, the proposed CL method offers the highest sensitivity and the least reagent consumption for the determination of Sudan IV.