scholarly journals Determination of 3,4,5-Trihydroxybenzoic Acid Exploiting a Visible-Light-Driven Photoelectrochemical Platform: Application in Wine and Tea Samples

2022 ◽  
Author(s):  
Kayni Lima ◽  
Ridvan Fernandes ◽  
Clenilton dos Santos ◽  
Flavio Damos ◽  
Rita de Cássia Luz
Keyword(s):  
Light Emitting Diode ◽  
Glass Slide ◽  
Experimental Conditions ◽  
Amperometric Determination ◽  
Light Emitting ◽  
Promising Tool ◽  
Visible Light Driven ◽  
Photoelectrochemical Method ◽  
Acid Determination

The present work is based on the development and application of a photoelectrochemical method for the amperometric determination of 3,4,5-trihydroxybenzoic acid in different samples. The method is based on the use of a photoelectrochemical platform based on a glass slide coated with fluorine-doped tin oxide, which has been modified with cadmium sulfide and poly(D-glucosamine) and subjected to a light-emitting diode (LED) lamp. The photoelectrochemical platform was sensitive to the increase of the concentration of the antioxidant 3,4,5-trihydroxybenzoic acid in the solution. Under the optimized experimental conditions, the photoelectrochemical method presented a linear response for a 3,4,5-trihydroxybenzoic acid concentration ranging from 0.2 up to 500 μmol L-1. The method was applied to 3,4,5-trihydroxybenzoic acid determination in samples of wines and teas with recoveries between 95.88 and 101.72%. The results obtained suggest that the developed platform is a promising tool for quantifying the 3,4,5-trihydroxybenzoic acid.

A Compact Microcontrolled Microfluidic System for Photometric Determination of Phosphate in Natural Water Samples

2015 ◽  
Vol 68 (7) ◽  
pp. 1108 ◽  
Author(s):  
Osmundo Dantas Pessoa-Neto ◽  
Tiago Almeida Silva ◽  
Vagner Bezerra dos Santos ◽  
Orlando Fatibello-Filho
Keyword(s):  
Light Emitting Diode ◽  
Flow Analysis ◽  
Photometric Determination ◽  
Microfluidic System ◽  
Experimental Conditions ◽  
Light Emitting ◽  
Experimental Parameters ◽  
Led Photometer

A compact environmentally friendly microcontrolled microfluidic device ideal for in situ phosphate determination was developed based on a microsystem based on low-temperature co-fired ceramics (LTCC) coupled to a light-emitting diode (LED)–photometer with a multicommutation flow analysis (MCFA) approach. The experimental parameters of the MCFA analyzer were optimized by chemometric studies. Under the best experimental conditions, limits of detection and quantification of 0.02 mg P L–1 and 0.07 mg P L–1, respectively, and a sampling frequency of 67 h–1 were estimated. Moreover, a low sample consumption of only 60 μL per determination was the other advantage that fully meets the requirements of sustainable research and green chemistry purposes.

scholarly journals Effects of Temperature and Host Concentration on the Supramolecular Enantiodifferentiating [4 + 4] Photodimerization of 2-Anthracenecarboxylate through Triplet-Triplet Annihilation Catalyzed by Pt-Modified Cyclodextrins

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1502 ◽  
Author(s):  
Ming Rao ◽  
Wanhua Wu ◽  
Cheng Yang
Keyword(s):  
Light Emitting Diode ◽  
Temperature Dependency ◽  
Light Emitting ◽  
Modified Cyclodextrins ◽  
Direct Irradiation ◽  
Visible Light Driven ◽  
Significant Temperature ◽  
Effects Of Temperature ◽  
532 Nm ◽  
Triplet Triplet Annihilation

Visible-light-driven photocatalytic supramolecular enantiodifferentiating dimerization of 2-anthracenecarboxylic acid (AC) through triplet-triplet annihilation (TTA), mediated by the Schiff base Pt(II) complex (Pt-1, Pt-2, and Pt-3) was studied. The host concentration and the temperature effects on the stereoselectivity were comprehensively investigated. Increasing the concentration of sensitizers/hosts significantly enhanced the conversion of the photoreaction but led to reduced enantioselectivities of the chiral photodimers 2 and 3 when the photoreaction was triggered by a 532 nm laser, which was in contrast with the results obtained by direct irradiation of AC with a 365 nm light-emitting diode (LED) lamp, due to the aggregation of the sensitizer/host in water. The cyclization of AC through triplet-triplet annihilation displayed significant temperature dependency when Pt-3 was employed as the sensitizer/host. Increasing the temperature from 0 °C to 30 °C with 5% equiv. of Pt-3 led to a great increase of the ee of 2 from 2.1% to 31.6%. However, hardly any temperature dependency was observed when the photodimerization was mediated by other sensitizers and/or hosts, or the photoreaction was triggered directly with a 365 nm LED lamp.

scholarly journals Effect of ceramic thicknesses and opacities on water sorption and solubility of a light-curing resin cement by different units

2021 ◽  
Vol 20 ◽  
pp. e211656
Author(s):  
Gabriela Alves de Cerqueira ◽  
Lais Sampaio Souza ◽  
Rafael Soares Gomes ◽  
Giselle Maria Marchi ◽  
Paula Mathias
Keyword(s):  
Water Sorption ◽  
Light Emitting Diode ◽  
Lithium Disilicate ◽  
Resin Cement ◽  
The Other ◽  
Experimental Conditions ◽  
Light Emitting ◽  
Light Curing

Aim: This study evaluated the water sorption and solubility of a light-cured resin cement, under four thicknesses and four opacities of a lithium disilicate ceramic, also considering three light-emitting diode (LED) units. Methods: A total of 288 specimens of a resin cement (AllCem Veneer Trans – FGM) were prepared, 96 samples were light-cured by each of the three light curing units (Valo – Ultradent / Radii-Cal – SDI / Bluephase II – Ivoclar Vivadent), divided into 16 experimental conditions, according to the opacities of the ceramic: High Opacity (HO), Medium Opacity (MO), Low Translucency (LT), High Translucency (HT), and thicknesses (0.3, 0.8, 1.5, and 2.0 mm) (n = 6). The specimens were weighed at three different times: Mass M1 (after making the specimens), M2 (after 7 days of storage in water), and M3 (after dissection cycle), for calculating water sorption and solubility. Results: The higher thickness of the ceramic (2.0 mm) significantly increased the values of water sorption (44.0± 4.0) and solubility (7.8±0.6), compared to lower thicknesses. Also, the ceramic of higher opacity (HO) generated the highest values of sorption and solubility when compared to the other opacities, regardless of the thickness tested (ANOVA-3 factors / Tukey’s test, α = 0.05). There was no influence of light curing units. Conclusion: Higher thicknesses and opacities of the ceramic increased the water sorption and solubility of the tested light-cured resin cement.

scholarly journals Determination of Dental Adhesive Composition throughout Solvent Drying and Polymerization Using ATR–FTIR Spectroscopy

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3886
Author(s):  
Arwa Almusa ◽  
António H.S. Delgado ◽  
Paul Ashley ◽  
Anne M. Young
Keyword(s):  
Light Exposure ◽  
Light Emitting Diode ◽  
Attenuated Total Reflectance ◽  
Drying Time ◽  
Light Emitting ◽  
Spectral Changes ◽  
One Step ◽  
Urethane Dimethacrylate ◽  
Kinetics Of

The of this study aim was to develop a rapid method to determine the chemical composition, solvent evaporation rates, and polymerization kinetics of dental adhesives. Single-component, acetone-containing adhesives One-Step (OS; Bisco, USA), Optibond Universal (OU; Kerr, USA), and G-Bond (GB; GC, Japan) were studied. Filler levels were determined gravimetrically. Monomers and solvents were quantified by comparing their pure Attenuated Total Reflectance-Fourier Transform Infra-Red (ATR–FTIR) spectra, summed in different ratios, with those of the adhesives. Spectral changes at 37 °C, throughout passive evaporation for 5 min, then polymerisation initiated by 20 s, and blue light emitting diode (LED) (600 mW/cm2) exposure (n = 3) were determined. Evaporation and polymerisation extent versus time and final changes were calculated using acetone (1360 cm−1) and methacrylate (1320 cm−1) peaks. OS, OU, and GB filler contents were 0, 9.6, and 5.3%. FTIR suggested OS and OU were Bis-GMA based, GB was urethane dimethacrylate (UDMA) based, and that each had a different diluent and acidic monomers and possible UDMA/acetone interactions. Furthermore, initial acetone percentages were all 40−50%. After 5 min drying, they were 0% for OS and OU but 10% for GB. Whilst OS had no water, that in OU declined from 18 to 10% and in GB from 25 to 20% upon drying. Evaporation extents were 50% of final levels at 23, 25, and 113 s for OS, OU, and GB, respectively. Polymerisation extents were all 50 and 80% of final levels before 10 and at 20 s of light exposure, respectively. Final monomer polymerisation levels were 68, 69, and 88% for OS, OU, and GB, respectively. An appreciation of initial and final adhesive chemistry is important for understanding the properties. The rates of evaporation and polymerisation provide indications of relative required drying and light cure times. UDMA/acetone interactions might explain the considerably greater drying time of GB.

On-site determination of the migration amount of fluorescent whitening agents from paper to finger by fluorescence spectrophotometry

2017 ◽  
Vol 9 (3) ◽  
pp. 465-472 ◽  
Author(s):  
Yang Yu ◽  
Xinghua Wang ◽  
Qiang Fei ◽  
Yong Yu ◽  
Sizhu Tian ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Light Emitting ◽  
Fluorescence Spectrophotometry ◽  
Fluorescent Whitening Agents ◽  
Local Students

We have established a light emitting diode fluorescence spectrophotometer (LED-FS) for quantitatively determining the amount of FWA that migrates from paper notebooks or pads, used by local students, to fingers.

Miniaturized UV-LED Array Chip Photochemical Vapor Generator Coupled with Point Discharge Optical Emission Spectrometer for Determination of Trace Selenium

2021 ◽  
Author(s):  
Mengtian Li ◽  
Yi Luo ◽  
Zhirong Zou ◽  
Fujian Xu ◽  
Xiaoming Jiang ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Optical Emission ◽  
Nano Tio2 ◽  
Light Emitting ◽  
Uv Led ◽  
Led Array ◽  
Point Discharge ◽  
Photochemical Vapor Generation ◽  
Optical Emission Spectrometer

An ultraviolet light emitting diode (UV-LED) array chip as irradiation source for nano-TiO2 catalyzed photochemical vapor generation (PCVG) was combined with a hollow electrode point discharge microplasma optical emission spectrometer...

scholarly journals Portable Instrument for Hemoglobin Determination Using Room-Temperature Phosphorescent Carbon Dots

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 825
Author(s):  
Fabio Murru ◽  
Francisco J. Romero ◽  
Roberto Sánchez-Mudarra ◽  
Francisco J. García Ruiz ◽  
Diego P. Morales ◽  
...  
Keyword(s):  
Carbon Dots ◽  
Room Temperature ◽  
Light Emitting Diode ◽  
Electronic System ◽  
Portable Device ◽  
Light Emitting ◽  
Current Converter ◽  
Reconfigurable Platform ◽  
Luminescence Characteristics

A portable reconfigurable platform for hemoglobin determination based on inner filter quenching of room-temperature phosphorescent carbon dots (CDs) in the presence of H2O2 is described. The electronic setup consists of a light-emitting diode (LED) as the carbon dot optical exciter and a photodiode as a light-to-current converter integrated in the same instrument. The reconfigurable feature provides adaptability to use the platform as an analytical probe for CDs coming from different batches with some variations in luminescence characteristics. The variables of the reaction were optimized, such as pH, concentration of reagents, and response time; as well as the variables of the portable device, such as LED voltage, photodiode sensitivity, and adjustment of the measuring range by a reconfigurable electronic system. The portable device allowed the determination of hemoglobin with good sensitivity, with a detection limit of 6.2 nM and range up to 125 nM.

scholarly journals Visible-Light-Driven Photocatalytic Activity of Magnetic BiOBr/SrFe12O19 Nanosheets

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 735 ◽  
Author(s):  
Taiping Xie ◽  
Jiao Hu ◽  
Jun Yang ◽  
Chenglun Liu ◽  
Longjun Xu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Electron Microscope ◽  
Visible Light ◽  
Uv Light ◽  
Light Emitting Diode ◽  
Active Species ◽  
Composite Catalyst ◽  
Light Emitting ◽  
Transmission Electron ◽  
Visible Light Driven

Magnetic BiOBr/SrFe12O19 nanosheets were successfully synthesized using the hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and UV-visible diffused reflectance spectra (UV-DRS), and the magnetic properties were tested using a vibration sample magnetometer (VSM). The as-produced composite with an irregular flaky-shaped aggregate possesses a good anti-demagnetization ability (Hc = 861.04 G) and a high photocatalytic efficiency. Under visible light (λ > 420 nm) and UV light-emitting diode (LED) irradiation, the photodegradation rates of Rhodamine B (RhB) using BiOBr/SrFe12O19 (5 wt %) (BOB/SFO-5) after 30 min of reaction were 97% and 98%, respectively, which were higher than that using BiOBr (87%). The degradation rate of RhB using the recovered BiOBr/5 wt % SrFe12O19 (marked as BOB/SFO-5) was still more than 85% in the fifth cycle, indicating the high stability of the composite catalyst. Meanwhile, after five cycles, the magnetic properties were still as stable as before. The radical-capture experiments proved that superoxide radicals and holes were main active species in the photocatalytic degradation of RhB.

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