Blue Red Light-emitting Diodes Research Articles

One-step solvothermal synthesis of nitrogen-doped carbon dots with efficient red emission from conjugated perylene for multiple applications

Despite its significance for applications related to plant growth, the development of carbon dots (CDs) with bright red emissions still faces multiple obstacles. Herein, red emission hydrophobic carbon dots (RH-CDs) featuring one emission peak centered at 594 nm and a shoulder emission peak at 630 nm with a quantum yield of 34 % and a wide full width at half maximum (FWHM) of 100 nm (580 nm–680 nm) were synthesized by adopting large conjugated perylene anhydride and aromatic amine precursors under solvothermal conditions. Density functional theory calculations support the method of using larger conjugated systems and higher graphite N doping to increase red emissions from CDs. With a post-surface functionalization strategy, polyvinylpyrrolidone (PVP)-modified RH-CDs (QY = 12 %) were utilized as an anti-counterfeiting ink for information printing. Moreover, both blue-red light-emitting diodes (LEDs) and light conversion poly (methyl methacrylate) (PMMA)-CDs film were fabricated with emission spectra that are consistent with the absorption spectra of plants, suggesting that the prepared RH-CDs may have widespread application potential as a stable fluorescent material in plant growth.

Evaluation of Plant Stress Monitoring Capabilities Using a Portable Spectrometer and Blue-Red Grow Light.

Remote sensing offers a non-destructive method to detect plant physiological response to the environment by measuring chlorophyll fluorescence (CF). Most methods to estimate CF require relatively complex retrieval, spectral fitting, or modelling methods. An investigation was undertaken to evaluate measurements of CF using a relatively straightforward technique to detect and monitor plant stress with a spectroradiometer and blue-red light emitting diode (LED). CF spectral response of tomato plants treated with a photosystem inhibitor were assessed and compared to traditional reflectance-based indices: normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI). The blue-red LEDs provided input irradiance and a “window” in the CF emission range of plants (~650 to 850 nm) sufficient to capture distinctive “two-peak” spectra and to distinguish plant health from day to day of the experiment, while within day differences were noisy. CF-based metrics calculated from CF spectra clearly captured signs of vegetation stress earlier than reflectance-based indices and by visual inspection. This CF monitoring technique is a flexible and scalable option for collecting plant function data, especially for indicating early signs of stress. The technique can be applied to a single plant or larger canopies using LED in dark conditions by an individual, or a manned or unmanned vehicle for agricultural or military purposes.

Randomized trial of three phototherapy methods for the treatment of acne vulgaris in Chinese patients

Acne vulgaris is common in Asian populations. We compared three methods of phototherapy for the treatment of moderate to severe facial acne vulgaris in Chinese patients. Patients were randomly assigned to receive photodynamic therapy (PDT), intense pulsed light (IPL) or blue-red light-emitting diode (LED) phototherapy to the right side of the face until the inflammatory lesion count reduced by ≥ 90%. Patients were examined at 1 and 3 months after the final treatment. We enrolled 150 patients (92 males; mean age, 28 years). At 1 month, ≥90% clearance or moderate improvement occurred in 46/50 (92%), 29/50 (58%) and 22/50 (44%) patients in the PDT, IPL and LED groups, respectively (mean number of sessions required, PDT: 3 ± 1.52; IPL: 6 ± 2.15; LED: 9 ± 3.34). Forty-six (92%) patients experienced mild to moderate pain, erythema and edema after PDT, which resolved within 5-7 days. Slight erythema and stinging were reported immediately after IPL and LED, resolving within 2 h. After 3 months, minimal papules and pustules were observed in 4 patients in the PDT group, 7 in the IPL group and 12 in the LED group, but no nodular pustules recurred. Phototherapy is efficacious for moderate to severe facial acne vulgaris.