Visible Diodes Research Articles

Additive manufacturing of porous ceramic structures by indirect powder bed fusion with laser beam using a novel polyamide/alumina-based feedstock

Porous alumina structures were developed by indirect Powder Bed Fusion with Laser Beam (PBF-LB), employing a novel feedstock (composite granules) based on alumina (Al2O3), bio-renewable polyamide 612 (PA612), and micron-sized graphite (MG) using a commercial PBF-LB machine that operates with a low-power visible light diode laser. Regular and slightly rounded composite granules were prepared via the thermally induced phase separation (TIPS) process in dimethyl sulfoxide (DMSO) using 0.05 vol% of PA612, 40/60 vol% of Al2O3/PA612 and 6.25 wt% of MG, and then characterized via density measurements, Hausner's ratio, SEM-EDS, particle size distribution, Raman spectroscopy, DSC, and TGA. Experimental conditions to be used in the PBF-LB process were determined in order to obtain high-quality green porous structures with a controlled geometry. After the heating treatments, sintered components with good structural integrity, a high open porosity associated with interconnected pores in the struts, and a ceramic matrix with microsized-equiaxial grains were obtained. The evaluation of the mechanical properties was performed by diametral compression testing. In order to improve these properties, a vacuum infiltration process involving a low-concentration alumina-ethanol suspension was used on pre-sintered discs. As a consequence of the infiltration process, the discs showed improved mechanical properties after sintering without the porosity having been significantly affected.

Dental Diode Lasers for Implant Uncovering: A Case Series.

Diode lasers are increasingly being utilized as an alternative to conventional soft tissue surgery. While originally diode lasers referred to wavelengths ranging from 810 through 980 nm, a visible diode laser with a 445-nm wavelength has emerged as an additional wavelength for soft tissue surgery. The goal of this case series was to demonstrate the clinical results of both visible and near infrared (NIR) wavelengths when utilized for second stage implant surgery. Ten patients with 23 implants were treated at Stony Brook University, Department of Periodontology for implant uncovering using both visible and nonvisible (NIR) diode lasers. The uncovering was done utilizing 445-nm, 970-nm, and 980-nm wavelengths at a power setting of 2 W in either continuous or pulsed modes. The fiber-optic tips were initiated using blue articulating paper. Either topical benzocaine or infiltration anesthesia was utilized prior to soft tissue removal with the initiated tip. All patients healed uneventfully without any postoperative complications. Visible and NIR diode lasers provide an alternative and safe method to uncover submerged at implants at second stage surgery.

Computational 3D resolution enhancement for optical coherence tomography with a narrowband visible light source.

Phase-preserving spectral estimation optical coherence tomography (SE-OCT) enables combining axial resolution improvement with computational depth of field (DOF) extension. We show that the combination of SE-OCT with interferometric synthetic aperture microscopy (ISAM) and computational adaptive optics (CAO) results in high 3D resolution over a large depth range for an OCT system with a narrow bandwidth visible light super-luminescent diode (SLD). SE-OCT results in up to five times axial resolution improvement from 8 µm to 1.5 µm. The combination with ISAM gives a sub-micron lateral resolution over a 400 µm axial range, which is at least 16 times the conventional depth of field. CAO can be successfully applied after SE and ISAM and removes residual aberrations, resulting in high quality images. The results show that phase-preserving SE-OCT is sufficiently accurate for coherent post-processing, enabling the use of cost-effective SLDs in the visible light range for high spatial resolution OCT.

Development of a compact 406 nm diode laser-based cavity-enhanced spectrometer for high-sensitive detection of NO2 levels in exhaust gas

Nitrogen dioxide (NO2) is an important air pollutant due to its environmental impact and adverse effects on human health. It is released into the atmosphere primarily through anthropogenic activities. Here, we report on the development of a simple, compact, and cost-effective robust optical detection method exploiting cavity-enhanced absorption spectroscopy for high-sensitive and selective measurement of NO2 levels in real-time using a visible diode laser operating at 406 nm. A typical detection limit of ∼330 ppb for NO2 was achieved with an optimum acquisition time of ∼3.9 s, at optimal cavity pressure of 100 Torr. The sensor system demonstrates an effective optical path-length of 180 m in a high-finesse 50 cm long optical cavity in an interference-free spectral region and aerosol-free conditions. The spectrometer was optimized, calibrated, and demonstrated for the detection of NO2 levels in vehicular exhaust gases.

Occurrence of Biogenic Amines in Wines from the Central European Region (Zone B) and Evaluation of Their Safety.

The decarboxylation of the corresponding amino acids by microorganisms leads to the formation of biogenic amines (BAs). From a toxicological point of view, BAs can cause undesirable physiological effects in sensitive individuals, particularly if their metabolism is blocked or genetically altered. The current study aimed to monitor and evaluate the content of eight biogenic amines (BAs) in 232 samples of wines (white, rosé, red) produced in the Central European region (Zone B). White wines (180 samples), rosé wines (17 samples), and red wines (35 samples) were analyzed. High-performance liquid chromatography equipped with a ultraviolet-visible diode array detector (UV/VIS DAD) was applied to identify and quantify the BAs present in wines. In general, histamine (HIS), tyramine (TYM), putrescine (PUT), cadaverine (CAD), phenylethylamine (PEA), spermine (SPN) and spermidine (SPD) were detected in all tested wine samples. Tryptamine (TRM) was not present in any of the samples examined. In white and red wines, SPD, TYM, and PUT were most often detected. Regarding rosé wines, the three major BAs were SPN, TYM, and CAD. The BA content in red wines was generally higher than in rosé and white wines. However, HIS concentrations above the recommended limit of 10 mg/L were detected in 9% of the red wine samples. In addition, alarming levels of PUT, HIS, TYM, and PEA, with serious potential impact on consumer health, were recorded in two red wine samples. On the whole, the presence and concentrations of BAs in wine should be constantly evaluated, primarily because alcohol intensifies the hazardous effects of BAs.

Speed of light measurement with a picosecond diode laser and a voltage-controlled oscillator

This work describes an experimental method for measuring the speed of light in air. It uses optical feedback from a visible picosecond diode laser operated below the threshold and a voltage-controlled oscillator to determine the time required for a pulse to travel a known distance. The experimental setup is compact, fitting into a space of 1 × 0.5 m2, and at the same time, can determine the speed of light with an uncertainty of 0.03%. The method does not require fast detectors or oscilloscopes.

Photocatalytic degradation of paracetamol using photo-Fenton-like metal-organic framework-derived CuO@C under visible LED

Metal-organic framework (MOFs) based photocatalysis has received great attention recently as a promising technology for sustainable environmental applications. Herein, hydrogen peroxide (H2O2) activation with a copper-based metal-organic framework-derived catalyst (CuO@C) was applied for the photodegradation of a widely used analgesic paracetamol drug (PCM) under an energy-efficient visible light-emitted diode (LED) as a light source for the first time. The incorporation of CuO@C with H2O2 offered a photo-Fenton-like reaction that accelerated the PCM photodegradation, where 95% of paracetamol was degraded in 60 min. Interestingly, a novel N-curve pH trend was observed due to an independent boost of the PCM degradation at extreme pHi 9.9. The redeposition of Cu to the CuO@C surface is likely the critical mechanism for minimizing Cu leaching and maintaining good catalyst reusability. Eight intermediates were identified and two of them were newly reported. Surprisingly, no dimerization route was observed as previously reported in other processes. Additionally, a mineralization degree of 68% was achieved which proved the merit of the CuO@C/H2O2/visible LED process for practical applications. This work can provide new insights on the application of Cu-based MOFs as rationale candidates for the remediation of emerging contaminants in wastewater by H2O2 activation.

PPDN and NTCDA radical anions formation in EMIM-DCA, BMIM-BF4, EMIM-Ac ionic liquid solutions under the steady state UV and Vis light illumination: A combined X-, K-band EPR and DFT study

The radical anion of Pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile (PPDN) in blends with imidazolium based room temperature ionic liquids (RTIL): EMIM-DCA, BMIM-BF4, EMIM-Ac has been detected by X-band continues wave (CW) electron paramagnetic resonance (EPR) under steady state Xe-lamp illumination in the temperature interval from 190 to 340 K. The radical anion of 1,4,5,8-Naphthalenetetracarboxylic dianhydride (NTCDA) was registered by X- and K-band CW EPR at room temperature under the visible light CW diode laser operated at 532 nm, and Xe-lamp as well. The experimental hyperfine coupling data of both anion radicals were confirmed by DFT calculation. The formation of PPDN•– NTCDA•– and fullerene derivative (FD) radical anions is attributed to the photoelectron transfer from an IL anion to PPDN, NTCDA and FD electron acceptors. Here, the electron transfer leads to an irreversibility of these reactions due to photo-induced decomposition of the IL anions in the presence of an effective electron acceptor and is supported in the above RTILs solutions by means of EPR. For the indirect confirmation of the EMIM-DCA, EMIM-AC, BMIM-BF4 anion degradation in solutions with PPDN and NTCDA up to the transient radical state, similar data of acetate anion [OCOCH3]– decomposition, under CW Xe-Lamp photolysis resulting in •CH3 formation and its stabilization at 77 K in EMIM-Ac suspension with some FD dissolved in DCB are introduced as well. However, the main goal of this study is dedicated to the features of rotational and translational diffusion kinetics of PPDN and NTCDA radical anions in IL solutions as well to the evaluation of their application as a spin probes in ILs study in liquid phase.

Measuring the speed of light using optical feedback from a picosecond diode laser

An experiment for measuring the speed of light by measuring the distance between regularly generated optical pulses is described. The experiment utilizes optical feedback from a visible picosecond diode laser to accurately determine the distance between two successive laser pulses. The required setup is compact, and it does not implement either a fast detector or an oscilloscope. This experiment is suitable for an undergraduate physics instructional laboratory course or as an independent student project.

On Daphnia’s path: a semi‐automatic system to analyze three‐dimensional movement patterns

AbstractAnalyzing movement is essential for understanding complex behavioral interactions. Up to date, there are different movement analysis methods. Previous studies working with 2D movement analysis systems provided first insights into this field. 2D systems can capture only two of three spatial dimensions and thus allow analyses of movements on surfaces. 3D systems include all three spatial dimensions. Thus, 3D movement analysis is essential for analyzing movements in air or in water. Especially during the last years, 3D movement analysis has progressed a lot thanks to technological advances. Unfortunately, these technological advanced systems are often very expensive and handling flexibility is limited. Therefore, we implemented a customizable 3D movement analysis system for aquatic organisms. The system is composed of an experimental arena, backgrounds with different contrasts, three visible light diode spots, one infrared diode spot for analysis in the dark, and two Raspberry Pi 3 Model B V 1.2 equipped with cameras without infrared filters. We assembled a user‐friendly system that is controlled directly via a graphical user interface (GUI). It not only delivers raw data but also runs detailed analyses of common behavioral parameters. The accuracy of those analyses can be enhanced by the integrated manual error‐correction method that allows to interrupt the automatic track analysis and to correct detection errors by hand. In our case study, we show the spectrum of opportunities of the system by determining the swimming behavior of the freshwater crustacean Daphnia magna. We successfully recorded its swimming behavior under visible light and infrared light (simulating darkness for the daphniids) conditions and analyzed swimming velocity, motion patterns, depth selection, and tendency of clustering. In our case study, we show that using the integrated manual error‐correction method leads to a clear accuracy improvement. Our movement analysis system is not restricted to aquaria but can be adopted to movements in cages and even open areas of different sizes both in water or air, which emphasizes its potential. Together with a user manual, the open‐source MATLAB algorithm and the recommended hardware components, the here presented system enables semi‐automatic 3D movement analysis, which can be adapted to the individual needs.

Thermoresponsive Nanocellulose Films as an Optical Modulation Device: Proof-of-Concept.

Flexible optoelectronic technologies are becoming increasingly important with the advent of concepts such as smart-built environments and wearable systems, where they have found applications in displays, sensing, healthcare, and energy harvesting. Parallelly, there is also a need to make these innovations environmentally sustainable by design. In the present work, we employ nanocellulose and its excellent film-forming properties as a basis to develop a green flexible photonic device for sensing applications. Cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) were used as matrix materials along with a black thermochromic pigment to prepare thermoresponsive hybrid films. Optical properties of nanocellulose films such as transparency and haze were tuned by varying pigment loading. Nearly 90% transparent CNF and CNC films could be tuned to reduce the transmission to as low as 4 and 17%, respectively. However, the films regained transparency to up to 60% when heated above the thermochromic transition temperature (31 °C). The thermoresponsive behavior of the prepared films was exploited to demonstrate an all-optical modulation device. Continuous infrared light (1300 nm) was modulated by using a 660 nm visible diode laser. The laser intensity was sufficient to cause a localized thermochromic transition in the films. The laser was pulsed at 0.3 Hz and a uniform cyclic modulation depth of 0.3 dB was achieved. The demonstrated application of functional nanocellulose hybrid films as a light switch (modulator) could be harnessed in various thermally stimulated sensing systems such as temperature monitoring, energy-saving, and anti-counterfeiting.

Multiple-graphene layer based p++–n–n−–n++ device on Si/3C-SiC (100) substrate: a highly sensitive visible photo-sensor

The current paper reports the prospects of a multiple-graphene-layer (MGL) based vertically doped p++–n–n––n++ avalanche photo-sensor in visible wavelength region (300 nm–800 nm). High carrier mobility, intrinsic optical and mechanical properties in graphene at room temperature, have made this material promising for various novel applications. The authors have used an indigenously developed and experimentally verified quantum-corrected field maximum classical drift-diffusion (QCFMCDD) mathematical model for studying the optical characteristics of MGL based p++–n–n––n++ avalanche photo-diode sensor. The validity of the simulator is established through a comparative study between the experimental and analytical observations under similar operating (structural/electrical/thermal) conditions. Additionally, the superiority of the QCFMCDD model over the conventional classical drift-diffusion model is established through this comprehensive study. The analysis reveals that the opto-electrical properties of the device-under-test improve significantly as a result of the incorporation of MGL in the low doped active region. The authors have compared the results with those of a Si/4H-SiC super-lattice avalanche photo-sensor at 500 nm wavelength of incident radiation. It is observed that graphene outperforms its Si/4H-SiC counterpart in terms of photo-responsivity (0.820 A W−1 vs. 0.650 A W−1) and quantum efficiency (84% vs. 62%) for optical irradiation with visible laser source. The opto-electrical performance of the 3 × 3 array type graphene photo-sensor is further analyzed and compared with those of its single array counterpart. The photo-responsivity as well as quantum efficiency increases by at least 30% in the case of the 3 × 3 photo-sensor array. In comparison to available photo detectors, reported so far in published literature, the designed photo-sensor shows overall performance betterment in the visible wavelength region. To the best of authors’ knowledge, this is the first report on MGL based 3 × 3 array type ultra fast highly sensitive visible avalanche diode photo-sensor.

Compact fiber optical interferometer technique to measure picometer displacements in biological piezoelectric materials

A simple and robust fiber optical interferometer was developed to non-invasively study the weak piezoelectric effect from thin samples. A biological sample from inter-molt dactyl clubs obtained from the mantis shrimp was used as the test sample. The non-contact technique can measure displacements better than 0.5 pm for samples subjected to large electric fields. The approach utilizes a simple visible diode laser, commercial optical fibers and, the phase dependent detection of an oscillating cavity at different frequencies from 0.5 kHz to 2.0 kHz. The piezoelectric constant of the biological samples was calculated from the optical interference fringes and determined to be in the range of 0.3–0.5 pm V−1. The noise of 20 fm Hz−0.5 in the setup is primarily due to thermally associated strains from current flow to the sample electrodes during the measurement.

Photon momentum induced precision small forces: a static and dynamic check

Practical means of generation and calibration of the small precision forces in static and dynamic regimes around 1 Hz by the usage of radiation pressure effect from 1 W continuous wave visible (diode) laser light is presented. The additive effect of the transfer of photon momentum, caused by non-overlapping multiply reflecting laser beam locked within a quasi-passive and/or active macroscopic cavity system, is employed. The effective laser power (partially trapped experimentally) is amplified, such that the optically generated forces are increased from hundreds of pN to sub-N level. The results presented in this paper should be seen as a means for extending the edge of practically verifiable lower limits of SI-traceable force metrology.

Effects of photobiomodulation on muscle strength in post-menopausal women submitted to a resistance training program.

The aim of this study was to compare the effects of resistance training of low volume and high intensity with or without photobiomodulation (PBM) on muscle strength and functional performance in post-menopausal women. Thirty-four post-menopausal women were randomized into resistance training (RTG, n = 17) or resistance training plus PBM (PBMG, n = 17). Individuals from both groups received the same RT protocol consisting of leg-press 45°, front lat pulldown, leg curl, chest press, and squat performed in two sets of 10 repetitions with a workload of 75% of one repetition maximum (1RM), twice per week, during 8weeks. PBMG individuals also received, prior to the exercise session, PBM through a cluster containing 7 visible diodes (630nm) and 7 infrared diodes (850nm) with power of 100mW each and energy of 4J per diode, applied to the quadriceps femoris muscle; individuals from RTG received placebo PBM prior to the sessions, applied with the same device switched off. Muscle strength (1RM; isometric dynamometer), functional performance (Time Up and Go; Berg Balance Scale; 6-min walk test), and quality of life (World Health Organization Quality of Life-Bref) were performed before and after 8weeks. Both groups increased muscle strength (p < 0.001) for all exercises, without group differences (p = 0.651). Quality of life (p = 0.015) and balance (p = 0.006) increased only in the RTG. The results suggest that PBM were not able for inducing additional benefits to RT to improve muscle strength in post-menopausal women.

Analysis of Phlebodium decumanum Fronds by High-Performance Liquid Chromatography by Ultraviolet-Visible and Quadrupole Time-of-Flight Tandem Mass Spectrometry (HPLC–UV–VIS–QTOF–MS/MS)

Phlebodium decumanum (P. decumanum), together with other tropical ferns commonly known as Calaguala, have been empirically applied since ancient times to ameliorate inflammatory disorders, skins diseases and even cancer. There are evidences of antineoplastic potential and anti-inflammatory, immunomodulatory and antioxidant properties of the extract. Preliminary studies have also shown direct antitumor activity of the extracts. In the present article, the phytochemical composition of a hydro-ethanolic extract of P. decumanum is investigated using high-performance liquid chromatography (HPLC) with ultraviolet–visible (UV–vis) diode array detection (DAD) and electrospray ionization (ESI) quadrupole time-of-flight tandem mass spectrometry (QTOF–MS/MS) detection. First, the chromatographic profile is established as a representative fingerprint of the compounds extracted from the fern. Then, a total of 122 chemicals, including 23 flavonoids, 47 phenolic acids (34 hydroxycinnamic acids and 13 hydroxybenzoic acids), 9 amino and amino-sugar derivatives, 24 organic acids and their derivatives, and other metabolites, have been characterized. Moreover, 12 unknown compounds were also detected, providing the first comprehensive characterization available on the phytochemical composition of the leaves of P. decumanum.

Comparison of antioxidant activity, content of polyphenols and flavonoids in liturgical and common wines

This article deals with the comparison of biologically active substances (antioxidant capacity, content of polyphenols and flavonoids) in samples of common and liturgical wines. For determination were chosen these varieties Pinot Noir, Red Traminer and Chardonnay. The total content of polyphenols and flavonoids were found by visible diode array spectrophotometer. For determination of total antioxidant capacity was used the DPPH test. Results of this paper did not prove a general difference between liturgical and common wines, although between individual samples a statistically significant difference was found. Furthermore, the results show considerably higher values of biologically active substances in red wines Pinot Noir against white wine Red Traminer and Chardonnay - the total antioxidant capacity was considerably in excess of values up to 30 times, the total content of polyphenols up to 50 times and the total content of flavonoids up to 50 times. From the content of biologically active substances point of view, the red wine is recommended for human health.

Progress in the development of solid-state laseres excited directly by visible InGaN diode lasers

Progress in the development of solid-state laseres excited directly by visible InGaN diode lasers

Visible-to-visible four-photon ultrahigh resolution microscopic imaging with 730-nm diode laser excited nanocrystals.

Further development of multiphoton microscopic imaging is confronted with a number of limitations, including high-cost, high complexity and relatively low spatial resolution due to the long excitation wavelength. To overcome these problems, for the first time, we propose visible-to-visible four-photon ultrahigh resolution microscopic imaging by using a common cost-effective 730-nm laser diode to excite the prepared Nd(3+)-sensitized upconversion nanoparticles (Nd(3+)-UCNPs). An ordinary multiphoton scanning microscope system was built using a visible CW diode laser and the lateral imaging resolution as high as 161-nm was achieved via the four-photon upconversion process. The demonstrated large saturation excitation power for Nd(3+)-UCNPs would be more practical and facilitate the four-photon imaging in the application. A sample with fine structure was imaged to demonstrate the advantages of visible-to-visible four-photon ultrahigh resolution microscopic imaging with 730-nm diode laser excited nanocrystals. Combining the uniqueness of UCNPs, the proposed visible-to-visible four-photon imaging would be highly promising and attractive in the field of multiphoton imaging.

Characterisation of dissolved organic matter in stormwater using high-performance size exclusion chromatography

Understanding the complexity of dissolved organic matter (DOM) in stormwater has drawn a lot of interest, since DOM from stormwater causes not only environmental impacts, but also worsens downstream aquatic quality associated with water supply and treatability. This study introduced and employed high-performance size exclusion chromatography (HPSEC) coupled with an ultraviolet–visible (UV–vis) diode array detector to assess changes in stormwater-associated DOM characteristics. Stormwater DOM was also analysed in relation to storm event characteristics, water quality and spectroscopic analysis. Statistical tools were used to determine the correlations within DOM and water quality measurements. Results showed that dissolved organic carbon (DOC) and UV absorbance at 254nm (UV254) as conventional DOM parameters were found to be correlated well to the changes in stormwater quality during each of the three storm events studied. Both detector wavelengths (210 and 254nm) and their ratio (A210/A254) were found to provide additional information on the physiochemical properties of stormwater-associated DOM. This study indicated that A210/A254 is an important parameter which could be used to estimate the DOM proportions of functional groups and conjugated carbon species. This study provided also an understanding of stormwater quality constituents through assessing variability and sensitivity for various parameters, and the additional information of rainfall characteristics on runoff quality data for a better understanding of parameter correlations and influences.