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Magnesium tetrapyrazinoporphyrazines: tuning of the pKa of red-fluorescent pH indicators
摘要： Magnesium (II) tetrapyrazinoporphyrazines (TPyzPzs) are excellent red fluorophores (λF ~ 663 nm, ΦF ~ 0.53 in THF). In this work, a series of magnesium (II) complexes of unsymmetrical TPyzPzs bearing one or two phenol substituents was prepared. Suitable substitutions on the phenolic moiety tuned its pKa in the range of 5.5 to 13. Deprotonation of the phenolic group at higher pH induced a strong donor (phenolate) in the macrocycle that led to pH-dependent quenching of the red fluorescence of these indicators. pH sensing was proven in water solutions after incorporation of TPyzPs into two delivery systems – microemulsions and liposomes. The latter also serves as a simple model of biomembranes. Finally, a wavelength-ratiometric probe was constructed by incorporation of a TPyzPz indicator and lipophilic pH-nonsensitive BODIPY dye into liposomes. Synthetic precursors for TPyzPzs, substituted pyrazine-2,3-dicarbonitriles, also represent donor-acceptor system and the pH-dependent changes in absorption spectra may be easily visible to the naked eye.
关键词： pH indicators,microemulsions,fluorescence,BODIPY,wavelength-ratiometric probe,liposomes,tetrapyrazinoporphyrazines,magnesium complexes
更新于2025-11-20 15:33:11
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Effect of Excitation Wavelength on Optical Performances of Quantum-Dot-Converted Light-Emitting Diode
摘要： Light-emitting diode (LED) combined with quantum dots (QDs) is an important candidate for next-generation high-quality semiconductor devices. However, the effect of the excitation wavelength on their optical performance has not been fully explored. In this study, green and red QDs are applied to LEDs of different excitation wavelengths from 365 to 455 nm. The blue light is recommended for exciting QDs from the perspective of energy utilization. However, QD LEDs excited at 365 nm have unique advantages in eliminating the original peaks from the LED chip. Moreover, the green or red light excited by ultraviolet light has an advantage in colorimetry. Even for the 455 nm LED with the highest QD concentration at 7.0 wt%, the color quality could not compete with the 365 nm LED with the lowest QD concentration at 0.2 wt%. A 117.5% (NTSC1953) color gamut could be obtained by the 365 nm-excited RGB system, which is 32.6% higher than by the 455 nm-excited solution, and this can help expand the color gamut of LED devices. Consequently, this study provides an understanding of the properties of QD-converted LEDs under different wavelength excitations, and offers a general guide to selecting a pumping source for QDs.
关键词： excitation wavelength,colorimetry,quantum dots,light-emitting diode
更新于2025-11-19 16:46:39
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Effect of UV wavelength on humic acid degradation and disinfection by-product formation during the UV/chlorine process
摘要： The efficiency of the ultraviolet (UV)/chlorine process strongly depends on UV wavelength because chlorine photolysis and its subsequent radical formation are highly wavelength-dependent. This study compared the degradation of humic acid (HA) during the UV/chlorine process by low pressure mercury lamp (LPUV, 254 nm) and ultraviolet light-emitting diode (UV-LED, 275 and 310 nm). The results indicated that HA degradation followed the pseudo-first-order kinetics, and the fluence-based degradation rate constants (kobs) were significantly affected by UV wavelength and solution pH. HA degradation decreased greatly with increasing solution pH during the UV/chlorine process at 254 nm, while the opposite trend was observed at 275 and 310 nm. In the meantime, kobs decreased in the order of 275 nm > 254 nm > 310 nm at pH > 7.0. The changes of chlorine molar absorption coefficients at different UV wavelengths resulted in the variation of chlorine photodecay rates (kobs, chlorine), and the synergistic effects of kobs, chlorine and chlorine quantum yields (Φchlorine) affected HA reduction. The formation of disinfection by-products (DBPs) during the UV/chlorine process was also evaluated. A significant suppression on DBP formation and DBP-associated calculated theoretical cytotoxicity were observed at 275 nm high UV fluence and alkaline pHs. These findings in this study demonstrate that UV wavelength at 275 nm is more suitable for HA degradation by the UV/chlorine advanced oxidation process in practical applications.
关键词： Disinfection by-products,Ultraviolet light-emitting diode (UV-LED),UV/chlorine,Humic acid,Toxicity,UV wavelength
更新于2025-11-19 16:46:39
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Low temperature fabrication of high quality gate insulator in metal-oxide-semiconductor capacitor using laser annealing
摘要： This paper reports the fabrication of a high quality gate oxide for metal-oxide-semiconductor field effect transistors using a continuous wave blue laser. A thin Zr metal layer was inserted between the dielectric and substrate to increase laser absorption and reduce the interface layer. A simulation of laser irradiation showed that metal layer insertion induces a significant increase in temperature during laser annealing compared to the dielectric without a metal layer. The laser annealed capacitor with a 1 nm-thick Zr metal layer showed superior electrical characteristics, such as high capacitance, low leakage current, low fixed charge density and low interface state density. Based on these results and the economic advantage of blue laser diodes, this technique can be a solution for low temperature processes, such as monolithic 3-dimensional integration, where low temperature processes are required.
关键词： 445 nm wavelength,Zirconium oxide,scavenging effect,laser anneal,blue,MOSCAP,continuous wave,visible laser
更新于2025-11-14 17:28:48
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An Improved Method for Determination of Pentosans in Pulps using Dual-Wavelength Spectroscopy
摘要： The aim of this study was to determine the pentosan content in pulps by a dual-wavelength spectrophotometric method. The method was based on the boiling reaction between pentosan and 12% hydrochloric acid, in which pentosan was subsequently converted to furfural. The concentration of furfural in the distillate was determined by the absorbance at 280 nm and 290 nm. Several different simultaneous equations were solved to obtain the concentrations of furfural in the distillate. The results showed that the method had an excellent accuracy (RSD ≤ 0.61%) and reproducibility (RSD = 3.25%). The spectral interference of the 5-hydroxymethyl-2-furaldehyde in the distillate was eliminated by the dual-wavelength measurement technique. Compared with the TAPPI method (colorimetric method), this method is simple, user-friendly, and practical and has high detection sensitivity.
关键词： Dual-wavelength spectroscopy,Furfural,HMF,Pentosans
更新于2025-09-23 15:23:52
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[Communications in Computer and Information Science] Futuristic Trends in Network and Communication Technologies Volume 958 (First International Conference, FTNCT 2018, Solan, India, February 9–10, 2018, Revised Selected Papers) || Future Perspectives in Elastic Optical Networks
摘要： The new generation Elastic Optical Networks (EONs) based on Orthogonal Frequency Division Multiplexing (OFDM) can accommodate exponentially increasing heterogeneous data traffic efficiently and economically. In EONs, the optimum channel spacing between various subcarriers is very crucial for its efficient performance. The use of Sub-Carrier Multiplexing (SCM) in EONs is visualized as an evolving field. This paper present the evaluation of SCM based EONs for both mathematical and simulative model. The designed SCM-EON network is analytically evaluated for its performance with different modulation techniques (Direct Modulation and External Modulation). The performance of system is also evaluated for amplification using Semiconductor Optical Amplifier (SOA) and Erbium Doped Fiber Amplifier (EDFA). Simulative results show that Optical Phase Modulation (OPM) along with EDFA offers enhanced performance for the proposed model. It has also been observed that OPM is a better technique for SCM and hence it can be deduced that the combination will boost EONs efficiency in handling network resources.
关键词： SCM,Elastic Optical Networks,OFDM,EDFA,OPM,Bandwidth variable-wavelength cross-connects (BV-WXC),Quadrature Amplitude Modulation (QAM),Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM),Mach-Zehnder modulator (MZM)
更新于2025-09-23 15:23:52
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Near-Infrared Hyperspectral Imaging Rapidly Detects the Decay of Postharvest Strawberry Based on Water-Soluble Sugar Analysis
摘要： This paper presents a novel strategy to detect the fungal decay in strawberry using reflectance near-infrared hyperspectral imaging (NIR-HSI, 1000–2500 nm). The variation of fructose, glucose, sucrose, and total water-soluble sugar (TWSS) content was analyzed using HPLC with a reference method during fungal infection in strawberry. The feasibility of quantifying sugar constituents relevant to the different stages of decay in strawberry was evaluated using NIR-HSI with key wavelengths selected via successive projection algorithm. The results showed that the predicted performance of TWSS content was acceptable within 2 and 2.603 for RPD, respectively. Five to seven key wavelengths were obtained based on sugar constituents, and excellent performance for classification accuracy among the three stages of decay was 89.4 to 95.4% for calibration and 87.0 to 94.4% for prediction, respectively. This rapid approach provides a new strategy for the selection of key wavelengths to detect the decay and sugar constituents in strawberries.
关键词： Strawberry,Key wavelength,Decay,Sugar content,Hyperspectral imaging
更新于2025-09-23 15:23:52
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Application of quantitative light-induced fluorescence technology for tooth bleaching treatment and its assessment: An in vitro study
摘要： Objectives: This study aimed to determine the effectiveness of combination of photocatalysts - low concentration of hydrogen peroxide (3.5%) and titanium dioxide (TiO2), activated at a wavelength of 405 nm using quantitative light-induced fluorescence (QLF) technology, and to quantify the tooth-bleaching effect using fluorescence images from QLF technology. Materials and Methods: Forty bovine incisors were extrinsically stained according to Stookey’s method. Two bleaching solutions were prepared by mixing 3.5% H2O2 with 0.05% of anatase and rutile nano-TiO2 powder. These solutions were applied to the stained teeth using a micro-brush and then irradiated for 15 minutes at either 306 or 405 nm to activate the bleaching agent. The color difference was assessed before and after every 5 minutes of treatment. The ?E and ?F were obtained from white-light and fluorescence images, respectively. Results: All the low H2O2/TiO2 treatments caused significant bleaching after irradiation at 306 and 405 nm (p<0.05). There was no significant difference between the wavelengths (p>0.05), but a greater bleaching effect was obtained with anatase-TiO2 at 306 nm and rutile-TiO2 at 405 nm. Analysis of the fluorescence images revealed that the ?F values decreased significantly in all the groups according to the treatment times (p<0.05). There was a statistically significant reverse correlation between ?E and ??F (r= -0.822, p<0.001). Conclusions: Low H2O2/TiO2 with 405 nm of QLF technology demonstrated greater bleaching effect. Furthermore, the fluorescent images from QLF technology showed a possibility for assessment of tooth bleaching.
关键词： Digital imaging,Tooth bleaching,Theragnosis,405 nm wavelength,Titanium dioxide,Quantitative light-induced fluorescence (QLF)
更新于2025-09-23 15:23:52
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Does the wavelength dependent photoisomerization process of the p?coumaric acid come out from the electronic state dependent pathways?
摘要： Similar to the anion photoactive yellow protein (PYP) chromophore, the neutral form of the PYP chromophore was also found to exhibit a the wavelength-dependent photoisomerization quantum yield. The isomerization quantum yield increases with the increasing excitation energy on the S1 state, while decreases when being excited to the S2 state. Does this wavelength dependent product yield come out from the specific reaction pathways of the S1 and S2 states? This would mean that, the relaxation pathway of the S2 state is distinct from that of the S1 state and does not involve twisting motion. Does it break Kasha's rule by exhibiting a direct transition from the S2 state to the ground state? The underlying mechanism needs further in. In this article, we employed the on-the-fly dynamics simulations and static electronic structure calculations to reveal the deactivation mechanism of the neutral form of the PYP chromophore. Our results indicated that the C_C twisting motion dominates the S1 state decay process. In contrast, for the decay process of the S2 state, an ultrafast transition from the S2 to the S1 state through a planar conical intersection is observed, and the excess energy activates a new reaction channel to the ground state characterized by a puckering distortion of the ring. This pathway competes with the photoisomerization channel. No direct transition from S2 to S0 is observed, hence Kasha's rule is valid for this process. Our calcualtions can provide a reasonable explanation of the wavelength-dependent isomerization quantum yield of neutral PYP chromophore, and we hope it can provide theoretical foundations for comparing the effect of protonation state on the dynamcal behaviors of PYP chromophore.
关键词： Wavelength dependent,Photoisomerization,Fluorescent protein,Nonadiabatic process
更新于2025-09-23 15:23:52
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Channel modeling and analysis of OWC-massive MIMO systems
摘要： In this paper, we study the difference between the uplink and downlink channels of short-range slant free-space optical wireless between Ground - alpine base stations using massive MIMO linear arrays at both ends. The uplink and downlink atmospheric loss, scintillation, beam spreading and pointing error model of linear array slant range are constructed. The uplink and downlink atmospheric loss, spatial coherence length, receiver beamwidth, pointing error variance, relative mean square error (RMSE) and bit error rate (BER) are compared and analyzed under different distances of different wavelengths of light waves. After simulation analysis, it is concluded that the uplink and downlink atmospheric losses are the same, the uplink receiver beamwidth is larger than the downlink, and the downlink coherence length and the pointing error variance are larger than the uplink, and both monotonously change with the wavelength of the light wave and the propagation distance.
关键词： Optical wireless communication,MSE,Wavelength,Channel modeling,Massive MIMO
更新于2025-09-23 15:23:52