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- 2018
- MPPT
- photovoltaic (PV) power systems
- Induction motor
- three-phase four switch inverter
- two-inductor boost converter
- Electrical Engineering and Automation
- Sree Buddha College of Engineering
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Pulse-diode-intermittent-pumped 2-μm acousto-optically Q-switched Tm:YAG laser
摘要： An innovative pulse-diode-intermittent-pumped 2-micron acousto-optically Q-switched Tm:YAG laser is presented for the first time, which can improve the output energy, while ensuring the operation repetition of laser. Maximum output energy of 6.83 mJ and minimum pulse width of 367.7 ns at Q-switched repetition rate of 200 Hz is obtained at pump energy of 86.2 mJ. The output wavelength is 2014.9 nm. The beam quality factor Mx2 is 1.59. The stability is larger than 98%.
关键词： Q-switch,Diode-pumped lasers,Tm:YAG
更新于2025-11-28 14:24:03
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C-band tunable performance of passively Q-switched erbium-doped fiber laser using Tin(IV) oxide as a saturable absorber
摘要： We report on the detailed study of wavelength tunability of passively Q-switched erbium doped fiber laser using Tin(IV) Oxide (SnO2) as saturable absorber (SA). As a typical n-type semiconductor, SnO2 has been widely used in gas sensors, oxidation catalyst, transparent conductor, and electrode materials in solar cell. Herein, we fabricated saturable absorber by compositing SnO2 nanoparticle with polyvinyl alcohol (PVA). The SnO2-SA is incorporated in the laser cavity by sandwiching it between two fiber ferrules. Q-switched laser operation can be continuously tuned from 1521 to 1565 nm, with a wavelength tuning range of up to 45 nm, covering almost the entire C-band. Q-switched pulse parameters such as repetition rate, average power, pulse width, pulse energy, and peak power at different wavelengths were studied in detail. Our experimental results suggest that the SnO2-SA is a suitable and cost-effective solution for broadband tunable laser applications with relatively simple fabrication process.
关键词： Tunability,C-band,Q-switch EDFL,SnO2
更新于2025-11-28 14:24:03
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Programmable Spectral Filter in C-Band Based on Digital Micromirror Device
摘要： Optical ?lters have been adopted in many applications such as recon?gurable telecommunication switches, tunable lasers and spectral imaging. However, most of commercialized ?lters based on a micro-electrical-mechanical system (MEMS) only provide a minimum bandwidth of 25 GHz in telecom so far. In this work, the programmable ?lter based on a digital micromirror device (DMD) experimentally demonstrated a minimum bandwidth of 12.5 GHz in C-band that matched the grid width of the International Telecommunication Union (ITU) G.694.1 standard. It was capable of ?ltering multiple wavebands simultaneously and ?exibly by remotely uploading binary holograms onto the DMD. The number of channels and the center wavelength could be adjusted independently, as well as the channel bandwidth and the output power. The center wavelength tuning resolution of this ?lter achieved 0.033 nm and the insertion loss was about 10 dB across the entire C-band. Since the DMD had a high power handling capability (25 KW/cm2) of around 200 times that of the liquid crystal on silicon (LCoS) chip, the DMD-based ?lters are expected to be applied in high power situations.
关键词： digital micromirror device,optical switch,programmable spectral ?lter
更新于2025-11-28 14:23:57
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Core-shell metal-organic frameworks with fluorescence switch to trigger an enhanced photodynamic therapy
摘要： The design of hybrid metal-organic framework (MOF) nanomaterials by integrating inorganic nanoparticle into MOF (NP@MOF) has demonstrated outstanding potential for obtaining enhanced, collective, and extended novel physiochemical properties. However, the reverse structure of MOF-integrated inorganic nanoparticle (MOF@NP) with multifunction has rarely been reported. Methods: We developed a facile in-situ growth method to integrate MOF nanoparticle into inorganic nanomaterial and designed a fluorescence switch to trigger enhanced photodynamic therapy. The influence of “switch” on the photodynamic activity was studied in vitro. The in vivo mice with tumor model was applied to evaluate the “switch”-triggered enhanced photodynamic therapy efficacy. Results: A core-satellites structure with fluorescence off and on function was obtained when growing MnO2 on the surface of fluorescent zeolitic imidazolate framework (ZIF-8) nanoparticles. Furthermore, A core-shell structure with photodynamic activity off and on function was achieved by growing MnO2 on the surface of porphyrinic ZrMOF nanoparticles (ZrMOF@MnO2). Both the fluorescence and photodynamic activities can be turned off by MnO2 and turned on by GSH. The GSH-responsive activation of photodynamic activity of ZrMOF@MnO2 significantly depleted the intracellular GSH via a MnO2 reduction reaction, thus triggering an enhanced photodynamic therapy efficacy. Finally, the GSH-reduced Mn2+ provided a platform for magnetic resonance imaging-guided tumor therapy. Conclusion: This work highlights the impact of inorganic nanomaterial on the MOF properties and provides insight to the rational design of multifunctional MOF-inorganic nanomaterial complexes.
关键词： Core-shell structure,Metal-organic frameworks,Fluorescence switch,Photodynamic therapy
更新于2025-11-21 11:08:12
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AuxAg1-x Nanocomposites with 40-Fold Emission Enhancement Formed by the Electrostatic Assembly of Gold Nanoclusters and Silver Nanoclusters for Bioimaging and Bioanalysis
摘要： Noble metal nanoclusters (NCs) have been widely used in bioimaging and bioanalysis due to their unique molecular-like structures and good biocompatibility. Bright nanomaterials with high quantum yields are in need for widespread applications. Unfortunately, the weak photoluminescence (PL) of metal NCs hampers their biomedical applications, and thus it is urgent to develop effective routes to enhance their brightness, especially in aqueous solutions. In this work, we reported a facile strategy to prepare highly luminescent AuxAg1-x nanocomposites (x: molar ratio of Au) by electrostatic-induced assembly of non-luminescent glutathione (GSH) stabilized silver NCs (GSH-Ag NCs) and weak orange-emitting GSH stabilized gold NCs (GSH-Au NCs) in aqueous solutions. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), UV-vis absorption spectroscopy and dynamic light scattering (DLS) shed light on the mechanism of PL enhancement. It was found that the positively charged gold nanoclusters and the negatively charged silver nanoclusters formed aggregates by electrostatic force, leading to a 40-fold fluorescence intensity enhancement compared with GSH-Au NCs. This was a novel method to strengthen the fluorescence of nanoclusters with such large enhancement in aqueous solutions. With the molar ratio of Au and Ag changing from 80:1 to 2:3, the emission maximum of the AuxAg1-x nanocomposites could be tuned from 590 to 548 nm. The electrostatic force of the Au0.50Ag0.50 nanocomposites enabled them to respond to pH. The Au0.50Ag0.50 nanocomposites were fluorescent turn-on and turn-off at pH 2.6 and pH 7.5, respectively. In this respect, they can be used as a fluorescent switch and be further used as a general recyclable pH probe in the range of 2.6-7.5. This work will inspire even better strategies to further improve the brightness of noble metal NCs.
关键词： nanocomposites,fluorescent switch,electrostatic force,silver nanoclusters,fluorescence enhancement,gold nanoclusters
更新于2025-11-14 15:23:50
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Dynamically Switching the Electronic and Electrostatic Properties of Indium Tin Oxide Electrodes with Photochromic Monolayers: Toward Photo-Switchable Optoelectronic Devices
摘要： The chemical modification of electrodes with organic materials is a common approach to tune the electronic and electrostatic landscape between interlayers in optoelectronic devices, thus facilitating charge injection at the electrode/semiconductor interfaces and improving their performance. The use of photochromic molecules for the surface modification allows dynamic control of the electronic and electrostatic properties of the electrode and thereby enables additional functionalities in such devices. Here, we show that the electronic properties of a transparent indium tin oxide (ITO) electrode are reversibly and dynamically modified by depositing organic photochromic switches (diarylethenes) in the form of self-assembled monolayers (SAMs). By combining a range of surface characterization and density functional theory calculations, we present a detailed picture of the SAM binding onto ITO, the packing density of molecules, their orientation, as well as the work function modification of the ITO surface due to the SAM deposition. Upon illumination with ultraviolet and green light, we observe a reversible shift of the frontier occupied levels by 0.7 eV, and concomitantly a reversible work function change of ca. 60 meV. Our results prove the viability of dynamic switching of the electronic properties of the electrode with external light stimuli upon modification with a monolayer of photochromic molecules, which could be used to fabricate ITO-based photo-switchable optoelectronic devices.
关键词： self-assembled monolayer,diarylethene,ITO,photochromic switch,interface electronic properties
更新于2025-11-14 14:32:36
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Investigation on formation process of metal atomic filament for metal sulfide atomic switch by electrical measurement
摘要： We have studied the formation process of the metal atomic filament for the metal sulfide atomic switches by the electrical measurement. The switching between ON and OFF states of the atomic switch is controlled by the application of the bias voltage for the atomic switches. The SET (OFF→ON) and RESET (ON→OFF) voltages were investigated for the atomic switch where the Ag2S or Cu2S layer was sandwiched between the Pt and Ag or Cu electrodes. The SET and RESET voltages of the Ag/Cu2S/Pt and Cu/Ag2S/Pt were close to those of the Ag/Ag2S/Pt atomic switch, and different from those of the Cu/Cu2S/Pt atomic switch. These results indicated that the dominant chemical species of the making and breaking part of the metal filament were Ag, and that the source of the metal filament was both the sulfide layer and the metal electrode.
关键词： Atom switch,I-V measurement,Ion migration
更新于2025-09-23 15:23:52
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Al <sup>3+</sup> -Morpholine-appended Anthracene Ensemble as a Dual Photonic Switch for H <sub/>2</sub> PO <sub/>4</sub><sup>?</sup> and CN <sup>?</sup> Ions and its Biological Applications
摘要： A highly selective Al3+-morpholine anthracene (1(cid:129)Al3+) chelate was designed as a novel ?uorescent photonic switch for H2PO4? and CN? ions. The in situ-generated Al3+ chelate could be used to detect H2PO4? ions only in the absence of CN? ions. In contrast, CN? ions effectively extruded Al3+ from the chelate, resulting in the regeneration of probe 1 with a concomitant revival of PET, resulting in a turn-off response. By exploiting the complexation- and decomplexation-aided off–on switching system through the sequential addition of Al3+ followed by H2PO4? or CN?, combinational photonic logic circuits, as well as image-guided ?uorogenic tracking, was demonstrated.
关键词： Aluminum,Photonic switch,Morpholino-anthracene,Image-guided ?uorogenic tracking,Combinational photonic logic circuit
更新于2025-09-23 15:23:52
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Optimizing the conductance switching performance in photoswitchable dimethyldihydropyrene/cyclophanediene single-molecule junctions
摘要： Designing molecular switches with high stability and performance is still a great challenge in the field of molecular electronics. For this aim, key factors influencing the charge transport properties of molecular devices require to be carefully addressed. Here, by using the nonequilibrium Green’s function method in combination with the density functional theory, effect of bridging manner (i.e., linkage sites) for dimethyldihydropyrene (DHP)/cyclophanediene (CPD) photoswitchable molecule sandwiched between two Au(111) electrodes has been theoretically investigated. The computational results show that the fully conjugated DHP is more conductive than the less conjugated CPD, manifesting an evident switching effect. It is also found that the ON/OFF switching performance of DHP/CPD is dramatically modulated by the bridging manner. Further analysis attributes the switching feature to the different alignments of conducting HOMO with the Fermi energy for DHP and CPD. And it also reveals that local bond contributions to the electron transmission pathway are closely related to both the conjugation characteristics and bridging manner of the core molecule. This work suggests that the bridging manner of core molecule in single-molecule junction plays an essential role in determining the switching performance and should be carefully addressed in future design of molecular switches.
关键词： Single-molecule switch,Density functional theory,Nonequilibrium Green’s function method
更新于2025-09-23 15:23:52
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Ruthenium(II) polypyridyl complex [Ru(phen)2dppz-idzo]2+ as a colorimetric molecular “light switch” and powerful stabilizer for the RNA triplex poly(U)·poly(A)*poly(U)
摘要： The interaction of [Ru(phen)2dppz-idzo]2+ (phen = 1,10-phenanthroline, dppz-idzo = dppz-imidazolone) with triplex RNA poly(U)?poly(A)*poly(U) was carried out by using spectroscopic and viscometric techniques in this work. Luminescent titrations suggest that [Ru(phen)2dppz-idzo]2+ shows better selectivity for poly(U)?poly(A)*poly(U) compared with poly(U)?poly(A) and poly(U), this complex exhibits a “light switch” effect with an emission enhancement factor of about 123 in the presence of poly(U)?poly(A)*poly(U). Significantly, this “light switch” behavior could even be observed by the naked eye under irradiation with UV light. To our knowledge, [Ru(bpy)2dppz-idzo]2+ is the first small molecule able to serve as a colorimetric molecular “light switch” for the triplex poly(U)?poly(A)*poly(U). Combined with the spectral and viscometric results as well as [Ru(phen)2dppz-idzo]2+ stabilizing the template duplex poly(U)?poly(A), we speculate that [Ru(phen)2dppz-idzo]2+ prefers to bind with the Hoogsteen base-paired strand (the third strand) of the triplex, thus the intercalating [Ru(phen)2dppz-idzo]2+ stabilizing the third strand is more marked in comparison with the Watson-Crick base-paired duplex of the triplex. The results obtained here may be useful for understanding the interaction of triplex RNA poly(U)?poly(A)*poly(U) with small molecule, particularly ruthenium(II) complexes.
关键词： Ru(II) complexes,Stabilization,Triplex RNA,Colorimetic molecular light switch
更新于2025-09-23 15:23:52