Multifunctional Switch Research Articles

Dual-mode multifunctional switchable polarization conversion metasurface based on VO2, Si, and graphene in THz region

In this paper, a dual-mode multifunctional switching terahertz metasurface polarization converter based on vanadium dioxide (VO2), photosensitive semiconductor silicon (Si) and graphene is designed. The converter can switch between transmission and reflection modes by adjusting the state of VO2. In the insulating state of VO2, the converter operates in transmission mode and performs linear-to-linear polarization conversion (LTL-PC) with a relative bandwidth of 166.0 %. Conversely, when VO2 is in the metallic state, the converter works in reflection mode. By adjusting the pump light intensity to modulate the state of Si, linear-to-circular polarization conversion (LTC-PC) and LTL-PC function can be achieved. Moreover, the Fermi level of graphene can be adjusted via electrostatic gate to further enhance the working bandwidth of the converter. In reflection mode, the relative bandwidths for LTL-PC, linear to left-circularly and right-circularly polarization conversion are 98.1 %, 87.0 % and 4.0 %, respectively. The metasurface polarization converter proposed in this paper has a variety of functions and a variety of control modes, and has the advantages of high polarization conversion rate and wide operating band, showing great potential in switching and tunable wideband terahertz converters and related applications.

Reversible near-infrared light-induced spin-state transition on layered Co-MOF

The spin-crossover (SCO) can be triggered by light or pressure changes, making it a promising system for multifunctional switches and memory devices at the molecular level. In this work, we have reported a NIR-responsive spin state switching system via doping layered Co(pyridine)2Ni(CN)4 (Co-MOF) into the stable polyvinylidene fluoride matrix for the first time. The layered Co-MOF has shown a rapid response of color change between gray-white and blue, which could be attributed to the SCO behavior triggered by NIR illumination. The new system ensures the soft network structures of the matrix to facilitate the homogeneous distribution of layered Co-MOF, both of which contribute to outstanding reversibility performance, including fast response, coloration in a short period, and decoloration in the ambient environment. This work provides a viable strategy to construct a new NIR-triggered SCO system for molecular switches and spintronic devices.

Multi-azobenzene moieties on rigid cyclotriphosphazene core: Synthesis, structural characterization, electrochemistry, and photoisomerization study

Multi-azobenzene derivatives capable of showing multi-stimuli responsive material can exhibit superior performance in biomedicine, the dye industry, cosmetics, and photonics. Here, a nucleophilic substitution reaction was employed to assemble two (Az2CPZ(biph)2) or four (Az4CPZ(biph)) or six (Az6CPZ) units of azobenzene moieties on the cyclotriphosphazene (CPZ) core. We have observed that the color of each compound varied by changing the number of azobenzene moieties on the CPZ core. These compounds were characterized by elemental analysis, 1H, 13C{1H}, and 31P{1H} NMR techniques. Single crystal X-ray diffraction techniques ensure the trans conformation in the azobenzene for Az2CPZ(biph)2 and Az4CPZ(biph). Electronic spectroscopy forAz2CPZ(biph)2,Az4CPZ(biph), andAz6CPZhaving π-π* transition around 325 nm show a hypsochromic shift with ∼25 nm compared to the parent molecule, 4-hydroxyazobenzene AzH. As a result of the electronic spectroscopy, the cis isomer formation enhanced upon increasing the concentration ofAz2CPZ(biph)2/Az4CPZ(biph)/Az6CPZ in DCM/DMF. The photoisomerization study confirms that these molecules having at least one azo moiety can switch from trans to cis conformation upon exposure to 365 nm light. Interestingly, the thin-layer chromatography (TLC) corroborated the switch of trans to cis conformation occurs at room temperature in a solution state even without UV irradiation. The proton NMR integration providesthe generationofthe cis-azobenzene moiety is about 12–20 % inAz2CPZ(biph)2upon exposure to 365 nm light for 15 to 60 mins. Additionally, TLC verifies the generation of multiple isomers that confirm multi-functional switch behavior when the sample with UV exposure time increases. Owing to these molecules undergoing a isomerization process (trans-azo⇌cis-azo) even without UV, their fluorescence gets quenched in the solution state. Cyclic voltammetry confirms the quasi-reversible type redox behavior of all compounds in dry dichloromethane. We believe the results presented in this work will be significant for dye and biomedical applications.

Bistable switch molecule DPACdCl4 showing four physical channels and high phase transition temperature

Multiple switchable physical channels within one material or device, encompassing optical, electrical, thermal, and mechanical pathways, can enable multifunctionality in mechanical-thermal-opto-electronic applications. Achieving integrated encryption and enhanced performance in storage and sensing presents a formidable challenge in the synthesis and functionality of new materials. In an effort to overcome the complexities associated with these multiple physical functions, this study investigates the large-size crystal of DPACdCl4 (DPA=diisopropylammonium), revealing significant features in rare multi-channel switches. This compound demonstrates the ability to switch between "OFF/0" and "ON/1" states in the mechanical-thermal-opto-electronic channels. Consequently, DPACdCl4 possesses four switchable physical channels, characterized by a higher phase transition temperature of 440.7 K and a competitive piezoelectric coefficient of 46 pC/N. Furthermore, solid-state NMR analysis indicates that thermally activated molecular vibrations significantly contribute to its multifunctional switching capabilities.

Bidirectional photomagnetism, exciplex fluorescence and dielectric anomalies in a spin crossover Hofmann-type coordination polymer.

Stepped spin crossover (SCO) complexes with three or more spin states have promising applications in high-order data storage, multi-switches and multi-sensors. Further synergy with other functionalities, such as luminescence and dielectric properties, will provide a good chance to develop novel multifunctional SCO materials. Here, a bent pillar ligand and luminescent pyrene guest are integrated into a three-dimensional (3D) Hofmann-type metal-organic framework (MOF) [Fe(dpoda){Au(CN)2}2]·pyrene (dpoda = 2,5-di-(pyridyl)-1,3,4-oxadiazole). The magnetic data show an incomplete and two-step SCO behavior with the sequence of 1 ↔ 1/2 ↔ 1/4. The rare bi-directional light-induced excited spin-state trapping (LIESST) effect and light-induced stepped thermal relaxation after LIESST are observed. The pyrene guests interact with dpoda ligands via offset face-to-face π⋯π interactions to form intermolecular exciplex emissions. The competition between thermal quenching and stepped SCO properties results in a complicated and stepped exciplex fluorescence. Moreover, the stepped dielectric property with higher dielectric permittivity at lower temperature may be related to the more frustrated octahedral distortion parameters in the intermediate spin states. Hence, a 3D Hofmann-type MOF with bent pillar ligands and fluorescent guests illustrates an effective way for the development of multifunctional switching materials.

A multifunctional switching bidirectional optical absorber based on a titanium nitride metamaterial.

In this paper, a novel type of tunable ultra-wide band and double-narrow band artificial electromagnetic absorption device is studied. This work uses a titanium nitride-titanium-tungsten (TiN-Ti-W) composite ring array, a TiN reflector layer, and a silver-titanium dioxide-silver (Ag-TiO2-Ag) three layer composite structure to prepare the absorption layer. The simulation results illustrate that the absorption rate can reach 96.6% when the absorption wavelength is 300-2800 nm. When the light source is backward incidence, ultra-narrow band absorption can occur at specific wavelengths of 465 nm and 932 nm. This proves that the absorber is in good agreement with the impedance matching theory. The research results of this work will provide a theoretical basis for the design and application of solar thermal energy conversion.

Genetic algorithm based terahertz multifunctional reconfigurable Dirac semi-metallic coded metasurface

Digitally encoded hypersurfaces show great potential in the field of electromagne-tic wave modulation. Currently, digitally encoded hypersurfaces in the terahertz band are mainly classified into two types: structure-encoded and controllable material-encoded. Once a structure-encoded hypersurface is fabricated, its function is fixed, which makes it difficult to adapt to changing application requirements. In contrast, the controllable material-encoded hypersurfaces can achieve dynamic regulation and multifunctional switching of terahertz beams by changing the external excitation, which shows good reconfigurability. To address this challenge, a Dirac semimetal-based encoded hypersurface is proposed in this paper. The Fermi energy level of the Dirac semimetal is varied by changing the bias voltage, which in turn dynamically adjusts its relative permittivity to obtain the coded unit. Besides, the traditional gradient-phase method encodes arrays by periodically arranging the cell structure, but there are limitations in the flexibility and accuracy of beam modulation. In order to break through these limitations, this paper employs a genetic algorithm for the inverse design of hypersurface coding arrays, which effectively improves the initiative and flexibility of beam modulation. In this paper, a three-layer terahertz-encoded hypersurface unit with a “back” structure composed of Dirac semimetallic materials is firstly designed, and the Dirac semimetallic dielectric constant is dynamically adjusted by using an applied bias voltage, so that the hypersurface unit is at 1.95 THz when the Fermi energy levels are 0.01 eV, 0.05 eV, 0.09 eV, and 0.55 eV can achieve 2bit coding. The results show that, for beam configuration, single-beam and multi-beam (two-beam to five-beam) modulation can be achieved at 1.95 THz within 40° pitch angle and 360° azimuth angle; for vortex beam generation, single-vortex beams with ±1 and ±2 topological charges can be generated, with mode purity exceeding 60%, and single-vortex, double-vortex and triple-vortex beams in pitch angle and 360° azimuth angle can be realised with the vortex-phase convolution. In terms of RCS reduction, in the frequency range of 1.72–2.51 THz, the hypersurface is able to achieve more than 10 dB of RCS reduction, especially in the frequency range of 1.82 THz, the maximum reduction value is up to 27.5 dB. achieves the diversity of functions, but also has a high degree of reconfigurability to meet the needs of complex application scenarios.

The functional switching on the operating modes of a piezoelectric semiconductor bipolar junction transistor via mechanical loadings

A nonlinear model was developed on piezoelectric bipolar junction transistors (PS-BJTs) subjected to mechanical loadings by disregarding the assumption of low injection and the approximation of depletion layer. It was found that a PS-BJT subjected to different mechanical loadings can exhibit distinct carrier flow directions, for example, a remarkable transition for an n+pn-type PS-BJT from a transistor unit with amplification capability to two parallel connected PN junctions by applying a pair of lateral tensile or compressive stresses at the emitter and collector interfaces. Further in-depth analysis revealed that shielding effect produced by base region carriers greatly varies according to different loading mode, which leads to changing degrees of mechanical reconstruction on emitter junction barrier. Consequently, an artificial electron pathway (AEP) is formed at the emitter junction by a specific loading configuration. It is just due to the form change of AEP to produce distinct carrier flow directions, which can realize multifunctional switching of electronic devices. In addition, we also found an interesting phenomenon that an AEP can be directly constructed to penetrate the emitter junction by applying mechanical loadings in the longitudinal direction such that electrons in emitter region can travel across the emitter interface directly to the collector region without regulated by the base current. Under that situation, the PS-BJT resembles a parallel combination of a PN junction and an NN junction. This research provides novel insights into the mechanical modulation of piezoelectric electronic devices and the design of novel logic circuits.

Homochiral Chemistry Strategy to Trigger Second-Harmonic Generation and Dual Dielectric Switches.

Switchable materials have attracted enormous interest due to their promising applications in important fields such as sensing, electronic components, and information storage. Nevertheless, obtaining multifunctional switching materials is still a problem worth investigating. Herein, by incorporating (Rac-, L-, D-2-amino-1-propanol) as the templating cation, we have obtained (Rac-, L-, D-HTMPA)CdCl3 (HTMPA = 1-hydroxy-N, N, N-trimethyl-2-propanaminium). We have adopted a chiral chemistry strategy that causes (Rac-HTMPA)CdCl3 in the central symmetric space to crystallize in the chiral space group. Based on the modulation of the homochiral strategy, (L-, D-HTMPA)CdCl3 shows a dual phasic transition at 269 and 326 K and a switchable second-harmonic generation response. In addition, (L-, D-HTMPA)CdCl3 is chiral switchable material to exhibit stable dual dielectric and second-harmonic generation (SHG) switches. This work provides an approach to exploring multifunctional chiral switchable materials.

A quintuple plasmon-induced transparency multifunction switch based on the polarization-sensitive graphene-based metamaterial

A monolayer metamaterial consisting of a rectangle graphene strip and four L-shaped graphene blocks was proposed to achieve a quintuple plasmon-induced transparency (quintuple-PIT). The numerical simulation results based on the finite difference time domain method agree well with the calculated results of the coupled mode theory. By modulating the Fermi energy level of graphene, an octuple-frequency asynchronous switch and a sextuple-frequency synchronous switch are designed and studied, which have excellent amplitude modulation degree (up to 97.7%), extinction ratio (up to 16.41 dB), insertion loss (low to 5.4%), and dephasing time(low to 3.86 ps). Furthermore, the results show that the proposed metamaterials has polarization-sensitive characteristics due to their non-central symmetry. Further research shows that the group index is as high as 604 which has a good slow light effect and can be used for optical storage. Hence, the quintuple-PIT proposed structure in this paper has good application value in the expansion of multi-function optical switches and the research of high-quality optical memory.

THE STATUS OF E-LEARNING IN THE 4.0 EDUCATION ERA (DESCRIPTIVE STUDY OF INFORMATIC ENGINEERING STUDENTS

The development of technology and revolution 4.0 is challenging in the education sector. The era of education has adjusted to the 4.0 revolution era, where the integration of digital technology is the main thing in the implementation of education. One way to be done is to take advantage of digital technology through e-learning. This study aims to see the position of e-learning based on the perspective of students or students in the Informatics Engineering department. This study used a quantitative approach with a descriptive study model conducted at the Informatics Engineering Department, Faculty of Engineering, State University of Gorontalo. Respondents were 87 students majoring in Informatics Engineering. The research instrument used questionnaires and interviews. Data analysis using descriptive statistics. The indicators related to the position of e-learning assessed are (1) student perceptions regarding the use of e-learning in learning and (2) the position of e-learning in the education era 4.0 based on student perceptions. The study's results found: (1) Learning by utilizing e-learning to support learning can run both theoretical and practical material optimally according to student perceptions. (2) The position of e-learning is essential in the era of education 4.0. not only as a system but a multifunctional switch to become a container and learning media. (3) Most students choose the game-based e-learning model of their interest in the learning process using e-learning

Dynamic molecular switches with hysteretic negative differential conductance emulating synaptic behaviour.

To realize molecular-scale electrical operations beyond the von Neumann bottleneck, new types of multifunctional switches are needed that mimic self-learning or neuromorphic computing by dynamically toggling between multiple operations that depend on their past. Here, we report a molecule that switches from high to low conductance states with massive negative memristive behaviour that depends on the drive speed and number of past switching events, with all the measurements fully modelled using atomistic and analytical models. This dynamic molecular switch emulates synaptic behavior and Pavlovian learning, all within a 2.4-nm-thick layer that is three orders of magnitude thinner than a neuronal synapse. The dynamic molecular switch provides all the fundamental logic gates necessary for deep learning because of its time-domain and voltage-dependent plasticity. The synapse-mimicking multifunctional dynamic molecular switch represents an adaptable molecular-scale hardware operable in solid-state devices, and opens a pathway to simplify dynamic complex electrical operations encoded within a single ultracompact component.

Gap switching in metal-organic coordination chains

We predict two switchable one-dimensional (1D) spin-polarized semiconductors based on metal-organic coordination chains constructed out of Fe, V, and zwitterionic quinone (ZQ) molecules using first-principle density functional theoretical analysis. The Fe-ZQ coordination chain can be converted from a semiconductor to a half-metal when oxidized by chlorine (Cl). Upon chlorination, the magnetic moment of the Fe-ZQ is increased from 4 μB to 5 μB, per iron atom. In addition, the bimetallic (Fe-ZQ-V-ZQ) ferromagnetic semiconducting coordination chain with a very small energy gap of only 90 meV can be converted to an antiferromagnetic semiconductor with a large gap of more than 1 eV when oxidized by chlorine. Its magnetic moment is found to be 8 μB per heterobimetallic unit (Fe and V) after chlorination, and 7 μB without chlorine. These unique properties, namely a switchable or reversible electronic and magnetic characteristics with a transition between different semiconducting states, make these coordination chains to be highly promising candidates for specific applications as multi-functional switch in nanoelectronics and spintronics.

Chiral control of spin-crossover dynamics in Fe(II) complexes.

Iron-based spin-crossover complexes hold tremendous promise as multifunctional switches in molecular devices. However, real-world technological applications require the excited high-spin state to be kinetically stable-a feature that has been achieved only at cryogenic temperatures. Here we demonstrate high-spin-state trapping by controlling the chiral configuration of the prototypical iron(II)tris(4,4'-dimethyl-2,2'-bipyridine) in solution, associated for stereocontrol with the enantiopure Δ- or Λ-enantiomer of tris(3,4,5,6-tetrachlorobenzene-1,2-diolato-κ2O1,O2)phosphorus(V) (P(O2C6Cl4)3- or TRISPHAT) anions. We characterize the high-spin-state relaxation using broadband ultrafast circular dichroism spectroscopy in the deep ultraviolet in combination with transient absorption and anisotropy measurements. We find that the high-spin-state decay is accompanied by ultrafast changes of its optical activity, reflecting the coupling to a symmetry-breaking torsional twisting mode, contrary to the commonly assumed picture. The diastereoselective ion pairing suppresses the vibrational population of the identified reaction coordinate, thereby achieving a fourfold increase of the high-spin-state lifetime. More generally, our results motivate the synthetic control of the torsional modes of iron(II) complexes as a complementary route to manipulate their spin-crossover dynamics.

Multifunctional Switch Based on Spin-Labeled Gold Nanoparticles.

The fabrication of multifunctional switches is a fundamental step in the development of nanometer-scale molecular spintronic devices. The anchoring of active organic radicals on gold nanoparticles (AuNPs) surface is little studied and the realization of AuNPs-based switches remains extremely challenging. We report the first demonstration of a surface molecular switch based on AuNPs decorated with persistent perchlorotriphenylmethyl (PTM) radicals. The redox properties of PTM are exploited to fabricate electrochemical switches with optical and magnetic responses, showing high stability and reversibility. Electronic interaction between the radicals and the gold surface is investigated by UV-vis, showing a very broad absorption band in the near-infrared (NIR) region, which becomes more intense when PTMs are reduced to anionic phase. By using multiple experimental techniques, we demonstrate that this interaction is likely favored by the preferentially flat orientation of PTM ligands on the metallic NP surface, as confirmed by first-principles simulations.

Metal ion modulation triggers dielectric double switching and green fluorescence in A2MX4-type compounds.

Multifunctional switching materials show great potential for applications in sensors, smart switches, and other fields due to their ability to integrate different physical channels in one single device. However, multifunctional responsive materials with multiple switching and luminescence properties have rarely been reported. Here, we report three organic-inorganic hybrids: [TMAA]2[CoCl4] (compound 1), [TMAA]2[CdBr4] (compound 2) and [TMAA]2[MnCl4] (compound 3). Compound 1 and compound 2 undergo two reversible phase transitions at high temperature (328.95/359.25 K and 350.45/393.15 K, respectively). Since the inorganic skeleton has a strong influence on the luminescence properties of such structured substances, Cd and Co were replaced with Mn, after which compound 3 was obtained as expected. The above strategy triggered bright green luminescence with a quantum yield of 35.19%, and significantly increased the phase transition temperature of compound 3 to above 400 K. The above results show that the regulation of the inorganic skeleton provides a new strategy for researchers to develop dual phase change/luminous materials.

High temperature hybrid perovskite multifunctional switching materials constructed through precise molecular design

Precise molecular design to construct a multifunctional hybrid perovskite switching material, [(R)-N-fluoroethyl-3-quinuclidinol]PbBr3, with a high Tp of 498 K.

Multi-functional switch effect in interlocking molecular rotators-on-graphene systems using electric fields

We investigate the molecular gears of interlocking rotating 1,2,3,4,5,6-benzenehexacarbonitrile molecules on a graphene nanoribbon. Interestingly, the double-induced switching effect has been demonstrated in our proposed system of molecular motor.

Multi-functional hybrid perovskites with triple-channel switches and optical properties

Triple-channel (dielectric/SHG/PL) switches with a one-dimensional perovskite structure are successfully obtained through the halogen substitution strategy. This work might inspire the further exploration of multi-functional switching materials.

Actively logical modulation of MEMS-based terahertz metamaterial

The integration of micro-electro-mechanical system (MEMS) with metamaterial has provided a novel route to achieve programmability via its reconfigurable capabilities. Here, we propose and demonstrate a MEMS-based metadevice by using switchable winding-shaped cantilever metamaterial (WCM) for active logical modulation. WCM can be actuated by external driving voltage, and the logical modulation bit is performed by releasing MEMS cantilevers to represent “on” and “off” states. While the underneath substrate surface of a MEMS-based metadevice is rough after releasing the cantilevers, the metadevice is allowed to operate on the reconfigurable switching state and avoid the snapping down of the device when the system is overloaded. Such a reconfigurable and programmable MEMS-based metadevice exhibits multifunctional characteristics to simultaneously perform the logic operations of “OR” and “AND” gates. By exploiting the tuning mechanism of the MEMS-based metadevice, the arbitrary metamaterial configuration can be implanted into WCM. This opens a wide avenue to further enlarge the operating frequency range and applications in optoelectronic fields. These unique results provide various possibilities in multifunctional switching, active logical modulating, and optical computing applications.