Rewritable Optical Recording Research Articles

Orchestrated Octuple C−H Activation: A Bottom‐Up Topology Engineering Approach toward Stimuli‐Responsive Double‐Heptagon‐Embedded Wavy Polycyclic Heteroaromatics

AbstractCuriosity‐driven innovations on the design and synthesis of nonplanar polycyclic aromatic/heteroaromatic compounds with new molecular topologies unfold exciting opportunities for harnessing their intriguing supramolecular properties and thereby the development of novel functional organic materials. This work presents such an innovative synthetic concept of a bottom‐up molecular topology engineering through a unique orchestrated octuple C−H activation reaction, toward the rapid synthesis of a novel class of double heptagon‐incorporated nitrogen‐doped laterally‐fused polycyclic compounds with rarely reported wavy structural configuration. The profound impact of the molecular wavy structures of these compounds on their properties is manifested by weak and tunable solid‐state intermolecular interactions controlling the electronic properties of the materials, leading to reversibly switchable fluorochromism in the solid state and thin films with mechanical force and solvent vapors as external stimuli, thereby indicating their potential applicability in rewritable fluorescent optical recording media, security papers, mechanosensors, volatile organic compound (VOC) sensors etc.

Orchestrated Octuple C-H Activation: A Bottom-Up Topology Engineering Approach toward Stimuli-Responsive Double-Heptagon-Embedded Wavy Polycyclic Heteroaromatics.

Curiosity-driven innovations on the design and synthesis of nonplanar polycyclic aromatic/heteroaromatic compounds with new molecular topologies unfold exciting opportunities for harnessing their intriguing supramolecular properties and thereby the development of novel functional organic materials. This work presents such an innovative synthetic concept of a bottom-up molecular topology engineering through a unique orchestrated octuple C-H activation reaction, toward the rapid synthesis of a novel class of double heptagon-incorporated nitrogen-doped laterally-fused polycyclic compounds with rarely reported wavy structural configuration. The profound impact of the molecular wavy structures of these compounds on their properties is manifested by weak and tunable solid-state intermolecular interactions controlling the electronic properties of the materials, leading to reversibly switchable fluorochromism in the solid state and thin films with mechanical force and solvent vapors as external stimuli, thereby indicating their potential applicability in rewritable fluorescent optical recording media, security papers, mechanosensors, volatile organic compound (VOC) sensors etc.

Solid-State Luminescence Stimulus-Responsive Property and Doped RTP Emission of Novel 7a,8,10,11-Tetrahydro-9H- pyrido[2',1':2,3][1,3]oxazino[6,5,4-ij]isoquinoline Derivative.

A novel 7a,8,10,11-tetrahydro-9H-pyrido[2',1':2,3][1,3]oxazino[6,5,4-ij]isoquinoline derivative (POIQ) is accidentally obtained from an isoquinoline derivative and iodine in dimethyl sulfoxide, which is demonstrated to undergo a mechanism of demethylation and thus intramolecular nucleophilic substitution. POIQ with twisted molecular conformation and loose stacking arrangement shows multifunctional optical properties including dual-state emission, mechanochromic, and solid-state acidochromic activities. Furthermore, an organic room temperature phosphorescence (RTP) doped system with green afterglow of 2 s is constructed using POIQ as the guest and easily available phenyl benzoate as the host, in which the host molecules assist in the transfer of the triplet excitons of the guest molecules. Rewritable optical recording media and information encryption are alsorealized based on multifunctional optical properties of this compound. This work provides inspiration for the development of N,O-containing fused-ring compounds with fluorescence/RTP properties.

Switching Monomer‐to‐Excimer Fluorescence by Noncovalent Interaction Competition Strategy

AbstractNoncovalent fluorescence switching materials with specific molecular packing motifs for desired performance are difficult to design accurately due to the complexity of intermolecular interactions. Herein, a noncovalent interaction competition strategy to design fluorescence‐switching materials by fine‐modulating hydrogen‐bond and π–π interactions is proposed. Hydrogen bonds are generated by nitrogen/oxygen‐containing units while π–π interactions are generated between polycyclic aromatic hydrocarbons. After these two interactions are balanced in strength, they attempt to induce the formation of respective molecule assemblies stably under controllable conditions. Through thermal stimulus produced by a laser, a reversible assembly transition with high‐contrast monomer‐to‐excimer fluorescence switching is achieved, which demonstrates promising applications in rewritable optical recording and time‐dependent anti‐counterfeiting. This strategy provides a crucial step toward the controllable switching of supramolecular assembly for information handling.

Phosphor SrZrO3:Sm3+ with fluorescence modulation and photochromic characteristics for erasable optical storage

At present, for inorganic photochromic materials, the single function limits their application level in the field of optical storage and anti-counterfeiting. Generally, the reversible modulation of photoluminescence is achieved through a photochromic process, thereby improving the ability of the photochromic material to store information. Here, we designed a Sm 3+ doped perovskite oxide (SrZrO 3 :Sm 3+ ) inorganic photochromic material. Combined with its red photoluminescence and photochromic properties, it can realize dual information storage and recognition functions. The fluorescence regulation function is realized by the doping of Sm 3+ , which is conducive to the application in the direction of optical switch. The mechanism of photoluminescence and photochromism was studied. Finally, a flexible film with SrZrO 3 :Sm 3+ material was fabricated to demonstrate rewritable optical recording and storage and reading of dual optical information.

Disparity in piezofluorochromism for twisted mono-carbazole-based AIEgens resulting from interchanging electron-rich substituents: effect of coplanarity on twisted π-conjugates

Newly established carbazole-based aggregation-induced emission-active fluorogens are recognized with piezo-fluorochromic features that vary with the effect of planarity. Suitable probe is demonstrated as a platform for rewritable optical recording.

Aggregation-Induced Emission-Active 1,4-Dihydropyridine-Based Dual-Phase Fluorescent Sensor with Multiple Functions.

A N-2-phenylethyl-substituted 1,4-dihydropyridine derivative (NDHP) containing 5,5-dimethylcyclohexane-1,3-dione and naphthylethylene was designed and synthesized. NDHP acts as a multifunctional fluorescent sensor in dual phases. The crystal structure analysis confirms that the NDHP molecules have highly twisted conformations. The twisted conformation results in aggregation-induced emission properties and solid-state emission, by restricting the intramolecular free rotation in the aggregated or solid state. In the solid state, NDHP exhibits reversible mechanochromic properties as a result of the transition between the amorphous and crystalline states. NDHP also exhibits a rare phenomenon of acid-fumed solid-state emission enhancement owing to the change in packing mode from a zigzag arrangement to J-aggregation. The solid-state stimuli-responsive fluorescence switching is applied to realize a rewritable optical recording media and a multiple output combinational logic system. In solution, NDHP shows a selective fluorescence response for environmentally harmful Hg2+ , with a limit of detection of 2.7 nm. This results from the "turn-on" responsive behavior owing to the Hg2+ -triggered aggregation of the NDHP molecules. NDHP is also used in the imaging of intracellular Hg2+ in HeLa cells. These findings provide a feasible and attractive route for developing multifunctional fluorescent sensors for use in dual phases.

Near-infrared nano-imaging spectroscopy using a phase change mask method.

We propose a technique that employs an optical mask layer of a phase-change material, e.g. GeSbTe, which is widely used for rewritable optical recording media, for realizing highly sensitive near-field imaging spectroscopy of single semiconductor quantum constituents at optical telecommunication wavelengths. Semiconductor quantum dots (QDs) have shown great promise as efficient single photon emitters and entangled photon sources, making them attractive for quantum communication and quantum information processing applications. Self-assembled InAs QDs on InP substrate are promising as near-infrared (NIR) single photon and entangled photon emitters. In order to clarify and control the optical properties of QDs for telecommunication devices, photoluminescence (PL) spectroscopy studies of single QDs with high spatial resolution at NIR wavelength is necessary. The most useful technique to attain this is by using near-field scanning optical miscroscopy (NSOM). However, NSOM has a lower PL collection efficiency at NIR wavelength than at visible wavelength [1]. This problem inhibits NIR-PL spectroscopy based on NSOM to be practically realized. Therefore, we deveopled a method to overcome the low NIR-PL spectroscopy by using a nanoaperture on an optical mask layer of phase-change material (PCM) [2]. Due to the large optical contrast between the crystalline and amorphous phases of the phase-change material at visible wavelengths and its high transparency at NIR wavelengths, an amorphous nanoaperture can be used to realize imaging spectroscopy with a high spatial resolution and a high collection efficiency (Fig.1). We demonstrate the effectiveness of the proposed method by performing numerical simulations and PL measurements of InAs/InP QDs.jmicro;63/suppl_1/i10-a/DFU089F1F1DFU089F1Fig. 1.Schematic illustration of phase change mask method PCM mask effect has also the potential to be applied in emission energy control of QDs. One of the main problems for realization of quantum communication applications is precise control of energy in QDs. We proposed a new approach to control the emission energy of QDs by applying a local strain using volume expansion of phase-change material [3-5]. We calculated the stress and energy shift distribution induced by volume expansion using finite element method. Simulation result reveals that redshift is obtained beneath the flat part of amorphous mark, while blueshift is obtained beneath the edge region of amorphous mark. Simulation result is accompanied by two experimental studies; two-dimensional PL intensity mapping of InAs/InP QD sample deposited by a layer of PCM, and an analysis on the relationship between PL intensity ratio and energy shift were performed.

A luminescent liquid crystal with multistimuli tunable emission colors based on different molecular packing structures

A novel luminescent liquid crystal, (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(4-(dodecyloxy)phenyl)acrylonitrile) (PDPA), is reported, which shows green, yellow and orange colors depending on the self-assembled structure. The luminescence of PDPA can vary between those three different colors invoked by mechanical shearing and thermal annealing. Moreover, an excellent liquid crystal phase transition of PDPA is observed using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) analysis. Finally, a prototype device is fabricated that demonstrates rewritable fluorescence optical recording with multistimuli luminescence tuning.

Near-infrared nano-spectroscopy of semiconductor quantum dots using a phase-change mask layer

We propose a technique that uses an optical mask layer of a phase-change material (PCM), which is used for rewritable optical recording media, to achieve highly sensitive near-field imaging spectroscopy of single semiconductor quantum constituents at optical telecommunication wavelengths. An amorphous nanoaperture allows imaging spectroscopy with a high spatial resolution and high collection efficiency. This is due to the large optical contrast between the crystalline and amorphous phases of the phase-change material at visible wavelengths and its high transparency at near-infrared wavelengths. We demonstrate the effectiveness of the method by numerical simulations and photoluminescence measurements of InAs/InP quantum dots.

Synthesis and Properties of a New Diarylethene Derivative

A novel photochromic diarylethene, 1-(2-ethyl-3-benzothiophenyl)-2-(2-methyl-5- (3-methoxyphenyl)-3-thienyl)perfluorocyclopentene (1o) was synthesized, and its photochromic and fluorescent properties were investigated. This compound exhibited reversible photochromism, changing from colorless to purple after irradiation with UV light both in solution and in PMMA amorphous film. Also, it exhibited good fluorescence switching in solution. Fatigue-resistant experiments showed that this compound had attractive properties for rewritable optical recording or photoswitches.

Multistimuli Two-Color Luminescence Switching via Different Slip-Stacking of Highly Fluorescent Molecular Sheets

Color tuning and switching of the solid-state luminescence of organic materials are attractive subjects for both the fundamental research and practical applications such as optical recording. We report herein cyanostilbene-based highly luminescent molecular sheets which exhibit two-color fluorescence switching in response to pressure, temperature, and solvent vapor. The origin for the multistimuli luminescence switching is the two-directional shear-sliding capability of molecular sheets, which are formed via intermolecular multiple C-H···N and C-H···O hydrogen bonds. The resulting two distinctive crystal phases are promoted by different modes of local dipole coupling, which cause a substantial alternation of π-π overlap. These changes can be directly correlated with the subsequent intermolecular excitonic and excimeric coupling in both phases, as demonstrated by an in-depth theory-assisted spectroscopic and structural study. Finally, we have prepared a first device demonstrator for rewritable fluorescent optical recording media which showed multistimuli luminescence tuning with fast response. Our multistimuli responsive system is unique in terms of the slip-stacking of molecular sheets and thus provides a novel concept of rewritable fluorescent optical recording media.

Influence of silver concentration in Agx(Sb0.33S0.67)100−x thin amorphous films on photoinduced crystallization

One of the recent applications of thin chalcogenide films is in rewritable optical data recording. This technology is based on reversible phase transition between crystalline and amorphous state. Currently, the primary materials for rewritable optical are Ge–Sb–Te and Ag–In–Sb–Te alloys, but materials research still continues due to the need for increased storage capacity and data recording rates. (Ag)–Sb–S thin films were prepared by thermal evaporation of Sb33S67 bulk and optically induced diffusion and dissolution of thermally evaporated Ag films. Prepared samples were characterized by electron microprobe (SEM-EDX), differential scanning calorimetry (DSC) and by UV–Vis–NIR and Raman spectroscopy. The phase-change recording processes in (Ag)–Sb–S films were carried out by photocrystallization experiments done by Ar+ ion laser. The laser exposed dots were studied by scanning electron microscopy (SEM) and transmission optical microscopy. Micro X-ray diffraction (μ-XRD) was used for the exposed dots crystallinity study. Photocrystallization kinetic curves (showing the dependence of optical transmission on laser exposure time) were also established. Crystallization mechanism of Agx(Sb0.33S0.67)100−x samples was discussed.

On RF magnetron-sputtering preparation of Ag–Sb–S thin films

One important application area of chalcogenide materials is rewritable optical data storage. This technology is based on a reversible phase transition between the crystalline and the amorphous state and vice versa. Currently dominant materials for rewritable optical recording are Ge–Sb–Te and Ag–In–Sb–Te alloys. Material research still continues due to the need for increasing storage capacity and data rates. Polycrystalline bulks of AgSbS 2 were prepared by melt-quench technique. Composition and homogeneity of these bulks were checked by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), crystallinity was studied by X-ray diffraction (XRD). Targets for RF magnetron sputtering were prepared from pulverized bulks by hot-pressing technique. Targets were characterized the same way as bulks. Thin Ag–Sb–S films were prepared by RF magnetron sputtering as potential candidates for rewritable optical data storage films. Composition and homogeneity of prepared thin films were characterized by SEM-EDX, Rutherford Back Scattering (RBS) and Elastic Recoil Detection Analysis (ERDA); character (amorphous/crystalline) was traced by XRD. Optical properties (spectral dependence of refractive index) were evaluated on the basis of UV–Vis–NIR spectroscopy and variable angle spectral ellipsometry (VASE). Crystallization abilities were studied by the measurement of thermal dependence of the prepared thin films optical transmission.

Mechanism of Properties of Noble ZnS–SiO2 Protection Layer for Phase Change Optical Disk Media

A ZnS–SiO2 composite dielectric is widely used in the optical stack designs of rewritable optical recording media as an index-matching medium and as a protection layer for the high-index chalcogenide (compound with sixth group element of S, Se, Te) phase change material used in these media. The addition of Si and O to ZnS is primarily intended to stabilize against crystalline grain growth of ZnS with high numbers of direct overwriting cycles. In this study, we carry out infrared (IR) spectroscopy to clarify the role of Si in this stabilization process. IR spectroscopy is performed on sputter as-deposited and annealed ZnS–SiO2 dielectric protection layers. We find that Si exists not in the SiO2 oxide phase but as [SiS4-nOn] tetrahedrons. Moreover, zinc and sulfur do not exist as ZnS, but in highly chemically disordered ZnS:O crystallites. The highly directional and rigid covalent bonds in the [SiS4-nOn] tetrahedrons are key to establishing thermal stability against the coalescence of ZnS. The importance of the Si–S bond also extends into a more thorough understanding of the low thermal conductivity of the ZnS–SiO2 material. The consideration of elastic implications allows us to predict an average phonon velocity less than 50% compared to that in SiO2. With this, we predict a thermal conductivity of 0.0067 W cm-1 K-1 for this material, which is in complete agreement with measured values.

Syntheses and optical properties of hybrid materials containing azobenzene groups via sol–gel process for reversible optical storage

AbstractWe focused on the synthesis and optical properties of new organic–inorganic hybrid materials containing azobenzene groups for rewritable optical recording media. Hybrid material (SGUR19‐n's) design has the structure of azobenzene group with urethane bonds in the silica network. The structures of the synthesized monomers and precursors were confirmed by FTIR and 1H NMR spectrophotometer. Also, we reported on the effects of the direction of the polarized beam, the intensity of the induced beam, and the structures of SGUR19‐n's materials on the diffraction efficiency of SGUR19‐n's films. It was revealed that SGUR19‐n's films prepared by the sol–gel process have adequate writing–erasing–rewriting properties when used as a reversible optical storage material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4811–4818, 2006

Ag-Sb-S Thin Films Prepared by RF Magnetron Sputtering and Their Properties

AbstractOne of the recent applications of thin chalcogenide films is rewritable optical data recording. This technology is based on reversible phase transition between crystalline and amorphous state and vice versa. Dominant materials for rewritable optical recording are Ge Sb Te and Ag In Sb Te alloys. Material research still continues due to need of increasing storage capacity and data rates. Thin Ag Sb S films were prepared by RF magnetron sputtering as potential candidates for rewritable optical data storage films.There were prepared polycrystalline bulks of AgSbS2. Composition and homogeneity of these bulks were checked by scanning electron microscopy with energy dispersive analysis (SEM EDX) structure and bonding relations were studied by Raman spectroscopy and × ray diffraction (XRD).Targets for RF magnetron sputtering were prepared from pulverized bulks by hot pressing technique. Targets were characterized the same way as bulks.Composition and homogeneity of prepared thin films were characterized by SEM EDX, character (amorphous/crystalline) was studied by XRD. Optical properties (spectral dependence of refractive index) were evaluated on basis of UV Vis NIR spectroscopy and variable angle spectral ellipsometry (VASE).Crystallization abilities were traced by thermal dependence of optical transmission of prepared thin films.

Rewritable phase-change optical recording in Ge2Sb2Te5 films induced by picosecond laser pulses

The phase transformation dynamics induced in Ge2Sb2Te5 films by picosecond laser pulses were studied using real-time reflectivity measurements with subnanosecond resolution. Evidence was found that the thermal diffusivity of the substrate plays a crucial role in determining the ability of the films to crystallize and amorphize. A film/substrate configuration with optimized heat flow conditions for ultrafast phase cycling with picosecond laser pulses was designed and produced. In this system, we achieved reversible phase transformations with large optical contrast (>20%) using single laser pulses with a duration of 30 ps within well-defined fluence windows. The amorphization (writing) process is completed within less than 1 ns, whereas crystallization (erasing) needs approximately 13 ns to be completed.

Multispeed rewritable optical-recording method with an initialization-free phase-change disk.

A new method of multispeed rewritable optical recording is presented. An initialization-free phase-change optical disk is proposed as a candidate for multispeed rewritable optical recording. The simulated results of the initialization-free disk at different linear velocities show that the cooling rate increases from approximately 18.69% to 37.96%. A model that combines the crystallization acceleration effect due to the additional layers and the rapid cooling rate due to the initialization-free disk structure is proposed as the physical mechanism of the multispeed recording method with an initialization-free disk. The dynamic optical-recording properties of the initialization-free DVD-RAM disk at different recording speeds shows that the initialization-free phase-change optical-recording disk is compatible with a broad range of recording speeds from 3.49 to 12.21 m/s.

Nanoscale silver oxide: A rewritable optical recording medium

Measurements are presented that demonstrate the possibility of rewritable optical recording on nanoscale silver oxide films. Three different sputtering techniques are studied, seeking an optimum and requisite film structure. Estimates of the energy requirements of the recording process are made for comparison with conventional thermal-based recording mechanisms. The recording process appears purely photonic and does not require optical heating to bring about the reversible physical changes that constitute the presence or absence of data. Although more complex than conventional optical recording techniques in that it requires the use of different wavelengths for the write and readout processes, and the presence or absence of data is signified by the emission or lack of radiation at yet a third wavelength, the advantages of its nonthermal nature should outweigh this additional complexity.