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Integration of atomically thin nonlinear optical (NLO) devices demands an out-of-plane (OP) emission dipole of second harmonic generation (SHG) to enhance the spontaneous emission for nanophotonics. However, the research on van der Waals (vdWs) materials with an OP emission dipole of SHG is still in its infancy. Here, by coupling back focal plane (BFP) imaging with numerical simulations and density functional theory (DFT) calculations, we demonstrate that vdWs Janus Nb 3 SeI 7 , ranging from bulk to the monolayer limit, exhibits a dominant OP emission dipole of SHG owing to the breaking of the OP symmetry. Explicitly, even-layered Nb 3 SeI 7 with C 6v symmetry is predicted to exhibit a pure OP emission dipole attributed to the only second-order susceptibility coefficient χ zxx . Meanwhile, although odd-layered Nb 3 SeI 7 with C 3v symmetry has both OP and IP dipole components (χ zxx and χ yyy ), the value of χ zxx is 1 order of magnitude greater than that of χ yyy , leading to an approximate OP emission dipole of SHG. Moreover, the crystal symmetry and OP emission dipole can be preserved under hydrostatic pressure, accompanied by the enhanced χ zxx and the resulting 3-fold increase in SHG intensity. The reported stable OP dipole in 2D vdWs Nb 3 SeI 7 can facilitate the rapid development of chip-integrated NLO devices.

Exploration of two-dimensional (2D) sliding ferroelectric (FE) materials with experimentally detectable ferroelectricity and value-added novel functionalities is highly sought for the development of 2D "slidetronics". Herein, based on first-principles calculations, we identify the synthesizable van der Waals (vdW) layered crystals HgX 2 (X = Br and I) as a new class of 2D sliding ferroelectrics. Both HgBr 2 and HgI 2 in 2D multilayered forms adopt the preferential stacking sequence, leading to room temperature stable out-of-plane (vertical) ferroelectricity that can be reversed via the sliding of adjacent monolayers. Owing to strong interlayer coupling and interfacial charge rearrangement, 2D HgI 2 layers possess strong sliding ferroelectricity up to 0.16 μC/cm 2 , readily detectable in experiment. Moreover, robust sliding ferroelectricity and interlayer sliding controllable Rashba spin texture of FE-HgI 2 layers enable potential applications as 2D spintronic devices such that the electric control of electron spin detection can be realized at the 2D regime.

Metallopolymers as organic-inorganic hybrid materials formulated by metal embedding organic polymers show great potential for novel heterogeneous catalysis, in terms of the facile structural design and tunability. Herein, the disadvantage of nonporous stacking of one-dimensional (1D) structures has been suppressed by chain modulation of the 1D metallopolymers, allowing for the convenient construction of porous assemblies with single-atom dispersion and accessible active sites. By postmodification, the Fe/CM-1 catalyst readily synthesized by coordinating the Fe(II) to the twisted chain of 1D Schiff-base polymer possesses expedient flexibility, showing the highest porosity, remarkable heterogeneous recyclability, and thus prominent catalytic activity for the selective oxidation of benzylamine and alcohols. Moreover, control experiments supported by computational studies demonstrated that the unique pincer structure of Fe/CM-1 effectively maintains the valence state of the anchored single-atom iron, facilitating single-electron transfer and promoting efficient iron redox cycling during the catalytic process. Notably, these 1D metallopolymers have the advantage of cost-effectiveness, easy preparation in gram-scale, and utilization in continuous reaction, providing inspirations for facile synthesis of efficient heterogeneous catalysts from the well-developed 1D metallopolymers.

Electromechanical phenomena in two-dimensional (2D) materials can be related to sizable electric polarizations and switchable spontaneous ferroelasticity, allowing them to be used as miniaturized electronic and memory devices. Even in a parent centrosymmetric (nonpolar) ferroelastic (FE) material, non-zero polarization can be produced around the FE domain wall, owing to the strain-gradient-induced flexoelectricity. Compared with the negligibly weak flexoelectric effect in bulk compounds, significant electric polarizations can be expected in 2D FE materials that sustain a large elastic strain and a strain gradient. Using first-principles calculations, we predict that spontaneous 2D ferroelasticity and domain-wall flexoelectricity can be simultaneously realized in synthetic HgX 2 (X = Br or I) monolayers. The FE phase renders three oriented variants, which form FE domain walls with a large strain gradient and the associated domain-wall flexoelectric polarizations. Our thermodynamic stability analysis and kinetic barrier simulations allow us to manipulate the domain-wall flexoelectricity via applied mechanical stress, thereby enabling future electromechanical applications in nanoelectronics.

Semimetallic two-dimensional (2D) Dirac materials beyond graphene, especially 2D materials with robust Dirac points against the spin-orbit coupling (SOC), are still highly sought. Herein, we theoretically demonstrate the InBi monolayer as a long-sought 2D Dirac material whose exotic Dirac Fermionic states cannot be gapped out by SOC. The InBi monolayer with the litharge crystal structure possesses not only 4-fold band degeneracy, linear energy dispersion, and ultrahigh Fermi velocity in the order of 10 5 m/s, but also spontaneous ferroelasticity that can lead to the orthorhombic lattice deformation and semimetallic electronic structure. Specifically, the symmetry protected spin-orbit Dirac points in 2D InBi are located at the Brillouin Zone (BZ) boundary and near the Fermi level in energy. More importantly, with coexisting spin-orbit Dirac points and spontaneous ferroelasticity, the InBi monolayer exhibits an additional advantage for engineering Dirac Fermionic states by ferroelastic (FE) strain. Energy levels of Dirac points are strongly coupled to FE strain, and the semimetallic electronic structure of the InBi monolayer is also susceptible to the FE strain induced carrier self-doping effect. Depending on the strain orientation within the InBi monolayer, electron and hole Fermi pockets will develop along the two planar directions, leading to the characteristic transport coefficients (as evidenced by our transport simulations based on Boltzmann formalism) for future experimental detection. FE strain tunable Dirac Fermionic states together with the carrier self-doping effect will benefit future development of ultrathin electronic devices with both high carrier mobility and controllable charge conductivities.

A series of symmetrical tetracyanobutadiene and tetracyanoquinodimethane derivatives with a D-A-D'-A-D structural configuration and silafluorene core (D') were designed and readily synthesized via a [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction. We found that the photophysical properties and HOMO and LUMO energy levels and gaps of the silafluorene derivatives could be profoundly remolded through CA-RE reactions and modulated by varying the peripheral donor units from phenyl, m -dimethoxyphenyl, and N , N -dimethylaniline to triphenylamine groups. After CA-RE reactions, the HOMO-LUMO gaps of 1a-1j are in the range of 1.75-2.78 eV, with significant decreases of 0.52-1.46 eV compared to those of the parent silafluorene compounds 2a-2j . The intriguing crystal structures of 1f and 1j were analyzed and elucidated to show their unique potential porosity. The stability, electrochemical, and computational studies were systematically performed to unveil the reshaped electron-donating and -withdrawing nature in one molecular system. 1h-1j with peripherally strong amino donors exhibit an intense and broad intramolecular charge transfer absorption band in the near-infrared region from 550 to 900 nm. The molecular design and synthesis reported here broaden the types and fields of D-A molecular systems for potential applications in organic optoelectronic devices.

Two-dimensional (2D) heterostructures show great potential in achieving negative differential resistance (NDR) effects by Esaki diodes and or resonant tunneling diodes. However, most of the reported Esaki diode-based NDR devices realized by bulk 2D films lack sufficient gate tunability, and the tuning of NDR behavior from appearing to vanishing remains elusive. Here, a gate-tunable NDR device is reported based on a vertically stacked black phosphorus (BP) and molybdenum disulfide (MoS 2 ) thin 2D heterojunction. At room temperature, a rectifying ratio of ∼6 orders of magnitude from a reverse rectifying diode to a forward rectifying diode by gate modulation is obtained. Through analyzing the temperature-dependent electrical properties, the tunneling mechanism at a certain gate voltage range is revealed. Moreover, the switchable and continuously gate-tunable NDR behavior is realized with a maximum peak-to-valley ratio of 1.23 at 77 K, as shown in the I DS mappings by sweeping V DS under different V GS . In addition, a compact model for gate-tunable NDR behavior in 2D heterostructures is proposed. To our best knowledge, this is the first demonstration of NDR behavior in BP-MoS 2 heterostructures. Consequently, this work sheds light on the gate-tunable NDR devices and reconfigurable logic devices for realizing ternary and reconfigurable logic systems.

High-performance electromagnetic interference (EMI) shielding materials with ultralow density, excellent flexibility, and good mechanical properties are highly desirable for aerospace and wearable electronics. Herein, honeycomb porous graphene (HPG) fabricated by laser scribing technology is reported for EMI shielding and wearable applications. Due to the honeycomb structure, the HPG exhibits an EMI shielding effectiveness (SE) up to 45 dB at a thickness of 48.3 μm. The single-piece HPG exhibits an ultrahigh absolute shielding effectiveness (SSE/t) of 240 123 dB cm 2 /g with an ultralow density of 0.0388 g/cm 3 , which is significantly superior to the reported materials such as carbon-based, MXene, and metal materials. Furthermore, MXene and AgNWs are employed to cover the honeycomb holes of the HPG to enhance surface reflection; thus, the SSE/t of the HPG/AgNWs composite membrane can reach up to 292 754 dB cm 2 /g. More importantly, the HPG exhibits excellent mechanical stability and durability in cyclic stretching and bending, which can be used to monitor weak physiological signals such as pulse, respiration, and laryngeal movement of humans. Therefore, the lightweight and flexible HPG exhibits excellent EMI shielding performance and mechanical properties, along with its low cost and ease of mass production, which is promising for practical applications in EMI shielding and wearable electronics.

Current wearable sensors are fabricated with substrates, which limits the comfort, flexibility, stretchability, and induces interface mismatch. In addition, the substrate prevents the evaporation of sweat and is harmful to skin health. In this work, we have enabled the substrate-free laser scribed graphene (SFG) electronic skin (e-skin) with multifunctions. Compared with the e-skin with the substrate, the SFG has good gas permeability, low impedance, and flexibility. Only assisted using water, the SFG can be transferred to almost any objects including silicon and human skin and it can even be suspended. Many through-holes like stomas in leaf can be formed in the SFG, which make it breathable. After designing the pattern, the gauge factor (GF) of graphene electronic skin (GES) can be designed as the strain sensor. Physiological signals such as respiration, human motion, and electrocardiogram (ECG) can be detected. Moreover, the suspended SFG detect vibrations with high sensitivity. Due to the substrate-free structure, the impedance between SFG e-skin and the human body decreases greatly. Finally, an ECG detecting system has been designed based on the GES, which can monitor the body condition in real time. To analyze the ECG signals automatically, a convolutional neural network (CNN) was built and trained successfully. This work has high potential in the field of health telemonitoring.

Thermoacoustic (TA) effect has been discovered for more than 130 years. However, limited by the material characteristics, the performance of a TA sound source could not be compared with magnetoelectric and piezoelectric loudspeakers. Recently, graphene, a two-dimensional material with the lowest heat capacity per unit area, was discovered to have a good TA performance. Compared with a traditional sound source, graphene TA sound sources (GTASSs) have many advantages, such as small volume, no diaphragm vibration, wide frequency range, high transparency, good flexibility, and high sound pressure level (SPL). Therefore, graphene has a great potential as a next-generation sound source. Photoacoustic (PA) imaging can also be applied to the diagnosis and treatment of diseases using the photothermo-acoustic (PTA) effect. Therefore, in this review, we will introduce the history of TA devices. Then, the theory and simulation model of TA will be analyzed in detail. After that, we will talk about the graphene synthesis method. To improve the performance of GTASSs, many strategies such as lowering the thickness and using porous or suspended structures will be introduced. With a good PTA effect and large specific area, graphene PA imaging and drug delivery is a promising prospect in cancer treatment. Finally, the challenges and prospects of GTASSs will be discussed.

Anethol trithione (ATT) has a wide range of physiological activities, but its use is limited due to its poor water solubility. To improve the solubility of ATT, we synthesized and characterized a novel phosphate prodrug (ATXP) relying on the availability of the hydroxy group in 5-(4-hydroxyphenyl)-3 H -1,2-dithiole3-thione (ATX), which was transformed from ATT rapidly and extensively in vivo. Our results showed that ATXP significantly improved drug solubility. ATXP was rapidly converted to ATX and reached a maximum plasma concentration with a T max of approximately 5 min after intravenous (iv) administration. Furthermore, after the oral administration of ATXP, the C max was 3326.30 ± 566.50 ng/mL, which was approximately 5-fold greater than that of the parent drug form, indicating that ATXP has greater absorption than that of ATT. Additionally, the oral phosphate prodrug ATXP increased the ATX in the area under the plasma concentration vs time curves (AUC 0- t = 3927.40 ± 321.50 and AUC 0-∞ = 4579.0 ± 756.30), making its use in practical applications more meaningful. Finally, compared to the vehicle, ATXP was confirmed to maintain the bioactivity of the parent drug for a significant reduction in infarct volume 24 h after reperfusion. Based on these findings, the phosphate prodrug ATXP is a potentially useful water-soluble prodrug with improved pharmacokinetic properties., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Most mute people cannot speak due to their vocal cord lesion. Herein, to assist mute people to "speak", we proposed a wearable skinlike ultrasensitive artificial graphene throat (WAGT) that integrated both sound/motion detection and sound emission in single device. In this work, the growth and patterning of graphene can be realized at the same time, and a thin poly(vinyl alcohol) film with laser-scribed graphene was obtained by a water-assisted transferring process. In virtue of the skinlike and low-resistant substrate, the WAGT has a high detection sensitivity (relative resistance changes up to 150% at 133 Ω) and an excellent sound-emitting ability (up to 75 dB at 0.38 W power and 2 mm distance). On the basis of the excellent mechanical-electrical performance of graphene structure, the sound detecting and emitting mechanisms of WAGT are realized and discussed. For sound detection, both the motion of larynx and vibration of vocal cord contribute to throat movements. For sound emission, a thermal acoustic model for WAGT was established to reveal the principle of sound emitting. More importantly, a homemade circuit board was fabricated to build a dual-mode system, combining the detection and emitting systems. Meanwhile, different human motions, such as strong and small throat movements, were also detected and transformed into different sounds like "OK" and "NO". Therefore, the implementation of these sound/motion detection acoustic systems enable graphene to achieve device-level applications to system-level applications, and those graphene acoustic systems are wearable for its miniaturization and light weight.

Materials that demonstrate near-infrared (NIR) absorption and can simultaneously convert the electromagnetic irradiation into heat are promising for photothermal therapy. Traditionally, such a material is either pure inorganic, such as CuS, Ag 2 S, and carbon nanotube, or pure organic, such as polyaniline, polypyrrole, and conjugated polymers. Here we show that strong NIR photothermal effect can also be achieved in inorganic-organic hybrid coordination polymers (CPs) or metal-organic frameworks (MOFs). Our strategy is to construct CPs with inorganic Ag-S components that are interlinked by the organic ligands into a higher-dimensional hybrid network. Interestingly, the two resulting CPs, [Ag(Py-4-CSS)] n 1 and [Ag 2 (Py-4-CSS)(Py-4-CSSS)] n 2 (Py-4-CSS = pyridine-4-dithiocarboxylate; Py-4-CSSS = pyridine-4-perthiocarboxylate), show disparate structures due to the varied coordination mode of the pyridine group. For 1, the N atom coordinates to the Ag + center and forms a two-dimensional square framework, while for 2, such a Ag-N bond is disconnected and forms only a one-dimensional structure. Interestingly, this difference leads to the distinct absorption properties in the NIR region. Under 800 nm radiation, the temperature of 1 can rise up to 24.5 °C in 3 min with photothermal conversion efficiency of 22.1%, which is about 2× that of pure inorganic Ag 2 S material and among the highest compared to various known inorganic materials, for example, Au nanoshells (13%), nanorods (21%), and Cu 2- x Se nanocrystals (22%) irradiated with 800 nm light, while for 2, the NIR absorption is absent. This result first demonstrates that the inorganic-organic hybrid approach can be applied to construct superior NIR photothermal materials, but the control of the structure is vital. Here the coordinating nitrogen atoms in 1 are conceived to be critical in promoting the charge transfer between the dithiocarboxylate ligands. To elucidate the response to NIR irradiation of 1, we measured the heat capacity and dielectric constant of 1 and also performed density functional theory calculations. Significantly, the large dielectric constant and flat energy bands indicates 1 is much easier to be polarized and has a high electron effective mass. Thus, unlike the pure inorganic material, such as Ag 2 S, in which electron and hole can quantum mechanically combine to give off light, the joint-force of organic ligands in 1 effectively enhances polaronic recombination into heat.

The double perovskite CaMnTi 2 O 6 , is a rare A-site ordered perovskite oxide that exhibits a sizable ferroelectric polarization and relatively high Curie temperature. Using first-principles calculations combined with detailed symmetry analyses, we identify the origin of the ferroelectricity in CaMnTi 2 O 6 . We further explore the material properties of CaMnTi 2 O 6 , including its ferroelectric polarization, dielectric and piezoelectric responses, magnetic order, electronic structure, and optical absorption coefficient. It is found that CaMnTi 2 O 6 exhibits room-temperature-stable ferroelectricity and moderate piezoelectric responses. Moreover, CaMnTi 2 O 6 is predicted to have a semiconducting energy band gap similar to that of BiFeO 3 , and its band gap can further be tuned via distortions of the planar Mn-O bond lengths. CaMnTi 2 O 6 exemplifies a new class of single-phase semiconducting ferroelectric perovskites for potential applications in ferroelectric photovoltaic solar cells.

An efficient and sensitive chiral analytical method was established for the determination of the chiral fungicide prothioconazole and its major chiral metabolite prothioconazole-desthio in agricultural and environmental samples using ultraperformance liquid chromatography-tandem mass spectrometry. The optical rotation and absolute configuration of enantiomers were identified by optical rotation detector and electronic circular dichroism spectra. The elution order of prothioconazole and its chiral metabolite enantiomers was R-(+)-prothioconazole-desthio, S-(-)-prothioconazole-desthio, R-(-)-prothioconazole, and S-(+)-prothioconazole. The mean recoveries from the samples was 71.8-102.0% with intraday relative standard deviations (RSDs) of 0.3-11.9% and interday RSDs of 0.9-10.6%. The formation of prothioconazole-desthio was studied in soil under field conditions and enantioselective degradation was observed for chiral prothioconazole. Remarkable enantioselective degradation was observed: R-prothioconazole degraded preferentially with EF values from 0.48 to 0.37. Although prothioconazole-desthio is the most remarkably bioactive metabolite, no obvious enantioselective behavior was observed in soil. These results may help to systematically evaluate prothioconazole and its metabolites in food and environmental safety.

Owing to its ideal semiconducting band gap and good carrier-transport properties, the fully inorganic perovskite CsSnI 3 has been proposed as a visible-light absorber for photovoltaic (PV) applications. However, compared to the organic-inorganic lead halide perovskite CH 3 NH 3 PbI 3 , CsSnI 3 solar cells display very low energy conversion efficiency. In this work, we propose a potential route to improve the PV properties of CsSnI 3 . Using first-principles calculations, we examine the crystal structures and electronic properties of CsSnI 3 , including its structural polymorphs. Next, we purposefully order Cs and Rb cations on the A site to create the double perovskite (CsRb)Sn 2 I 6 . We find that a stable ferroelectric polarization arises from the nontrivial coupling between polar displacements and octahedral rotations of the SnI 6 network. These ferroelectric double perovskites are predicted to have energy band gaps and carrier effective masses similar to those of CsSnI 3 . More importantly, unlike nonpolar CsSnI 3 , the electric polarization present in ferroelectric (CsRb)Sn 2 I 6 can effectively separate the photoexcited carriers, leading to novel ferroelectric PV materials with potentially enhanced energy conversion efficiency.

Realization of biological synapses using electronic devices is regarded as the basic building blocks for neuromorphic engineering and artificial neural network. With the advantages of biocompatibility, low cost, flexibility, and compatible with printing and roll-to-roll processes, the artificial synapse based on organic transistor is of great interest. In this paper, the artificial synapse simulation by ion-gel gated organic field-effect transistors (FETs) with poly(3-hexylthiophene) (P3HT) active channel is demonstrated. Key features of the synaptic behaviors, such as paired-pulse facilitation (PPF), short-term plasticity (STP), self-tuning, the spike logic operation, spatiotemporal dentritic integration, and modulation are successfully mimicked. Furthermore, the interface doping processes of electrolyte ions between the active P3HT layer and ion gels is comprehensively studied for confirming the operating processes underlying the conductivity and excitatory postsynaptic current (EPSC) variations in the organic synaptic devices. This study represents an important step toward building future artificial neuromorphic systems with newly emerged ion gel gated organic synaptic devices.

Recent works demonstrated that the superconductivity at two-dimensional (2-D) can be achieved in Li-decorated graphene (Nature Phys. 2012, 8, 131 and Proc. Natl. Acad. Sci. 2015, 112, 11795). Inspired by the progress made in graphene, we predict by using the first-principles calculations that Li-incorporated B monolayers (Li-B monolayers) can be alternative 2-D superconductors. First-principles cluster expansion approach was used to evaluate the structural diversity and energetic stability of the 2-D Li-B monolayers by treating them as ternary Lix⬡yB1-x-y pseudoalloys (⬡ refers to B hexagonal hole). After thoroughly exploring the Li-B configuration space, several well-ordered and stable Li-B monolayers were identified. Detailed analyses regarding the electronic structures and lattice dynamics properties of the predicted Li-B monolayers were performed. Compared with the non-superconducting pure B-sheet, some predicted Li-B monolayers can exhibit the phonon-mediated superconducting properties above the liquid helium temperature.

The noncovalent functionalization of boron nitride nanotubes (BNNTs) with perylene-derived molecules has been reported experimentally [Wang et al. J. Am. Chem. Soc. 2008, 130, 8144]. Here we study the structural and electronic properties for the perylene-derivative functionalized BNNTs using first-principles calculations. Our calculations highlight the electronic structure modifications of BNNT through the noncovalent functionalization and demonstrate that van der Waals interactions between the adsorbed perylene derivatives and host BN layers facilitate the functionalization. We also provide an explanation for the red-shift of optical adsorption bands observed in experiment and discuss improvements in theoretical calculations of noncovalently functionalized BNNTs.

Recent measurements on cathodoluminescences spectra of natural and isotope-substituted boron nitride nanotubes (BNNTs) surprisingly suggest the existence of pronounced radiative transitions in BN tubes, which are possibly induced by the oxygen substitutional impurities of the samples. [Han, W. Q. et al. Nano Lett. 2008, 8, 491] However, the structural pattern of the O-doped BN tube is unknown, as a result, how does the substitutional impurity in BNNT contribute to the observed radiative transitions is still a puzzle. Using first-principle calculations, we predict a novel, stable O-doped BNNT configuration. Such a structure contains one B(3)O(6) group, which is similar to the structural unit of boron oxide. Our calculations demonstrate that this type of O substitutional impurity can result in some donor-like gap states in the electronic structure and lead to the significant changes on the optical properties of BNNTs. The vibrational properties of the O-doped BNNT and boron oxide are also investigated. Our work elucidates the origins for experimental findings and provides a strong theoretical evidence on the existence of O substitutional impurity-induced radiative transitions in BNNT systems.

A multistep synthesis was achieved to obtain 3,8-bis(4-mercaptophenyl)-1,10-phenanthroline, which has two free thiol end groups with a molecular length of 1.89 nm, and its ruthenium(II) complex. Five single-crystal structures and UV-vis spectra of related intermediates in methanol and the solid state were studied in order to obtain additional information on the molecules as well as on the supramolecular interactions in the structures. Thermal and electrochemical properties of related Ru(II) complexes were also involved. 3,8-Bis(4-mercaptophenyl)-1,10-phenanthroline and one of its ruthenium(II) complexes were then treated with gold nanoparticles (Au-NPs) via in situ thiol-to-thiol ligand exchange in the presence of two facing Au electrodes with a 1 x 1 microm(2) gap. Stable molecular junctions composed of self-assembled films were produced as revealed by an obvious increase of the conductivity between the Au electrodes, wherein dithiols-bridged Au-NPs were attached to the electrodes by means of Au-S-bonded contacts. Temperature-dependent current-voltage (I-V) measurements for the junctions were performed in the temperature range of 7-300 K, and classical Arrhenius plots and their linear fits were obtained to determine the average activation energies (DeltaE) of these devices. It is found that when the Ru(II) ion is introduced, the conductivity of the nanodevice is increased and the energy barrier is lowered under the same experimental conditions.

Screening of effective food-processing cellulase for digestion of cell walls of coffee beans was carried out, and the cellulase from Trichoderma sp. was selected. The digestion of the cell walls of green and roasted coffee beans was carried out by sequential procedures of alkali boiling (0.1 M Na2CO3 buffer, pH 10, and 0.1 M NaOH), cellulase digestion, autoclaving with 0.1 M NaOH, and cellulase redigestion. The total digestion yields were >95 and >96%, respectively. The cell walls became thin, and the final residues of the cell walls were easily broken into small pieces. The neutral sugar analysis of the digestion or the extract and the residues and the microscopy observations with staining with toluidine blue O, Yariv reagent, and calcofluor for the residue in each step were investigated. Four structures, the galactomannan-cellulose (center part), the membrane of the arabinogalactan protein, the cellulose-rich galactomannan layer, and the arabinogalactan protein-rich layers (outer part), were found in the cell walls.