Solid-state materials with extended structures have revealed many interesting structure-related characteristics. Among many, materials crystallizing in noncentrosymmetric (NCS) space groups have ...attracted massive attention attributable to a variety of superb functional properties such as ferroelectricity, pyroelectricity, piezoelectricity, and nonlinear optical (NLO) properties. In fact, the characteristics are pivotal to many industrial applications such as laser systems, optical communications, photolithography, energy harvesting, detectors, and memories. Thus, for the past several decades, a great deal of synthetic effort has been vigorously made to realize these technologically important properties by improving the occurrence of macroscopic NCS space groups. A bright approach to increase the incidence of NCS structures was combining local asymmetric units during the initial synthesis process. Although a significant improvement has been achieved in obtaining new NCS materials using this strategy, the majority of solid-state materials still crystallize in centrosymmetric (CS) structures as the locally unsymmetrical units are easily lined up in an antiparallel manner. Therefore, discovering an effective method to control the framework structure and the macroscopic symmetry is an imminent ongoing challenge. In order to more effectively control the overall symmetry of solid-state compounds, it is critical to understand how the backbone and the subsequent centricity are affected during the crystallization. In this Account, several factors influencing the framework structure and centricity of solid-state materials are described in order to more systematically discover novel NCS materials. Recent studies on crystalline solid-state materials suggest three factors affecting the local coordination environment as well as the overall symmetry of the framework structure: (1) size variations of the various template cations, (2) a variable backbone arrangement occurring from the hydrogen-bonding interactions, and (3) the presence of framework flexibility. With regard to the first factor, the impact of size of the various metal cations and coordination numbers on the alignment of other adjacent polyhedra, linkers, and lone pairs determining the framework geometries of mixed metal oxides is analyzed. The second factor considers the regulation of crystallographic centricity determined by the availability of hydrogen-bonding interactions between anionic frameworks containing local asymmetric polyhedra and organic cations. Finally, the third factor explores the framework architecture and the space group symmetry influenced by the flexibility of polyhedra revealing variable coordination numbers. The centricity and framework of new solid-state materials might be controlled by using a variety of synthetically controllable asymmetric units such as organic structure-directing cations and linkers with different sizes and functional groups.
A novel intrusion detection system (IDS) using a deep neural network (DNN) is proposed to enhance the security of in-vehicular network. The parameters building the DNN structure are trained with ...probability-based feature vectors that are extracted from the in-vehicular network packets. For a given packet, the DNN provides the probability of each class discriminating normal and attack packets, and, thus the sensor can identify any malicious attack to the vehicle. As compared to the traditional artificial neural network applied to the IDS, the proposed technique adopts recent advances in deep learning studies such as initializing the parameters through the unsupervised pre-training of deep belief networks (DBN), therefore improving the detection accuracy. It is demonstrated with experimental results that the proposed technique can provide a real-time response to the attack with a significantly improved detection ratio in controller area network (CAN) bus.
Exploring novel functional materials
via
chemical substitution-oriented design is an emerging strategy. The method can be expanded to the discovery of high performance ultraviolet (UV) nonlinear ...optical (NLO) solid state materials by a careful tuning of the substituted atoms. This minireview presents a brief introduction to chemical substitution-oriented design including single-site substitution, dual-site substitution, and multisite substitution. Several state-of-the-art UV NLO materials such as K
3
VO(O
2
)
2
CO
3
-type, KBe
2
BO
3
F
2
(KBBF)-type, Ca
5
(PO
4
)
3
(OH)-type, and KTiOPO
4
(KTP)-type phases successfully discovered by the chemical substitution method are discussed.
A brief introduction to chemical substitution-oriented design to discover high performance ultraviolet (UV) nonlinear optical (NLO) solid state materials is presented.
Owing to their various important structure-driven properties, functional layered materials have been of great interest. In this feature article, a series of recently discovered novel layered ...materials with heavy metal lone pair cations containing Pb2+, Bi3+, and Te4+ are introduced. The layered materials include (1) the first Pb2+-Kemp's triacid coordination complex showing selective CO2 adsorption and an intercalative ligand addition reaction, Pb3C6(CH3)3(CO2)3H62DMF3, (2) a tailor-made polar lead borate chloride with a very strong second-harmonic generation (SHG) response, Pb2BO3Cl, (3) a white light emitting single component Pb+-based coordination polymer exhibiting high quantum efficiency and thermal stability, PbNC5H3(CO2)2, (4) noncentrosymmetric (NCS) n = 3 Dion–Jacobson layered perovskites with a variety of NCS characteristics, polar RbBi2Ti2NbO10 and nonpolar CsBi2Ti2TaO10, (5) layered bismuth oxyfluoride nitrates revealing photocatalytic properties and large SHG, Bi2OF3(NO3) and Bi6O6F5(NO3), (6) a layered bismuth tellurium nitrate hydroxide with multiple NCS chromophores, Bi2Te2O6(NO3)2(OH)2(H2O), (7) a mixed-valent layered tellurite–tellurate with robust ion-exchange behavior, Na2Te2O6·1.5H2O, and (8) a metastable lithium molybdenum tellurite undergoing Li+-exchange-driven facile structural transformation reactions, Li2Mo3TeO12. The syntheses, structures, representative properties, and structure–property relationships for the layered materials are presented.
To develop high‐performance nonlinear optical (NLO) materials for infrared (IR) applications, we have applied a rational element‐composition design strategy and investigated the unexplored ...PbO–PbCl2–PbI2 system. By doing so, we discovered a new polar lead mixed oxyhalide, Pb18O8Cl15I5, the first synthetic metal oxyhalide combining both Cl− and I−. Pb18O8Cl15I5 reveals an unprecedented structural feature with two different dimensional types of oxocentered Pb–O units, namely, O4Pb88+ clusters and OPb22+ chains. Centimeter‐sized single crystals of Pb18O8Cl15I5 have been successfully grown under ambient conditions. Remarkably, Pb18O8Cl15I5 satisfies all fundamental yet rigorous criteria for high‐performance IR NLO materials, exhibiting the widest IR transparency (up to 16.0 μm) among oxide‐based crystals, strong second‐harmonic generation response (1.05×AgGaS2), superior birefringence (0.086 at 636 nm), and a high laser‐induced damage threshold (8.5×AgGaS2).
Noncentrosymmetric Pb18O8Cl15I5, the first mixed oxyhalide in the PbO–PbCl2–PbI2 system, was found to have an unprecedented structural architecture featuring two types of oxocentered Pb–O units with different dimensionality (see picture). Characterization based on the large single crystal revealed that Pb18O8Cl15I5 outperformed AgGaS2 in key properties for high‐performance infrared nonlinear optical materials (see picture).
Exosomes are nanoscale-sized membrane vesicles secreted by almost all cell types into the extracellular environment upon fusion of multivesicular bodies and plasma membrane. Biogenesis of exosomes is ...a protein quality control mechanism, and once released, exosomes transmit signals to other cells. The applications of exosomes have increased immensely in biomedical fields owing to their cell-specific cargos that facilitate intercellular communications with neighboring cells through the transfer of biologically active compounds. The diverse constituents of exosomes reflect their cell of origin and their detection in biological fluids represents a diagnostic marker for various diseases. Exosome research is expanding rapidly due to the potential for clinical application to therapeutics and diagnosis. However, several aspects of exosome biology remain elusive. To discover the use of exosomes in the biomedical applications, we must better understand the basic molecular mechanisms underlying their biogenesis and function. In this comprehensive review, we describe factors involved in exosomes biogenesis and the role of exosomes in intercellular signaling and cell-cell communications, immune responses, cellular homeostasis, autophagy, and infectious diseases. In addition, we discuss the role of exosomes as diagnostic markers, and their therapeutic and clinical implications. Furthermore, we addressed the challenges and outstanding developments in exosome research, and discuss future perspectives.
Second-order nonlinear optical (NLO) materials have drawn enormous academic and technological attention attributable to their indispensable role in laser frequency conversion and other greatly ...facilitated applications. The exploration of new NLO materials with high performances thus has long been an intriguing research field for chemists and material scientists. However, an ideal NLO material should simultaneously satisfy quite a few fundamental yet rigorous criteria including a noncentrosymmetric structure, large NLO coefficients, desired transparent range, large birefringence, high laser damage threshold, and availability of a large-size single crystal. Therefore, the identification of promising compound systems, targeted design, and experience-based syntheses are crucial to discover novel NLO materials working in the spectral region of interest. As an important family of mixed-anion compounds, versatile metal oxyhalides containing metal-centered oxyhalide functional units (MO
m
X
n
(X = F, Cl, Br, and I)) are becoming a marvelous branch for interesting NLO materials. Especially, when the central metals are d
0
/d
10
transition metals or heavy post-transition metals, a number of novel NLO materials with superior functionalities are expected. Our thorough review on the recent achievements of metal oxyhalides for NLO materials are divided into the fast-growing NLO metal oxyhalides with single type halogen anions and the newly identified NLO metal oxyhalides with mixed halogen anions. Here we mainly focus on the design strategy, structural chemistry, NLO-related properties, and structure-property correlation of the metal oxyhalides with relatively large NLO responses. We hope this review can provide an insight on the rational design and future development of emerging metal oxyhalides for NLO and other applications.
Nonlinear optical metal oxyhalides could provide a new insight into the target design and exploratory synthesis of new functional materials with intriguing chemical and physical properties.
Exosomes are extracellular vesicles that contain a specific composition of proteins, lipids, RNA, and DNA. They are derived from endocytic membranes and can transfer signals to recipient cells, thus ...mediating a novel mechanism of cell-to-cell communication. They are also thought to be involved in cellular waste disposal. Exosomes play significant roles in various biological functions, including the transfer of biomolecules such as RNA, proteins, enzymes, and lipids and the regulation of numerous physiological and pathological processes in various diseases. Because of these properties, they are considered to be promising biomarkers for the diagnosis and prognosis of various diseases and may contribute to the development of minimally invasive diagnostics and next generation therapies. The biocompatible nature of exosomes could enhance the stability and efficacy of imaging probes and therapeutics. Due to their potential use in clinical applications, exosomes have attracted much research attention on their roles in health and disease. To explore the use of exosomes in the biomedical arena, it is essential that the basic molecular mechanisms behind the transport and function of these vesicles are well-understood. Herein, we discuss the history, biogenesis, release, isolation, characterization, and biological functions of exosomes, as well as the factors influencing their biogenesis and their technical and biological challenges. We conclude this review with a discussion on the future perspectives of exosomes.
Four chiral coordination polymers (CPs), M(S,S)‐C14H14N2O6 and M(R,R)‐C14H14N2O6 (M=Zn or Cd), have been exclusively synthesized in high yields with the aid of newly designed chiral ligand under ...hydrothermal condition. The CPs crystallizing in the orthorhombic nonpolar space group, C2221, reveal three‐dimensional framework structures composed of MO4 tetrahedra and the corresponding homochiral linkers. Powder second‐harmonic generation (SHG) measurements indicate that the nonpolar CPs reveal very strong SHG efficiency of ca. 5–9 times that of KH2PO4 and exhibit type‐I phase‐matching behavior. Density functional theory calculations suggest that the unusually large SHG efficiency found from the nonpolar CPs should be attributable to the synergistic effect of polarizable metal cations and enhanced hyperpolarizability in the donor‐acceptor system originating from the hydrogen bonding in the coordinated linkers.
Systematically synthesized new noncentrosymmetric nonpolar chiral coordination polymers exhibit unusually strong second‐harmonic generation efficiencies attributable to the synergistic effect of polarizable metal cations and increased hyperpolarizability in the donor–acceptor system originating from the robust hydrogen bonding in the coordinated linkers.
Cancer represents a group of heterogeneous diseases characterized by uncontrolledgrowth and spread of abnormal cells, ultimately leading to death. Nanomedicine plays a significantrole in the ...development of nanodrugs, nanodevices, drug delivery systems and nanocarriers. Someof the major issues in the treatment of cancer are multidrug resistance (MDR), narrow therapeuticwindow and undesired side effects of available anticancer drugs and the limitations of anticancerdrugs. Several nanosystems being utilized for detection, diagnosis and treatment such as theranosticcarriers, liposomes, carbon nanotubes, quantum dots, polymeric micelles, dendrimers and metallicnanoparticles. However, nonbiodegradable nanoparticles causes high tissue accumulation andleads to toxicity. MDR is considered a major impediment to cancer treatment due to metastatictumors that develop resistance to chemotherapy. MDR contributes to the failure of chemotherapiesin various cancers, including breast, ovarian, lung, gastrointestinal and hematological malignancies.Moreover, the therapeutic efficiency of anticancer drugs or nanoparticles (NPs) used alone is lessthan that of the combination of NPs and anticancer drugs. Combination therapy has long beenadopted as the standard first-line treatment of several malignancies to improve the clinical outcome.Combination therapy with anticancer drugs has been shown to generally induce synergistic drugactions and deter the onset of drug resistance. Therefore, this review is designed to report andanalyze the recent progress made to address combination therapy using NPs and anticancer drugs.We first provide a comprehensive overview of the angiogenesis and of the different types of NPscurrently used in treatments of cancer; those emphasized in this review are liposomes, polymericNPs, polymeric micelles (PMs), dendrimers, carbon NPs, nanodiamond (ND), fullerenes, carbonnanotubes (CNTs), graphene oxide (GO), GO nanocomposites and metallic NPs used forcombination therapy with various anticancer agents. Nanotechnology has provided the convenienttools for combination therapy. However, for clinical translation, we need continued improvementsin the field of nanotechnology.
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