The layer-by-layer (LbL) adsorption technique offers an easy and inexpensive process for multilayer formation and allows a variety of materials to be incorporated within the film structures. Therefore, the LbL assembly method can be regarded as a versatile bottom-up nanofabrication technique. Research fields concerned with LbL assembly have developed rapidly but some important physicochemical aspects remain uninvestigated. In this review, we will introduce several examples from physicochemical investigations regarding the basics of this method to advanced research aimed at practical applications. These are selected mostly from recent reports and should stimulate many physical chemists and chemical physicists in the further development of LbL assembly. In order to further understand the mechanism of the LbL assembly process, theoretical work, including thermodynamics calculations, has been conducted. Additionally, the use of molecular dynamics simulation has been proposed. Recently, many kinds of physicochemical molecular interactions, including hydrogen bonding, charge transfer interactions, and stereo-complex formation, have been used. The combination of the LbL method with other fabrication techniques such as spin-coating, spraying, and photolithography has also been extensively researched. These improvements have enabled preparation of LbL films composed of various materials contained in well-designed nanostructures. The resulting structures can be used to investigate basic physicochemical phenomena where relative distances between interacting groups is of great importance. Similarly, LbL structures prepared by such advanced techniques are used widely for development of functional systems for physical applications from photovoltaic devices and field effect transistors to biochemical applications including nano-sized reactors and drug delivery systems.

All-inorganic CsPbI 3 perovskite is emerging to be an alternative light-harvesting material in solar cells owing to the enhanced stability and comparable photovoltaic performance compared to organic−inorganic hybrid perovskites. However, the desirable black phase α-CsPbI 3 is not stable at room temperature and degrades rapidly to a nonperovskite yellow phase δ-CsPbI 3 . Herein, we introduce a compositional engineering approach via incorporating Bi 3+ in CsPbI 3 to stabilize the α-phase at room temperature. Fully inorganic solar cells based on the Bi-incorporated α-CsPb 1−x Bi x I 3 compounds demonstrate a high PCE of 13.21% at an optimal condition (incorporation of 4 mol % Bi 3+ ) and maintain 68% of the initial PCE for 168 h under ambient conditions without encapsulation. This is the first attempt of partial substitution of the "B"-site of the perovskite to stabilize the α-CsPbI 3 , which paves the way for further developments of such perovskites and other optoelectronic devices.O rganic−inorganic halide perovskite materials have attracted tremendous research interest owing to their intriguing optical characteristics as well as promising application in next-generation optoelectronic devices. 1−6 Among the various hybrid halide perovskites, CH 3 NH 3 PbI 3 (MAPbI 3 ) and HC(NH 2 ) 2 PbI 3 (FAPbI 3 ) have been frequently studied and have achieved power conversion efficiencies (PCEs) exceeding 20% in solar cells. 7−15 However, due to the hygroscopicity and thermally unstable nature of organic cation MA + , MAPbI 3 is thermally unstable and vulnerable to moisture. 16−20 Even for the more thermostable FAPbI 3 , the presence of hygroscopic FA + also makes it suffer from the moisture stability issue. 8,21−23 In order to improve the stability and photovoltaic performance of the devices, a series of Cs-incorporated systems have been developed, 24−34 such as Cs x MA 1−x PbI 3 , 24 Cs x FA 1−x PbI 3 , 27,28,30 FA 0.83 Cs 0.17 Pb-(I 1−x Br x ) 3 , 31 and Cs x (MA 0.17 FA 0.83 ) 1−x Pb(I 0.83 Br 0.17 ) 3 . 29,32 However, these Cs-incorporated systems still face big challenges for the long-term stability due to the remaining organic components.Recently, all-inorganic cesium lead halide perovskites (CsPbX 3 ) are emerging to be alternative light-harvesting materials in solar cells and have exhibited excellent ability to resist moisture and heat. 35−39 Nevertheless, CsPbBr 3 has a very large band gap of 2.3 eV, which is unable to absorb light with long-range wavelengths and usually results in low PCE of the solar cells. 38−40 Compared to CsPbBr 3 , black phase α-CsPbI 3 (Figure 1a) has a more suitable band gap of 1.73 eV for solar

Materials fabrication with nanoscale structural precision based on bottom-up-type self-assembly has become more important in various current disciplines in chemistry including materials chemistry, organic chemistry, physical chemistry, analytical chemistry, biochemistry, colloid and surface chemistry, and supramolecular chemistry. Although the design of new materials based on nanoscale self-assembly is anticipated as a key concept, preparing complete three-dimensional structures at nanoscale precision remains a difficult target using current technologies. Rather, dimension-reduced approaches such as layering of two-dimensional nanostructures into precisely controlled lamellar nanomaterials are currently achievable. In particular, layer-by-layer (LbL) assembly is known as a highly versatile method for fabrication of controlled layered structures from various kinds of component materials using very simple, inexpensive, and rapid procedures. Therefore, fabrication of multilayer films through the LbL deposition process has attracted growing interest from various research communities. The high versatility and flexibility of LbL assembly is continuously creating new concepts, new materials, new procedures, and new applications. In this highlight review, we focus on nanoarchitectonics by LbL assembly. After an initial introduction on the invention and a brief history of the LbL assembly technique, innovations and the evolution of the technique are described based mainly on recent examples, which are categorized into two sections: (i) developments in methodology (technical, material, and phenomenological aspects with expansion of concept) and (ii) progress in applications (physical, chemical/biochemical, and biomedical applications).

Although mesoporous materials have well-defined pore structures, these fine materials can surprisingly be produced by employing a set of conventional and simple procedures such as mixing, heating, filtration, and washing, using low-cost materials. They can be regarded as easy-to-make bulk nanostructured materials. Mesoporous materials have great potential for use in both macroscopic applications and nanotechnology. In this account, we introduce examples of recent developments in mesoporous materials involving innovations in their components and structural designs and concentrating on our own recent progress. These examples include syntheses of mesoporous silica, metal oxides, semiconductive materials, metals, alloys, organic composites, biomaterial composites, carbon, carbon nitride, and boron nitride, as innovative components. As structural innovations for mesoporous materials, various film preparations, pore alignments, and hierarchic structures are described together with their related functions including sensing and controlled release of target molecules. Why Mesoporous Materials? Bulk Quantities and Precise StructuresThere is little doubt that nanotechnology and related technologies are making significant contributions to current research and development which will eventually be felt in our day-to-day lives. Device miniaturization in such products as cellular phones and portable computers has irrevocably changed our lifestyles. Portable devices allow us to work and communicate wherever we are in the world in contrast to the previous situation where machine operation required a human presence. Greater freedom in our work and leisure dispositions should diminish over-concentration of populations in cities and may ultimately reduce energy consumption and waste production.So far, device innovations have been due to development of top-down approaches, especially sophisticated microfabrication techniques. 17 However, those top-down techniques are not useful for materials innovation where chemical processes are used as the operating principle. Rather, so-called bottom-up approaches are expected to create novel functional materials having well-controlled structural features with nanometric precision. Bottom-up approaches rely on self-assembly processes to form selected structures through spontaneous association of atoms, molecules, clusters, and particles. 818 Furthermore, assisted assembly techniques using external influences are provided by LangmuirBlodgett (LB) method 1928 and layer-by-layer (LbL) adsorption 2936 and provide significant contributions for materials' fabrication. According to these concepts, molecular complex formation, 3741 molecular array control, 4252 and microscopic structural design 5361 have been widely investigated leading to generation of a large quantity of scientific knowledge.Ideally, materials should be produced in a series of easy processes to yield bulk quantity without loss of nanometric structural features and some categories of material already satisfy this condition. For exampl...

Nanoporous carbon (NPC) is prepared by direct carbonization of Al-based porous coordination polymers (Al-PCP). By applying the appropriate carbonization temperature, both high surface area and large pore volume are realized for the first time. Our NPC shows much higher porosity than other carbon materials (such as activated carbons and mesoporous carbons). This new type of carbon material exhibits superior sensing capabilities toward toxic aromatic substances.

mechanisms operate with excellent fl exibility/adaptability originating from cooperation of multiple dynamic systems. [ 1 ] In most cases, the functional components of these systems are assembled through non-covalent dynamic interactions. Although their assembled structures are often ambiguous, or "fuzzy," functions of biological systems are signifi cantly superior to any of the so far precisely constructed artifi cial machines and devices. Thus, fabrication of bio-like systems might be one of the ultimate goals of the science and technology of functional materials. There has already been some success in the synthesis of excellent new materials, [ 2 ] but these are still far inferior to biological materials systems from the point-of-view of specifi city, effi ciency, and adaptability, although incremental progress involving existing technological concepts may not change this situation. A certain paradigm shift in construction concepts of functional materials is necessary to establish an advanced approach towards truly dynamic functions.Fabrication of functional materials requires control of organization of their components with nanometer precision. The novel technological concept of nanotechnology has been established over the past few decades with a view to exploit nanometer-sized phenomena and to fabricate functional materials by precisely controlling the materials' structures at the nanoscale. [ 3 ] Several strategies of nanotechnology are simple extensions of the corresponding successful microtechnologies to nanofabrication. However, the control of nanoscale events and structures requires different approaches to those commonly applied in microtechnology. This is because physical phenomena at the nanoscale are quite different from microscopic phenomena. Effects occurring at the microscopic level are often similar to those occurring in the macroscopic regime. In contrast, nanoscale phenomena involving nanometer-sized objects are strongly infl uenced by thermal/statistical fl uctuations, mutual interactions, and possibly quantum effects between components. In many cases, such mutual actions are dynamically integrated, often resulting in unexpected properties and effects so that components of nanoscale systems cannot be controlled by intuitive means. To understand and therefore control nanoscale phenomena and to Objects in all dimensions are subject to translational dynamism and dynamic mutual interactions, and the ability to exert control over these events is one of the keys to the synthesis of functional materials. For the development of materials with truly dynamic functionalities, a paradigm shift from "nanotechnology" to "nanoarchitectonics" is proposed, with the aim of design and preparation of functional materials through dynamic harmonization of atomic-/molecular-level manipulation and control, chemical nanofabrication, self-organization, and fi eld-controlled organization. Here, various examples of dynamic functional materials are presented from the atom/molecularlevel to macroscopic dimensions. Thes...

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Nowadays a wide variety of synthesis techniques are utilized to produce nanoporous materials. In this review, we summarize the general principles of templated synthesis using various types of templates and cover recent developments in this area.