Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

This Review focuses on noncovalent functionalization of graphene and graphene oxide with various species involving biomolecules, polymers, drugs, metals and metal oxide-based nanoparticles, quantum dots, magnetic nanostructures, other carbon allotropes (fullerenes, nanodiamonds, and carbon nanotubes), and graphene analogues (MoS2, WS2). A brief description of π–π interactions, van der Waals forces, ionic interactions, and hydrogen bonding allowing noncovalent modification of graphene and graphene oxide is first given. The main part of this Review is devoted to tailored functionalization for applications in drug delivery, energy materials, solar cells, water splitting, biosensing, bioimaging, environmental, catalytic, photocatalytic, and biomedical technologies. A significant part of this Review explores the possibilities of graphene/graphene oxide-based 3D superstructures and their use in lithium-ion batteries. This Review ends with a look at challenges and future prospects of noncovalently modified graph...

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Noncovalent Functionalization of Graphene and Graphene Oxide for Energy Materials, Biosensing, Catalytic, and Biomedical Applications

A diverse spectrum of technology drivers such as improved thermal barriers, higher efficiency thermoelectric energy conversion, phase-change memory, heat-assisted magnetic recording, thermal management of nanoscale electronics, and nanoparticles for thermal medical therapies are motivating studies of the applied physics of thermal transport at the nanoscale. This review emphasizes developments in experiment, theory, and computation in the past ten years and summarizes the present status of the field. Interfaces become increasingly important on small length scales. Research during the past decade has extended studies of interfaces between simple metals and inorganic crystals to interfaces with molecular materials and liquids with systematic control of interface chemistry and physics. At separations on the order of ∼1 nm, the science of radiative transport through nanoscale gaps overlaps with thermal conduction by the coupling of electronic and vibrational excitations across weakly bonded or rough interface...

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Nanoscale thermal transport. II. 2003–2012

Recently, perovskite CH3NH3PbI3 sensitizer has attracted great attention due to its superb light-harvesting characteristics. Organometallic or organic materials were mostly used as sensitizers for solid-state dye-sensitized solar cells at early stages. Inorganic nanocrystals have lately received attention as light harvesters due to their high light-absorbing properties. Metal chalcogenides have been investigated with solid-state dye-sensitized solar cells; however, the best power conversion efficiency was reported to be around 6%. CH3NH3PbX3 (X = Cl, Br, or I) perovskite sensitizer made a breakthrough in solid-state mescoscopic solar cells, where the first record efficiency of around 10% was reported in 2012 using submicrometer-thick TiO2 film sensitized with CH3NH3PbI3. A rapid increase in efficiency approaching 14% followed shortly. In this Perspective, recent progress in perovskite-sensitized solid-state mesoscopic solar cells is reviewed. On the basis of the recent achievements, a power conversion eff...

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Organometal Perovskite Light Absorbers Toward a 20% Efficiency Low-Cost Solid-State Mesoscopic Solar Cell

Starting with the history of the fundamental science of the relation of structure to composition delineated completely by Goldschmidt, we use the perovskite structure to illustrate the enormous pow...

The perovskite structure—a review of its role in ceramic science and technology

A RECENT communication by Gibson1 sought to show that X-ray powder photographs of graphite contained 'extra' reflexions that could not be explained on the basis of the co-existence of the hexagonal and rhombohedral structures described by Lipson and Stokes2. It is of some importance that the crystal structure of graphite should be correctly specified3, and, because of our experience in examining by X-ray methods graphites from many different sources, we have thought it useful to investigate the validity of the observations made by Gibson. Besides the particular problem of the structure of graphite, there are also involved some questions of X-ray technique on which comment appears called for.

Structure of Graphite

IN a previous communication1, it was recorded that precision X-ray powder methods with a large-diameter camera show that the structure of nickel oxide is not strictly cubic, but only pseudo-cubic. Splitting of some of the X-ray reflexions into more than one component is explained if a small distortion of the cubic lattice along an octahedral axis is assumed, so that the true symmetry is rhombohedral hexagonal.

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Compounds of the Structural Type of Calcium Titanate

IT has been shown by one of us1 that, at ordinary temperatures, the structure of nickel oxide is slightly deformed from face-centred cubic symmetry. Later work2 proved that at − 180° C. an increase in the rhombohedral deformation occurs. On the other hand, it was found that the departure from cubic symmetry vanishes at a temperature of about 200° C.

Structure of Monoxides of some Transition Elements at Low Temperatures

Introduction. Whilst we know a good deal about the crystalline state through the advance of X-ray analysis our knowledge of the \"vitreous\" (with which we may group the \"amorphous\") and liquid states of matter is far less complete. It is almost common practice to refer to glass as a \"supercooled liquid\". As J e f f r i e s 1 ) says in au excellent discussion of the present position, this is a dangerous half truth. For, whilst glass represents the substance obtained by rapidly cooling the viscous liquid through the temperature range of the maximum velocity of crystallisation, it has many properties of the normal solid; its viscosity is, to all intents and purposes, infinite, it possesses rigidity. When crystalline substances are heated the energy of vibration of the atoms in the lattice increases and with it the amplitude. If the temperature be further increased the energy of vibration becomes greater than the restoring forces; atoms break free and the lattice is destroyed. It does not follow that the atoms remain permanently free in the liquid state. Polymerisation may occur and the groups of atoms or molecules may at any given instant be striving after the regular arrangement which obtains for crystals. Similarly when the liquid is suddenly cooled to form a glass there must be some tendency for the atoms to group themselves together so that the potential energy t e n d s to a minimum. This naturally leads to the question Do the \"units\" of a glass or amorphous substance consists of exceedingly small crystals? If so it ought to be possible to detect them by means of X-ray diffraction. In a recent note to Nature) we have been able to show that many glasses do consist

13. X-ray Diffraction and the Structure of Vitreous Solids — I

THE development of modern X-ray powder photographic methods has opened up now possibilities for the examination of the fine structure of crystalline substances. The high resolution and definition of the reflexions, particularly in the high-order lines, which is obtainable with such circular cameras as that described by Bradley, Lipson and Fetch1, has not only meant an increase in accuracy of lattice parameter measurements, but has also enabled interesting phenomena in alloys to be observed2. The detection of extra reflexions in powder photographs of graphite3 has led to the description of a second crystalline form4, which apparently co-exists with the structure established by Bernal.

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H. P. Rooksby

Papers

Structure of Graphite

Compounds of the Structural Type of Calcium Titanate

Structure of Monoxides of some Transition Elements at Low Temperatures

13. X-ray Diffraction and the Structure of Vitreous Solids — I

Structure of Nickel Oxide