Search results for "porous material"

Improving the Long‐Term Stability of Doped Spiro‐Type Hole‐Transporting Materials in Planar Perovskite Solar Cells

2021

The improvement of the long-term stability of perovskite-based solar cells (PSCs) toward commercialization is closely linked to the development of cutting-edge charge-transporting materials. The progress on the design and the synthesis of new hole-transporting materials (HTMs) is synergistically attaining both top efficiencies and promising stability. Herein, the synthesis and characterization of two doped-HTMs based on electron-rich spiranic cores, namely, 9H-quinolinophenoxazine (spiro-POZ) and 9H-quinolinophenothiazine (spiro-PTZ), are presented. The novel HTMs exhibit excellent solubility, optimal highest occupied molecular orbital energy, and excellent thermal stability with glass tran…

Organic-inorganic and all-inorganic lead halide nanoparticles [Invited]

2015

Organic-inorganic (hybrid) and all-inorganic lead halide perovskites, in particular APbX(3) where A is an organic cation (methylammonium or formamidinium) or cesium cation and X = Cl, Br, I, respectively, are of great interest in photovoltaic devices and as luminescent materials for light-emitting devices. It has recently been demonstrated that they can be prepared not only as nanoparticulate material by using the pores of mesoporous films, but also as colloidal nanoparticles, which exhibit enhanced optical properties with respect to the bulk material. We summarize here the methods reported for their preparation as well as their optical features. Experimental and theoretical studies on this…

Hybrid molecular materials for optoelectronic devices

2005

Hybrid molecular materials based on semiconductor nanocrystalline metal oxides are a subject of intense research for the development of optoelectronic devices. Such devices follow the strategy of combining high surface area mesoporous materials with optically and electrochemically active molecules. Photovoltaic devices, molecular sensors and biosensors are some of the examples discussed in this paper.

Preparation and characterization of activated carbon from date stones by physical activation with steam

2008

Abstract Activated carbons are produced from wastes of Algerian date stones by pyrolysis and physical activation in the presence of water vapor into a heated fixed-bed reactor. The effect of pyrolysis temperature and activation hold time on textural and chemical surface properties of raw date stones and carbon materials produced are studied. As expected, the percentage yield decreases with increase of activation temperature and hold time. The characterization of carbon materials is performed by scanning electron microscopy (SEM). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption (BET). Results show the presence of cellulose and hemicellulose in …

High-Temperature Stable Gold Nanoparticle Catalysts for Application under Severe Conditions: The Role of TiO2 Nanodomains in Structure and Activity

2015

Metal nanoparticles with precisely controlled size are highly attractive for heterogeneous catalysis. However, their poor thermal stability remains a major concern in their application at realistic operating conditions. This paper demonstrates the possibility of synthesizing gold nanoparticles with exceptional thermal stability. This has been achieved by using a simple conventional deposition–precipitation technique. The material employed as catalyst consists of gold supported on a TiO2-impregnated SiO2 bimodal mesoporous support. The resulting material shows gold nanoparticles with a narrow size distribution around 3.0 nm, homogeneously dispersed over the TiO2/SiO2 material. Most interesti…

Three dimensional nanoscale analysis reveals aperiodic mesopores in a covalent organic framework and conjugated microporous polymer.

2019

The integrated analytical approach developed in this study offers a powerful methodology for the structural characterisation of complex molecular nanomaterials. Structures of a covalent organic framework based on boronate esters (COF-5) and a conjugated microporous polymer (Aza-CMP) have been investigated by a combination of several electron microscopy techniques elucidating the three-dimensional topology of the complex polycrystalline (COF) and non-crystalline (CMP) materials. Unexpected, aperiodic mesoporous channels of 20-50 nm in diameter were found to be penetrating the COF and CMP particles, which cannot be detected by X-ray diffraction techniques. The mesopores appear to be stable un…

Role of TiO2 in Highly Efficient Solar Cells

2021

Titanium dioxide (TiO2) is a naturally occurring oxide of titanium. It has a wide range of applications. It has three metastable phases, which can be synthesized easily by chemical routes. Usage of TiO2 in thin-film solar cells has gained much attention in increasing the performance of the cell. The objectives are to harvest the freely available earth’s energy and to gain expertise in yielding a maximum conversion efficiency. Various strategies are employed to face the challenges in improving the efficiency of solar cells. This study provides a broad view of the usage of different forms of TiO2 layers, like nanochannel, porous, nanotubes, and mesoporous layers, in enhancing electron injecti…

Pore shape affects the determination of the pore size of ordered mesoporous silicas by mercury intrusion.

2008

MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of surface roughness on pore size measurement by mercury intrusion, as the inner surface of the mesoporous channels is much rougher in the case of SBA-15 than MCM-41. In the case of MCM-41, the pressure of mercury intrusion is related to the pore size by the classical Washburn−Laplace law, while in the case of SBA-15, the pressure of intrusion is much higher than expected and classical models underevaluate the size of the channels. Defects on the pore surface of SBA-15 affect the mercury intrusion in a similar way as the deviation from cylindrical geometry does for the pores of spongelike silica gl…

Frontispiece: Self-Immolative Linkers as Caps for the Design of Gated Silica Mesoporous Supports

2016

Electrochemistry of Mesoporous Organosilica of MCM-41 Type Containing 4,4′-Bipyridinium Units: Voltammetric Response and Electrocatalytic Effect on 1…

2003

The electrochemistry of a novel organic−inorganic material in which 4,4‘-bipyridinium units (BP) are covalently attached to the walls of a periodic mesoporous organisilica (PMO) of the MCM-41 type is described. The pristine material (BP@PMO), having its internal space completely filled by the cetyltrimethylammonium structure-directing agent, is almost electrochemically silent. In contrast, the extracted material obtained after removal of the structure-directing agent (BP@PMO-ex) exhibits two reduction peaks at −0.36 and −0.75 V vs AgCl/Ag in contact with aqueous electrolytes. BP@PMO-ex shows a remarkable electrocatalytic effect on the oxidation of 1,4-dihydrobenzoquinone (H2Q) that is studi…