Understanding the stability of zeolitic imidazolate framework-8 (ZIF-8) under physiological conditions is critical in biotechnology and biomedicine for biosensing, biocatalysis, and drug delivery.

Focused electron beam induced deposition (FEBID) is an important synthesis method as it is an extremely flexible tool for fabricating functional (3D) structures with nanometer spatial resolution. However, FEBID has historically suffered from carbon impurities up to 90 at %, which significantly limits the intended functionalities. In this study we demonstrate that MeCpPtIVMe3 deposits can be fully purified by an electron-beam assisted approach using H2O vapor at room temperature, which eliminates sample and/or gas heating and complicated gas delivery systems, respectively. We demonstrate that local pressures of 10 Pa results in an electron-limited regime, thus enabling high purification rates of better than 5 min·nA–1·μm–2 (30 C·cm–2) for initially 150 nm thick deposits. Furthermore, TEM measurements suggest the purification process for the highly compact deposits occurs via a bottom-up process.

MOFs have demonstrated outstanding properties for the protection and controlled release of different bio-entities, from proteins to living cells. Carbohydrates, as pure molecules or as a component of proteins and cells, perform essential biological functions. Thus, an understanding of the role of carbohydrates in the formation of MOF-based bio-composites will facilitate their application to biotechnology and medicine. Here, we investigate the role of carbohydrate molecular weight and chemical functionalization in the formation of carbohydrate@MOF composites. We find that chemical functionalization, such as carboxylation, that leads to an enhancement of metal cation concentration at the surface of the molecule triggers the rapid self-assembly of the MOF material, zeolitic-imidazolate framework 8 (ZIF-8). Furthermore, we determine the encapsulation efficiency and measure the release properties of the carbohydrate under controlled conditions. Our findings show that MOFs can be used to prepare a new class of biocomposites for the delivery of carbohydrate-based therapeutics. † Electronic supplementary information (ESI) available: Additional figures, movies and experimental details. Substrates used and their formulas, schematic overviews of the performed syntheses and workups, time-dependent MOFformation experiments induced by different carbohydrates and concentrations, yield calculations, SEM image of ZIF-8 on glass and paper, FTIR spectra of the starting materials and the obtained products, schematic of the ion-permeable spherical model, kinetics studies, UV-Vis analyses, photographs of solutions using different polysaccharides, and video showing the succesfull biomimetic mineralisation of CM-dextran. SeeCarbohydrate-based therapeutics are relevant drugs for the treatment of cancer, diabetes, viral and bacterial infections. Therefore the efficient encapsulation and controlled release of carbohydrates has great potential in biomedicine. Here, we present a successful strategy to trigger the spontaneous crystallization of metal-organic frameworks (MOFs) on carbohydrates. The encapsulation of carbohydrates within ZIF-8 and polymorphs (zinc-imidazolate-based MOFs) can be obtained in water. The identification of conditions suitable for the successful preparation of the composite were experimentally and computationally identified. By controlling the chemical functionalization of the carbohydrate, the formation of bio-composites can be obtained in seconds. A 100% encapsulation efficiency was obtained. The controlled release of carbohydrates from the MOF biocomposite was demonstrated. This proof-of-concept study shows that a new generation of MOF biocomposites can be exploited for biomedical applications.

Cu(2)ZnSnSe(4) nanoparticles have high potential to be used as ink for printable solar cells. Using transmission electron microscopy we show that these nanoparticles exhibit a broad range of chemical heterogeneity. These results are contrary to the interpretation of previous experimental work and will have considerable impact on the development of these nanoparticles.

Summary Two commercial instruments that permit a gaseous environment in their specimen chamber have been investigated, namely, a ‘FEI Quanta 600 FEG’ environmental scanning electron microscope and a ‘LEO SUPRA 35VP FESEM’ low vacuum scanning electron microscope. The gas flow field is first computed by the direct simulation Monte Carlo method and the gas density gradient, speed, Mach number and temperature are found in the transition region from high pressure to vacuum. The electron beam transfer characteristics are then derived for different accelerating voltages and pressures and a comparison is made among different situations and with some published works. Certain physical parameters are analysed and discussed to establish a figure of merit that can be used as a standard performance specification for commercial environmental scanning electron microscope and low vacuum scanning electron microscope.