Graphene Quantum Dots

Graphene quantum dots (GQDs) are nanometer‐sized fragments of graphene that show unique properties, which makes them interesting candidates for a whole range of new applications. This review article gives an overview of the synthesis, properties and applications of GQDs. Synthesis methods discussed include top‐down and bottom‐up approaches. Properties such as luminescence up‐ and down‐conversion have been used in applications ranging from energy conversion to bio‐analytics. This article provides an overview of the state‐of‐the‐art and highlights promising findings as well as potential future directions of the research field.     

Liquid crystal and solution phases of sodium dodecyl-p-benzene sulphonate (NaLAS) and octa-oxyethylene glycol hexadecyl ether (C16E8): 1:1 mixtures in water

The liquid crystals and other phases formed when the mixed surfactant system sodium dodecyl-p-benzene sulphonate (NaLAS) and octa-oxyethylene glycol hexadecyl ether (C₁₆E₈, 1:1 by weight) is dispersed in water have been investigated using optical microscopy, X-ray diffraction and differential scanning calorimetry. Despite the fact that neat LAS is a multi-phase solid and C₁₆E₈ is a crystalline solid, when the two are mixed at temperatures above the melting temperature of the C₁₆E₈ with no water present, what appears to be a metastable gel phase formed containing only a small volume fraction of un-dissolved LAS (ca. 5%). Moreover, when water is added to the system, the phase behaviour of the mixture considerably differs to that of either of the individual components. We report a detailed phase study on this mixture here particularly focussing on the ‘neat’ mixture. The phase behaviour when water is added is also discussed. Particularly interesting is the presence of a micellar phase between the hexagonal and lamellar phases thought to be due to weak interactions between micelles during the transition from rods to discs. In addition, the presence of a low temperature intermediate phase is discussed.     

Applications of the MFI-UF to measure and predict particulate fouling in RO systems

The MFI-UF was developed to include smaller colloidal particles not measured in the existing Silt Density Index (SDI) and MFI_0.45 fouling indices. This research investigates the application of the MFI-UF to measure and predict the particulate fouling potential of reverse osmosis (RO) feedwater and also to assess pretreatment efficiency. MFI-UF measurements were carried out at the IJssel Lake and River Rhine RO pilot plants of the influent feedwater, RO concentrate and after pretreatment processes. Pretreatment efficiency was compared based on MFI-UF, MFI_0.45, and SDI measurements. The MFI-UF of the influent feedwater was approximately 700–2400 times higher than the corresponding MFI_0.45 and SDI, due to the retention of smaller particles. A pretreatment efficiency of ≥80%, was found by the MFI-UF at both pilot plants. For the larger particles the MFI_0.45 gave a 90–100% reduction. Minimum predicted run times for a 15% flux decline from MFI-UF measurements were shorter than that observed at the IJssel Lake pilot plant. This may be explained by problems with the ultrafiltration (UF) pretreatment at the time and/or almost negligible particle deposition in the RO pilot systems. Moreover, it was shown that cake resistance increased with ionic strength in MFI-UF tap water experiments and therefore, a correction of the MFI-UF index is required for salinity effects in RO concentrate.     

An interferometric linear in-plane position transducer

When mutally coherent light beams overlap on an optically rough surface, the scattered light fields or speckle patterns interfere. The intensity at any point depends on the phase difference between the light fields. By matching the sensitive area of a photodetector to speckle size, an electronic signal is obtained which can be used to monitor in-plane rigid body translations of the surface with interferometric precision. Two reliable methods of obtaining directional sensitivity based on polarization properties are described and it is shown that depolarization effects due to rough surfaces, do not cause any difficulty. Intensitivity to motion orthogonal to the plane of the apparatus is demonstrated.     

Simple phase-shifting lateral shearing interferometer

A phase-shifting electronic speckle pattern shearing interferometer with a very simple shearing device is proposed. Two partially reflective glass plates are used to introduce the shear in this new interferometer. The reflection coefficients of the coatings on the two plates are 0.3 and 0.7. The distance between the two glass plates controls the size of the shear. The proposed new interferometric system is simple, flexible, and low cost.     

Luminescent oligo(tetraphenyl)silole nanoparticles as chemical sensors for aqueous TNT

Colloidal oligo(tetraphenyl)silole nanoparticles in THF/H2O suspensions show increased luminescence and offer a method to detect TNT in an aqueous environment.     

Simple versatile shearing interferometer suitable for measurements on a microscopic scale

Micro-electromechanical systems (MEMS) behave differently from massive samples. Conventional testing and inspection techniques usually fail at the microscale. Recently there has been an increasing interest in the application of optical techniques for microstructure testing, because they are high-resolution, non-contact, full-field, fast and relatively inexpensive. New interferometric systems, which are suitable for microscopic optical metrology, are of interest for engineering and industrial applications.A modified electronic speckle pattern shearing interferometer (ESPSI) with a very simple shearing device has been designed for metrology applications on the microscale. The shearing device consists of two partially reflective glass plates. The reflection coefficients of the coatings are 0.3 and 0.7, respectively. The distance and the tilt between the two glass plates control the size of the shear. A long working distance microscope objective is attached to the CCD camera to form a field of view variable over several millimetres in width. The suitability of the system for microscopic measurements is demonstrated. The capability of the system for phase shifting is also demonstrated. The results obtained are promising for future applications of the ESPSI system for testing and characterisation of MEMS.     

Asymmetric Isothiourea‐Catalysed Formal [3+2] Cycloadditions of Ammonium Enolates with Oxaziridines

A highly enantioselective Lewis base‐catalysed formal [3+2] cycloaddition of ammonium enolates and oxaziridines to give stereodefined oxazolidin‐4‐ones in high yield is described. Employing an enantioenriched oxaziridine in this process leads to a matched/mis‐matched effect with the isothiourea catalyst and allowed the synthesis of either syn‐ or anti‐stereodefined oxazolidin‐4‐ones in high d.r., yield and ee. Additionally, the oxazolidin‐4‐one products have been derivatised to afford functionalised enantioenriched building blocks.