A type of glass modifications occurring after femto‐second laser irradiation gives rise to strong (10−2) from birefringence. This form birefringence is thought to be related to index nanostructure (called nanogratings). Analyzing induced tracks in fused silica using scanning electron microscopy (SEM) with nm resolution shows that nanostructures are porous nanoplanes with an average index lower than typical silica (Δn ∼ –0.20). Their origin is explained as arising from fast decomposition of the glass under localized, high‐intensity femtosecond laser radiation where strong nonlinear, multiphoton‐induced photoionization leads to plasma generation. Mechanistic details include Coulombic explosions characteristic of strong photoionization and the production of self‐trapped exciton (STE). Rapid relaxation of these STE prevents recombination and dissociated atomic oxygen instead recombines with each other to form molecular oxygen pointed out using Raman microscopy. Some of it is dissolved in the condensed glass whilst the rest is trapped within nanovoids. A chemical recombination can only occur at 1200 °C for many hours. This explains the thermal stability of such a nanostructure. Precise laser translation and control of these birefringent nanoporous structures allo arbitrarily tuning and positioning within the glass, an important tool for controlling optical properties for photonic applications, catalysts, molecular sieves, composites and more.

A regenerated optical fibre Bragg grating that survives temperature cycling up to 1,295°C is demonstrated. A model based on seeded crystallisation or amorphisation is proposed.

Regenerated gratings seeded by type I gratings in boron-codoped germanosilicate optical fiber written with 193 nm are shown to withstand temperatures beyond 1000 degrees C.

A need still exists for a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method that can detect broad classes of glutathione (GSH) conjugates and provide characterization of their structures. We now describe the development of a method that multiplexes high-resolution accurate mass analysis with isotope pattern triggered data-dependent product ion scans, for simultaneous detection and structural elucidation of GSH conjugates within a single analysis using a LTQ/Orbitrap. This method was initially developed to detect GSH conjugates generated from incubating 10 microM test compound with pooled human liver microsomes fortified with NADPH-regenerating system and a 2:1 ratio of 5 mM glutathione and [(13)C(2) (15)N-Gly]glutathione. The GSH conjugates were detected by isotope search of mass defect filtered and control subtracted full scan accurate MS data using MetWorks software. This was followed by elucidation of reactive intermediate structures using chemical formulae for both protonated molecules and their product ions from accurate masses in a single analysis. The mass accuracies measured for the precursor and product ions by the Orbitrap were <2 ppm in external mass calibration mode. Successful detection and characterization of GSH conjugates of acetaminophen, tienilic acid, clozapine, ticlopidine and mifepristone validated this method. In each case, the detected GSH conjugates were within the top five hits by isotope search. This method also has a broader detection capability since it is independent of the collision-induced dissociation behavior of the GSH conjugates. Furthermore, this method is amenable to a broad class of reactive intermediate trapping agents as exemplified by the simultaneous detection and structural elucidation of the cyano-N-methylene iminium ion conjugates of verapamil and its O-desmethyl metabolites, which we report for the first time. In addition to the chemically tagged reactive intermediates, this method also provides information on stable metabolites from the full scan accurate MS data.

Performance evaluation of accurate mass measurement by the LTQ/Orbitrap, at a resolving power of 60,000 and in external calibration mode, indicated that the Orbitrap is capable of providing high mass accuracy of <2 ppm for over 24 h post-calibration. This, together with limited trade-off between sensitivity and resolving power plus a wide dynamic range for mass accuracy, suggested that the LTQ/Orbitrap is an ideal analytical tool for structural elucidation of metabolites. The application of the LTQ/Orbitrap to identification of human liver microsomal metabolites of carvedilol was evaluated, using parent mass list triggered data-dependent multiple-stage accurate mass analysis, at a resolving power of 60,000 in external calibration mode. A metabolite identification workflow was developed to utilize chemical formulas from high-resolution accurate mass measurements to confirm structures of product ions of a drug proposed by Mass Frontier, illustrated by identification of structures used to establish lineage of product ions of carvedilol, which later served as a template for identification of its metabolites. A total of 58 in vitro metabolites of carvedilol were detected using 5-ppm mass tolerance filters for theoretical m/z of protonated molecules of predicted metabolites in addition to product ions and neutral mass losses diagnostic of carvedilol. The chemical formulas with unsaturation numbers calculated from the accurate m/z of precursor and product ions can be used to assign, with a high degree of confidence, the structures of metabolites and the sites of metabolism. The mass accuracies obtained for all full scan MS and MSn spectra were <2 ppm. The majority of the metabolites identified agreed with those previously reported except for those that have not been reported before. For example, several glutathione conjugates of carvedilol were reported for the first time, which may explain the reported hepatotoxicity during clinical trials and recent clinical use.

No abstract

An optical fiber-based smartphone spectrometer incorporating an endoscopic fiber bundle is demonstrated. The endoscope allows transmission of the smartphone camera LED light to a sample, removing complications from varying background illumination. The reflected spectra collected from a surface or interface is dispersed onto the camera CMOS using a reflecting diffraction grating. A spectral resolution as low as δλ∼2.0  nm over a bandwidth of Δλ∼250  nm is obtained using a slit width, ω_slit=0.7  mm. The instrument has vast potential in a number of industrial applications including agricultural produce analysis. Spectral analysis of apples shows straightforward measurement of the pigments anthocyanins, carotenoid, and chlorophyll, all of which decrease with increasing storage time.

A structured optical fibre is drawn from a 3D-printed structured preform. Preforms containing a single ring of holes around the core are fabricated using filament made from a modified butadiene polymer. More broadly, 3D printers capable of processing soft glasses, silica and other materials are likely to come on line in the not-so-distant future. 3D printing of optical preforms signals a new milestone in optical fibre manufacture.In recent years, there has been an explosion of interest in 3D printing technologies and there is now a vast range of 3D printing methods that are finding new applications every day in a whole host of areas from science and engineering to medicine and the arts [1]. They are set to revolutionise manufacturing. Fused deposition modelling (FDM) is one of the most commonly used techniques, being the first and simplest demonstration of 3D printing in the late 1980s [2]. It is especially suited for instrument prototype casings such as those required for novel smartphone spectrometers [3]. In FDM, a polymer is fed through a heated nozzle which melts the polymer -essentially a fancy thermal glue gun using a finite extrusion nozzle with programmable xyz positioning capability. Optical polymerisation methods using both light emitting diodes (LEDs) and lasers offer higher resolution and are increasingly popular; however, they do not have the same material range given the specific absorption and monomer polymerization requirements. Selective laser sintering (SLS) is another popular technique where a high power laser is utilised to fuse not only plastic, but glass, metal or ceramic particles or powders into 3D objects [4]. A 3D profile is achieved by scanning the laser on the horizontal plane layer-by-layer, lowering the printing bed between each layer. All these methods have their particular rate limiting steps determined by the consolidation process details and the need for full xyz scanning. More recently, holographic imaging using projectors promises significantly accelerated production of the 3D printed object by removing the requirement for xy scanning [5]. FDM, SLS and other related variants are experiencing tremendous growth world-wide, particularly for rapid prototyping and manufacturing. 3D printing is also being applied to cellular assembly processing of biomedical interest [6]. 3D printing technologies are reaching most fields, including more recently photonics. For example, a company called Luxexcel is already producing high transparency Fresnel lenses by printing with polymethylmethacrylate (PMMA) filament [7]. Most interesting, is recent work demonstrating directprint short, solid plastic fibre [8] and "light pipes" [9] using transparent polymers, the first 3D printed waveguides.Here, we explore harnessing 3D printing for optical fibre fabrication. We see it as revolutionising the manufacture of all optical fibre fabrication, including glass optical fibres as 3D glass printing comes on line [10,11]. Whilst there is debate as to the merits of the technology for conventional step-index...