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Femtosecond laser written photonic and microfluidic circuits in diamond

Vibhav Bharadwaj, Ottavia Jedrkiewicz, J P Hadden, Belén Sotillo, María Ramos Vázquez, Paola Dentella, Toney T Fernandez, Andrea Chiappini, Argyro N Giakoumaki, Thien Le Phu, Monica Bollani, Maurizio Ferrari, Roberta Ramponi, Paul E Barclay and Shane M Eaton

J. Phys.: Photonics 1 (2019) 022001


Diamond has attracted great interest in the quantum optics community thanks to its nitrogen vacancy (NV) center, a naturally occurring impurity that is responsiblefor the pink coloration of some diamond crystals. The NV spin state with the brighter luminescence yield can be exploited for spin readout, exhibiting millisecond spin coherence times at ambient temperature. In addition, the energy levels of the ground state triplet of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platformfor efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Integrated diamond photonics would be beneficial for optical magnetometry, due to the enhanced light–matter interaction and associated collection efficiency provided by waveguides, and for quantum information, by means of the optical linking of NV centers for long-range entanglement. Diamond is also compellingfor microfluidic applications due to its outstanding biocompatibility, with sensingfunctionality provided by NV centers. Furthermore, laser written micrographitic modifications could lead to efficient and compact detectors of high energy radiation in diamond. However, it remains a challenge to fabricate optical waveguides, graphitic lines, NVs and microfluidics in diamond. In this Review, we describe a disruptive laser nanofabrication method based on femtosecond laser writing to realize a 3D micro-nano device toolkitfor diamond. Femtosecond laser writing is advantageous compared to other state of the art fabrication technologies due to its versatility in forming diverse micro and nanocomponents in diamond.We describe how high quality buried optical waveguides, low roughness microfluidic channels, and on-demand NVs with excellent spectral properties can be laser formed in single-crystal diamond.We show the first integrated quantum photonic circuit in diamond consisting of an optically addressed NV for quantum information studies. The rapid progress of the field is encouraging but there are several challenges which must be met to realize future quantum technologies in diamond.We elucidate how these hurdles can be overcome using femtosecond laserfabrication, to realize both quantum computing and nanoscale magnetic field sensing devices in synthetic diamond.

Divergent Terpyridine-Based Coordination for the Constructionof Photoactive Supramolecular Structures

A. Agosti, E. Kuna, G. Bergamini. Eur. J. Inorg. Chem., 2019, DOI: 10.1002/ejic.201801263.


Exploring new materials to manipulate luminescentradiation and investigate the interaction of light and matter isone of the most compelling prospects of our century. Supra-molecular chemistry has unraveled the opportunity to synergis-tically combine the chemical and optoelectronic properties ofthe most diverse classes of compounds. Among these, ter-pyridines have acted as pivotal ligand units that enable self-assembly of multicomponent chromophoric systems. In this re-view we therefore elucidate the metal-coordinating ability of these materials, that promote a plethora of aggregation-in-duced phenomena. In particular, fluorescence tuning, reversiblestimuli-responsive phosphorescence enhancement and low-dimensional complexation have been demonstrated for carbonand sulfur based terpyridine oligomeric structures. Commonthread of such processes is the versatile application of light asa trigger for spectroscopic investigation and output for superioroptical, medical and sensing devices.


Valeria Italia, Argyro N. Giakoumaki, Silvio Bonfadini, Vibhav Bharadwaj, Thien Le Phu, Shane M. Eaton, Roberta Ramponi, Giacomo Bergamini, Guglielmo Lanzani and Luigino Criante Micromachines 2019, 10(1), 23. Special Issue Glassy Materials Based Microdevices


In recent years, there has been significant research on integrated microfluidic devices. Microfluidics offer an advantageous platform for the parallel laminar flow of adjacent solvents of potential use in modern chemistry and biology. To reach that aim, we worked towards the realization of a buried microfluidic Lab-on-a-Chip which enables the separation of the two components by exploiting the non-mixing properties of laminar flow. To fabricate the aforementioned chip, we employed a femtosecond laser irradiation technique followed by chemical etching. To optimize the configuration of the chip, several geometrical and structural parameters were taken into account. The diffusive mass transfer between the two fluids was estimated and the optimal chip configuration for low diffusion rate of the components was defined.

Tailored Synthesis of N-Substituted peri-Xanthenoxanthene Diimide (PXXDI) and Monoimide (PXXMI) Scaffolds

Andrea Sciutto , Andrey Berezin, Matteo Lo Cicero, Tanja Miletić , Antoine Stopin, and Davide Bonifazi
J. Org. Chem., 2018, 83 (22), pp 13787–13798


The tailored synthesis of homo (A2) and hetero (AB) N-substituted peri-xanthenoxanthene diimides (PXXDIs) and peri-functionalized PXX monoimides (PXXMIs) from 3-hydroxy naphthalic anhydride is described. As A2-type PXXDIs could be synthesized in one step, AB-type PXXDIs and PXXMIs were prepared through a modular approach capitalizing on sequential Suzuki coupling, imidation, and Pummerer reactions with very high yields. In view of their potential applications as organic semiconductors, self-organization studies were performed through liquid deposition on surfaces, depicting the formation of islands, needles, and rods.

Comment on “Zemplén transesterification: a name reaction that has misled us for 90 years” 

Cristofer Pezzetta, Sofja Tshepelevitsh, Ivo Leito c and Giovanni Poli
Green Chem., 2018,20, 2392-2394 



The recent title paper reports that the Zemplén transesterification can be accomplished equally well using catalytic amounts of NaOH in MeOH instead of the classical catalytic amounts of MeONa in dry MeOH, which led the authors to propose a modified mechanism for this transformation. Simple proton transfer considerations show that, in the above modified conditions, the original methoxy anion-catalysed mechanistic path still holds against the proposed hydroxy anion-catalysed one, when hydrogen bonding is taken into account.!divAbstract

Oxygen-Doped Zig-Zag Molecular Ribbons

Andrey Berezin, Nicolas Biot, Tommaso Battisti, and Davide Bonifazi*



The synthesis of a zig-zag oxygen-doped molecular rhombic ribbon has been achieved. This includes oxidative C@C and C@O bond formations that allowed the stepwise elongation and planarization of an oxa-congener of 2,7- periacenoacene. X-ray diffraction analysis corroborated the flat structure and the zig-zag topology of the O-doped edges. Photophysical and electrochemical investigations showed that the extension of the peri-xanthenoxanthene (PXX) into the molecular ribbon induces a noticeable shrinking of the molecular band gap devised by a rising of the HOMO energy level, a desirable property for p-type organic semiconductors.

Asymmetric Photocatalytic C−H Functionalization of Toluene and Derivatives

Daniele Mazzarella, Giacomo E. M. Crisenza, and Paolo Melchiorre*
J. Am. Chem. Soc., 2018, 140 (27), pp 8439–8443ABSTRACT


Reported herein is a visible-light-mediated organocatalytic direct C−H functionalization of toluene derivatives to afford enantioenriched β-benzylated aldehydes from the corresponding enals. The process combines the oxidative power of a chiral excited-state iminium ion and the basic nature of its counteranion to trigger the generation of benzylic radicals by means of a sequential multisite proton-coupled electron transfer mechanism. This study shows that feedstock chemicals generally used as solvents, such as toluene and xylene derivatives, can be used as substrates for making chiral molecules with high enantioselectivity.

Direct Stereoselective Installation of Alkyl Fragments at the β-Carbon of Enals via Excited Iminium Ion Catalysis

Charlie Verrier, Nurtalya Alandini, Cristofer Pezzetta, Mauro Moliterno, Luca Buzzetti, Hamish B. Hepburn, Alberto Vega-Peñaloza, Mattia Silvi, and Paolo Melchiorre*
ACS Catal., 2018, 8 (2), pp 1062–1066


The direct introduction of sp3 carbon fragments at the β position of α,β-unsaturated aldehydes is greatly complicated by competing 1,2-addition manifolds. Previous catalytic enantioselective conjugate addition methods, based on the use of organometallic reagents or ground-state iminium ion activation, could not provide general and efficient solutions. We report herein that, by turning them into strong oxidants, visible light excitation of chiral iminium ions triggers a stereocontrolled radical pathway that exclusively affords highly enantioenriched β-substituted aldehydes bearing a variety of alkyl fragments.

Efficient and Selective Photocatalytic Oxidation of Benzylic Alcohols with Hybrid Organic–Inorganic Perovskite Materials

Haowei Huang, Haifeng Yuan*, Kris P. F. Janssen, Guillermo Solís-Fernández, Ying Wang, Collin Y. X. Tan†, Dries Jonckheere, Elke Debroye, Jinlin Long, Jelle Hendrix, Johan Hofkens*, Julian A. Steele, and Maarten B. J. Roeffaers*
ACS Energy Lett., 2018, 3 (4), pp 755–759



The impressive optoelectronic performance and low production cost of metal halide perovskites have inspired applications well beyond efficient solar cells. Herein, we widen the materials engineering options available for the efficient and selective photocatalytic oxidation of benzylic alcohols, an industrially significant reaction, using formamidinium lead bromide (FAPbBr3) and other perovskite-based materials. The best performance was obtained using a FAPbBr3/TiO2hybrid photocatalyst under simulated solar illumination. Detailed optical studies reveal the synergetic photophysical pathways arising in FAPbBr3/TiO2 composites. An experimentally supported model rationalizing the large conversion enhancement over the pure constituents shows that this strategy offers new prospects for metal halide perovskites in photocatalytic applications.

Templated chromophore assembly on peptide scaffolds: a structural evolution

Dr. Lou Rocard  Darren Wragg  Dr. Samuel Alexander Jobbins  Lorenzo Luciani  Prof. Dr. Johan Wouters Dr. Stefano Leoni  Prof. Dr. Davide Bonifazi



The use of a template bearing pre-programmed receptor sites selectively accommodating chromophores at given positions is an attractive approach for engineering artificial light-harvesting systems. Indulging this line of thought, this work tackles the creation of tailored antenna architectures with yellow, red and blue chromophores exploiting three dynamic covalent reactions simultaneously, namely disulfide exchange, acyl hydrazone and boronic ester formations. The effect of various structural modifications, such as the chromophores as well as their spatial organization (distance, orientation, order), on the energy transfer within the antennas was studied by means of steady-state UV-Vis absorption and fluorescence spectroscopies. This systematic study allowed a significant improvement of the energy transfer efficiencies across the chromophores to a noticeable 22 and 15%, for the yellow and red donors to the blue acceptor, respectively. Metadynamics simulations suggested that the conformational properties of the antennas are driven by intramolecular chromophoric stacking interactions that, forcing the α-helix to fold on itself, annul any effects deriving from the programming of the spatial arrangement of the receptor sides in the peptide backbone.

Customizing Photoredox Properties of PXX‐based Dyes through Energy Level Rigid Shifts of Frontier Molecular Orbitals

Andrea Sciutto  Dr. Andrea Fermi  Dr. Andrea Folli  Tommaso Battisti  Dr. Joseph M. Beames Prof. Dr. Damien M. Murphy  Prof. Dr. Davide Bonifazi
Chem.Eur.J.2018,24,4382 –4389


Here we describe the synthesis of electron‐rich PXX derivatives in which the energy levels of the excited states have been rigidly shifted through the insertion of imide groups. This has allowed the development of a new series of oxygen‐doped photoredox‐active chromophores with improved oxidizing and reducing properties. Capitalizing on the dehalogenation of organic halides as a model reaction, we could investigate the photooxidative and photoreductive potential of these molecules in model chemical transformations. Depending on the substrate, solvent and dye the reaction mechanism can follow different paths. This prompted us to consider the first chemoselective transformation protocol, in which two different C−Br bonds could be chemoselectively reacted through the sequential photoactivation of two different colorants.

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