Lab-in-a-tube: ultracompact components for on-chip capture and detection of individual micro-/nanoorganisms

A review of present and future on-chip rolled-up devices, which can be used to develop lab-in-a-tube total analysis systems, is presented. Lab-in-a-tube is the integration of numerous rolled-up components into a single device constituting a microsystem of hundreds/thousands of independent units on a chip, each individually capable of sorting, detecting and analyzing singular organisms. Such a system allows for a scale-down of biosensing systems, while at the same time increasing the data collection through a large, smart array of individual biosensors. A close look at these ultracompact components which have been developed over the past decade is given. Methods for the capture of biomaterial are laid out and progress of cell culturing in three-dimensional scaffolding is detailed. Rolled-up optical sensors based on photoluminescence, optomechanics, optofluidics and metamaterials are presented. Magnetic sensors are introduced as well as electrical components including heating, energy storage and resistor devices.     

On-chip electrochemical detection of CdS quantum dots using normal and multiple recycling flow through modes

A flexible hybrid polydimethylsiloxane (PDMS)-polycarbonate (PC) microfluidic chip with integrated screen printed electrodes (SPE) was fabricated and applied for electrochemical quantum dots (QDs) detection. The developed device combines the advantages of flexible microfluidic chips, such as their low cost, the possibility to be disposable and amenable to mass production, with the advantages of electrochemistry for its facility of integration and the possibility to miniaturize the analytical device. Due to the interest in biosensing applications in general and particularly the great demand for labelling alternatives in affinity biosensors, the electrochemistry of cadmium sulfide quantum dots (CdS QDs) is evaluated. Square wave anodic stripping voltammetry (SWASV) is the technique used due to its sensitivity and low detection limits that can be achieved. The electrochemical as well as the microfluidic parameters of the developed system are optimized. The detection of CdS QDs in the range between 50 to 8000 ng mL(-1) with a sensitivity of 0.0009 μA/(ng mL(-1)) has been achieved. In addition to the single in-chip flow through measurements, the design of a recirculation system with the aim of achieving lower detection limits using reduced volumes (25 μL) of sample was proposed as a proof-of-concept.     

Structures of uranyl peroxide hydrates: a first-principles study of studtite and metastudtite

The structures of the only known minerals containing peroxide, namely studtite [(UO(2))O(2)(H(2)O)(4)] and metastudtite [(UO(2))O(2)(H(2)O)(2)], have been investigated using density functional theory. The structure of metastudtite crystallizing in the orthorhombic space group Pnma (Z = 4) is reported for the first time at the atomic level and the computed lattice parameters, a = 8.45, b = 8.72, c = 6.75 ?, demonstrate that the unit cell of metastudtite is larger than previously reported dimensions (Z = 2) derived from experimental X-ray powder diffraction data.     

Synthetic routes to [Au(NHC)(OH)] (NHC = N-heterocyclic carbene) complexes

New procedures for the synthesis of [Au(NHC)(OH)] are reported. Initially, a two-step reaction via the digold complex [{Au(NHC)}(2)(μ-OH)][BF(4)] was probed, enabling the preparation of the novel [Au(SIPr)(OH)] complex and of its previously reported congener [Au(IPr)(OH)]. After further optimization, a one-step procedure was developed.     

Polyatomic anion assistance in the assembly of [2]pseudorotaxanes

We describe the use of polyatomic anions for the quantitative assembly of ion-paired complexes displaying pseudorotaxane topology. Our approach exploits the unique ion-pair recognition properties exhibited by noncovalent neutral receptors assembled through hydrogen-bonding interactions between a bis-calix[4]pyrrole macrocycle and linear bis-amidepyridyl-N-oxides. The complexation of bidentate polyatomic anions that are complementary in size and shape to the receptor's cavity, in which six NH hydrogen-bond donors converge, induces the exclusive formation of four particle-threaded assemblies.     

Development of a selective chemical etch to improve the conversion efficiency of Zn-rich Cu2ZnSnS4 solar cells

Improvement of the efficiency of Cu(2)ZnSnS(4) (CZTS)-based solar cells requires the development of specific procedures to remove or avoid the formation of detrimental secondary phases. The presence of these phases is favored by the Zn-rich and Cu-poor conditions that are required to obtain device-grade layers. We have developed a selective chemical etching process based on the use of hydrochloric acid solutions to remove Zn-rich secondary phases from the CZTS film surface, which are partly responsible for the deterioration of the series resistance of the cells and, as a consequence, the conversion efficiency. Using this approach, we have obtained CZTS-based devices with 5.2% efficiency, which is nearly twice that of the devices we have prepared without this etching process.     

On the accessibility to conical intersections in purines: hypoxanthine and its singly protonated and deprotonated forms

The dynamics following electronic excitation of hypoxanthine and its nucleoside inosine were studied by femtosecond fluorescence up-conversion. Our objective was to explore variants of the purinic DNA bases in order to determine the molecular parameters that increase or reduce the accessibility to ground state conical intersections. From experiments in water and methanol solution we conclude that both dominant neutral tautomers of hypoxanthine exhibit ultrashort excited state lifetimes (τ < 0.2 ps), which are significantly shorter than in the related nucleobase guanine. This points to a more accessible conical intersection for the fluorescent state upon removal of the amino group, present in guanine but absent in hypoxanthine. The excited state dynamics of singly protonated hypoxanthine were also studied, showing biexponential decays with a 1.1 ps component (5%) besides a sub-0.2 ps ultrafast component. On the other hand, the S(1) lifetimes of the singly deprotonated forms of hypoxanthine and inosine show drastic differences, where the latter remains ultrafast but the singly deprotonated hypoxanthine shows a much longer lifetime of 19 ps. This significant variation is related to the different deprotonation sites in hypoxanthine versus inosine, which gives rise to significantly different resonance structures. In our study we also include multireference perturbation theory (MRMP2) excited state calculations in order to determine the nature of the initial electronic excitation in our experiments and clarify the ordering of the states in the singlet manifold at the ground state geometry. In addition, we performed multireference configuration interaction calculations (MR-CIS) that identify the presence of low-lying conical intersections for both prominent neutral tautomers of hypoxanthine. In both cases, the surface crossings occur at geometries reached by out of plane opposite motions of C2 and N3. The study of this simpler purine gives several insights into how small structural modifications, including amino substitution and protonation site and state, determine the accessibility to conical intersections in this kind of heterocycles.     

In situ growth of metal particles on 3D urchin-like WO3 nanostructures

Metal/semiconductor hybrid materials of various sizes and morphologies have many applications in areas such as catalysis and sensing. Various organic agents are necessary to stabilize metal nanoparticles during synthesis, which leads to a layer of organic compounds present at the interfaces between the metal particles and the semiconductor supports. Generally, high-temperature oxidative treatment is used to remove the organics, which can extensively change the size and morphology of the particles, in turn altering their activity. Here we report a facile method for direct growth of noble-metal particles on WO(3) through an in situ redox reaction between weakly reductive WO(2.72) and oxidative metal salts in aqueous solution. This synthetic strategy has the advantages that it takes place in one step and requires no foreign reducing agents, stabilizing agents, or pretreatment of the precursors, making it a practical method for the controlled synthesis of metal/semiconductor hybrid nanomaterials. This synthetic method may open up a new way to develop metal-nanoparticle-loaded semiconductor composites.     

Regioselective ring expansion of 2,4-diiminoazetidines via cleavage of C-N and C(sp3)-H bonds: efficient construction of 2,3-dihydropyrimidinesulfonamides

A highly regioselective base-mediated ring expansion of 2,4-diiminoazetidines via cleavage of C-N and C(sp(3))-H bonds is achieved for the first time to afford efficiently 2,3-dihydropyrimidinesulfonamides. The mechanism of the ring expansion via tandem 4π electrocyclic ring-opening/1,5-H shift/6π electrocyclic ring-closing is well confirmed by the trapping experiments of two key intermediates and deuterium labeling studies.     

Study of the antioxidant mechanisms of Trolox and eugenol with 2,2'-azobis(2-amidinepropane)dihydrochloride using ultra-high performance liquid chromatography coupled with tandem mass spectrometry

The study of antioxidant mechanisms is a difficult task that involves the monitoring and identification of unknown intermediate and final products. Most of the time, the lifetime of intermediates is too short to allow their isolation and subsequent identification by nuclear magnetic resonance (NMR). The developments of ultra-high performance liquid chromatography (UHPLC) coupled with the advances in the acquisition rates of mass spectrometry could facilitate the research on antioxidant mechanisms. This work is based on the reaction involved in the Oxygen Radical Antioxidant Capacity (ORAC) and Total Radical trapping Antioxidant Parameter (TRAP) assays. Hence, the reaction between 2,2'-azobis(2-amidinepropane)dihydrochloride (AAPH) radicals and an antioxidant was carried out in the thermostatized autosampler of a chromatographic device. Then, the reaction media were injected every six minutes, and the compounds were separated by UHPLC and detected by mass spectrometry in scan mode. Nine consecutive injections were registered in a unique file, then the evolution of the reaction for one hour in a single run was monitored. In this way, the reaction mechanisms of Trolox and eugenol with AAPH were studied, leading to the detection of nine and thirteen different compounds, respectively. An exhaustive analysis of the spectra obtained in product ion scan mode led to the identification of the compounds. Most of them were species previously found in the literature, but others have never been reported, so tentative structures were suggested. All this allowed the proposal of several steps within the antioxidant mechanisms of Trolox and eugenol, showing the great performance of UHPLC-MS/MS to complement the use of NMR in antioxidant mechanistic studies.