Shear‐Controlled Micro/Nanometer‐Scaled Super‐Hydrophobic Surfaces with Tunable Sliding Angles from Single Component Isotactic Poly(propylene)

Summary: With the proper selection of shear and thermal conditions, super‐hydrophobic polymeric surfaces (contact angle > 150°) with tunable sliding angles (from less than 1° to higher than 90°) can be prepared from pure isotactic poly(propylene) (iPP) without any further modification with low‐surface‐energy components under ambient atmosphere. The formed surfaces have naturally good thermal properties, chemical and moisture resistance, low density, and potentially low manufacturing cost.

SEM images of formed super‐hydrophobic surfaces and related two extreme sliding angles (contact angles of these surfaces are higher than 150°).     

A new phase modulated binomial‐like selective‐inversion sequence for solvent signal suppression in NMR

A new 8 ‐pulse P hase M odulated binomial‐like selective inversion pulse sequence, dubbed ‘8PM’, was developed by optimizing the nutation and phase angles of the constituent radio‐frequency pulses so that the inversion profile resembled a target profile. Suppression profiles were obtained for both the 8PM and W5 based excitation sculpting sequences with equal inter‐pulse delays. Significant distortions were observed in both profiles because of the offset effect of the radio frequency pulses. These distortions were successfully reduced by adjusting the inter‐pulse delays. With adjusted inter‐pulse delays, the 8PM and W5 based excitation sculpting sequences were tested on an aqueous lysozyme solution. The 8 PM based sequence provided higher suppression selectivity than the W5 based sequence. Two‐dimensional nuclear Overhauser effect spectroscopy experiments were also performed on the lysozyme sample with 8PM and W5 based water signal suppression. The 8PM based suppression provided a spectrum with significantly increased (~ doubled) cross‐peak intensity around the suppressed water resonance compared to the W5 based suppression. Copyright © 2016 John Wiley & Sons, Ltd.     

Extending the Scope of Singlet‐State Spectroscopy

Different decoupling sequences are tested—using various shaped radio‐frequency (RF) pulses—to achieve the longest possible lifetimes of singlet‐state populations over the widest possible bandwidths, that is, ranges of offsets and relative chemical shifts of the nuclei involved in the singlet states. The use of sinc or refocusing broadband universal rotation pulses (RE‐BURP) for decoupling during the intervals where singlet‐state populations are preserved allows one to extend the useful bandwidth with respect to prior state‐of‐the‐art methods based on composite‐pulse WALTZ decoupling. The improved sinc decoupling sequences afford a more reliable and sensitive measure of the lifetimes of singlet states in pairs of spins that have widely different chemical shifts, such as the two aromatic protons H⁵ and H⁶ in uracil. Similar advantages are expected for nucleotides in RNA and DNA. Alternative approaches, in particular frequency‐modulated decoupling sequences, also appear to be effective in preserving singlet‐state populations, even though the profiles of the apparent relaxation rate constants as a function of the offset are somewhat perturbed. The best decoupling sequences prove their utility in sustaining longer lifetimes of singlet states than previously achieved for the side‐chain tyrosine protons in bovine pancreatic trypsin inhibitor (BPTI) at 600 MHz (14.1 T), where the differences of chemical shifts between coupled protons are a challenge.     

Broadband excitation pulses for high‐field solid‐state nuclear magnetic resonance spectroscopy

In nuclear magnetic resonance spectroscopy, experimental limits due to the radiofrequency transmitter and/or coil means that conventional radiofrequency pulses (“hard pulses”) are sometimes not sufficiently powerful to excite magnetization uniformly over a desired range of frequencies. Effects due to nonuniform excitation are most frequently encountered at high magnetic fields for nuclei with a large range of chemical shifts. Using optimal control theory, we have designed broadband excitation pulses that are suitable for solid‐state samples under magic‐angle‐spinning conditions. These pulses are easy to implement, robust to spinning frequency variations, and radiofrequency inhomogeneities, and only four times as long as a corresponding hard pulse. The utility of these pulses for uniformly exciting ¹³C nuclei is demonstrated on a 900 MHz (21.1 T) spectrometer. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation and properties of high‐pretilt‐angle polyimides based on an alicyclic dianhydride and long alkyloxy side‐group‐containing diamines

A series of polyimides were prepared by a solution polycondensation reaction between 3‐carboxylmethylcyclopentane‐1,2,4‐tricarboxylic dianhydride and 4‐alkyloxybenzene‐1,3‐diamines in N‐methyl‐2‐pyrrolidone and chemical imidization with triethylamine and acetic anhydride. These polyimides possess great organo‐solubility, high optical transparency, and high pretilt angles. They are soluble not only in strong polar aprotic organic solvents such as N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, m‐cresol, and 1,4‐butyrolactone but also in common low‐boiling‐point solvents such as chloroform and tetrahydrofuran, and some are even soluble in acetone. They exhibit high transparency at wavelengths greater than 320 nm. They can generate pretilt angles greater than 5°, and some can even achieve pretilt angles greater than 10°. The pretilt angle of a polyimide increases with the increasing length of the alkyloxy side group. The polyimides possess glass‐transition temperatures between 180 and 230 °C and thermal decomposition temperatures (onset temperatures) of about 435 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1943–1950, 2000     

Effect of oxidized silicon (SiOx) surfaces functionalization on real‐time PCR by Lab‐on‐a‐chip microdevices

There is a great need to improve the biocompatibility of silicon‐based lab‐on‐chip substrate materials for reliable quantitative analysis of biological solutions. These advanced microdevice surfaces need not only be biocompatible but also have surfaces of defined wettability characteristics. The inhibition of biomolecular activity due to microdevice surface interaction is common and can result in inaccurate results or decreased reaction yields. In this work we investigate different techniques for the chemical functionalization of oxidized silicon (SiO_x) surfaces in order to: (i) obtain defined hydrophobic/hydrophilic surfaces; and (ii) increase the efficiency of performing Real‐Time Polymerase Chain Reaction (PCR) on a silicon‐based lab‐on‐chip. Silicon oxide surfaces are functionalized by grafting alkylic chain silanes and poly(ethylene glycol) (PEG) chains to the surfaces, rendering them hydrophobic or hydrophilic. Functionalized surfaces are characterized through contact angle and atomic force microscopy (AFM) measurements, showing stable hydrophobic surfaces with contact angles of 69–78° and layer thicknesses of 11–15 Å and hydrophilic surfaces displaying contact angles of 5–6° and thicknesses of 22–52 Å. PCR experiments carried out directly on bare silicon oxide lab‐on‐chip surfaces show low yields of DNA amplification. Hydrophobic surfaces decrease the inhibition of PCR. Hydrophilic surfaces are a major improvement on the bare silicon oxide exhibiting the same maximum reaction yield as obtained with a standard thermocycler. We have found that the best results are associated with PEG modified surfaces, which prove very suitable for the fabrication of reliable PCR silicon lab‐on‐chips. Copyright © 2011 John Wiley & Sons, Ltd.     

A toolbox of HSQC experiments for small molecules at high 13C‐enrichment. Artifact‐free,fully 13C‐homodecoupled and JCC‐encoding pulse sequences

A set of modified HSQC experiments designed for the study of ¹³C‐enriched small molecules is introduced. It includes an improved sensitivity‐enhanced HSQC experiment eliminating signal artifacts because of high‐order ¹³C magnetization terms generated at high ¹³C enrichment. A broadband homonuclear ¹³C decoupling sequence based on Zangger and Sterk's method simplifies the complex ¹³C–¹³C multiplet structure in the F1 dimension of HSQC. When recording spectra at high resolution, the combination with a multiple‐site modulation of the selective pulse outperforms the constant‐time HSQC in terms of sensitivity and reliability. Finally, two pulse sequences reintroducing selected J_CC couplings with selective pulses facilitate their assignments and measurements either in the splitting of the resulting doublets or by modulation of the signal amplitude. A sample of uniformly 92% ¹³C‐enriched cholesterol is used as an example. Copyright © 2013 John Wiley & Sons, Ltd.     

Alternating copolymers of 2,6‐bis(p‐dihexylaminostyryl)anthracene‐9,10‐diyl and N‐octylcarbazole with large two‐photon cross sections

We report the synthesis, thermal, one‐ and two‐photon properties of poly(2,6‐bis(p‐dihexylaminostyryl)anthracene‐9,10‐diyl‐alt‐N‐octylcarbazole‐3,6‐/2,7‐diyl) ( P1/P2 ). The as‐synthesized polymers exhibit number‐average molecular weights of 1.7 × 10⁴ for P1 and 2.1 × 10⁴ g/mol for P2 . They emit strong one‐ and two‐photon excitation fluorescence with the peak around 502 nm, and the fluorescence quantum yields around 0.76 in chloroform. In film state, P1 and P2 show different red‐shift emission with the peaks at 512 nm and 523 nm, respectively. The DSC measurement reveals that as‐synthesized polymers are all amorphous aggregates with the glass transition temperatures of 131 °C for P1 and 152 °C for P2 . The solution two‐photon absorption (TPA) properties of P1 and P2 in chloroform are measured by the two‐photon‐induced fluorescence method using femtosecond laser pulses (120 fs). The TPA cross sections (δ) are measured over the range of 700–900 nm. The maximal δ of P1 and P2 all appear at ～800 nm and are 1010 GM and 940 GM per repeating unit, respectively. This suggests that no notable interactions among structure units that impair their fluorescence and TPA properties, and the polymers with large δ can be obtained by using the high TPA‐active units as building blocks. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Depth profiles of ceramic tiles by using orthogonal double‐pulse laser induced breakdown spectrometry

The potential of a double pulse (DP) excitation scheme for in‐depth characterization of ceramic samples using laser induced breakdown spectrometry (LIBS) has been demonstrated. For this purpose, two Q‐switched Nd:YAG lasers in orthogonal configuration were employed, the first one to ablate the sample (1064 nm) and the second one (532 nm) to excite the ablated material. Light emission was collected by a spectrograph and detected by an intensified charge‐coupled device (CCD) detector. Optimal conditions such as relative laser beam positions, laser pulse energies, inter‐pulse separation and CCD delay time were studied. Depth profiles were evaluated on the basis of various elemental compositions in both layers of ceramic samples. The depth resolution with DP configuration was improved by almost twofold as compared to the single‐pulse approach. The reproducibility of the depth profiles is also twice better with double pulse LIBS. Copyright © 2009 John Wiley & Sons, Ltd.     

Selective Excitation with Asymmetric Adiabatic Pulses for NMR Spectroscopy

Existing selective pulses are mainly constructed in the forms of classically shaped pulses, such as the Gaussian pulses, or generated by using numerical optimization methods. However, all of these pulses are highly sensitive to radiofrequency (RF) intensity variation, which means their performance is highly dependent on the accuracy and stability of the RF intensity. Even a slight RF intensity deviation can cause severe degradation in the excitation profile. To solve this problem, we propose a method for narrow selective excitation by sequential application of a pair of phase‐opposite asymmetric adiabatic pulses, all within two scans. By retaining the adiabatic character, the new method is highly robust to RF intensity variation. Moreover, it has flexible excitation bandwidth, ranging from line‐selective to narrow‐band‐selective pulses. The method is tested both in numerical simulations and solution‐state NMR experiments.     

A two‐stage surface treatment for the long‐term stability of hydrophilic SU‐8

The use of SU‐8 photoresist as a structuring material for portable capillary‐flow cytometry devices has been restricted by the near‐hydrophobic nature of the SU‐8 surface. In this work, we evaluate the use of chemical and plasma treatments to render the SU‐8 surface hydrophilic and characterise the resulting surface utilising a combination of techniques including contact angle goniometry, atomic force microscopy and X‐ray photoelectron spectroscopy. In particular, for low‐power plasma treatments, we find that the chemistry of the plasma used to modify the SU‐8 surface and the incorporation of O₂ on that modified surface are paramount for improved surface wettability, whilst plasma‐induced surface roughness is not a necessary requirement. We demonstrate a technique to obtain a hydrophilic SU‐8 surface with contact angle as low as 7° whilst controlling and significantly reducing the level of surface roughness generated via the applied plasma. An additional chemical treatment step is found to be essential to stabilise the activated SU‐8 surface, and incubation of the samples with ethanolamine is demonstrated as an effective second‐stage treatment. Application of the optimised two‐stage surface treatment to cross‐linked SU‐8 is shown to result in a smooth hydrophilic surface that remains stable for over 3 months. Copyright © 2015 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.     

Theoretical study of the surface excitation parameter from reflection‐electron‐energy‐loss spectra

A theoretical method to determine the so‐called surface excitation parameter (SEP) is presented. This method is based on the modelling of reflection‐electron‐energy‐loss spectroscopy and more particularly on the analysis of energy‐differential inelastic electron scattering cross sections calculated within the model. The SEP is extracted from theoretical cross‐section spectrum by calculating the ratio between the surface loss component of the spectrum and the elastic peak intensity. The calculations have been performed entirely with the dielectric function, using the software QUEELS (Quantitative analysis of Electron Energy Losses at Surfaces) recently developed by Yubero and Tougaard [Surf. Interface Anal. 2004; 36 : 824]. The angular distribution of SEP is calculated for angles between 10° and about 70° for aluminium and silicon. We propose also an extension of the method for materials (e.g. copper) that do not present clear surface and volume plasmons. Copyright © 2005 John Wiley & Sons, Ltd.     

cis‐Bis(3,6‐di­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II) and cis‐bis(3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II)

The title complexes, [Pt(C₄H₇NO)₂I₂], (I), and [Pt(C₄H₉NO)₂I₂], (II), possess similar square‐planar coordination geometries with modest distortions from ideality. For (I), the cis‐L—Pt—L angles are in the range 87.0 (4)–94.2 (3)°, while the trans angles are 174.4 (3) and 176.4 (3)°. For (II), cis‐L—Pt—L are 86.1 (8)–94.2 (6)° and trans‐L—Pt—L are 174.4 (6) and 177.4 (5)°. One 3,6‐di­hydro‐2H‐1,2‐oxazine ligand in (I) is rotated so that the N—O bond is out of the square plane by approximately 70°, while the N—C bond is only ca 20° out of the plane. The other oxazine ligand is rotated so that the N—C bond is about 80° out of the plane, while the N—O bond is out of the plane by approximately 24°. In (II), the 3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine ligands are also positioned with one having the N—O bond further out of the plane and the other having the N—C bond positioned in that fashion. Both ligands, however, are rotated approximately 90° compared with their positions in (I). In both complexes, this results in an unsymmetrical distortion of the I—Pt—N bond angles in which one is expanded and the other contracted. These features are compared to those of reported cis‐di­amine­di­iodo­platinum(II) complexes.     

Near neighbor approximation in nuclear magnetic resonance

A new way to deal with the excitation by multiple effective RF fields with interference is presented using the coherent averaging theory. It significantly simplifies the calculation of the effect of RF interference that occurs in the excitations by periodic pulses and phase-incremented pulses (PIPs). This approach shows that each neighboring RF field contributes to an excitation profile an offset shift, which is termed the Bloch-Siegert offset shift (BSOS). The BSOS depends not only on the strengths of both RF fields that interfere with each other but also on their relative phase between the two RF fields. Consequently, it can be positive, negative, and zero. In addition, the BSOS is also inversely proportional to the frequency separation of the two RF fields. Therefore, only a few near neighbors need to be taken into account in most cases, resulting in a near neighbor approximation (NNA). The BSOS for two multiband excitation profiles, one by a periodic pulse and the other by a PIP, are calculated using the NNA. The results are in good agreement with the computer simulated ones.     

Constant amplitude broadband refocusing pulses from numerical optimization

Broadband refocusing pulses for high-field NMR can be constructed with broadband 90× pulses from numerical optimization of Bloch simulations concatenated with their time and phase reversed transformations. This work describes the search for minimal duration 18-kHz modulation frequency constant amplitude refocusing pulses made in this manner for bandwidths of 40, 60 and 80 kHz. Variants optimized at multiple frequencies and with sine squared amplitude truncation also are described. The resulting pulses are expected to have immediate application especially for (13)C refocusing in multidimensional experiments.     

Hartmann–Hahn 2D‐map to optimize the RAMP–CPMAS NMR experiment for pharmaceutical materials

Cross polarization–magic angle spinning (CPMAS) is the most used experiment for solid‐state NMR measurements in the pharmaceutical industry, with the well‐known variant RAMP–CPMAS its dominant implementation. The experimental work presented in this contribution focuses on the entangled effects of the main parameters of such an experiment. The shape of the RAMP–CP pulse has been considered as well as the contact time duration, and a particular attention also has been devoted to the radio‐frequency (RF) field inhomogeneity. ¹³ C CPMAS NMR spectra have been recorded with a systematic variation of ¹³ C and ¹H constant radiofrequency field pair values and represented as a Hartmann‐Hahn matching two‐dimensional map. Such a map yields a rational overview of the intricate optimal conditions necessary to achieve an efficient CP magnetization transfer. The map also highlights the effects of sweeping the RF by the RAMP–CP pulse on the number of Hartmann–Hahn matches crossed and how RF field inhomogeneity helps in increasing the CP efficiency by using a larger fraction of the sample. In the light of the results, strategies for optimal RAMP–CPMAS measurements are suggested, which lead to a much higher efficiency than constant amplitude CP experiment. Copyright © 2012 John Wiley & Sons, Ltd.     

p‐Cresyl 2,3‐an­hydro‐5‐deoxy‐5‐phthal­imido‐1‐thio‐α‐d‐lyxo­furan­oside

The crystal structure of the title compound, C₂₀H₁₇NO₄S, (I), was determined in order to compare the solution and solid‐state conformations. The mol­ecule was synthesized as a building block for incorporation into oligosaccharides comprised of conformationally restricted furan­ose residues. The furan­ose ring adopts an envelope conformation with the ring O atom displaced above the plane (an ^OE conformation). The pseudorotational phase angle (P) is 88.6° and the puckering amplitude (τ_m) is 31.5°. The C₂—C₁—S—C(Ph) torsion angle is ?163.2 (2)°, which places the aglycone in the exo‐anomeric effect preferred position. The C1—S—C14 bond angle is 99.02 (13)° and the plane of the cresyl moiety is oriented nearly parallel to the four in‐plane atoms of the furan­ose ring envelope. The orientation about the C4—C5 bond is gauche–gauche [Bock & Duus (1994). J. Carbohydr. Chem. 13 , 513–543].     

Fingerprints of Phalaenopsis Tissues in Growth and Spike Induction Periods—A Solid‐state 13C NMR Approach

Solid‐state Nuclear Magnetic Resonance (ss‐NMR) ¹³C single‐pulse excitation spectroscopy in combination with the magic‐angle spinning (MAS) technique was applied to a series of Phalaenopsis tissues, including the leaf, sheath, stem, and root, at different growth and spiking periods. Compared with{¹H}/¹³C cross‐polarization MAS spectra, the ¹³C single‐pulse excitation MAS spectra displayed very distinct spectral patterns, recognizable as fingerprints of the tissues studied. ¹Here, we demonstrate that solid‐state ¹³C single‐pulse excitation NMR spectroscopy provides a direct and robust analytical tool for studying the various tissues of Phalaenopsis in different growth and spiking induction periods.     

trans‐4‐Bromo‐ONN‐azoxy­benzene at 100 K

The crystal structure of the α isomer of trans‐4‐bromo­azoxy­benzene [systematic name: trans‐1‐(bromophenyl)‐2‐phenyl­diazene 2‐oxide], C₁₂H₉BrN₂O, has been determined by X‐ray dif­frac­tion. The geometries of the two mol­ecules in the asymmetric unit are slightly different and are within ∼0.02 Å for bond lengths, ∼2° for angles and ∼3° for torsion angles. The azoxy bridges in both mol­ecules have the typical geometry observed for trans‐azoxy­benzenes. The crystal network contains two types of planar mol­ecules arranged in columns. The torsion angles along the Ar—N bonds are only 7 (2)°, on either side of the azoxy group.