Condensation and freezing of droplets on superhydrophobic surfaces

Superhydrophobic coatings are reported as promising candidates for anti-icing applications. Various studies have shown that as well as having ultra water repellency the surfaces have reduced ice adhesion and can delay water freezing. However, the structure or texture (roughness) of the superhydrophobic surface is subject to degradation during the thermocycling or wetting process. This degradation can impair the superhydrophobicity and the icephobicity of those coatings. In this review, a brief overview of the process of droplet freezing on superhydrophobic coatings is presented with respect to their potential in anti-icing applications. To support this discussion, new data is presented about the condensation of water onto physically decorated substrates, and the associated freezing process which impacts on the freezing of macroscopic droplets on the surface.     

Engineered hydrogen-bonded polymer multilayers: from assembly to biomedical applications

Over the last two decades the layer-by-layer (LbL) assembly technique has become a highly versatile platform for the synthesis of nanoengineered thin films and particles. The widespread need for highly functional and responsive materials for applications in biomedicine-such as drug and gene delivery-has recently led to considerable efforts in the assembly of LbL materials, particularly films that can be subsequently stabilised and functionalised through a range of chemistries. In this tutorial review, recent developments in hydrogen-bonded LbL-assembled materials will be discussed, focusing on the design of materials with enhanced stimuli-responsive characteristics. Emphasis will be given to materials engineered for biomedical applications, specifically films/capsules that afford controlled loading and release of therapeutic cargo for application in vitro and in vivo.     

Surface active benzodiazepine-bromo-alkyl conjugate for potential GABAA-receptor purification

A conjugable analogue of the benzodiazepine 5-(2-hydroxyphenyl)-7-nitro-benzo[e][1,4]diazepin-2(3H)-one containing a bromide C(12)-aliphatic chain (BDC) at nitrogen N1 was synthesized. One-pot preparation of this benzodiazepine derivative was achieved using microwave irradiation giving 49% yield of the desired product. BDC inhibited FNZ binding to GABA(A)-R with an inhibition binding constant K(i) = 0.89 μM and expanded a model membrane packed up to 35 mN m(-1) when penetrating in it from the aqueous phase. BDC exhibited surface activity, with a collapse pressure π = 9.8 mN m(-1) and minimal molecular area A(min) = 52 ?(2)/molecule at the closest molecular packing, resulted fully and non-ideally mixed with a phospholipid in a monolayer up to a molar fraction x? 0.1. A geometrical-thermodynamic analysis along the π-A phase diagram predicted that at low x(BDC) (<0.1) and at all π, including the equilibrium surface pressures of bilayers, dpPC-BDC mixtures dispersed in water were compatible with the formation of planar-like structures. These findings suggest that, in a potential surface grafted BDC, this compound could be stabilize though London-type interactions within a phospholipidic coating layer and/or through halogen bonding with an electron-donor surface via its terminal bromine atom while GABA(A)-R might be recognized through the CNZ moiety.     

Conjugated "B-entacenes": polycyclic aromatics containing two borepin rings

The synthesis and characterization of functionalized bora-acenes (B-entacenes) where Stille and Sonogashira cross-couplings were used to attach a series of electron-donating and -withdrawing substituents is reported. Photophysical, electrochemical, and computational analyses revealed that the LUMO level can be tuned by changing the para-conjugated substituent. Furthermore, the dimethylamino-functionalized molecule exhibited intense solvatochromism due to the intramolecular charge-transfer interaction.     

Vibrational analysis of x-ray absorption fine structure thermal factors by ab initio molecular dynamics: the Zn(II) ion in aqueous solution as a case study

In this work, we consider a new combination of vibrational analysis and normal-like mode decomposition of Debye-Waller factors of solvated ions entirely based on molecular dynamics data. Such a novel time-dependent analysis procedure provides a direct link between x-ray absorption fine structure parameters and normal mode contributions for an ion-solvent system. The potentialities of such a methodology rely on two fundamental aspects which distinguish it from already available tools. First, a general vibrational analysis that does not require any Gaussian or harmonic model for describing atomic fluctuations in liquids. Second, a very accurate sampling of the short range motions around the structural probe via the recently developed atom centered density matrix propagation/general liquid optimized boundary method. This novel molecular dynamics methodology is based on an integrated ab initio/classical potential using localized basis functions and nonperiodic boundary conditions. As a case study we have chosen the Zn(II) ion in aqueous solution. The consistency of our results and the observed good agreement with experiments show how the key support to advanced structural techniques from molecular dynamics can be further expanded and investigated.     

Functionalized dibenzoborepins as components of small molecule and polymeric π-conjugated electronic materials

We present the synthesis and characterization of dibenzo[b,f]borepins (DBBs) functionalized at the para and meta position with respect to the boron center in order to understand how regiochemical issues influence photophysical and electrochemical properties. An expanded synthetic repertoire is presented, using palladium catalysis (to perform Stille, Suzuki, Buchwald-Hartwig, and Sonogashira cross-coupling reactions) and lithium-halogen exchange to synthesize a series of extended π-conjugated DBBs. These chemistries are enabled by the use of a sterically bulky Mes* (2,4,6-tri-tert-butylphenyl) group on boron and the inclusion of reactive bromide handles on the DBB core. Photophysical, electrochemical, and computational analyses of these compounds indicate that relative to the protio-DBB the installation of groups at the meta positions decreases the optical band gap while para substitution raises the electron affinity of the system. Thus, both the HOMO-LUMO gap and specific frontier molecular orbital levels can be tuned by the installation of different conjugated substituents.     

Nanostructured polymer assemblies formed at interfaces: applications from immobilization and encapsulation to stimuli-responsive release

In recent years, interfacial properties have been tailored with nanostructured polymer assemblies to generate materials with specific properties and functions for application in diverse fields, including biomaterials, drug delivery, catalysis, sensing, optics and corrosion. This perspective begins with a brief introduction of the assembly techniques that are commonly employed for the synthesis of nanostructured polymer materials, followed by discussions on how the interfaces influence the properties and thus the functionalities of the polymer materials prepared. Applications of the interfacial polymer nanostructures, particularly for the immobilization and encapsulation of cargo, are then reviewed, focusing on stimuli-responsive cargo release from the polymer nanostructured assemblies for controlled delivery applications. Finally, future research directions in these areas are briefly discussed.     

Gas chromatographic quantitative analysis of methanol in wine: operative conditions, optimization and calibration model choice

The influence of the wine distillation process on methanol content has been determined by quantitative analysis using gas chromatographic flame ionization (GC-FID) detection. A comparative study between direct injection of diluted wine and injection of distilled wine was performed. The distillation process does not affect methanol quantification in wines in proportions higher than 10%. While quantification performed on distilled samples gives more reliable results, a screening method for wine injection after a 1:5 water dilution could be employed. The proposed technique was found to be a compromise between the time consuming distillation process and direct wine injection. In the studied calibration range, the stability of the volatile compounds in the reference solution is concentration-dependent. The stability is higher in the less concentrated reference solution. To shorten the operation time, a stronger temperature ramp and carrier flow rate was employed. With these conditions, helium consumption and column thermal stress were increased. However, detection limits, calibration limits, and analytical method performances are not affected substantially by changing from normal to forced GC conditions. Statistical data evaluation were made using both ordinary (OLS) and bivariate least squares (BLS) calibration models. Further confirmation was obtained that limit of detection (LOD) values, calculated according to the 3sigma approach, are lower than the respective Hubaux-Vos (H-V) calculation method. H-V LOD depends upon background noise, calibration parameters and the number of reference standard solutions employed in producing the calibration curve. These remarks are confirmed by both calibration models used.     

Sulpholane as a solvent for titration of barbiturates and sulpha drugs

Sulpholane (tetramethylenesulphone) has been used as the medium for non-aqueous potentiometric titration of barbiturates and sulpha drugs with tetrabutylammonium hydroxide. Recoveries for 0.1-0.3 mmole of barbituric acid, phenobarbital, amobarbital, barbital, secobarbital, sulphapyridine, sulphadiazine and sulphamerazine were generally in the range 99-101%. A glass-calomel electrode system was used: common acid-base indicators give no colour change in the medium used.     

Conductance behavior of electrolytes in 1,3-dimethylethyleneurea and 1,3-dimethylpropyleneurea at 25°C

1,3-Dimethylethyleneurea (DMEU) and 1,3-dimethylpropyleneurea (DMPU) were investigated as electrolytic media for a number of alkali metal and triisoamylbutylammonium salts via conductivity measurements over a concentration range of 1–100×10^–4 M at 25°C. The data were analyzed by the Fuoss-Shedlovsky, Fuoss-Onsager, and expanded Pitts equations. The limiting equivalent conductivities were about 1.5 times greater in DMEU than in DMPU, which is exactly the ratio of the viscosities. From the Fuoss-Onsager analysis, all salts studied were found to be essentially unassociated in both solvents. From the expanded Pitts equation the extent of association was small, but within a salt series the equation indicated that association decreased in the order iodides, thiocyanates > perchlorate > tetraphenylborates. Neither solvent differentiated between sodium and potassium ion mobilities, indicating a type of solvation behavior different from that in acyclic urea solvents such as tetramethyl- and tetraethylurea.