We propose microporous networks (MPNs) of a light emitting spiro-carbazole based polymer (PSpCz) as luminescent sensor for nitro-aromatic compounds. The MPNs used in this study can be easily synthesized on arbitrarily sized/shaped substrates by simple and low-cost electrochemical deposition. The resulting MPN afford an extremely high specific surface area of 1300 m2/g, more than three orders of magnitude higher than that of the thin films of the respective monomer. We demonstrate, that the luminescence of PSpCz is selectively quenched by nitro-aromatic analytes, e.g. nitrobenzene, 2,4-DNT and TNT. In striking contrast to a control sample based on non-porous spiro-carbazole, which does not show any luminescence quenching upon exposure to TNT at levels of 3 ppm and below, the microporous PSpCz shows a clearly detectable response even at TNT concentrations as low as 5 ppb, clearly demonstrating the advantage of microporous films as luminescent sensors for traces of explosive analytes. This level states the vapor pressure of TNT at room temperature.

In this work, we report on aluminum oxide (AlO) gas permeation barriers prepared by spatial ALD (SALD) at atmospheric pressure. We compare the growth characteristics and layer properties using trimethylaluminum (TMA) in combination with an Ar/O remote atmospheric pressure plasma for different substrate velocities and different temperatures. The resulting AlO films show ultralow water vapor transmission rates (WVTR) on the order of 10 gmd. In notable contrast, plasma based layers already show good barrier properties at low deposition temperatures (75 °C), while water based processes require a growth temperature above 100 °C to achieve equally low WVTRs. The activation energy for the water permeation mechanism was determined to be 62 kJ/mol.

Conjugated microporous polymer (CMP) thin films often show fast and amplified signal response and potential for developing portable sensing devices. Here, we elucidate electrochemical generation of three CMP thin films and their fluorescence response to trinitrotoluene (TNT). A tetra­(carbazolylphenyl)­ethylene monomer TPETCz-derived CMP thin film (PTPETCz, S BET: 930 m2/g) displayed fluorescence (λmax = 525 nm) quenching to nearly 95% in 3 min, when the CMP film is exposed to 33 ppb TNT vapors. Interestingly, PTPETCz is highly sensitive (30% quenching) to TNT vapors of low concentrations (5–10 ppb) and also remarkably selective toward TNT compared to other analytes. In contrast, an only mere response was observed when a nonporous monomer TPETCz-film was exposed to 0.2 ppm TNT. So, the microporosity and extended π-conjugation of the polymer facilitating suitable host–guest interactions is found to be essential toward highly sensitive detection of TNT. Fluorenone-cored CMP thin films (PFLCz) showed no response, while PTPEFLCz containing both tetraphenylethylene and fluorenone structural units showed nearly 70% of emission quenching in the presence of 0.2 ppm TNT. Therefore, the presence of electron-donating TPE core is a prerequisite for efficient photoinduced electron transfer from polymer to nitroarenes.

The authors report the preparation of transparent conductive gas permeation barriers based on thin films of tin oxide (SnOx) grown by spatial atomic layer deposition (ALD) at atmospheric pressure. They present a comparative study using tetrakis(dimethylamino)tin(IV) and various oxidants (atmospheric pressure oxygen plasma, ozone, and water) at process temperatures in the range of 80–165 °C. Specifically, for oxygen plasma or ozone as oxidant, the authors confirm self-limited ALD growth with a growth per cycle (GPC) of 0.16 and 0.11 nm for 80 and 150 °C, respectively, comparable to the classical vacuum-based ALD of SnOx. On the contrary, for water-based processes the GPC is significantly lower. Very notably, while SnOx grown with water as oxidant shows only a very limited electrical conductivity [10−3 (Ω cm)−1], atmospheric pressure oxygen plasma affords SnOx layers with an electrical conductivity up to 102 (Ω cm)−1. At the same time, these layers are excellent gas permeation barriers with a water vapor transmission rate as low as 7 × 10−4 g m−2 day−1 (at 60 °C and 60% rH). ALD growth will be demonstrated at substrate velocities up to 75 mm/s (i.e., 4.5 m/min), which renders spatial plasma assisted ALD an excellent candidate for the continuous manufacturing of transparent and conductive gas permeation barriers based on SnOx.

This paper reports on aluminum oxide (Al2O3) thin film gas permeation barriers fabricated by atmospheric pressure atomic layer deposition (APPALD) using trimethylaluminum and an Ar/O2 plasma at moderate temperatures of 80 °C in a flow reactor. The authors demonstrate the ALD growth characteristics of Al2O3 films on silicon and indium tin oxide coated polyethylene terephthalate. The properties of the APPALD-grown layers (refractive index, density, etc.) are compared to that deposited by conventional thermal ALD at low pressures. The films films deposited at atmospheric pressure show water vapor transmission rates as low as 5 × 10−5 gm−2d−1.

The gas-phase molecular layer deposition (MLD) of conformal and highly luminescent monolayers of tris(8-hydroxyquinolinato)aluminum (Alq3) is reported. The controlled formation of Alq3 monolayers is achieved for the first time by functionalization of the substrate with amino groups, which serve as initial docking sites for trimethyl aluminum (TMA) molecules binding datively to the amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting formation of highly luminescent Alq3 monolayers is afforded. The growth process and monolayer formation were studied and verified by in situ quartz crystal monitoring, optical emission and absorption spectroscopy, and X-ray photoelectron spectroscopy. The nature of the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces and porous structures with high surface areas, as demonstrated in this work for silica aerogels. The concept presented here paves the way to highly sensitive luminescent sensors and dye-sensitized metal oxides for future applications (e.g., in photocatalysis and solar cells).

A general avenue for the controlled preparation of conformal and highly luminescent monolayers of metal chelate complexes is presented, among them tris(8-hydroxyquinolinato)aluminium (Alq3) and bis(8-hydroxyquinoline)zinc (Znq2). Alq3 is an extremely important model compound for organic electronic applications - it has been the electron transporter and luminescent material in the first efficient hetero-structure organic light emitting diode (OLED). The controlled formation of Alq3 or Znq2 monolayers is achieved by functionalization of the substrate with amino groups which serve as initial docking sites for trimethyl aluminum (TMA) or diethyl zinc (DEZ) molecules which datively bind to the amine. Subsequent exposure to 8-hydroxyquinoline (8-HQ) results in the self-limiting formation of highly luminescent monolayers on arbitrary surfaces, e.g. curved 3D objects or highly porous silica aerogels. The growth mechanism is studied by in-situ quartz crystal microbalance and ex-situ by highly sensitive (time-resolved) optical absorption/emission spectroscopy and photo-electron spectroscopy.