Pc Films Research Articles

Structural and Magnetic Depth Profiling and Their Correlation in Self-Assembled Co and Fe Based Phthalocyanine Thin Films

The family of phthalocyanine (Pc) is suitable functional molecules in the field of molecular electronics because of their thermal stability and the possibility to tune their structure, chemical, magnetic, and transport properties by means of different metallic cations within the Pc molecular cage. Here we report the depth dependent chemical composition and magnetization of iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc) and binuclear (Co–Fe)-phthalocyanine [(Co–Fe)Pc] thin films grown on sapphire substrates by molecular beam epitaxy. The binuclear (Co–Fe)Pc films grown by coevaporation of pure FePc and CoPc exhibited a new structure (binuclear) which show drastically different conducting and magnetic properties. Using X-ray reflectivity (XRR) and polarized neutron reflectivity (PNR), we demonstrated that the structural changes in binuclear (Co–Fe)Pc films as compared to pure film is responsible for about three to four order reduction in resistivity and presence of ferromagnetism in this film at l...

Antimicrobial polycarbonates for biomedical applications

BackgroundPolycarbonate (PC) is one of the most widely used engi-neering polymers due to its unusual combination of opti-cal clarity, heat resistance,high impact strength anddimensional stability over wide thermal range [1]. Lowwater absorption, ease of sterilization and biocompatibilityof PC have led to its use in a wide range of medical equip-ment, including critical medical devices [2]. The preven-tion of biofilm formation on the internal medical devicesis of great importance since it can initiate a degradationprocess of the material, as well as cause infections andhealth related problems [3]. In order to obtain antimicro-bial properties, polymers are usually compounded withorganic or inorganic biocides [4,5]. However, the use oforganic biocides as additives for PC is significantly limiteddue to their insufficient thermal stability in the tempera-ture range used for PC processing (300 – 320 °C).The aimof research was to develop novel low toxic biocides forPC having sufficient thermal stability for the joint meltprocessing with PC resin.Materials and methodsTwo kinds of potential antimicrobial additives for PC havebeen synthesized: imidazolium and guanidinium ionenes,as well as imidazolium based ionic liquids. PC films con-taining from 1 to 10 wt% of biocides were prepared by sol-vent casting or by compression molding methods. Thethermal stability of novel biocides as well as modified PCwas investigated by using thermogravimetric analysis(TGA). Antimicrobial testing of PC composites were per-formed using a model bacteriaPseudomonas fluorescensSBW25 with a help of classical microbiological methodsfor bacterial suspension as well as a live-dead assay forbiofilms [6].ResultsAccording to TGA data, the thermal stability of PC sam-ples containing biocidal additives was found to be in therange of 350-425

Coherently strained epitaxial Pb(Zr1−xTix)O3 thin films

Coherently strained Pb(Zr1−xTix)O3, 0.2 ≤ x ≤ 0.35, thin films were grown by pulsed laser deposition on (001) and (111) oriented SrTiO3 substrates. A buffer layer of Pb(Zr0.6Ti0.4)O3 was used to improve the lattice matching and induce compressive strain in Zr-rich compositions. The (001)pc (pc = pseudocubic) films showed an increased ferroelectric transition temperature, TC, compared to bulk ceramics, but the transition from an untilted to a tilted ferroelectric (TTilt) exhibited only a modest increase in temperature. This suggests that it may be possible to enlarge the untilted ferroelectric phase field by compressive strain. Consistent with previous work on relaxed PZT films, coherently strained PZT films do not exhibit an abrupt transition from an untilted to a tilted state; rather, a region of non-zero tilt exists above TTilt. (111)pc films also showed an increased ferroelectric transition temperature with a weak strain dependence on TTilt. The compressive strain in (111)pc films induced a preferred domain structure with only 180° domain walls, in contrast to bulk materials and relaxed films which are polydomain.

Self-assembly of phthalocyanines on quartz crystal microbalances for QCM liquid sensing applications

After their widespread use in gas sensors, phthalocyanines are applied as sorption matrices for quartz crystal microbalance (QCM) sensors in liquid phase, as well. In order to enhance sensor performance, the application of ultrathin Pc films is envisaged. In this work, QCM liquid sensors functionalized in a self-assembly process with phthalocyanines are proposed and evaluated for the first time. An asymmetric tetra substituted nickel phthalocyanine having a thiol linker group to covalently attach to the gold electrode of the QCM and three hexyloxy groups was synthesized. The sensor is assessed in its sensing characteristics in water using selected organic compounds. The sensor responses are fast and recovery after analyte exposure is quick. Detection limits for organic compounds down to sub-ppm levels can be reached. The results demonstrate that the application of phthalocyanines as self-assembled monolayers is very effective to obtain high performing QCM liquid sensors. Besides, layers of alkyloxy substituted phthalocyanines have been previously found unsuitable for the use with the QCM in liquids due to the low adhesion of the Pc layer to the transducer. Thus, the covalent attachment is an excellent way to expand the list of available phthalocyanines as sensitive compounds for such sensors in liquids.

Synthesis, characterization, electrochemistry and VOC sensing properties of novel metallophthalocyanines with four cyclohexyl-phenoxyphthalonitrile groups

The precursor [4,4′-cyclohexylidenebis(2-cyclohexylphenoxyphthalonitrile)] 3 was prepared by the reaction of 4-nitrophthalonitrile 1 and 1,1-bis[3-cyclohexyl-4-hydroxyphenyl]cyclohexane 2 in dry DMF in presence of dry K2CO3. The mononuclear phthalocyanines 4–6 were obtained from compound 3 by addition of the corresponding metal salts [Co(OAc)2·4H2O, Zn(OAc)2·2H2O, Cu(OAc)2]. The new compounds were characterized by elemental analysis, IR, UV–vis, 1H NMR and MALDI-TOF mass spectrometry techniques. The response and recovery behaviors, sensitivity and selectivity of the spin coated films to different organic vapors have been investigated by means of conductivity measurements. The effect of humidity on the VOC vapor detection of the Pc films was also investigated. It was observed that the initial film conductivities was strongly influenced from relative humidity but, humidity had practically very small influences on the response and recovery characteristics of the sensors. The results offer a potential application for such phthalocyanine derivatives for the detection of volatile organic compounds, even at room temperature. Electrochemical and in situ spectroelectrochemical measurements confirmed that Co(II) phthalocyanine displays both metal- and ligand-based one-electron redox processes, while Zn(II) and Cu(II) phthalocyanine complexes show only ligand-based one-electron redox processes. Cyclic voltammetry provided information on the position of the energy levels of the highest occupied and the lowest unoccupied molecular orbitals, and thus the electrochemical band gaps of the complexes. The results reflected the semiconducting nature of the complexes.

Photoluminescence manipulation based on composite photonic crystal surfaces

A series of composite PC films with different morphologies are fabricated through a facile approach. The effects of different surface morphologies and the stopband positions of composite PC films on photoluminescence (PL) behaviors are systematically investigated. We observe that the PL on composite PC surfaces can be manipulated. When dyes enter into interstitial space of PC films without photo-crosslinkage, inhibited spontaneous emission is evident and emission is enhanced at the blue edge of photonic stopband. When dyes are deposited on outer surface of composite PC films, inhibited spontaneous emission disappears, but an obvious enhancement of the emission is achieved, where the composite PC surface acted as a Bragg mirror. The study will be of great guideline for future development of highly efficient optical devices.

Honeycomb-patterned phthalocyanine films with photo-active antibacterial activities

We report honeycomb-patterned phthalocyanine (Pc) films fabricated by self-assembly of dodecyloxy-azo-Zinc phthalocyanine (daZnPc) using the breath figure (BF) technique. These ultrathin Pc films exhibit a robust photo-dependent antibacterial effect against Escherichia coli (E. coli).

Monolayer properties of synthesized tyrosyl esters

Abstract Lipase-catalyzed synthesis of eight fatty acid tyrosyl esters ( TyC 2 to TyC 18:1 ) was investigated using non commercial lipases from Rhizopus oryzae and Staphylococcus xylosus immobilized onto CaCO 3 . The monomolecular film technique was used to compare the ability of the various synthesized tyrosyl fatty acid esters to form a stable monolayer at the air/water interface and their capacity to interact with a phospholipid monolayer. The measurements of surface pressure versus the molecular area shows that, in contrast to tyrosol esterified with short and medium chains (acetic ( TyC 2 ), propionic ( TyC 3 ), caprylic ( TyC 8 ) and capric ( TyC 10 ) acids), tyrosol esterified with long chains: lauric ( TyC 12 ), palmitic ( TyC 16 ), stearic ( TyC 18 ) and oleic ( TyC 18:1 ) acids are able to form a stable monolayer at the air/water interface. A direct correlation was observed between the length of the saturated acyl chain of the derivatives and their corresponding collapse pressures. The presence of unsaturation reduces the collapse pressure value. The interaction of tyrosyl esters with a phospholipid monolayer was studied and the critical surface pressure ( π c ) of each ester was determined. Only medium and long chain ( TyC 8 to TyC 18:1 ) derivatives esters were found to interact efficiently with DiC 12 PC film.

Enhanced Cl2 response of ultrathin bi-nuclear (cobalt–iron) phthalocyanine films

Abstract Ultrathin bi-nuclear (cobalt–iron) phthalocyanine, (Co–Fe)Pc films (thickness: ∼20 nm) were grown on (0 0 0 1) Al 2 O 3 substrates by molecular beam epitaxy. These films showed very high mobility ∼110 cm 2 V −1 s −1 at room temperature, which are nearly two orders of magnitude higher as compared to the pure CoPc and FePc films prepared under identical conditions. We demonstrated that due to high mobility of bi-nuclear phthalocyanine films, they exhibit enhanced response for chlorine (Cl 2 ) gas as compared to pure CoPc and FePc films.

Kinetic properties of pancreatic and intestinal sPLA2 from chicken and mammals using the monomolecular film technique

The interfacial kinetic and binding data for the pancreatic and intestinal sPLA2 from bird and mammals show that these enzymes have dramatically different ability to bind and hydrolyse phospholipids. The main conclusions from our experimental data indicate that phosphatidylcholine monolayers (PC), in contrast to phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), were resistant to the hydrolysis by human intestinal sPLA2. Conversely, chicken intestinal sPLA2 was found to be able to hydrolyse all the phospholipids tested, including PC. The experiments show also that the interfacial penetrating ability of chicken sPLA2 (from intestine and pancreas) was higher than their mammalian’s orthologs. This observation is confirmed by the activity of pancreatic chicken PLA2 measured on PC film showing that the interfacial pressure window that permits sPLA2 activity was very large, between 5 and 20dynescm−1, compared with the porcine pancreatic sPLA2-IB which was inactive at pressure above 15dynescm−1.In trying to establish a structure–function relationship, we examined the surface electrostatic potentials of the various sPLA2 from chicken and mammals. We reported in this study that the binding, orientation and persistence of sPLA2 at the lipid–water interface is probably governed by the electrostatic and hydrophobic forces operative at this surface. These variations argue strongly that these enzymes are not isoforms and that they are expected to have functions other than the release of lipid mediators for the biosynthesis of the eicosanoids.

Optimization of Laser Transmission Joining Process between Different Thermoplastics using Response Surface Methodology

In order to determine the optimum joint conditions, four key process parameters affecting the joint quality of laser transmission joint of 1mm thick PET film and PC film，namely，laser power, scanning speed, clamping pressure and scanning number are optimized by response surface methodology in this paper. The interaction effect of main process parameters on joint quality is researched. The samples are tested using a multi-axis microtester in order to determine joint strength. The morphology of the joining area is observed with an optical microscope. Design Expert analysis indicates that the best laser power, scanning speed, clamping pressure and scanning number on joint quality were 35.7W, 5.0mm/s, 0.75MPa, 3, respectively. Finally, the experimental results are consistent with the predicted, which illustrates that the developed mathematical models can predict the responses adequately.

Magnetic disparities at the interfaces of Co–pentacene–Co hybrid structures

We investigated two series of ultrathin ferromagnet-organic semiconductor (FM-OSC) hybrid structures fabricated with reversed layer orders in ultra-high vacuum conditions to emulate the interfaces of FM/OSC/FM organic spin-valves. Using X-ray photoemission electron microscopy (PEEM), the magnetic responses of the cobalt (Co) layer in contact with the pentacene (Pc) film were investigated on a microscopic scale. According to the PEEM images acquired on Pc (1.8 nm)/Co bilayers, the Co top layer was found to turn on its ferromagnetic order after its thickness reaches 2.2 nm. Also, upon the onset of magnetic contrast, the element-specific images revealed that the Pc/Co bilayers exhibit a complex domain pattern whose average dimension is at least two orders of magnitude smaller than that of the pattern found in Co (2.4 nm)/Pc bilayers. Further X-ray photoelectron spectroscopy investigations suggest that the magnetic disparities observed between Co/Pc and Pc/Co bilayers are correlated with the different chemistries occurred at their interfaces.

Oriented growth of zinc(II) phthalocyanines on polycarbonate alignment substrates: Effect of substrate temperature on in-plane orientation

Highly oriented films of zinc(II) tetra-tert-butyl-phthalocyanine (ttb-ZnPc) and zinc(II) phthalocyanine (ZnPc) have been deposited on oriented and nanostructured substrates of bisphenol A polycarbonate. The polycarbonate substrates were prepared by a simple method that combines (i) the mechanical rubbing of an amorphous PC film and (ii) the solvent induced crystallization generating oriented crystalline lamellae with a high in-plane orientation. The preparation conditions yielding alignment layers with high orienting capability and improved thermal stability have been optimized. The effects of the substrate temperature (Ts) on the morphology, the in-plane orientation and the optical properties of the phthalocyanine films have been investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM) and polarized UV–vis absorption spectroscopy. For both phthalocyanines, the in-plane orientation is observed to increase with increasing Ts in the range 100–170°C as indicated by an increase of the dichroic ratio of the optical absorption with Ts. However, contrary to ZnPc, the high in-plane orientation of ttb-ZnPc is not related to the growth of elongated nanocrystals but simply to the orientation of columnar stacks parallel to the PC lamellae with a rather short 0.33nm intermolecular stacking period and an inter-stack period of 1.65nm. For similar growth conditions, a better orientation of ttb-ZnPc is achieved on PC substrates as compared to substrates of friction transferred polytetrafluoroethylene (PTFE). These results show that PC alignment layers are an interesting alternative to substrates of oriented PTFE for a large range of substrate temperatures up to 170°C.

Planar and textured heterojunction organic photovoltaics based on chloroindium phthalocyanine (ClInPc) versus titanyl phthalocyanine (TiOPc) donor layers

Planar and textured heterojunction solar cells (OPVs) are reported for vacuum deposited chloroindium phthalocyanine (ClInPc)/C 60 heterojunctions, and their response compared to previously explored OPVs based on titanyl phthalocyanine (TiOPc)/C 60 heterojunctions. As for TiOPc/C 60 OPVs, the photoelectrical activity of ClInPc/C 60 OPVs extends well into the near infrared, with good activity out to ca. 900 nm. As-deposited ClInPc films (Phase I) produce open-circuit photopotentials, V OC as high as ca. 0.8 V (Phase I form of ClInPc), ca. 0.15 V larger than previously observed for Phase I TiOPc/C 60 OPVs. The offsets in frontier orbital energies ( E HOMO Pc – E LUMO C 60 ) revealed by UV-photoemission studies (UPS) are slightly smaller for ClInPc/C 60 versus TiOPc/C 60 heterojunctions, and the interface dipole contribution (shift in local vacuum level) to these offsets is in the opposite direction for ClInPc/C 60 versus TiOPc/C 60 heterojunctions, or missing altogether, suggesting differences in molecular interaction at the Pc/C 60 interface. Higher V OC values are correlated with lower reverse saturation currents, J o , for ClInPc/C 60, versus other Pc or pentacene/C 60 heterojunctions, suggesting weak intermolecular interactions at the ClInPc/C 60 interface and large barriers to dark charge injection. Solvent annealing of the ClInPc films enhances the near-IR response, and textures the Pc film, enhancing the Pc/C 60 interfacial contact area and the short-circuit photocurrent, J SC . J SC under AM 1.5 illumination conditions was estimated by integration of the incident photon current efficiency (IPCE) response, to compare relative power conversion efficiencies for the two different device types. The estimated efficiency of Phase I ClInPc/C 60 OPVs is ca. 2.6%. The estimated AM 1.5 efficiency of ClInPc/C 60 OPVs with solvent annealed Pc layers is estimated to be ca. 3.3%, arising from the extensive texturing achieved of the Pc layer, which nearly doubles J SC for the Phase II versus Phase I Pc films.

Photonic Crystals in Bioassays

AbstractPhotonic crystal (PC) based bioassay techniques have many advantages in sensitive biomolecular screening, label‐free detection, real‐time monitoring of enzyme activity, cell morphology research, and so on. This study provides an overall survey of the basic concepts and up‐to‐date research concerning the very promising use of PC materials for bioassays. It includes the design and application of PC films, PC microcarriers, PC fibers, and PC optofluidics for fluorescence enhancement or label‐free bioassays. Emphasis is given to the description of the functional structures of different PC materials and their respective sensing mechanisms. Examples of detecting various types of analytes are presented. This article promotes communication among chemistry, biology, medicine, pharmacy, and material science.

Direct fabricating patterns using stamping transfer process with PDMS mold of hydrophobic nanostructures on surface of micro-cavity

The transfer stamping process has been used to fabricate thin-film pattern in recent years. Due to the characteristics of the materials of molds and inks, residual inks on the cavities of mold and residual layers on the substrate are still a problem. To solve the problem, we present a concept for fabrication of hydrophobic nanostructures on the cavities of microstructures of the mold, which can effectively decrease the ink residing on the cavities of the mold during coating. First, the periodic nanopores are fabricated on the anodic aluminum oxide (AAO). Second, AAO membrane is employed as the template for fabricating nanostructures on the PC film by embossing. And then, by partial protrusion of the nano-structured PC film into the micro-holes of the mold, an array of protruded convex microstructures is formed. After that, polydimethylsiloxane (PDMS) mold is casted from the embossed PC film. The contact angle of nanostructures on the micro-cavities of PDMS mold is about 145°. Micro-patterns with no residual layers have been successfully transferred on the poly(ethylene terephthalate) (PET) substrate using a transfer stamping process with this PDMS mold.

Solution processed tetrasubstituted zinc phthalocyanine as an active layer in organic field effect transistors

Spun films of liquid crystalline peripheral-tetrasubstituted zinc (II) phthalocyanine (Pc) derivatives have been employed as active organic semiconducting layers in the fabrication of organic field effect transistors. The Pc molecules in the thin film formulation are stacked perpendicular to the substrate. Values of 1.8×10−4 cm2 V−1 s−1 and 103 were estimated for the field-effect mobility and on/off ratio, respectively, from the hysteresis-free transistor characteristics. The transistor can be switched on and off at a relatively low value of 3.7 V for threshold voltage. The carrier transport is believed to be largely determined by the multidomain Pc film structure.

Gold Nanoparticle-Containing Membranes from in Situ Reduction of a Gold(III)−Aminoethylimidazolium Aurate Salt

The first example of polycarbonate membranes (PC) modified using layer-by-layer (LBL) adsorption of a polyelectrolyte (PE)/AuNPs system [PE = poly(ethylenimine), PEI; poly(acrylic acid) sodium salt, PAA] in which the AuNPs formation occurs via the in situ postdeposition reduction of the incorporated novel gold(III)−aminoethylimidazolium aurate salt [Cl3AuNH2(CH2)2ImMe)][AuCl4] (1) is reported. The reduction of 1 to give gold nanoparticles stabilized by an amino-functionalized ionic liquid (ILNH2-AuNPs), was carried out either by the PAA itself during the LBL deposition or by the combined action of PAA and ascorbic acid, the latter added at the end of the deposition process. The different membranes were characterized with AFM, SEM, TEM, UV−vis, and XRD. The XRD analysis revealed that the presence of ILNH2 caused a remarkable increase of gold nanoparticles with (111) planes parallel to the PC film. The catalytic activity of the modified membranes in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4 was investigated and found higher than membranes modified with preformed citrate-stabilized gold nanoparticles (citr-AuNPs) solutions.

Fatigue Properties of Nano-Crystalline Nickel Electrodeposited Thin Films

Nickel nanocrystalline thin films were produced by electrodeposition using sulfamate solution. Three types of thin films with different grain sizes were produced : CC films were made under constant current, PC films under pulse current, and CC-ally films under constant current with grain refinement additive. The grain size gets smaller in the order of CC, PC, and CC-ally films down to nanometers. The fracture strength and yield strength in tension tests follows the Hall-Petch relation, and the elongation was largest for CC-ally films. The fatigue strength increased with decreasing grain size, following the Hall-Petch relation down to about 10nm. The resistance to fatigue crack propagation decreased for nano grain-sized films. The threshold stress intensity factor was the smallest for PC and CC-ally films. In the intermediate-rate range, the propagation rate increased with decreasing grain size when compared at the same stress intensity factor. The fatigue fracture surface near the threshold consisted of granular features whose size decreased with decreasing grain size. At high stress intensity factors, striations were observed on the fracture surface of CC films, while only fine granular feature was observed for CC-ally films. On the specimen surface near the fatigue fracture surface of CP and CC-ally films, the small grain boundary fracture facets were observed at high stress intensity factors, while not observed near the threshold. For CC films, slip bands were seen together with the grain boundary fracture facets.

Recent studies chemical sensors based on phthalocyanines

Phthalocyanines (Pcs) are organic compounds able to act as chemical recognition systems because of the various physical effects induced in them by interaction with a large number of gases. The gas response, stability and other sensing characteristics of the Pc films are affected by many factors, such as film morphology, molecular orientation and so on. The interaction between the Pc coatings and the gas molecules may be classified in terms of irreversible chemical affinity, reversible (usually charge transfer) chemical reaction or sorption. The nature of the interactions between the coating and vapor molecules determines the selectivity, sensitivity, signal kinetics, and the reversibility of the sensor. The magnitude of these interactions may be conveniently described in the frame of the linear sorption energy relationship (LSER) model that has been shown to be very efficient at predicting the behavior of polymer-based sensors. In this paper, the effect of coating parameters on sensing properties and sensing mechanism are reviewed. We have proposed an alternative way to achieve optimal sensor performance: liquid crystalline Pcs forming self-ordered thin films of defined area and thickness simply by heating the sample over the phase transition temperature and synthetized mesomorphic and functionalized phthalocyanines, to develop sensors based on mass-sensitive transducers (quartz crystal microbalance, QCM). Phthalocyanines used are discussed in terms of their physical and chemical properties, as well as their sensing properties: sensitivity, selectivity and reversibility. We showed our results with LSER and the results are in good agreement with this theory.