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Materials, Volume 2, Issue 3 (September 2009), Pages 710-1416

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Open AccessArticle Charge Transport in Carbon Nanotubes-Polymer Composite Photovoltaic Cells
Materials 2009, 2(3), 710-718; doi:10.3390/ma2030710
Received: 21 May 2009 / Accepted: 26 June 2009 / Published: 29 June 2009
Cited by 12 | PDF Full-text (285 KB) | HTML Full-text | XML Full-text
Abstract
We investigate the dark and illuminated current density-voltage (J/V) characteristics of poly(2-methoxy-5-(2-ethylhexyloxy)1-4-phenylenevinylene) (MEH-PPV)/single-walled carbon nanotubes (SWNTs) composite photovoltaic cells. Using an exponential band tail model, the conduction mechanism has been analysed for polymer only devices and composite devices, in terms [...] Read more.
We investigate the dark and illuminated current density-voltage (J/V) characteristics of poly(2-methoxy-5-(2-ethylhexyloxy)1-4-phenylenevinylene) (MEH-PPV)/single-walled carbon nanotubes (SWNTs) composite photovoltaic cells. Using an exponential band tail model, the conduction mechanism has been analysed for polymer only devices and composite devices, in terms of space charge limited current (SCLC) conduction mechanism, where we determine the power parameters and the threshold voltages. Elaborated devices for MEH-PPV:SWNTs (1:1) composites showed a photoresponse with an open-circuit voltage Voc of 0.4 V, a short-circuit current density JSC of 1 µA/cm² and a fill factor FF of 43%. We have modelised the organic photovoltaic devices with an equivalent circuit, where we calculated the series and shunt resistances. Full article
Open AccessArticle Isopropyl Myristate-Modified Polyether-Urethane Coatings as Protective Barriers for Implantable Medical Devices
Materials 2009, 2(3), 719-733; doi:10.3390/ma2030719
Received: 13 May 2009 / Accepted: 18 June 2009 / Published: 30 June 2009
Cited by 3 | PDF Full-text (225 KB) | HTML Full-text | XML Full-text
Abstract
Polyurethane films have potential applications in medicine, especially for packaging implantable medical devices. Although polyether-urethanes have superior mechanical properties and are biocompatible, achieving water resistance is still a challenge. Polyether based polyurethanes with two different molecular weights (PTMO1000, PTMO2000) were prepared from [...] Read more.
Polyurethane films have potential applications in medicine, especially for packaging implantable medical devices. Although polyether-urethanes have superior mechanical properties and are biocompatible, achieving water resistance is still a challenge. Polyether based polyurethanes with two different molecular weights (PTMO1000, PTMO2000) were prepared from 4,4’-diphenylmethane diisocyanate and poly(tetra-methylene oxide). Polymer films were introduced using different concentrations (0.5-10 wt %) of isopropyl myristate lipid (IPM) as a non-toxic modifying agent. The physical and mechanical properties of these polymers were characterised using physical and spectroscopy techniques (FTIR, Raman, DSC, DMA, tensile testing). Water contact angle and water uptake of the membranes as a function of IPM concentration was also determined accordingly. The FTIR and Raman data indicate that IPM is dispersed in polyurethane at ≤ 2wt% and thermal analysis confirmed this miscibility to be dependent on soft segment length. Modified polymers showed increased tensile strength and failure strain as well as reduced water uptake by up to 24% at 1-2 wt% IPM. Full article
Open AccessArticle Dynamic Response during PEM Fuel Cell Loading-up
Materials 2009, 2(3), 734-748; doi:10.3390/ma2030734
Received: 16 June 2009 / Accepted: 25 June 2009 / Published: 7 July 2009
Cited by 5 | PDF Full-text (863 KB) | HTML Full-text | XML Full-text
Abstract
A study on the effects of controlling and operating parameters for a Proton Exchange Membrane (PEM) fuel cell on the dynamic phenomena during the loading-up process is presented. The effect of the four parameters of load-up amplitudes and rates, operating pressures and [...] Read more.
A study on the effects of controlling and operating parameters for a Proton Exchange Membrane (PEM) fuel cell on the dynamic phenomena during the loading-up process is presented. The effect of the four parameters of load-up amplitudes and rates, operating pressures and current levels on gas supply or even starvation in the flow field is analyzed based accordingly on the transient characteristics of current output and voltage. Experiments are carried out in a single fuel cell with an active area of 285 cm2. The results show that increasing the loading-up amplitude can inevitably increase the possibility of gas starvation in channels when a constant flow rate has been set for the cathode; With a higher operating pressure, the dynamic performance will be improved and gas starvations can be relieved. The transient gas supply in the flow channel during two loading-up mode has also been discussed. The experimental results will be helpful for optimizing the control and operation strategies for PEM fuel cells in vehicles. Full article
(This article belongs to the Special Issue Energy Technology for the 21st Century - Materials and Devices)
Open AccessArticle Compostability of Co-Extruded Starch/Poly(Lactic Acid) Polymeric Material Degradation in an Activated Inert Solid Medium
Materials 2009, 2(3), 749-764; doi:10.3390/ma2030749
Received: 27 May 2009 / Revised: 19 June 2009 / Accepted: 23 June 2009 / Published: 8 July 2009
Cited by 7 | PDF Full-text (328 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work was to estimate the biodegradation of a co-extruded starch/poly(lactic acid) polymeric material using a vermiculite based inert solid medium which could simulate compost medium and enable us to achieve complete carbon balances. At the end of the [...] Read more.
The aim of this work was to estimate the biodegradation of a co-extruded starch/poly(lactic acid) polymeric material using a vermiculite based inert solid medium which could simulate compost medium and enable us to achieve complete carbon balances. At the end of the test the mineralisation rate was compared to those obtained for co-extruded starch/poly(lactic acid) polymeric material degradation in compost. It was shown that the mineralisation rate after 45 days of degradation was similar in activated vermiculite medium to the one in compost. A protocol for both extraction and quantification of the carbon included in the different degradation by-products was proposed and the carbon balance of the polymer degradation was followed during the test with a satisfactory accuracy. As the non-degraded PLA and starch material had been retrieved during the test, the evolution of the glass transition temperature and the molecular weight of PLA could be followed. A two-step degradation mechanism was highlighted in inert solid medium, showing the fundamental role of abiotic reactions for PLA degradation in compost. Full article
Open AccessArticle Hoffmeister Series Ions Protect Diphtheria Toxoid from Structural Damages at Solvent/Water Interface
Materials 2009, 2(3), 765-775; doi:10.3390/ma2030765
Received: 1 June 2009 / Accepted: 11 July 2009 / Published: 13 July 2009
Cited by 3 | PDF Full-text (232 KB) | HTML Full-text | XML Full-text
Abstract
During the W1/O phase (in the W1/O/W2 process) of protein microencapsulation within poly-lactide-co-glycolide (PLGA), hydrophobic interfaces are expanded where interfacial adsorption occurs followed by protein unfolding and aggregation. Spectroscopic and immunological techniques were used to ascertain the [...] Read more.
During the W1/O phase (in the W1/O/W2 process) of protein microencapsulation within poly-lactide-co-glycolide (PLGA), hydrophobic interfaces are expanded where interfacial adsorption occurs followed by protein unfolding and aggregation. Spectroscopic and immunological techniques were used to ascertain the effects of the Hoffmeister series ions on Diphtheria toxoid (Dtxd) stability during the W1/O phase. A correlation was established between salts used in aqueous solutions and the changes in Dtxd solubility and conformation. The Dtxd α-helical content was quite stable thus leading to the conclusion that encapsulation was followed by protein aggregation, with minor exposition of hydrophobic residues and a small change at the S-S dihedral angle. Dtxd aggregation is 95% avoided by the chaotropic SCN-. This was used to prepare a stable Dtxd and immunologically recognized/PLGA formulation in the presence of 30 mM SNC-. The recovery increased by 10.42% or 23.2% when microencapsulation was within the -COOMe or -COOH (12kDa) PLGA, respectively. In conclusion, the aim of this work was achieved, which was to obtain the maximum of Dtxd stability after contact with CH2Cl2 to begin its PLGA microencapsulation within ideal conditions. This was a technological breakthrough because a simple solution like salt addition avoided heterologous proteins usage. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
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Open AccessArticle Nitrate-Melt Synthesized HT-LiCoO2 as a Superior Cathode-Material for Lithium-Ion Batteries
Materials 2009, 2(3), 857-868; doi:10.3390/ma2030857
Received: 16 June 2009 / Accepted: 17 July 2009 / Published: 27 July 2009
Cited by 9 | PDF Full-text (782 KB) | HTML Full-text | XML Full-text
Abstract
An electrochemically-active high-temperature form of LiCoO2 (HT-LiCoO2)is prepared by thermally decomposing its constituent metal-nitrates at 700 ºC. The synthetic conditions have been optimized to achieve improved performance with the HT-LiCoO2cathode in Li-ion batteries. For this purpose, the [...] Read more.
An electrochemically-active high-temperature form of LiCoO2 (HT-LiCoO2)is prepared by thermally decomposing its constituent metal-nitrates at 700 ºC. The synthetic conditions have been optimized to achieve improved performance with the HT-LiCoO2cathode in Li-ion batteries. For this purpose, the synthesized materials have been characterized by powder X-ray diffraction, scanning electron microscopy, and galvanostatic charge-discharge cycling. Cathodes comprising HT-LiCoO2 exhibit a specific capacity of 140 mAhg-1 with good capacity-retention over several charge-discharge cycles in the voltage range between 3.5 V and 4.2 V, and can sustain improved rate capability in contrast to a cathode constituting LiCoO2 prepared by conventional ceramic method. The nitrate-melt-decomposition method is also found effective for synthesizing Mg-/Al- doped HT-LiCoO2; these also are investigated as cathode materials for Li-ion batteries. Full article
(This article belongs to the Special Issue Energy Technology for the 21st Century - Materials and Devices)
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Open AccessArticle Efficient Syntheses of [(n-C4H9)4N]4[α-Mo8O26] and [(n-C4H9)4N]2[Mo2O7]
Materials 2009, 2(3), 869-875; doi:10.3390/ma2030869
Received: 16 June 2009 / Revised: 30 June 2009 / Accepted: 27 July 2009 / Published: 28 July 2009
Cited by 1 | PDF Full-text (328 KB) | HTML Full-text | XML Full-text
Abstract Efficient and simple syntheses of [(n-C4H9)4N]4[a-Mo8O26] (I) and [(n-C4H9)4N]2[Mo2O7] (II) from MoO3 and aqueous [(n-C4H9)4N]OH are described. The yield is 72% for I and 73% for II. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessArticle Shear Strength of Exterior Plywood Panels Pressed at Low Temperature
Materials 2009, 2(3), 876-882; doi:10.3390/ma2030876
Received: 5 July 2009 / Revised: 21 July 2009 / Accepted: 3 August 2009 / Published: 4 August 2009
Cited by 1 | PDF Full-text (103 KB) | HTML Full-text | XML Full-text
Abstract
Plywood manufactured from thin veneer sheets of different species is one of the most traditional structural composite panels. The objective of this study was to produce experimental plywood panels using a temperature of 100 °C, which is 10 to 30% lower than [...] Read more.
Plywood manufactured from thin veneer sheets of different species is one of the most traditional structural composite panels. The objective of this study was to produce experimental plywood panels using a temperature of 100 °C, which is 10 to 30% lower than typical press temperature of plywood manufacture. It was determined that shear strength characteristics of the samples were not adversely influenced as function of reduced press temperature. This process can be considered as a promising way to save substantial amounts of energy during pressing processes, which results in a major reduction in overall production costs. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Surface Hydrophobic Modification of Fifth-Generation Hydroxyl-Terminated Poly(amidoamine) Dendrimers and Its Effect on Biocompatibility and Rheology
Materials 2009, 2(3), 883-902; doi:10.3390/ma2030883
Received: 25 June 2009 / Revised: 24 July 2009 / Accepted: 31 July 2009 / Published: 4 August 2009
Cited by 3 | PDF Full-text (747 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Water-soluble, commercially-available poly(amidoamine) (PAMAM) dendrimers are highly-branched, well-defined, monodisperse macromolecules having an ethylenediamine core and varying surface functional groups. Dendrimers are being employed in an increasing number of biomedical applications. In this study, commercially obtained generation 5 hydroxyl-terminated (G5OH) PAMAM [...] Read more.
Water-soluble, commercially-available poly(amidoamine) (PAMAM) dendrimers are highly-branched, well-defined, monodisperse macromolecules having an ethylenediamine core and varying surface functional groups. Dendrimers are being employed in an increasing number of biomedical applications. In this study, commercially obtained generation 5 hydroxyl-terminated (G5OH) PAMAM dendrimers were studied as potential proteomimetics for ophthalmic uses. To this end, the surface of G5OH PAMAM dendrimers were hydrophobically modified with varying amounts of dodecyl moieties, (flexible long aliphatic chains), or cholesteryl moieties (rigid lipid found in abundance in biological systems). Dendrimers were characterized by 1H-NMR, DLS, DSC and HPLC. The hydrophobic modification caused aggregation and molecular interactions between dendrimers that is absent in unmodified dendrimers. In vitro tissue culture showed that increasing the amount of dodecyl modification gave a proportional increase in toxicity of the dendrimers, while with increasing cholesteryl modification there was no corresponding increase in toxicity. Storage and loss modulus were measured for selected formulations. The hydrophobic modification caused an increase in loss modulus, while the effect on storage modulus was more complex. Rheological properties of the dendrimer solutions were comparable to those of porcine lens crystallins. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
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Open AccessArticle Porous Thermoelectric Materials
Materials 2009, 2(3), 903-910; doi:10.3390/ma2030903
Received: 20 June 2009 / Revised: 25 July 2009 / Accepted: 28 July 2009 / Published: 5 August 2009
Cited by 11 | PDF Full-text (1391 KB) | HTML Full-text | XML Full-text
Abstract
Thermoelectric materials are sometimes prepared using a sintering process in which the achievement of a high density is often one of the objectives. However, it has recently been shown that the introduction of a highly porous material is desirable in synthetic transverse [...] Read more.
Thermoelectric materials are sometimes prepared using a sintering process in which the achievement of a high density is often one of the objectives. However, it has recently been shown that the introduction of a highly porous material is desirable in synthetic transverse thermoelements. Porosity may also be an advantage in conventional longitudinal thermoelectric modules in which a high thermal flux density creates problems, but heat transfer within the pores can degrade the thermoelectric figure of merit. The amount of this degradation is calculated and it is shown that it can be small enough to be acceptable in practical devices. Full article
(This article belongs to the Special Issue Porous Materials)
Open AccessArticle Properties of Strandboard Panels Manufactured from Eastern Redcedar
Materials 2009, 2(3), 926-933; doi:10.3390/ma2030926
Received: 5 July 2009 / Revised: 23 July 2009 / Accepted: 13 August 2009 / Published: 14 August 2009
Cited by 4 | PDF Full-text (243 KB) | HTML Full-text | XML Full-text
Abstract
This study evaluated physical and mechanical properties of experimental strandboard panels with random flake alignment manufactured from eastern redcedar (Juniperus virginiana L.) logs. Panels were made at two density levels of 0.65 g/cm3 and 0.78 g/cm3 using phenol formaldehyde [...] Read more.
This study evaluated physical and mechanical properties of experimental strandboard panels with random flake alignment manufactured from eastern redcedar (Juniperus virginiana L.) logs. Panels were made at two density levels of 0.65 g/cm3 and 0.78 g/cm3 using phenol formaldehyde adhesive applied at a rate of 8%. Mechanical properties including modulus of elasticity and modulus of rupture, and internal bond strength of the panels in addition to their thickness swelling characteristics were evaluated. As expected, mechanical properties of the samples improved with increasing panel density. Thickness swelling of the samples for 2- and 24-h water soaking test ranged from 6.32% to 18.41%. Both physical and mechanical properties of the panels showed acceptable results, comparable to those found in past studies using other species to manufacture similar types of product. Based on initial findings of this study it appears that eastern redcedar, which is an under-utilized invasive resource, has potential as a raw material for structural panel manufacture. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Cytotoxic Evaluation of Elastomeric Dental Impression Materials on a Permanent Mouse Cell Line and on a Primary Human Gingival Fibroblast Culture
Materials 2009, 2(3), 934-944; doi:10.3390/ma2030934
Received: 29 June 2009 / Revised: 27 July 2009 / Accepted: 11 August 2009 / Published: 14 August 2009
PDF Full-text (546 KB) | HTML Full-text | XML Full-text
Abstract
The need for clinically relevant in vitro tests of dental materials is widely recognized. Nearly all dental impression materials are introduced into the mouth just after mixing and allowed to set in contact with the oral tissues. Under these conditions, the materials [...] Read more.
The need for clinically relevant in vitro tests of dental materials is widely recognized. Nearly all dental impression materials are introduced into the mouth just after mixing and allowed to set in contact with the oral tissues. Under these conditions, the materials may be toxic to cells or may sensitize the tissues. The aim of the present study is to evaluate the potential cytotoxicity of new preparations of elastomeric dental impression materials: A) four vinylpolysiloxanes: Elite H-D Putty and Elite H-D Light Body (Zhermack, Badia Polesine, Rovigo, Italy); Express Putty and Express Light Body (3M ESPE AG Seefeld, Germany) and B) two polyethers: Impregum Penta and Permadyne Penta L (3M ESPE AG Seefeld, Germany). The cytotoxicity of these impression materials were examined using two different cell lines: Balb/c 3T3 (permanent cell line) and human gingival fibroblasts (primary cell line) and their effects were studied by indirect and direct tests. The direct tests are performed by placing one sample of the impression materials in the centre of the Petri dishes at the time of the seeding of cells. The cell growth was evaluated at the 12th and 24th hours by cell number. The indirect tests were performed by incubating a square of 1 cm diameter impression material in 5 mL of medium at 37 °C for 24 hours (“eluates”). Subconfluent cultures are incubated with “eluates” for 24 hours. The MTT-formazan production is the method used for measuring the cell viability. The results indicate that: a) polyether materials are cytotoxic under both experimental conditions; b) among vinylpolysiloxanes, only Express Light Body (3M ESPE AG Seefeld, Germany) induces clear inhibition of cellular viability of Balb/c 3T3 evaluated by direct and indirect tests and c) the primary cell line is less sensitive to the toxic effect than the permanent cell line. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
Open AccessArticle Biocompatibility of Collagen Membranes Assessed by Culturing Human J111 Macrophage Cells
Materials 2009, 2(3), 945-957; doi:10.3390/ma2030945
Received: 29 June 2009 / Revised: 4 August 2009 / Accepted: 14 August 2009 / Published: 18 August 2009
Cited by 2 | PDF Full-text (1040 KB) | HTML Full-text | XML Full-text
Abstract
We have carried out an in vitro study on the interactions of human macrophages (J111 cell line) with different scaffolds made of type I and II collagen, isolated from horse tendon and from horse articular and trachea cartilage, in order to assess [...] Read more.
We have carried out an in vitro study on the interactions of human macrophages (J111 cell line) with different scaffolds made of type I and II collagen, isolated from horse tendon and from horse articular and trachea cartilage, in order to assess growth properties and biocompatibility of these membranes. We have therefore evaluated cell adhesion and proliferation as well as cytokine production considered an indicator of macrophage activation. The inflammatory response is in fact one of the major causes of collagen destruction thus interfering with cell and tissue behaviour. Moreover, the morphology of cells, seeded on membranes selected for the best characteristics, was described. Results might be relevant for in vivo application such ad “tissue engineering” and/or specialized cells implants. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
Open AccessArticle Synthesis of Aryliron Complexes [CpFe(CO)2Ar] by Palladium-Catalyzed Reactions of [CpFe(CO)2I] with Arylzinc, -Boron, or -Indium Reagents
Materials 2009, 2(3), 978-991; doi:10.3390/ma2030978
Received: 17 July 2009 / Revised: 19 August 2009 / Accepted: 20 August 2009 / Published: 20 August 2009
Cited by 7 | PDF Full-text (529 KB) | HTML Full-text | XML Full-text
Abstract
Transmetalation between [CpFe(CO)2I] and arylzinc iodide-lithium chloride complexes proceeds in the presence of catalytic amounts of palladium acetate and N,N,N’,N’-tetramethyl-1,2-cyclohexanediamine to yield the corresponding aryliron complexes [CpFe(CO)2Ar]. Phenylation of [CpFe(CO)2I] also takes place when triphenylindium is [...] Read more.
Transmetalation between [CpFe(CO)2I] and arylzinc iodide-lithium chloride complexes proceeds in the presence of catalytic amounts of palladium acetate and N,N,N’,N’-tetramethyl-1,2-cyclohexanediamine to yield the corresponding aryliron complexes [CpFe(CO)2Ar]. Phenylation of [CpFe(CO)2I] also takes place when triphenylindium is used under similar conditions. Arylboronic acids undergo arylation in the presence of cesium carbonate and a palladium-N-heterocyclic carbene complex, PEPPSI. The present methods are useful for the facile synthesis of various functionalized [CpFe(CO)2Ar]. The products [CpFe(CO)2Ar] represent an interesting class of aryl metals that undergo several transformation. Full article
(This article belongs to the Special Issue Organometallic Compounds)
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Open AccessArticle Advances for the Topographic Characterisation of SMC Materials
Materials 2009, 2(3), 1084-1103; doi:10.3390/ma2031084
Received: 15 July 2009 / Revised: 20 August 2009 / Accepted: 26 August 2009 / Published: 27 August 2009
Cited by 3 | PDF Full-text (1460 KB) | HTML Full-text | XML Full-text
Abstract
For a comprehensive study of Sheet Moulding Compound (SMC) surfaces, topographical data obtained by a contact-free optical method (chromatic aberration confocal imaging) were systematically acquired to characterise these surfaces with regard to their statistical, functional and volumetrical properties. Optimal sampling conditions (cut-off [...] Read more.
For a comprehensive study of Sheet Moulding Compound (SMC) surfaces, topographical data obtained by a contact-free optical method (chromatic aberration confocal imaging) were systematically acquired to characterise these surfaces with regard to their statistical, functional and volumetrical properties. Optimal sampling conditions (cut-off length and resolution) were obtained by a topographical-statistical procedure proposed in the present work. By using different length scales specific morphologies due to the influence of moulding conditions, metallic mould topography, glass fibre content and glass fibre orientation can be characterized. The aim of this study is to suggest a systematic topographical characterization procedure for composite materials in order to study and recognize the influence of production conditions on their surface quality. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Syntheses and Functional Properties of Phthalocyanines
Materials 2009, 2(3), 1127-1179; doi:10.3390/ma2031127
Received: 27 June 2009 / Revised: 19 August 2009 / Accepted: 24 August 2009 / Published: 28 August 2009
Cited by 28 | PDF Full-text (577 KB) | HTML Full-text | XML Full-text
Abstract
Metal phthalocyanine tetrasulfonic acids, metal phthalocyanine octacarboxylic acids, metal octakis(hexyloxymethyl)phthalocyanines, and metal anthraquinocyanines have been synthesized. Then, zinc bis(1,4-didecylbenzo)-bis(3,4-pyrido)porphyrazines, the cyclotetramerization products of a 1:1 mixture of 3,6-didecylphthalonitrile and 3,4-dicyanopyridine, were synthesized. Futher, subphthalocyanine and its derivatives, with substituents such as thiobutyl [...] Read more.
Metal phthalocyanine tetrasulfonic acids, metal phthalocyanine octacarboxylic acids, metal octakis(hexyloxymethyl)phthalocyanines, and metal anthraquinocyanines have been synthesized. Then, zinc bis(1,4-didecylbenzo)-bis(3,4-pyrido)porphyrazines, the cyclotetramerization products of a 1:1 mixture of 3,6-didecylphthalonitrile and 3,4-dicyanopyridine, were synthesized. Futher, subphthalocyanine and its derivatives, with substituents such as thiobutyl and thiophenyl moieties were synthesized. Electrochemical measurements were performed on the abovementioned phthalocyanine derivatives and analogues in order to examine their electron transfer abilities and electrochemical reaction mechanisms in an organic solvent. Moreover, 1,4,8,11,15,18,22,25-octakis(thiophenylmethyl) phthalocyanes were synthesized. The Q-bands of the latter compounds appeared in the near-infrared region. Furthermore, non-colored transparent films in the visible region can be produced. Full article
(This article belongs to the Special Issue Functional Colorants)
Open AccessArticle Two-Way Bending Properties of Shape Memory Composite with SMA and SMP
Materials 2009, 2(3), 1180-1192; doi:10.3390/ma2031180
Received: 16 July 2009 / Revised: 20 August 2009 / Accepted: 24 August 2009 / Published: 1 September 2009
Cited by 18 | PDF Full-text (413 KB) | HTML Full-text | XML Full-text
Abstract
A shape memory composite (SMC) was fabricated with a shape memory alloy (SMA) and a shape memory polymer (SMP), and its two-way bending deformation and recovery force were investigated. The results obtained can be summarized as follows: (1) two kinds of SMA [...] Read more.
A shape memory composite (SMC) was fabricated with a shape memory alloy (SMA) and a shape memory polymer (SMP), and its two-way bending deformation and recovery force were investigated. The results obtained can be summarized as follows: (1) two kinds of SMA tapes which show the shape memory effect (SME) and superelasticity (SE) were heat-treated to memorize the round shape. The shape-memorized round SMA tapes were arranged facing in the opposite directions and were sandwiched between the SMP sheets. The SMC belt can be fabricated by using the appropriate factors: the number of SMP sheets, the pressing force, the heating temperature and the hold time. (2) The twoway bending deformation with an angle of 56 degrees in the fabricated SMC belt is observed based on the SME and SE of the SMA tapes during heating and cooling. (3) If the SMC belt is heated and cooled by keeping the bent form, the recovery force increases during heating and degreases during cooling based on the two-way properties of the SMC. (4) The development and application of high-functional SMCs are expected by the combination of the SMA and the SMP with various kinds of phase transformation temperatures, volume fractions, configurations and heating-cooling rates. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Optimization of Optical Properties of Polycarbonate Film with Thiol Gold-Nanoparticles
Materials 2009, 2(3), 1193-1204; doi:10.3390/ma2031193
Received: 10 July 2009 / Revised: 28 August 2009 / Accepted: 31 August 2009 / Published: 2 September 2009
Cited by 6 | PDF Full-text (235 KB) | HTML Full-text | XML Full-text
Abstract
A new nanostructured composite film based on thiol gold nanoparticles dispersed in polycarbonate and prepared by evaporating a solution of 1-dodecanthiol gold nanoparticles and polycarbonate was developed for applications as optical lenses. Lenses with superior mechanical properties, coloring and UV ray absorption [...] Read more.
A new nanostructured composite film based on thiol gold nanoparticles dispersed in polycarbonate and prepared by evaporating a solution of 1-dodecanthiol gold nanoparticles and polycarbonate was developed for applications as optical lenses. Lenses with superior mechanical properties, coloring and UV ray absorption and with the same transparency as the matrix were obtained. The supporting highly transparent polycarbonate matrix and the chloroform solution of thiol gold nanoparticles, 3 nm mean size, was mixed according to a doping protocol employing different concentrations of thiol gold nanoparticles vs. polycarbonate. The presence of nanoparticles in the polymer films was confirmed by the spectrophotometric detection of the characteristic absorbance marker peak at 540–580 nm. The nanostructured films obtained show a better coverage in the UV-vis range (250–450 nm) even at very low doping ratios, of the order of 1:1,000. These results offer a very promising approach towards the development of efficient nanostructured materials for applications to optical lenses. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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Open AccessArticle Characterization by SEM, TEM and Quantum-Chemical Simulations of the Spherical Carbon with Nitrogen (SCN) Active Carbon Produced by Thermal Decomposition of Poly(vinylpyridine-divinylbenzene) Copolymer
Materials 2009, 2(3), 1239-1251; doi:10.3390/ma2031239
Received: 15 July 2009 / Accepted: 4 September 2009 / Published: 7 September 2009
Cited by 3 | PDF Full-text (1117 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Amorphous Spherical Carbon with Nitrogen (SCN) active carbon has been prepared by carbonization of poly(vinylpyridine-divinylbenzene) (PVPDVB) copolymer. The PVPDVB dehydrogenation copolymer has been quantum chemically (QC) simulated using cluster and periodic models. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy [...] Read more.
Amorphous Spherical Carbon with Nitrogen (SCN) active carbon has been prepared by carbonization of poly(vinylpyridine-divinylbenzene) (PVPDVB) copolymer. The PVPDVB dehydrogenation copolymer has been quantum chemically (QC) simulated using cluster and periodic models. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) studies of the resulting product have conformed the QC computation results. Great structural similarity is found both at the nano- and micro-levels between the N-doped SCN carbon and its pure carbonic SKS analog. Full article
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Open AccessArticle Photo-Induced Phase Transitions to Liquid Crystal Phases: Influence of the Chain Length from C8E4 to C14E4
Materials 2009, 2(3), 1305-1322; doi:10.3390/ma2031305
Received: 28 August 2009 / Revised: 14 September 2009 / Accepted: 16 September 2009 / Published: 17 September 2009
Cited by 2 | PDF Full-text (987 KB) | HTML Full-text | XML Full-text
Abstract
Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i) with n [...] Read more.
Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i) with n = 8, 10, 12, 14; cyclohexane/H2O. We were interested in understanding the effect of chain length increase on the dynamics of transformation from the microemulsion phase to the liquid crystal phase. Applying light pump (pulse)/x-ray probe (pulse) techniques, we could demonstrate that entropy and diffusion control are the driving forces for the kind of phase transition investigated. Full article
(This article belongs to the Special Issue Liquid Crystals)
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Open AccessArticle Optical Properties of Nitrogen-Substituted Strontium Titanate Thin Films Prepared by Pulsed Laser Deposition
Materials 2009, 2(3), 1388-1401; doi:10.3390/ma2031388
Received: 27 August 2009 / Revised: 17 September 2009 / Accepted: 21 September 2009 / Published: 22 September 2009
Cited by 9 | PDF Full-text (490 KB) | HTML Full-text | XML Full-text
Abstract
Perovskite-type N-substituted SrTiO3 thin films with a preferential (001) orientation were grown by pulsed laser deposition on (001)-oriented MgO and LaAlO3 substrates. Application of N2 or ammonia using a synchronized reactive gas pulse produces SrTiO3-x:Nx films [...] Read more.
Perovskite-type N-substituted SrTiO3 thin films with a preferential (001) orientation were grown by pulsed laser deposition on (001)-oriented MgO and LaAlO3 substrates. Application of N2 or ammonia using a synchronized reactive gas pulse produces SrTiO3-x:Nx films with a nitrogen content of up to 4.1 at.% if prepared with the NH3 gas pulse at a substrate temperature of 720 °C. Incorporating nitrogen in SrTiO3 results in an optical absorption at 370-460 nm associated with localized N(2p) orbitals. The estimated energy of these levels is ≈2.7 eV below the conduction band. In addition, the optical absorption increases gradually with increasing nitrogen content. Full article
Open AccessArticle A Novel Approach for Automated Analysis of Cell Attachment and Spreading Based on Backscattered Electron Imaging by Scanning Electron Microscopy
Materials 2009, 2(3), 1402-1416; doi:10.3390/ma2031402
Received: 17 August 2009 / Revised: 21 September 2009 / Accepted: 23 September 2009 / Published: 24 September 2009
Cited by 3 | PDF Full-text (1431 KB) | HTML Full-text | XML Full-text
Abstract
The development of new materials for biological application requires in vitro testing of cell/surface interactions. Cell adhesion and spreading are difficult to quantify as most materials are non-transparent and transmission microscopy cannot be used. Contrast in reflection microscopy is rather poor. We [...] Read more.
The development of new materials for biological application requires in vitro testing of cell/surface interactions. Cell adhesion and spreading are difficult to quantify as most materials are non-transparent and transmission microscopy cannot be used. Contrast in reflection microscopy is rather poor. We propose an alternative method for the automated screening of cell attachment and spreading using backscattered electron imaging of scanning electron microscopy. The enhanced cell contrast permits study of cell/material interactions by little differences between cells and material. Full article
(This article belongs to the Special Issue Advances in Biomaterials)

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Open AccessReview Cork Composites: A Review
Materials 2009, 2(3), 776-789; doi:10.3390/ma2030776
Received: 22 May 2009 / Revised: 1 July 2009 / Accepted: 15 July 2009 / Published: 16 July 2009
Cited by 42 | PDF Full-text (444 KB) | HTML Full-text | XML Full-text
Abstract
Cork is a material which has been used for mankind for the last 5,000 years and it is a strategic material used for multiple applications, from wine bottles to aeronautics. Many of current cork materials are composites, in particular cork materials for [...] Read more.
Cork is a material which has been used for mankind for the last 5,000 years and it is a strategic material used for multiple applications, from wine bottles to aeronautics. Many of current cork materials are composites, in particular cork materials for floor and wall coverings and several other building and industrial applications. Recent developments in cork research have shifted from the classical cork-wine relationship to quality and environmental issues, exploitation of cork industry residues and new cork based materials. In recent years a number of new cork based composite materials were developed. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Metallic Scaffolds for Bone Regeneration
Materials 2009, 2(3), 790-832; doi:10.3390/ma2030790
Received: 19 June 2009 / Revised: 20 July 2009 / Accepted: 21 July 2009 / Published: 23 July 2009
Cited by 89 | PDF Full-text (377 KB) | HTML Full-text | XML Full-text
Abstract
Bone tissue engineering is an emerging interdisciplinary field in Science, combining expertise in medicine, material science and biomechanics. Hard tissue engineering research is focused mainly in two areas, osteo and dental clinical applications. There is a lot of exciting research being performed [...] Read more.
Bone tissue engineering is an emerging interdisciplinary field in Science, combining expertise in medicine, material science and biomechanics. Hard tissue engineering research is focused mainly in two areas, osteo and dental clinical applications. There is a lot of exciting research being performed worldwide in developing novel scaffolds for tissue engineering. Although, nowadays the majority of the research effort is in the development of scaffolds for non-load bearing applications, primarily using soft natural or synthetic polymers or natural scaffolds for soft tissue engineering; metallic scaffolds aimed for hard tissue engineering have been also the subject of in vitro and in vivo research and industrial development. In this article, descriptions of the different manufacturing technologies available to fabricate metallic scaffolds and a compilation of the reported biocompatibility of the currently developed metallic scaffolds have been performed. Finally, we highlight the positive aspects and the remaining problems that will drive future research in metallic constructs aimed for the reconstruction and repair of bone. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
Open AccessReview Biodegradable Polymers in Bone Tissue Engineering
Materials 2009, 2(3), 833-856; doi:10.3390/ma2030833
Received: 2 July 2009 / Revised: 21 July 2009 / Accepted: 24 July 2009 / Published: 24 July 2009
Cited by 29 | PDF Full-text (648 KB) | HTML Full-text | XML Full-text
Abstract
The use ofdegradable polymers in medicine largely started around the mid 20th century with their initial use as in vivo resorbing sutures. Thorough knowledge on this topic as been gained since then and the potential applications for these polymers were, and [...] Read more.
The use ofdegradable polymers in medicine largely started around the mid 20th century with their initial use as in vivo resorbing sutures. Thorough knowledge on this topic as been gained since then and the potential applications for these polymers were, and still are, rapidly expanding. After improving the properties of lactic acid-based polymers, these were no longer studied only from a scientific point of view, but also for their use in bone surgery in the 1990s. Unfortunately, after implanting these polymers, different foreign body reactions ranging from the presence of white blood cells to sterile sinuses with resorption of the original tissue were observed. This led to the misconception that degradable polymers would, in all cases, lead to inflammation and/or osteolysis at the implantation site. Nowadays, we have accumulated substantial knowledge on the issue of biocompatibility of biodegradable polymers and are able to tailor these polymers for specific applications and thereby strongly reduce the occurrence of adverse tissue reactions. However, the major issue of biofunctionality, when mechanical adaptation is taken into account, has hitherto been largely unrecognized. A thorough understanding of how to improve the biofunctionality, comprising biomechanical stability, but also visualization and sterilization of the material, together with the avoidance of fibrotic tissue formation and foreign body reactions, may greatly enhance the applicability and safety of degradable polymers in a wide area of tissue engineering applications. This review will address our current understanding of these biofunctionality factors, and will subsequently discuss the pitfalls remaining and potential solutions to solve these problems. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
Open AccessReview Eco-Challenges of Bio-Based Polymer Composites
Materials 2009, 2(3), 911-925; doi:10.3390/ma2030911
Received: 25 July 2009 / Revised: 3 August 2009 / Accepted: 6 August 2009 / Published: 10 August 2009
Cited by 46 | PDF Full-text (423 KB) | HTML Full-text | XML Full-text
Abstract
In recent years bio-based polymer composites have been the subject of many scientific and research projects, as well as many commercial programs. Growing global environmental and social concern, the high rate of depletion of petroleum resources and new environmental regulations have forced [...] Read more.
In recent years bio-based polymer composites have been the subject of many scientific and research projects, as well as many commercial programs. Growing global environmental and social concern, the high rate of depletion of petroleum resources and new environmental regulations have forced the search for new composites and green materials, compatible with the environment. The aim of this article is to present a brief review of the most suitable and commonly used biodegradable polymer matrices and NF reinforcements in eco-composites and nanocomposites, with special focus on PLA based materials. Full article
(This article belongs to the Special Issue Biodegradability of Materials)
Open AccessReview Design, Fabrication, and Properties of High Damping Metal Matrix Composites—A Review
Materials 2009, 2(3), 958-977; doi:10.3390/ma2030958
Received: 30 July 2009 / Revised: 14 August 2009 / Accepted: 17 August 2009 / Published: 18 August 2009
Cited by 27 | PDF Full-text (415 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays it is commonly considered that high damping materials which have both the good mechanical properties as structural materials and the high damping capacity for vibration damping are the most direct vibration damping solution. In metals and alloys however, exhibiting simultaneously high [...] Read more.
Nowadays it is commonly considered that high damping materials which have both the good mechanical properties as structural materials and the high damping capacity for vibration damping are the most direct vibration damping solution. In metals and alloys however, exhibiting simultaneously high damping capacity and good mechanical properties has been noted to be normally incompatible because the microscopic mechanisms responsible for internal friction (namely damping capacity) are dependent upon the parameters that control mechanical strength. To achieve a compromise, one of the most important methods is to develop two-phase composites, in which each phase plays a specific role: damping or mechanical strength. In this review, we have summarized the development of the design concept of high damping composite materials and the investigation of their fabrication and properties, including mechanical and damping properties, and suggested a new design concept of high damping composite materials where the hard ceramic additives exhibit high damping capacity at room temperature owing to the stress-induced reorientation of high density point defects in the ceramic phases and the high damping capacity of the composite comes mainly from the ceramic phases. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Polymer Layered Silicate Nanocomposites: A Review
Materials 2009, 2(3), 992-1057; doi:10.3390/ma2030992
Received: 9 August 2009 / Revised: 19 August 2009 / Accepted: 20 August 2009 / Published: 20 August 2009
Cited by 67 | PDF Full-text (2984 KB) | HTML Full-text | XML Full-text
Abstract
This review aims to present recent advances in the synthesis and structure characterization as well as the properties of polymer layered silicate nanocomposites. The advent of polymer layered silicate nanocomposites has revolutionized research into polymer composite materials. Nanocomposites are organic-inorganic hybrid materials [...] Read more.
This review aims to present recent advances in the synthesis and structure characterization as well as the properties of polymer layered silicate nanocomposites. The advent of polymer layered silicate nanocomposites has revolutionized research into polymer composite materials. Nanocomposites are organic-inorganic hybrid materials in which at least one dimension of the filler is less than 100 nm. A number of synthesis routes have been developed in the recent years to prepare these materials, which include intercalation of polymers or pre-polymers from solution, in-situ polymerization, melt intercalation etc. The nanocomposites where the filler platelets can be dispersed in the polymer at the nanometer scale owing to the specific filler surface modifications, exhibit significant improvement in the composite properties, which include enhanced mechanical strength, gas barrier, thermal stability, flame retardancy etc. Only a small amount of filler is generally required for the enhancement in the properties, which helps the composite materials retain transparency and low density. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Cell Guidance by 3D-Gradients in Hydrogel Matrices: Importance for Biomedical Applications
Materials 2009, 2(3), 1058-1083; doi:10.3390/ma2031058
Received: 10 July 2009 / Revised: 18 August 2009 / Accepted: 24 August 2009 / Published: 25 August 2009
Cited by 20 | PDF Full-text (634 KB) | HTML Full-text | XML Full-text
Abstract
Concentration gradients of soluble and matrix-bound guidance cues in the extracellular matrix direct cell growth in native tissues and are of great interest for design of biomedical scaffolds and on implant surfaces. The focus of this review is to demonstrate the importance [...] Read more.
Concentration gradients of soluble and matrix-bound guidance cues in the extracellular matrix direct cell growth in native tissues and are of great interest for design of biomedical scaffolds and on implant surfaces. The focus of this review is to demonstrate the importance of gradient guidance for cells as it would be desirable to direct cell growth onto/into biomedical devices. Many studies have been described that illustrate the production and characterization of surface gradients, but three dimensional (3D)-gradients that direct cellular behavior are not well investigated. Hydrogels are considered as synthetic replacements for native extracellular matrices as they share key functions such as 2D- or 3D-solid support, fibrous structure, gas- and nutrition permeability and allow storage and release of biologically active molecules. Therefore this review focuses on current studies that try to implement soluble or covalently-attached gradients of growth factors, cytokines or adhesion sequences into 3D-hydrogel matrices in order to control cell growth, orientation and migration towards a target. Such gradient architectures are especially desirable for wound healing purposes, where defined cell populations need to be recruited from the blood stream and out of the adjacent tissue, in critical bone defects, for vascular implants or neuronal guidance structures where defined cell populations should be guided by appropriate signals to reach their proper positions or target tissues in order to accomplish functional repair. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
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Open AccessReview Biodegradability of Poly(hydroxyalkanoate) Materials
Materials 2009, 2(3), 1104-1126; doi:10.3390/ma2031104
Received: 15 July 2009 / Revised: 19 August 2009 / Accepted: 24 August 2009 / Published: 28 August 2009
Cited by 12 | PDF Full-text (1667 KB) | HTML Full-text | XML Full-text
Abstract
Poly(hydroxyalkanoate) (PHA), which is produced from renewable carbon resources by many microorganisms, is an environmentally compatible polymeric material and can be processed into films and fibers. Biodegradation of PHA material occurs due to the action of extracellular PHA depolymerase secreted from microorganisms [...] Read more.
Poly(hydroxyalkanoate) (PHA), which is produced from renewable carbon resources by many microorganisms, is an environmentally compatible polymeric material and can be processed into films and fibers. Biodegradation of PHA material occurs due to the action of extracellular PHA depolymerase secreted from microorganisms in various natural environments. A key step in determining the overall enzymatic or environmental degradation rate of PHA material is the degradation of PHA lamellar crystals in materials; hence, the degradation mechanism of PHA lamellar crystals has been studied in detail over the last two decades. In this review, the relationship between crystal structure and enzymatic degradation behavior, in particular degradation rates, of films and fibers for PHA is described. Full article
(This article belongs to the Special Issue Biodegradability of Materials)
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Open AccessReview Novel Nanocomposite Materials for Advanced Li-Ion Rechargeable Batteries
Materials 2009, 2(3), 1205-1238; doi:10.3390/ma2031205
Received: 12 August 2009 / Revised: 30 August 2009 / Accepted: 2 September 2009 / Published: 3 September 2009
Cited by 16 | PDF Full-text (1054 KB) | HTML Full-text | XML Full-text
Abstract
Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. Nanocomposite materials will have a further enhancement in properties compared to their constituent phases. This Review describes [...] Read more.
Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. Nanocomposite materials will have a further enhancement in properties compared to their constituent phases. This Review describes some recent developments of nanocomposite materials for high-performance Li-ion rechargeable batteries, including carbon-oxide nanocomposites, polymer-oxide nanocomposites, metal-oxide nanocomposites, and silicon-based nanocomposites, etc. The major goal of this Review is to highlight some new progress in using these nanocomposite materials as electrodes to develop Li-ion rechargeable batteries with high energy density, high rate capability, and excellent cycling stability. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Modelling of Grain Growth Kinetics in Porous Ceramic Materials under Normal and Irradiation Conditions
Materials 2009, 2(3), 1252-1287; doi:10.3390/ma2031252
Received: 10 July 2009 / Revised: 28 August 2009 / Accepted: 2 September 2009 / Published: 10 September 2009
Cited by 7 | PDF Full-text (501 KB) | HTML Full-text | XML Full-text
Abstract
Effect of porosity on grain growth is both the most frequent and technologically important situation encountered in ceramic materials. Generally this effect occurs during sintering, however, for nuclear fuels it also becomes very important under reactor irradiation conditions. In these cases pores [...] Read more.
Effect of porosity on grain growth is both the most frequent and technologically important situation encountered in ceramic materials. Generally this effect occurs during sintering, however, for nuclear fuels it also becomes very important under reactor irradiation conditions. In these cases pores and gas bubbles attached to the grain boundaries migrate along with the boundaries, in some circumstances giving a boundary migration controlled by the movement, coalescence and/or sintering of these particles. New mechanisms of intergranular bubble and pore migration which control the mobility of the grain boundary under normal and irradiation conditions are reviewed in this paper. Full article
(This article belongs to the Special Issue Porous Materials)
Open AccessReview Optimization of the Laser Properties of Polymer Films Doped with N,N´-Bis(3-methylphenyl)-N,-diphenylbenzidine
Materials 2009, 2(3), 1288-1304; doi:10.3390/ma2031288
Received: 1 August 2009 / Revised: 3 September 2009 / Accepted: 7 September 2009 / Published: 10 September 2009
Cited by 2 | PDF Full-text (163 KB) | HTML Full-text | XML Full-text
Abstract
This review compiles the work performed in the field of organic solid-state lasers with the hole-transporting organic molecule N,-bis(3-methylphenyl)-N,-diphenylbenzidine system (TPD), in view of improving active laser material properties. The optimization of the amplified spontaneous [...] Read more.
This review compiles the work performed in the field of organic solid-state lasers with the hole-transporting organic molecule N,-bis(3-methylphenyl)-N,-diphenylbenzidine system (TPD), in view of improving active laser material properties. The optimization of the amplified spontaneous emission characteristics, i.e., threshold, linewidth, emission wavelength and photostability, of polystyrene films doped with TPD in waveguide configuration has been achieved by investigating the influence of several materials parameters such as film thickness and TPD concentration. In addition, the influence in the emission properties of the inclusion of a second-order distributed feedback grating in the substrate is discussed. Full article
(This article belongs to the Special Issue Functional Colorants)
Open AccessReview Reversible Thermochromic Nanocomposites Based on Thiolate-Capped Silver Nanoparticles Embedded in Amorphous Polystyrene
Materials 2009, 2(3), 1323-1340; doi:10.3390/ma2031323
Received: 30 August 2009 / Revised: 15 September 2009 / Accepted: 16 September 2009 / Published: 18 September 2009
Cited by 14 | PDF Full-text (761 KB) | HTML Full-text | XML Full-text
Abstract
Technologically useful reversible thermochromic materials can be prepared using very simple polymer-embedded nanostructures. In particular, silver nanoparticles capped by long-chain alkyl-thiolate molecules (i.e., Agx(SCnH2n+1)y, with n > 10) spontaneously organize in aggregates because of [...] Read more.
Technologically useful reversible thermochromic materials can be prepared using very simple polymer-embedded nanostructures. In particular, silver nanoparticles capped by long-chain alkyl-thiolate molecules (i.e., Agx(SCnH2n+1)y, with n > 10) spontaneously organize in aggregates because of the interdigitation phenomenon involving the linear alkyl chains bonded at surfaces of neighboring nanoparticles. Owing to the alkylchain interdigitation, nanoparticles very close to each other result and an interaction among their surface plasmon resonances may take place. Surface plasmon interaction causes a splitting of the absorption band whose characteristics depend on the aggregate shape. Since shape-less aggregates are generated, a multiple-splitting of the silver surface plasmon absorption band is observed, which causes a broad absorption spreading on the whole visible spectral region. Amorphous polystyrene containing interdigitated silver nanoparticles has a dark-brown or black coloration, depending on the nanoparticle numerical density, but since the inter-particle distance slightly increases at melting point of interdigitation crystallites a reversible termochromic effect is observed at this special temperature. In particular, the material coloration changes from dark-brown to yellow which is the coloration produced by the surface plasmon absorption of isolated silver nanoparticles. This reversible thermochromism can be finely controlled by modifying the structure of thiolate groups, and precisely, the strength of interactions acting inside the interdigitation crystallites. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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Open AccessReview Increased Biocompatibility and Bioactivity after Energetic PVD Surface Treatments
Materials 2009, 2(3), 1341-1387; doi:10.3390/ma2031341
Received: 29 June 2009 / Revised: 31 August 2009 / Accepted: 18 September 2009 / Published: 21 September 2009
Cited by 11 | PDF Full-text (2497 KB) | HTML Full-text | XML Full-text
Abstract
Ion implantation, a common technology in semiconductor processing, has been applied to biomaterials since the 1960s. Using energetic ion bombardment, a general term which includes conventional ion implantation plasma immersion ion implantation (PIII) and ion beam assisted thin film deposition, functionalization of [...] Read more.
Ion implantation, a common technology in semiconductor processing, has been applied to biomaterials since the 1960s. Using energetic ion bombardment, a general term which includes conventional ion implantation plasma immersion ion implantation (PIII) and ion beam assisted thin film deposition, functionalization of surfaces is possible. By varying and adjusting the process parameters, several surface properties can be attuned simultaneously. Extensive research details improvements in the biocompatibility, mainly by reducing corrosion rates and increasing wear resistance after surface modification. Recently, enhanced bioactivity strongly correlated with the surface topography and less with the surface chemistry has been reported, with an increased roughness on the nanometer scale induced by self-organisation processes during ion bombardment leading to faster cellular adhesion processes. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)

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