Pub Date : 2008-11-26DOI: 10.2174/1874067700802010022
G. Seifert, M. Bartel, H. Graener
The vibrational relaxation of the liquid dihalomethanes CH2I2, CH2Br2 and CH2Cl2 has been studied by a com- bination of IR/IR and IR/Raman pump-probe techniques applying a time resolution of ~2 ps. Careful analysis of the re- sults shows a general trend of decreasing relaxation rates from dichloromethane to diiodomethane, with few individual deviations. Possible explanations for these observations are discussed.
{"title":"Relaxation of the CH2 Stretching Modes of Liquid Dihalomethanes","authors":"G. Seifert, M. Bartel, H. Graener","doi":"10.2174/1874067700802010022","DOIUrl":"https://doi.org/10.2174/1874067700802010022","url":null,"abstract":"The vibrational relaxation of the liquid dihalomethanes CH2I2, CH2Br2 and CH2Cl2 has been studied by a com- bination of IR/IR and IR/Raman pump-probe techniques applying a time resolution of ~2 ps. Careful analysis of the re- sults shows a general trend of decreasing relaxation rates from dichloromethane to diiodomethane, with few individual deviations. Possible explanations for these observations are discussed.","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"109 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117206977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-24DOI: 10.2174/1874067700802010017
T. Dolidze, S. Rondinini, A. Vertova, M. Longhi, D. Khoshtariya
Electrochemical performance of a (Ru(NH3)6) 3+/2+ redox couple at gold electrodes modified by alkanethiol self assembled monolayer (SAM) films of the type (-SH -(CH2)n - CH3) with different number of methylene units (n = 2 to 10) in the presence and absence of glucose additives has been studied using fast scan cyclic and steady-state voltammetry. Specific scatter of measured rate constants caused by enhanced sensitivity of this probe to minor defects of SAMs has been observed in a general agreement with the published data for thicker SAMs (n = 9 to 18). In addition, we have disclo- sed the anomalous viscosity-imposed drop of the heterogeneous rate constant for the case of Au electrodes modified by thinner n-alkanethiol SAMs (n = 2, 4). Taking into the account the fact of (Ru(NH3)6) 3+/2+ couple's capability to penetrate into the SAM interior, we ascribe the obtained results to the manifestation of the solvent-friction mechanism under the condition where the redox species presumably together with a few of solvating water molecules reside in a SAM's peri- pheral interior marked by much higher local viscosity (slower dielectric relaxation) compared to the electrolyte solution.
{"title":"Charge-Transfer Patterns for [Ru(NH3)6]3+/2+ at SAM Modified Gold Electrodes: Impact of the Permeability of a Redox Probe","authors":"T. Dolidze, S. Rondinini, A. Vertova, M. Longhi, D. Khoshtariya","doi":"10.2174/1874067700802010017","DOIUrl":"https://doi.org/10.2174/1874067700802010017","url":null,"abstract":"Electrochemical performance of a (Ru(NH3)6) 3+/2+ redox couple at gold electrodes modified by alkanethiol self assembled monolayer (SAM) films of the type (-SH -(CH2)n - CH3) with different number of methylene units (n = 2 to 10) in the presence and absence of glucose additives has been studied using fast scan cyclic and steady-state voltammetry. Specific scatter of measured rate constants caused by enhanced sensitivity of this probe to minor defects of SAMs has been observed in a general agreement with the published data for thicker SAMs (n = 9 to 18). In addition, we have disclo- sed the anomalous viscosity-imposed drop of the heterogeneous rate constant for the case of Au electrodes modified by thinner n-alkanethiol SAMs (n = 2, 4). Taking into the account the fact of (Ru(NH3)6) 3+/2+ couple's capability to penetrate into the SAM interior, we ascribe the obtained results to the manifestation of the solvent-friction mechanism under the condition where the redox species presumably together with a few of solvating water molecules reside in a SAM's peri- pheral interior marked by much higher local viscosity (slower dielectric relaxation) compared to the electrolyte solution.","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115030894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-08-15DOI: 10.2174/1874067700802010013
Youngkyoo Kim, D. Choi, Hwajeong Kim
Here we report improved operation stability of passive matrix organic light-emitting displays (PM-OLED) by melting a hole-injecting layer (HIL) that is the first organic layer contacting anode. The PM-OLED displays fabricated in this work are consisted of 128� 128 pixels in which each pixel has a dimension of 200μm� 200μm. The exact thermal tran- sition behaviour of hole-injecting material was first examined using a differential scanning calorimeter in order to decide the melting temperature for the HIL melting process (300 o C/3min). Results show that the display with the untreated (as- coated) HIL exhibited large leakage current which eventually resulted in damages (black cross-talk lines) to the display during operation. However, no cross-talk defect was observed for the PM-OLED display with the thermally treated (melted) HIL, which was supported by the absence of leakage current at reverse bias. Since the breakthrough works on organic light-emitting devices (OLED) based on either low-molecular-weight mate- rials (i.e., small molecules) (1) or polymers (2), OLED dis- plays are now in market even though their applications are limited to small size display for MP3 players, mobile phones, car front panel devices, shavers, etc (3, 4). This suc- cessful debut of OLED display into market can be mainly attributed to remarkable advances in organic semiconductor materials and process technology (3-5). However, these OLED displays do still suffer from their short lifetime though the thermal stability of organic materi- als themselves has been significantly improved when it comes to the test device measurement (4, 6, 7). In case of OLED displays made using small molecules, it has been re- ported that a progressive electrical short (PES) phenomenon is responsible for the degradation of display pixels during long time operation (8). This report claimed that the PES phenomenon is closely related to the formation of unstable defects in organic layers which eventually leads to cata- strophic degradation of whole layers in pixels. In this report the PES phenomenon could be healed by thermal treatment at temperatures below 100 o
{"title":"Melting Effect of Hole-Injecting Layer on the Performance of Passive Matrix Organic Light-Emitting Displays","authors":"Youngkyoo Kim, D. Choi, Hwajeong Kim","doi":"10.2174/1874067700802010013","DOIUrl":"https://doi.org/10.2174/1874067700802010013","url":null,"abstract":"Here we report improved operation stability of passive matrix organic light-emitting displays (PM-OLED) by melting a hole-injecting layer (HIL) that is the first organic layer contacting anode. The PM-OLED displays fabricated in this work are consisted of 128� 128 pixels in which each pixel has a dimension of 200μm� 200μm. The exact thermal tran- sition behaviour of hole-injecting material was first examined using a differential scanning calorimeter in order to decide the melting temperature for the HIL melting process (300 o C/3min). Results show that the display with the untreated (as- coated) HIL exhibited large leakage current which eventually resulted in damages (black cross-talk lines) to the display during operation. However, no cross-talk defect was observed for the PM-OLED display with the thermally treated (melted) HIL, which was supported by the absence of leakage current at reverse bias. Since the breakthrough works on organic light-emitting devices (OLED) based on either low-molecular-weight mate- rials (i.e., small molecules) (1) or polymers (2), OLED dis- plays are now in market even though their applications are limited to small size display for MP3 players, mobile phones, car front panel devices, shavers, etc (3, 4). This suc- cessful debut of OLED display into market can be mainly attributed to remarkable advances in organic semiconductor materials and process technology (3-5). However, these OLED displays do still suffer from their short lifetime though the thermal stability of organic materi- als themselves has been significantly improved when it comes to the test device measurement (4, 6, 7). In case of OLED displays made using small molecules, it has been re- ported that a progressive electrical short (PES) phenomenon is responsible for the degradation of display pixels during long time operation (8). This report claimed that the PES phenomenon is closely related to the formation of unstable defects in organic layers which eventually leads to cata- strophic degradation of whole layers in pixels. In this report the PES phenomenon could be healed by thermal treatment at temperatures below 100 o","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"129 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127388694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-07-07DOI: 10.2174/1874067700802010006
S. Guha
Polyfluorenes reveal a complex interplay between emissive properties and intra- and intermolecular structure. Vibrational frequencies and intensities determined by Raman spectroscopy are strongly influenced by variations in the backbone as well as side chain conformations. Changes in the structural and electronic properties of two side group substi- tuted polyfluorenes (PF): ethyl-hexyl substituted PF (PF2/6) and dioctyl substituted PF (PF8) as a function of solvent, thermal cycling, and hydrostatic pressure via Raman scattering are presented. The vibrational frequencies and intensities of fluorene oligomers with various alkyl side chain conformations are calculated using hybrid density-functional theory. A comparison of the computed vibrational spectra of single chain fluorene oligomers with our experimental data shows that the conformational isomers in PF8 are a direct consequence of the side chain conformation.
{"title":"Raman Spectroscopic Studies of Polyfluorenes","authors":"S. Guha","doi":"10.2174/1874067700802010006","DOIUrl":"https://doi.org/10.2174/1874067700802010006","url":null,"abstract":"Polyfluorenes reveal a complex interplay between emissive properties and intra- and intermolecular structure. Vibrational frequencies and intensities determined by Raman spectroscopy are strongly influenced by variations in the backbone as well as side chain conformations. Changes in the structural and electronic properties of two side group substi- tuted polyfluorenes (PF): ethyl-hexyl substituted PF (PF2/6) and dioctyl substituted PF (PF8) as a function of solvent, thermal cycling, and hydrostatic pressure via Raman scattering are presented. The vibrational frequencies and intensities of fluorene oligomers with various alkyl side chain conformations are calculated using hybrid density-functional theory. A comparison of the computed vibrational spectra of single chain fluorene oligomers with our experimental data shows that the conformational isomers in PF8 are a direct consequence of the side chain conformation.","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128712583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-01-25DOI: 10.2174/1874067700802010001
T. Négadi
The genetic code structure into distinct multiplet-classes as well as the numeric degeneracies of the latter are revealed by a two-step process. First, an empirical inventory of the degeneracies (of the shuffled multiplets) in two speci- fic equal moieties of the experimental genetic code table is made and transcribed in the form of a sequence of integers. Second, a Godel Encoding procedure is applied to the latter sequence delivering, as an output, a Godel Number the digits of which, from the decimal representation, could remarkably describe the amino acids and the stops and allow us also to compute the exact degeneracies, class by class. The standard and the vertebrate mitochondrial genetic codes are conside- red and their multiplet structure is fully established.
{"title":"The Genetic Code via Gödel Encoding","authors":"T. Négadi","doi":"10.2174/1874067700802010001","DOIUrl":"https://doi.org/10.2174/1874067700802010001","url":null,"abstract":"The genetic code structure into distinct multiplet-classes as well as the numeric degeneracies of the latter are revealed by a two-step process. First, an empirical inventory of the degeneracies (of the shuffled multiplets) in two speci- fic equal moieties of the experimental genetic code table is made and transcribed in the form of a sequence of integers. Second, a Godel Encoding procedure is applied to the latter sequence delivering, as an output, a Godel Number the digits of which, from the decimal representation, could remarkably describe the amino acids and the stops and allow us also to compute the exact degeneracies, class by class. The standard and the vertebrate mitochondrial genetic codes are conside- red and their multiplet structure is fully established.","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128116931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-12-18DOI: 10.2174/1874067700701010033
B. Bozzini, C. Mele, L. D'urzo
In this paper in situ visible electroreflectance measurements have been carried out in order to extract new electrochemical information from the dependence of R/R on the frequency of potential modulation. The behaviour of some typical components of a Au electrodeposition bath has been investigated: a metal salt (KAu(CN)2), a supporting electrolyte (NaClO4), a metal cation complexing agent (KCN). The voltammetric behaviour of the relevant systems has been investigated by means of Cyclic Voltammetry (CV) and Electrochemical Impedance Spectrometry (EIS). The optical and current density dynamics have been compared applying a potential square-wave modulation with frequencies in the range 1÷300 Hz and have been found to exhibit clearly different time-constants. Sensitivity to the electrolyte chemistry and radiation-wavelength have been proved for optical impedance.
{"title":"An Optical Impedance Investigation of a Gold Electrodeposition System","authors":"B. Bozzini, C. Mele, L. D'urzo","doi":"10.2174/1874067700701010033","DOIUrl":"https://doi.org/10.2174/1874067700701010033","url":null,"abstract":"In this paper in situ visible electroreflectance measurements have been carried out in order to extract new electrochemical information from the dependence of R/R on the frequency of potential modulation. The behaviour of some typical components of a Au electrodeposition bath has been investigated: a metal salt (KAu(CN)2), a supporting electrolyte (NaClO4), a metal cation complexing agent (KCN). The voltammetric behaviour of the relevant systems has been investigated by means of Cyclic Voltammetry (CV) and Electrochemical Impedance Spectrometry (EIS). The optical and current density dynamics have been compared applying a potential square-wave modulation with frequencies in the range 1÷300 Hz and have been found to exhibit clearly different time-constants. Sensitivity to the electrolyte chemistry and radiation-wavelength have been proved for optical impedance.","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123731190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-11-27DOI: 10.2174/1874067700701010025
L. J. Bonales, Hernán Ritacco, J. E. F. Rubio, R. Rubio, F. Monroy, F. Ortega
Particle tracking has been shown to be a powerful technique for measuring bulk and interfacial rheology of flu- ids. The Brownian motion of microparticles trapped at interfaces is very sensitive to the viscosity of the subphase, and to the contact angle of the particles. The Stokes-Einstein relation is fulfilled if the friction factor is properly taken into ac- count. The diffusion coefficient of the latex microparticles spread on surfactant monolayers allows one to calculate the shear viscosity of the monolayer using Danov's theory. Good agreement was found with previous results for monolayers of pentadecanoic acid. The method has also been used to study monolayers of n-dodecanol. Moreover, the shear viscosity of a polymer monolayer has been calculated by particle tracking, and the results show good agreement with data obtained by canal viscosimetry. The temperature dependence of the shear viscosity shows the existence of a glass transition for monolayers of poly(4-hydroxystyrene).
{"title":"Dynamics in Ultrathin Films: Particle Tracking Microrheology of Langmuir Monolayers","authors":"L. J. Bonales, Hernán Ritacco, J. E. F. Rubio, R. Rubio, F. Monroy, F. Ortega","doi":"10.2174/1874067700701010025","DOIUrl":"https://doi.org/10.2174/1874067700701010025","url":null,"abstract":"Particle tracking has been shown to be a powerful technique for measuring bulk and interfacial rheology of flu- ids. The Brownian motion of microparticles trapped at interfaces is very sensitive to the viscosity of the subphase, and to the contact angle of the particles. The Stokes-Einstein relation is fulfilled if the friction factor is properly taken into ac- count. The diffusion coefficient of the latex microparticles spread on surfactant monolayers allows one to calculate the shear viscosity of the monolayer using Danov's theory. Good agreement was found with previous results for monolayers of pentadecanoic acid. The method has also been used to study monolayers of n-dodecanol. Moreover, the shear viscosity of a polymer monolayer has been calculated by particle tracking, and the results show good agreement with data obtained by canal viscosimetry. The temperature dependence of the shear viscosity shows the existence of a glass transition for monolayers of poly(4-hydroxystyrene).","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124894651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-10-24DOI: 10.2174/1874067700701010018
G. T. Rengarajan, D. Enke, M. Beiner
The influence of nanoconfinement on the crystallization behavior of acetaminophen, a polymorphic drug occur- ring in three different crystalline forms, is investigated. Differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS) data for a series of controlled porous glasses (CPGs) filled with acetaminophen are presented. The re- sults show clearly that (i) the usually inaccessible crystalline form III of acetaminophen can be produced in pores with di- ameters between 22 and 103 nm and that (ii) the life time of amorphous acetaminophen is significantly increased in 10 nm pores. Bulk melting temperature and heat of melting of form III are estimated based on the Gibbs-Thomson equation. The experimental findings are confronted with the predictions of theoretical approaches aimed to describe thermodynamics and crystallization kinetics in nano-sized systems in order to understand the physical background of the observed changes.
{"title":"Crystallization Behavior of Acetaminophen in Nanopores","authors":"G. T. Rengarajan, D. Enke, M. Beiner","doi":"10.2174/1874067700701010018","DOIUrl":"https://doi.org/10.2174/1874067700701010018","url":null,"abstract":"The influence of nanoconfinement on the crystallization behavior of acetaminophen, a polymorphic drug occur- ring in three different crystalline forms, is investigated. Differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS) data for a series of controlled porous glasses (CPGs) filled with acetaminophen are presented. The re- sults show clearly that (i) the usually inaccessible crystalline form III of acetaminophen can be produced in pores with di- ameters between 22 and 103 nm and that (ii) the life time of amorphous acetaminophen is significantly increased in 10 nm pores. Bulk melting temperature and heat of melting of form III are estimated based on the Gibbs-Thomson equation. The experimental findings are confronted with the predictions of theoretical approaches aimed to describe thermodynamics and crystallization kinetics in nano-sized systems in order to understand the physical background of the observed changes.","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"24 8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128791070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-07-31DOI: 10.2174/1874067700701010010
D. Ingert
The use of masks coming from research field as different as colloids, polymers or nanomaterials is a recently emerging field. Recent advances in this area have developed a variety of practical routes which have a great potential to overcome or at least complete the high-cost lithographic techniques. This review focuses on three techniques that try to reduce to the nanometer range, the size of the mask. The major difference between these procedures is related to the type of mask used. The first technique is called colloidal lithography, the mask is a monodispersed-beads template. The second is the block copolymer lithography and the third technique is the nanocrystal lithography, the mask used is a nano-object. For these three parts, the synthetic routes, the improvements and the applications as well as the limitations will be pre- sented. I. INTRODUCTION Nanotechnology research is led by the demand for ever smaller device features that are required to improve perform- ance and decrease costs in microelectronics, communication and data storage. Lithographic methods are in the centre of this nanotechnology. Rapid replication of features below 50nm is currently a significantly unsolved problem. Generat- ing patterned surfaces at the nanoscale is beyond the limits of standard photolithography techniques. The wavelengths of photons limit the minimum feature sizes in the sub-100nm scale. Thus it appears that whatever technologies are used for fabrication in this region it does not represent simple engi- neering extensions of conventional photolithography. There exists an opportunity to introduce news ideas in replication of meso and nanostructures. Indeed, very few methods pro- vide the ability to work in the sub-50-nm scale (1-3). The well-established methods for the fabrication of nanometer- scale structures (2), such as scanning probe, electron and ion beam lithography provide resolution and integration density required for the industrials demands but the level of throughput rate is far below the requirement. There is a need for alternative simple techniques in order to save processing time and costs (4,5). This need has given rise to different kinds of approaches like, for example, nanoimprint lithogra- phy and soft lithography with the use of self-assembly monolayers (SAMs) (3,6,7). However, for both the mold fabrication problems remain unsolved. In this review we will focus on three techniques that try to reduce to the nanometer range, the size of the mask keep- ing a large surface coverage. The major difference between these procedures is related to the type of mask used while the standard techniques to pattern the substrate like metal depo- sition or ion-plasma etching are kept similar. The main re- quirements present in an efficient method for replication are flexibility in the engraved substrate, fidelity in the replica- tion, low density of defects and large patterned surface. Be- cause all of these characteristics are never present in a sin
{"title":"Alternative Masks for Nanolithography","authors":"D. Ingert","doi":"10.2174/1874067700701010010","DOIUrl":"https://doi.org/10.2174/1874067700701010010","url":null,"abstract":"The use of masks coming from research field as different as colloids, polymers or nanomaterials is a recently emerging field. Recent advances in this area have developed a variety of practical routes which have a great potential to overcome or at least complete the high-cost lithographic techniques. This review focuses on three techniques that try to reduce to the nanometer range, the size of the mask. The major difference between these procedures is related to the type of mask used. The first technique is called colloidal lithography, the mask is a monodispersed-beads template. The second is the block copolymer lithography and the third technique is the nanocrystal lithography, the mask used is a nano-object. For these three parts, the synthetic routes, the improvements and the applications as well as the limitations will be pre- sented. I. INTRODUCTION Nanotechnology research is led by the demand for ever smaller device features that are required to improve perform- ance and decrease costs in microelectronics, communication and data storage. Lithographic methods are in the centre of this nanotechnology. Rapid replication of features below 50nm is currently a significantly unsolved problem. Generat- ing patterned surfaces at the nanoscale is beyond the limits of standard photolithography techniques. The wavelengths of photons limit the minimum feature sizes in the sub-100nm scale. Thus it appears that whatever technologies are used for fabrication in this region it does not represent simple engi- neering extensions of conventional photolithography. There exists an opportunity to introduce news ideas in replication of meso and nanostructures. Indeed, very few methods pro- vide the ability to work in the sub-50-nm scale (1-3). The well-established methods for the fabrication of nanometer- scale structures (2), such as scanning probe, electron and ion beam lithography provide resolution and integration density required for the industrials demands but the level of throughput rate is far below the requirement. There is a need for alternative simple techniques in order to save processing time and costs (4,5). This need has given rise to different kinds of approaches like, for example, nanoimprint lithogra- phy and soft lithography with the use of self-assembly monolayers (SAMs) (3,6,7). However, for both the mold fabrication problems remain unsolved. In this review we will focus on three techniques that try to reduce to the nanometer range, the size of the mask keep- ing a large surface coverage. The major difference between these procedures is related to the type of mask used while the standard techniques to pattern the substrate like metal depo- sition or ion-plasma etching are kept similar. The main re- quirements present in an efficient method for replication are flexibility in the engraved substrate, fidelity in the replica- tion, low density of defects and large patterned surface. Be- cause all of these characteristics are never present in a sin","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124405000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-07-26DOI: 10.2174/1874067700701010005
D. Parker, C. Salzemann, I. Lisiecki
Recently, it has been shown that nanoparticles with a narrow size distribution can self-organize into highly or- dered fcc supra-crystals. This new generation of materials have been found to exhibit unique collective properties, which arise from the periodic ordering of the nanoparticles. Using the expertise we have to control the ordering of cobalt nanoparticles in 3D assemblies, we have been able to carry out a carefully controlled comparative investigation of the magnetic properties of a supracrystal and a disordered assembly. In this letter, we report for the first time a new intrinsic effect of supra-crystal order on the magnetic behavior which we attribute to a decrease in the distribution of energy barri- ers, arising from nanoparticle ordering. We also show that these assemblies can be annealed at 350°C to give a structural transition of the Co nanoparticles from an fcc to hcp phase. This annealing does not induce either coalescence or oxidation of the nanocrystals.
{"title":"A New Intrinsic Magnetic Property Due to the Mesoscopic Ordering of Cobalt Nanocrystals in Supra-Crystals","authors":"D. Parker, C. Salzemann, I. Lisiecki","doi":"10.2174/1874067700701010005","DOIUrl":"https://doi.org/10.2174/1874067700701010005","url":null,"abstract":"Recently, it has been shown that nanoparticles with a narrow size distribution can self-organize into highly or- dered fcc supra-crystals. This new generation of materials have been found to exhibit unique collective properties, which arise from the periodic ordering of the nanoparticles. Using the expertise we have to control the ordering of cobalt nanoparticles in 3D assemblies, we have been able to carry out a carefully controlled comparative investigation of the magnetic properties of a supracrystal and a disordered assembly. In this letter, we report for the first time a new intrinsic effect of supra-crystal order on the magnetic behavior which we attribute to a decrease in the distribution of energy barri- ers, arising from nanoparticle ordering. We also show that these assemblies can be annealed at 350°C to give a structural transition of the Co nanoparticles from an fcc to hcp phase. This annealing does not induce either coalescence or oxidation of the nanocrystals.","PeriodicalId":250297,"journal":{"name":"The Open Physical Chemistry Journal","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134202679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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