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An electrochemical sensor using copper oxide nanodots (CuO nanodots–ITO) developed from a block copolymer template is demonstrated for sensitive and selective determination of dopamine (DA). The current signal of CuO nanodots–ITO was linear with the concentration of DA in the range between 0.12 and 56.87 μM (R = 0.9975) with a sensitivity of 326.91 μA mM–1 cm–2 and a detection limit of 0.03 μM. Furthermore, the anti-interference ability of the present sensor to possible interfering substances including ascorbic acid, uric acid, acetaminophen, epinephrine, hydrogen peroxide, phenol, catechol, hydroquinone, and some inorganic compounds has been investigated. Our work highlights the significance of using a bottom-up nanofabrication technique to create a robust and reliable dopamine sensor that has critical importance in neurological disorders.

This is an open access article published under an ACS AuthorChoice License. See Standard ACS AuthorChoice/Editors' Choice Usage Agreement - https://pubs.acs.org/page/policy/authorchoice_termsofuse.html Achieving ultrasmall dimensions of materials and retaining high throughput are critical fabrication considerations for nanotechnology use. This article demonstrates an integrated approach for developing isolated sub-20 nm silicon oxide features through combined "top-down" and "bottom-up" methods: nanoimprint lithography (NIL) and block copolymer (BCP) lithography. Although techniques like those demonstrated here have been developed for nanolithographic application in the microelectronics processing industry, similar approaches could be utilized for sensor, fluidic, and optical-based devices. Thus, this article centers on looking at the possibility of generating isolated silica structures on substrates. NIL was used to create intriguing three-dimensional (3-D) polyhedral oligomeric silsesquioxane (POSS) topographical arrays that guided and confined polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) BCP nanofeatures in isolated regions. A cylinder forming PS-b-PDMS BCP system was successfully etched using a one-step etching process to create line-space arrays with a period of 35 nm in confined POSS arrays. We highlight large-area (>6 μm) coverage of line-space arrays in 3-D topographies that could potentially be utilized, for example, in nanofluidic systems. Aligned features for directed self-assembly application are also demonstrated. The high-density, confined silicon oxide nanofeatures in soft lithographic templates over macroscopic areas illustrate the advantages of integrating distinct lithographic methods for attaining discrete features in the deep nanoscale regime.

Activated carbons (ACs) were prepared from a lignocellulosic-based waste material by a chemical impregnation method using KOH, NaOH or CaCl2 as the activating agent. These ACs were characterized by different techniques such as N2 adsorption, FTIR, XRD and SEM. Electrostatic properties viz. pH and pHpzc of AC suspensions in aqueous media were measured. The concentration of surface oxygenated functional groups of the ACs was estimated following the Boehm titration method. Cyclic voltammetry was conducted in H2SO4 after fabricating two-electrode capacitor cells of the ACs. The correlation of AC surface chemistry and morphology with electrochemical performance (capacitance) of powdered electrodes is analyzed and discussed.

Polyhedral oligomeric silsequioxane (POSS) derivatives have been successfully employed as substrates for graphoepitaxial directed self-assembly (DSA) of block copolymers (BCPs). Tailored POSS materials of tuned surface chemistry are subject to nanoimprint lithography (NIL) resulting in topographically patterned substrates with dimensions commensurate with the BCP block length. A cylinder forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) BCP is synthesized by sequential living anionic polymerization of styrene and hexamethylcyclotrisiloxane. The patterned POSS materials provide a surface chemistry and topography for DSA of this BCP and after solvent annealing the BCP shows well-ordered microphase segregation. The orientation of the PDMS cylinders to the substrate plane could be controlled within the trench walls by the choice of the POSS materials. The BCP patterns are successfully used as on-chip etch mask to transfer the pattern to underlying silicon substrate. This soft graphoepitaxy method shows highly promising results as a means to generate lithographic quality patterns by nonconventional methods and could be applied to both hard and soft substrates. The methodology might have application in several fields including device and interconnect fabrication, nanoimprint lithography stamp production, nanofluidic devices, lab-on-chip, or in other technologies requiring simple nanodimensional patterns.

The integration of block copolymer (BCP) self-assembled nanopattern formation as an alternative lithographic tool for nanoelectronic device fabrication faces a number of challenges such as defect densities, feature size, pattern transfer, etc. Key barriers are the nanopattern process times and pattern formation on current substrate stack layers such as hard masks (e.g., silicon nitride, Si3N4). We report a rapid microwave assisted solvothermal (in toluene environments) self-assembly and directed self-assembly of a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) BCP thin films on planar and topographically patterned Si3N4 substrates. Hexagonally arranged, cylindrical structures were obtained and good pattern ordering was achieved. Factors affecting BCP self-assembly, notably anneal time and temperature, were studied and seen to have significant effects. Graphoepitaxy within the topographical structures provided long range, translational alignment of the patterns. The effect of surface topography feature size and spacing was investigated. The solvothermal microwave based technique used to provide periodic order in the BCP patterns showed significant promise and ordering was achieved in much shorter periods than more conventional thermal and solvent annealing methods. The implications of the work in terms of manufacturing technologies are discussed.

The self-assembly of a lamellar-forming polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) diblock copolymer (DBCP) was studied herein for surface nanopatterning. The DBCP was synthesized by sequential living anionic polymerization of styrene and hexamethylcyclotrisiloxane (D3). The number average molecular weight (Mn), polydispersity index (Mw/Mn) and PS volume fraction (φps) of the DBCP were MnPS = 23.0 kg mol−1, MnPDMS = 15.0 kg mol−1, Mw/Mn = 1.06 and φps = 0.6. Thin films of the DBCP were cast and solvent annealed on topographically patterned polyhedral oligomeric silsesquioxane (POSS) substrates. The lamellae repeat distance or pitch (λL) and the width of the PDMS features (dL) are ~35 nm and ~17 nm, respectively, as determined by SEM. The chemistry of the POSS substrates was tuned, and the effects on the self-assembly of the DBCP noted. The PDMS nanopatterns were used as etching mask in order to transfer the DBCP pattern to underlying silicon substrate by a complex plasma etch process yielding sub-15 nm silicon features.

Cylinder-forming polystyrene- block -polydimethylsiloxane (PS- b -PDMS, 27.2k- b -11.7k, SD39) block copolymer having a total molecular weight of 39 kg mol −1 was exploited to achieve in-plane morphologies of lines, dots and antidots. Brush-free self-assembly of the SD39 on silicon substrates was investigated using solvents that were PS or PDMS selective, neutral and non-solvents based on their Hansen solubility parameters. The different morphologies were achieved with annealing times ranging from 10 min to 1 h at room temperature. The SD39 patterns were used as an etch mask for transferring the pattern into the underlying substrate. Directed self-assembly and hierarchical directed self-assembly on block copolymer templates for confinement of dots was successfully demonstrated. The strategy for achieving multiple morphologies using one BCP by mere choice of the annealing solvents on unmodified substrates provides a simplified method for surface nanopatterning, templated growth of nanomaterials and nanofabrication.

Block copolymer (BCP) lithography makes use of the microphase separation properties of BCPs to pattern ordered nanoscale features over large areas. This work presents the microphase separation of an asymmetric polystyrene-block-poly(ferrocenyl dimethylsilane) (PS-b-PFS) BCP that allows ordered arrays of nanostructures to be formed by spin casting PS-b-PFS on substrates and subsequent solvent annealing. The effects of the solvent annealing conditions on self-assembly and structural stability are discussed.

'Directing' block copolymer (BCP) patterns is a possible option for future semiconductor device patterning, but pattern transfer of BCP masks is somewhat hindered by the inherently low etch contrast between blocks. Here, we demonstrate a 'fab' friendly methodology for forming well-registered and aligned silicon (Si) nanofins following pattern transfer of robust metal oxide nanowire masks through the directed self-assembly (DSA) of BCPs. A cylindrical forming poly(styrene)-block-poly(4-vinyl-pyridine) (PS-b-P4VP) BCP was employed producing 'fingerprint' line patterns over macroscopic areas following solvent vapor annealing treatment. The directed assembly of PS-b-P4VP line patterns was enabled by electron-beam lithographically defined hydrogen silsequioxane (HSQ) gratings. We developed metal oxide nanowire features using PS-b-P4VP structures which facilitated high quality pattern transfer to the underlying Si substrate. This work highlights the precision at which long range ordered [similar]10 nm Si nanofin features with 32 nm pitch can be defined using a cylindrical BCP system for nanolithography application. The results show promise for future nanocircuitry fabrication to access sub-16 nm critical dimensions using cylindrical systems as surface interfaces are easier to tailor than lamellar systems. Additionally, the work helps to demonstrate the extension of these methods to a 'high [small chi]' BCP beyond the size limitations of the more well-studied PS-b-poly(methyl methylacrylate) (PS-b-PMMA) system.

A new enzyme-free sensor based on iron oxide (Fe3O4) nanodots fabricated on an indium tin oxide (ITO) substrate via a block copolymer template was developed for highly sensitive and selective detection of hydrogen peroxide (H2O2). The self-assembly-based process described here for Fe3O4 formation is a simple, cost-effective, and reproducible process. The H2O2 response of the fabricated electrodes was linear from 2.5 × 10–3 to 6.5 mM with a sensitivity of 191.6 μA mM–1cm–2 and a detection limit of 1.1 × 10–3 mM. The electrocatalytic activity of Fe3O4 nanodots toward the electroreduction of H2O2 was described by cyclic voltammetric and amperometric techniques. The sensor described here has a strong anti-interference ability to a variety of common biological and inorganic substances.

Block copolymers (BCP) are highly promising self-assembling precursors for scalable nanolithography. Very regular BCP nanopatterns can be used as on-chip etch masks. The first step in the processing of BCP thin films is usually the chemical modification of the substrate surface, typically by grafting of a brush layer that renders the surface energy neutral relative to the constituent blocks. We provide here a first study on rapid, low temperature self-assembly of PS- b -PDMS (polystyrene- block -polydimethylsiloxane) on silicon substrates without a brush layer. We show that it forms line and antidot patterns after short solvo-thermal annealing. Unlike previous reports on this system, low temperature and short annealing time provide self-assembly in homogeneous thin films covering large substrate areas. This on-chip mask was then used for pattern transfer to the underlying silicon substrate. SEM (scanning electron microscope) images reveal silicon nanowires relative to the PDMS patterns of the BCP mask.

The need for materials for high energy storage has led to very significant research in supercapacitor systems. These can exhibit electrical double layer phenomena and capacitances up to hundreds of F/g. Here, we demonstrate a new supercapacitor fabrication methodology based around the microphase separation of PS-b-PMMA which has been used to prepare copper nanoelectrodes of dimension -13 nm. These structures provide excellent capacitive performance with a maximum specific capacitance of -836 F/g for a current density of 8.06 A/g at a discharge current as high as 75 mA. The excellent performance is due to a high surface area: volume ratio. We suggest that this highly novel, easily fabricated structure might have a number of important applications.

Germanium nanowires (GeNWs) have importance in emerging device applications because of their high hole mobility. Reported here is the fabrication of GeNWs on a SiO 2 insulator substrate from a phase separated lamellar PS-b-PMMA block copolymer (BCP) by a simple and reproducible method. The parent BCP film was selectively etched to remove PMMA block generating PS template which was then used to fabricate GeNWs using a thermal evaporation technique. XRD, Raman and TEM cross-section analysis reveal the formation of GeNWs on SiO2 substrates. Thermal treatment of the GeNWs was used to probe thermal stability and crystallisation properties. It was observed that thermal treatment of GeNWs resulted in red-shifts in the Raman spectra. The results demonstrate an exciting nanofabrication technique for creating high density nanowires for the nanoelectronic industry.

We report here the graphoepitaxial alignment of a lamellar forming PS-b-PMMA block copolymer (BCP) for directed self-assembly using topographical patterns (simple line structures) of hydrogen silsesquioxane (HSQ). The system demonstrates the importance of the sidewall chemistry on translational alignment of BCP domains. A method was developed where a silicon substrate was precoated with a hydroxyl-terminated random copolymer brush of PS-r-PMMA prior to the HSQ feature formation process. The brush ordains the vertical (to the substrate plane) alignment of the BCP lamellar microdomains. Translational BCP alignment is a result of PMMA selectively wetting the HSQ. The formed BCP pattern was selectively etched to remove the PMMA domain allowing direct imaging and to demonstrate capability in forming an on-chip mask.

Block copolymer (BCP) microphase separation at surfaces might enable the generation of substrate features in a scalable, manufacturable, bottom-up fashion provided that pattern structure, orientation, alignment can be strictly controlled. A further requirement is that self-assembly takes place within periods of the order of minutes so that continuous manufacturingprocesses do not require lengthy pretreatments and sample storageleading to contamination and large facility costs. We report here microwave-assisted solvothermal (in toluene environments) self-assembly and directed self-assembly of a very low molecular weight cylinder-forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) BCP on planar and patterned silicon nitride (Si3N4) substrates. Good pattern ordering was achieved in the order of minutes. Factors affecting BCP self-assembly, notably anneal time and temperature were studied and seen to have significant effects. Graphoepitaxy to direct self-assembly in the BCP yielded promising results producing BCP patterns with long-range translational alignment commensurate with the pitch period of the topographic patterns. This rapid BCP ordering method is consistent with the standard thermal/solvent anneal processes.

This paper describes the fabrication of nanodimensioned silicon structures on silicon wafers from thin films of a poly(styrene)-block-poly(dimethylsiloxane) (PS-b-PDMS) block copolymer (BCP) precursor self-assembling into cylindrical morphology in the bulk. The structure alignment of the PS-b-PDMS (33 k–17 k) was conditioned by applying solvent and solvothermal annealing techniques. BCP nanopatterns formed after the annealing process have been confirmed by scanning electron microscope (SEM) after removal of upper PDMS wetting layer by plasma etching. Silicon nanostructures were obtained by subsequent plasma etching to the underlying substrate by an anisotropic dry etching process. SEM images reveal the formation of silicon nanostructures, notably of sub-15 nm dimensions.

Poly(styrene)-block-poly(dimethylsiloxane) (PS-b-PDMS) is an excellent block copolymer (BCP) system for self-assembly and inorganic template fabrication because of its high Flory–Huggins parameter (χ ~ 0.26) at room temperature in comparison to other BCPs, and high selective etch contrast between PS and PDMS block for nanopatterning. In this work, self-assembly in PS-b-PDMS BCP is achieved by combining hydroxyl-terminated poly(dimethylsiloxane) (PDMS-OH) brush surfaces with solvent vapor annealing. As an alternative to standard brush chemistry, we report a simple method based on the use of surfaces functionalized with silane-based self-assembled monolayers (SAMs). A solution-based approach to SAM formation was adopted in this investigation. The influence of the SAM-modified surfaces upon BCP films was compared with polymer brush-based surfaces. The cylinder forming PS-b-PDMS BCP and PDMS-OH polymer brush were synthesized by sequential living anionic polymerization. It was observed that silane SAMs provided the appropriate surface chemistry which, when combined with solvent annealing, led to microphase segregation in the BCP. It was also demonstrated that orientation of the PDMS cylinders may be controlled by judicious choice of the appropriate silane. The PDMS patterns were successfully used as an on-chip etch mask to transfer the BCP pattern to underlying silicon substrate with sub-25 nm silicon nanoscale features. This alternative SAM/BCP approach to nanopattern formation shows promising results, pertinent in the field of nanotechnology, and with much potential for application, such as in the fabrication of nanoimprint lithography stamps, nanofluidic devices or in narrow and multilevel interconnected lines.

The present invention relates to an etching mask comprising silicon containing block copolymers produced by self-assembly techniques onto silicon or graphene substrate. Through the use of the etching mask, nanostructures having long linear features having sub-10 nm width can be produced.

Block copolymer (BCP) microphase separation at substrate surfaces might enable the generation of substrate features in a scalable, bottom-up fashion, provided that the pattern structure, orientation, and alignment can be strictly controlled. The PS-b-PDMS (polystyrene-b-polydimethylsiloxane) system is attractive because it can form small features and the two blocks can be readily differentiated during pattern transfer. However, PS-b-PDMS offers a considerable challenge, because of the chemical differences in the blocks, which leads to poor surface wetting, poor pattern orientation control, and structural instabilities. These challenges are considerably greater when line patterns must be created, and this is the focus of the current work. Here, we report controlled pattern formation in cylinder-forming PS-b-PDMS by anchoring different types of hydroxyl-terminated homopolymer and random copolymer brushes on planar and topographically patterned silicon substrates for the fabrication of nanoscale templates. It is demonstrated that non-PDMS-OH-containing brushes may be used, which offers an advantage for substrate feature formation. To demonstrate the three-dimensional (3-D) film structure and show the potential of this system toward applications such as structure generation, the PDMS patterns were transferred to the underlying substrate to fabricate nanoscale features with a feature size of ~14 nm.

Block copolymer lithography based on block copolymer (BCP) self-assembly can be used to develop soft mask nanoscale templates for subsequent pattern transfer to generate substrate features. Self-assembly of lamellar polystyrene- b -polymethylmethacrylate BCP of varying molecular weights to generate silicon nanoscale features is reported here. It has also been demonstrated that the feature size can be controlled by a plasma over-etch process and discussed.

a Catalan Institute of Nanotechnology, Campus de la UAB, Edifici CM3, 08193 Bellaterra, Spain; b Tyndall National Institute, Lee Maltings, Prospect Row, Cork, Ireland; c Department of Chemistry, University College Cork, Cork, Ireland; d Profactor GmbH, Functional Surfaces and Nanostructures, 4407 Steyr-Gleink, Austria; e Laboratoire des Technologies de la Microelectronique (CNRS), 38054 Grenoble, France; f Intel Ireland Limited, Collinstown Industrial Estate, Leixlip, Co. Kildare, Ireland; g Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland; h Catalan Institute of Research and Advanced Studies (ICREA), 08010 Barcelona, Spain, i Physics Department, Universitat Autonoma de Barcelona, Campus de la UAB, 08193 Bellaterra, Spain clivia.sotomayor@icn.cat

The thermodynamics of self-assembling systems are discussed in terms of the chemical interactions and the intermolecular forces between species. It is clear that there are both theoretical and practical limitations on the dimensions and the structural regularity of these systems. These considerations are made with reference to the microphase separation that occurs in block copolymer (BCP) systems. BCP systems self-assemble via a thermodynamic driven process where chemical dis-affinity between the blocks driving them part is balanced by a restorative force deriving from the chemical bond between the blocks. These systems are attracting much interest because of their possible role in nanoelectronic fabrication. This form of self-assembly can obtain highly regular nanopatterns in certain circumstances where the orientation and alignment of chemically distinct blocks can be guided through molecular interactions between the polymer and the surrounding interfaces. However, for this to be possible, great care must be taken to properly engineer the interactions between the surfaces and the polymer blocks. The optimum methods of structure directing are chemical pre-patterning (defining regions on the substrate of different chemistry) and graphoepitaxy (topographical alignment) but both centre on generating alignment through favourable chemical interactions. As in all self-assembling systems, the problems of defect formation must be considered and the origin of defects in these systems is explored. It is argued that in these nanostructures equilibrium defects are relatively few and largely originate from kinetic effects arising during film growth. Many defects also arise from the confinement of the systems when they are ‘directed’ by topography. The potential applications of these materials in electronics are discussed.

A commercial grade carbon black was chemically modified using mineral acids (either with HNO3 or H2SO4 or mixture) and the sorption performance of the virgin and modified forms were investigated. Chemical modification resulted in the creation of surface acidic functional groups (COOH, SO2OH) and was verified by FTIR spectra. This was further verified by TGA analysis revealing higher weight loss characteristics of the modified carbons in comparison to virgin carbon black. Morphological changes were observed from BET surface area measurements and SEM analysis. XRD study revealed the change of graphitic crystallite size as a result of modification. The suspension pH of the materials in deionized water and the point of zero charge (pHpzc) in inert electrolyte were determined. The measured values of suspension pH and pHpzc for all the carbons were found to be acidic with more acidic character in the modified carbons. These materials were used as sorbents for the removal of arsenic from aqueous medium and showed excellent adsorption performance.

Block copolymer (BCP) self-assembly is a low-cost means to nanopattern surfaces. Here, we use these nanopatterns to directly print arrays of nanodots onto a conducting substrate (Indium Tin Oxide (ITO) coated glass) for application as an electrochemical sensor for ethanol (EtOH) and hydrogen peroxide (H2O2) detection. The work demonstrates that BCP systems can be used as a highly efficient, flexible methodology for creating functional surfaces of materials. Highly dense iron oxide nanodots arrays that mimicked the original BCP pattern were prepared by an ‘insitu’ BCP inclusion methodology using poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO). The electrochemical behaviour of these densely packed arrays of iron oxide nanodots fabricated by two different molecular weight PS-b-PEO systems was studied. The dual detection of EtOH and H2O2 was clearly observed. The as-prepared nanodots have good long term thermal and chemical stability at the substrate and demonstrate promising electrocatalytic performance.

High-mobility materials and non-traditional device architectures are of key interest in the semiconductor industry because of the need to achieve higher computing speed and low power consumption. In this article, we present an integrated approach using directed self-assembly (DSA) of block copolymers (BCPs) to form aligned line-space features through graphoepitaxy on germanium on insulator (GeOI) substrates. Ge is an example of a high mobility material (III–V, II–VI) where the chemical activity of the surface and its composition sensitivity to etch processing offers considerable challenges in fabrication compared to silicon (Si). We believe the methods described here afford an opportunity to develop ultrasmall dimension patterns from these important high-mobility materials. High-quality metal oxide enhanced pattern transfer to Ge is demonstrated for the realization of nanofins with sub-10 nm feature size. Graphoepitaxial alignment of a poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) BCP was achieved using predefined hydrogen silsesquioxane (HSQ) topography at a GeOI substrate. Subsequent impregnation of the aligned BCP templates with a salt precursor in situ and simple processing was used to generate robust metal oxide nanowire (e.g., Fe3O4, γ-Al2O3, and HfO2) hardmask arrays. Optimized plasma based dry etching of the oxide modified substrate allowed the formation of high aspect ratio Ge nanofin features within the HSQ topographical structure. We believe the methodology developed has significant potential for high-resolution device patterning of high mobility semiconductors. We envision that the aligned Ge nanofin arrays prepared here via graphoepitaxy might have application as a replacement channel material for complementary metal–oxide–semiconductor (CMOS) devices and integrated circuit (IC) technology. Furthermore, the low capital required to produce Ge nanostructures with DSA technology may be an attractive route to address technological and economic challenges facing the nanoelectronic and semiconductor industry.

The physicochemical factors such as equilibrium time, solution pH, initial concentration of Cd(II), particle size and temperature that control the adsorption of Cd(II) from aqueous solutions onto pyrite has been investigated through batch experiments. Prior to this study, pyrite was characterized through chemical and XRD-analysis. The point of zero charge, pH pzc was determined using the batch equilibrium technique and was found to be 6.4. The equilibrium time was 30 min at the solution pH of 6.0. The pH influence of Cd(II) adsorption was remarkable and maximum metal uptake was observed at 6.0 which is closer to pH pzc . Under this weakly acidic condition Cd(II) ions are responsible for adsorption. Concentration dependence of metal uptake indicates that saturation of pyrite surface by adsorbate occurs at an initial Cd(II) concentration of 350 mg/L and the corresponding metal uptake was 576.5 mg/L of −150 mesh size pyrite at pH 6.0 and 30 °C. Particle size affects the adsorption capacity to a great extent and a decrease in particle diameter enhances metal uptake. The effect of temperature on adsorption performance reveals that the effective temperature for Cd(II) adsorption is 30 °C. The empirical Freundlich isotherm was applied to represent the adsorption process, which fits the experimental data quite well. The work reveals that natural pyrite is a very good choice as an adsorbent for the removal of toxic metals from industrial wastewater and bears significant industrial implications.

The desulfurization reaction involving direct electron transfer from potassium ferrocyanide, K4[Fe(CN)6], successfully removed organic sulfur from a subbituminous coal. The temperature variation of desulfurization revealed that increase of temperature enhanced the level of sulfur removal. Moreover, the desulfurization reaction was found to be dependent on the concentration of K4[Fe(CN)6]. Gradual increase in the concentration of K4[Fe(CN)6] raised the magnitude of desulfurization, but at higher concentration the variation was not significant. The removal of organic sulfur from unoxidized coal slightly increased with reduced particle size. Desulfurization from oxidized coals (prepared by aerial oxidation) revealed a higher level of sulfur removal in comparison to unoxidized coal. Highest desulfurization of 36.4 wt % was obtained at 90 °C and 0.1 M concentration of K4[Fe(CN)6] in the 100-mesh size oxidized coal prepared at 200 °C. Model sulfur compound study revealed that aliphatic types of sulfur compounds...

This communication reports a novel process of the formation of elemental sulphur (S 0 ) that involves a specific electron transfer process (ETP) from a model organic sulphur compound thiourea. Solubility of CuCl in different systems were studied at 30 °C. Treatment of Cu + as CuCl with naphthalene, an electron transfer agent taken in a protic solvent ethanol produces ion-radical i.e., naphthalenide anion. Formation of this ion-radical was proved by the solubility of copper in the absence and presence of naphthalene as well as by the absorption study at 30 °C. Increased solubility of copper in a system containing CuCl, naphthalene and thiourea in ethanol further proved the generation of ion-radical. Production of (S 0 ) in the temperature range of 30–40 °C suggested the cleavage of C S bond present in the organic sulphur compound. The effect of reaction time revealed that the formation of S 0 was not continuous. Temperature had a profound influence on the formation of S 0 as substantial increase in the formation of S 0 was observed for every 5 °C rise in temperature. The method succeeded in removing 66.4 mol% sulphur from thiourea as S 0 at 6 h and 40 °C. Discontinuity in the formation of S 0 inferred trapping of minor amount of it by the dissolved S 2− ion leading to the formation of probably S 2 2− , the formation of which proceeded at a slow rate. Pseudo-first-order kinetic model was used to unfold the rates of formation of S 0 . In the temperature range of 30–40 °C, intrinsic rate constant of S 0 generation was found in the range of (8.3–40.6) × 10 −6 s −1 . The S 0 formation process possessed an activation energy of 114.9 kJ mol −1 and a preexponential factor of 5.8 × 10 14 s −1 . The way by which S 0 was formed has a considerable relevance in the desulphurization of organic sulphur compound and the recovery of S 0 from fossil fuels.

Thermogravimetric investigation has been undertaken to evaluate the kinetic and thermodynamic parameters and the influence of pyrite concentration on coal pyrolysis in inert atmosphere. Weight loss up to 150 °C are 4.3 wt.%, 5.5 wt.% and 7.0 wt.% in 1%, 5% and 10% pyrite blended coals, respectively, and in the raw coal (8.2 wt.%) suggests that the presence of pyrite can influence loss of moisture and volatile matter characteristics. The essential weight loss is restricted in the temperature range of 220–650 °C for all the samples. DTA shows two peaks in that region; the first one is related with the primary carbonisation of coal and the second, which appears at a relatively higher temperature, is attributed to the decomposition of pyrite, both shifting to higher temperature with increasing pyrite concentration. Further presence of pyrite in substantial amount decreases the reactivity of coal for pyrolysis; however, its negligible amount has no significant impact on carbonisation. Kinetic study reveals that, with increase in temperature, the rate constants continuously increase; however, the trend is irregular for activation energy (range: 20.42–36.17 kJ mol−1 from Arrhenius equation and 28.72–38.29 kJ mol−1 from Coats and Redfern equation) and frequency factor (range: 1.35–2.11×10−4 s−1) for all the samples. It has been inferred that decomposed products of pyrite rather than pyrite itself were the real catalyst for enhancing coal pyrolysis; non-stoichiometric pyrrhotite accelerates carbonisation and/or elemental sulphur stabilises free radicals through cross linking. The pyrolytic reaction in all the systems proceeds with the absorption of heat, decrease in randomness and non-spontaneous in nature. It is suggested that the carbonisation process is a diffusion controlled reaction rather than thermodynamically controlled.

A chemical oxidative desulphurisation method for coal organic sulphur has been presented using peroxyacetic acid produced in situ as an oxidant. Sulphur is removed to the extent 6.92–10.02 wt.% at 1–4 h while at 24 h, it increases to 13.41 wt.%. To understand the influence of metal ions on desulphurisation, each of six metal ions of variable valence states (Cu+, Ni2+, Co2+, Sn2+, Pd2+ and Sb3+) was externally added. Lowest sulphur loss with Ni2+ ion (2.26–9.46 wt.% at 1–4 h and 11.01 wt.% at 24 h) while highest desulphurisation with Pd2+ ion (23.15–32.32 wt.% at 1–4 h and 32.75 wt.% at 24 h) are observed. Application of the pseudo-first order kinetics shows rate constants for all the systems in the range (0.70–6.78)×10−5 s−1. The activation energy and frequency factor for these systems fall in the range (8.46–12.66) kJ/mol and (1.15–2.64)×10−3 s−1, respectively. Low frequency factor represents an associated type of desulphurisation reaction involving intermediate activated complexes. The sulphur loss reaction is non-spontaneous in nature and proceeds with the absorption of heat. Occurrence of the reaction is due to the increase in randomness which is governed by the decomposition of activated complex to products and is influenced by the characteristic property of a metal ion. Study of model sulphur compounds (methionine and dibenzothiophene) reveals that the desulphurisation reaction under the experimental conditions is primarily due to aliphatic sulphur compounds. The method described here is simple with low-cost and easily available chemical, and therefore, has considerable technological interest.

Dissolution of pyrite involving oxidation by hydrogen peroxide (H 2 O 2 ) in the presence of metal ions (Ni 2+ , Co 2+ and Sn 2+ ) has been investigated. Before oxidation, pure and well crystalline structure of the acid washed pyrite sample, used in the present investigation, was confirmed by X-ray diffraction and chemical analysis. Oxidation of pyrite was examined by the determination of soluble sulfur. The rate of oxidation of pyrite with H 2 O 2 is best represented by determining the rates of total soluble sulfur production. Each experiment was carried out for short (1–4 h) and extended (24 h) time periods. Pyrite is oxidized by H 2 O 2 (1:1) up to the extent of 31.3% at short time period, which however remained the same even at extended time period. Increased amount of soluble sulfur has been observed when pyrite was oxidized by H 2 O 2 (1:1) in the presence of Ni 2+ or Co 2+ or Sn 2+ ion at short time period. The effectiveness of these metal ions in relation to pyrite oxidation at short time period decreases in the order Co 2+ >Sn 2+ >Ni 2+ , while at extended time period the order is Co 2+ >Ni 2+ >Sn 2+ . With Co 2+ ion, the highest pyrite oxidation is obtained both at short (34.0%) and extended (35.0%) time period, while it is the lowest 31.3% with Ni 2+ ion at short time and 25.3% with Sn 2+ ion at extended time period. The effect of chloride ion on the rate of oxidation of pyrite is not pronounced in the metal ion containing systems. Substantial depletion in the concentration of externally added metal ions is in good agreement with the level of oxidation and infers certain adsorption or precipitation of metal ions on pyrite surface. The results of this study throw a new light of the influence of metal ions in the dissolution of pyrite in oxidation systems and has considerable applications in fields of demineralization, desulfurization and environmental science.

A new mathematical approach for the estimation of apparent activation energy is proposed for non-isothermal dynamic process in both weight loss and weight gain conditions and is tested in different organic and inorganic systems. Satisfactory agreement between the new approach and the classical Arrhenius equation is observed. The proposed equations are applicable to a particular change occurring at two specified reaction temperatures at a constant heating rate without recording the intermediate weight changes and the temperatures. The principal advantages of this model are that the knowledge of rate constant and the graphical work are not necessary for the determination of activation energy. Moreover, the order of the reaction course is the one which yields maximum value of activation energy. Direct determination feature further simplifies the new approach and is considered as a pragmatic achievement in academic and technological fields.

This paper reports the results of desulphurization of organic sulphur from a subbituminous Meghalaya coal by the electron transfer process accomplished with the metal ion Co2+. The process was studied both in presence and absence of naphthalene which is used as an electron transfer agent. Temperature dependence on desulphurization unfolded that as the temperature is raised from 25 to 50 °C, there is increase in desulphurization performance. Model organic sulphur compounds study revealed that the desulphurization process is effective with aliphatic type of compounds. Infrared spectroscopic study revealed the release of easily removable sulphur compounds as the band intensities due to −S O and −SO2 groups have declined considerably in their respective regions in the desulphurized coals. The degree of desulphurization is 28.5 wt.% in the presence of naphthalene and 24.6 wt.% in absence of naphthalene, both at 4 h and 50 °C. The sulphur extrusion process is continuous and application of a first-order kinetic model produced specific rate constants of the desulphurization reaction in the two systems, at different temperatures, which falls in the range of (1.3–2.9)×10−5 s−1. The activation energy of the sulphur-loss reaction in the system containing naphthalene (26.8 kJ mol−1) is about 12% lower than that of the system without naphthalene (30.6 kJ mol−1). The frequency factor of the sulphur removal reaction in the systems have been found to be in the range of 0.8–3.2 s−1, suggesting low amount of successful collisions and an associated type of reaction. The desulphurization reaction is nonspontaneous in nature, proceeds with the absorption of heat and there is reduction in the degree of disorderliness in the system as predicted by the transition state theory.

The intent of this paper is to investigate the effects of leaching time and temperature on the level of desulfurization of organic sulfur by an electron-transfer process involving the transition-metal ion Ni2+ from a sub-bituminous Indian coal. The electron-transfer process was accomplished both in the presence and the absence of naphthalene with unoxidized and oxidized samples. Desulfurization has been determined to be greater in oxidized samples. The presence of naphthalene enhanced the amount of desulfurization both in unoxidized and oxidized samples, revealing that it serves as an excellent electron-transfer agent. Increases in reaction time and temperature increased the level of desulfurization. The electron-transfer process, in the presence of naphthalene, succeeded in removing a maximum of 16.3 wt % organic sulfur from unoxidized coal and 18.7 wt % from oxidized coal at 50 °C and 4 h. Study of a model sulfur compound indicated that the desulfurization is primarily due to aliphatic-type compounds, s...

A block copolymer self-assembly holds great promise as a rapid, cheap and scalable approach to nanolithography. We present a straightforward method for fabrication of sub-10 nm line patterns from a lamellar polystyrene-b-polydimethylsiloxane (SD) block copolymer with a total average molecular weight of 10.5 kg mol−1. Thin SD films directly spin cast onto silicon substrates and on graphene, form regular line patterns of sub-10 nm pitch on the substrates after a few minutes of annealing at 45 °C in the presence of toluene vapour. Perfect pattern alignment was achieved by confining the films inside the trenches of graphoepitaxial substrates. The SD template was furthermore used as a lithographic mask to fabricate high-quality sub-10 nm graphene nanoribbons. This was realized by one step oxygen plasma treatment, which accomplishes three tasks: hardening the PDMS block by oxidation, and etching both the PS block and the graphene under PS. Raman analysis supports the formation of graphene nanoribbons with an average distance between defects corresponding to the oxidized PDMS pitch, with no sign of defects generated in the ribbon channel. This suggests a high degree of protection of the nanoribbons by the hard oxidized PDMS mask formed in situ during oxygen plasma etching.

The need for materials for high energy storage has led to very significant research in supercapacitor systems. These can exhibit electrical double layer phenomena and capacitances up to hundreds of F/g. Here, we demonstrate a new supercapacitor fabrication methodology based around the microphase separation of PS-b-PMMA which has been used to prepare copper nanoelectrodes of dimension -13 nm. These structures provide excellent capacitive performance with a maximum specific capacitance of -836 F/g for a current density of 8.06 A/g at a discharge current as high as 75 mA. The excellent performance is due to a high surface area: volume ratio. We suggest that this highly novel, easily fabricated structure might have a number of important applications.

The nanometer range structure produced by thin films of diblock copolymers makes them a great of interest as templates for the microelectronics industry. We investigated the effect of annealing solvents and/or mixture of the solvents in case of symmetric Poly (styrene-block-4vinylpyridine) (PS-b-P4VP) diblock copolymer to get the desired line patterns. In this paper, we used different molecular weights PS-b-P4VP to demonstrate the scalability of such high χ BCP system which requires precise fine-tuning of interfacial energies achieved by surface treatment and that improves the wetting property, ordering, and minimizes defect densities. Bare Silicon Substrates were also modified with polystyrene brush and ethylene glycol self-assembled monolayer in a simple quick reproducible way. Also, a novel and simple in situ hard mask technique was used to generate sub-7nm Iron oxide nanowires with a high aspect ratio on Silicon substrate, which can be used to develop silicon nanowires post pattern transfer.

This paper reports a relatively simple low-temperature non-isothermal oxidative desulphurisation of coal organic sulphur by weakening the CS bond using HgCl 2 solution to an inorganic sulphur-free high-sulphur Indian coal. When oxidised from 50°C to 150°C in air under normal atmospheric pressure, there is continuous decrease of organic sulphur content in the samples of the feed and Hg-treated coals. Desulphurisation is more in the Hg-treated coal (4.97–14.53 wt.%) than in the feed coal (3.72–10.93 wt.%). Kinetic study reveals that the oxidative desulphurisation process follows pseudo-first order kinetics and the rate constants have been found to be in the range (3.09–5.06)×10 −5 s −1 for feed coal and (4.19–6.80)×10 −5 s −1 for Hg-treated coal. The activation energies for the sulphur loss reaction in the oxidative desulphurisation process by using the pseudo-first order kinetic (feed coal: 2.21×10 2 J mol −1 ; Hg-treated coal: 1.53×10 2 J mol −1 ) have been found to be almost similar to those calculated by applying the Coats and Redfern's equation (feed coal: 2.19×10 2 J mol −1 ; Hg-treated coal: 1.53×10 2 J mol −1 ). However, the value is higher (feed coal: 3.50×10 2 J mol −1 ; Hg-treated coal: 2.70×10 2 J mol −1 ) when Horowitz and Metzger's equation is applied. The frequency factors computed by the pseudo-first order kinetics are very low and have been found to be 2.66×10 −5 s −1 for feed coal and 3.96×10 −5 s −1 for Hg-treated coal, suggesting very low rate of successful collisions for the formation of the activated complex. Evaluation of thermodynamic parameters viz., Δ H , Δ U , Δ S and Δ G , reveals that this oxidative desulphurisation process is non-spontaneous in nature and the degree of non-spontaneity of such a process in the feed coal is more relative to that of the Hg-treated coal.

This paper describes a simple oxidative method of desulphurisation of coal organic sulphur carried out by using hydrogen peroxide as an oxidant. Desulphurisation achieved up to the extent of 3.70–6.25 wt% in 1–4 h whereas at 24 h, it increases to 9.24 wt%. When metal ions are externally added to the system containing coal and hydrogen peroxide, desulphurisation is reduced considerably in the presence of Ni 2+ ion while the presence of Cu + , Co 2+ , Sn 2+ , Pd 2+ and Sb 3+ ions enhance the rate of desulphurisation in 1–4 h. At 24 h, except Cu + and Sn 2+ ions, the presence of other metal ions increases the magnitude of desulphurisation. Highest desulphurisation is obtained in a short time period with Pd 2+ ion (28.14 wt%) whereas it is 31.12 wt% in the presence of Sb 3+ ion at 24 h. The desulphurisation reaction follows pseudo-first order kinetics in all the systems and the rate constants fall in the range of (1.02–8.68)×10 −5 s −1 implying a slow, steady process which is supported by the exceptionally low frequency factor. The activation energy for desulphurisation in the systems falls in the range of 8.74–13.67 kJ mol −1 . The positive value of Gibbs free energy of activation represents a non-spontaneous reaction. The reaction proceeds with the absorption of heat (endothermic) as revealed by the positive value of enthalpy of activation. Sufficiently low positive values of entropy of activation and frequency factors attribute an associated reaction and proceed through the initial formation of activated complexes. Model study reveals that the process is effective with aliphatic sulphur compounds. The non-spontaneous nature of the reaction is largely due to the resistance offered by the macro-aromatic sulphur compounds. Pragmatic desulphurisation has been achieved in the process developed here and is therefore of considerable technological interest.

A systematic study has been made on the desulphurisation of organic sulphur in both feed and mercury-treated coal for their unoxidised samples as well as their oxidised samples prepared at 50, 100 and 150°C in air under normal atmospheric pressure. A continuous increase of organic sulphur loss has been observed; the magnitude of which is substantial in mercury-treated samples. Formation of oxidised organic sulphur functionalities (SO and –SO2) are identified by infrared spectroscopy. The band in the region 1080–1020 cm−1 assignable to SO stretch for all oxidised sulphur species (sulphoxide, sulphone, sulphonic acid, sulfenic acid and sulphinic acid) while the band in the region 1350–1320 cm−1 attributable to assymmetric and 1170–1120 cm−1 to symmetric for –SO2 stretch for sulphones, sulphonic acid and sulphinic acid, increase in intensity up to 100°C which decline at 150°C. The absorbance of these bands are qualitatively correlated with those of aliphatic and aromatic C–H content. The aliphatic C–H content follows similar pattern as observed for the absorbance for SO and –SO2 strech; however, the trend is exactly similar with the mercury-treated sample. The difference of absorbance between SO and –SO2 gives an indication of the extent of sulphoxide and sulfenic acid formation. Mercury has a catalytic effect in both accelerating the oxidised species formation and their desulphurisation. This study further reveals that up to 50°C desulphurisation is primarily due to the release of free radicals of sulphur species while SO species along with these radicals predominantly removed beyond 50°C. Knowledge gained from this study would be helpful for various coal conversion processes.

In this paper, experiments have been undertaken to understand the nature of organic sulphur compounds retained after oxidation at 50,100 and 150°C for both feed and Hg-treated coals as well as the extent of desulphurization by the electron transfer process. It has been observed that oxidation of coal in air resulted in the predominant formation of disulphide compounds. Besides these compounds, aliphatic thiol compounds seem to have been leached out by the electron transfer process. Maximum desulphurization achieved by the electron transfer process carried out in absence of naphthalene is 19.17 wt% in feed coal and 17.78 wt% in Hg-treated coal of the total organic sulphur for the samples oxidized at 100°C. The desulphurization reaction has been found to follow pseudo-first-order kinetics and their rate constants have been calculated. The activation energies and frequency factors calculated for these coal samples are found to be in the range 21.28–25.53 kJ mol−1 and 5.01×10 −4 –28.18×10 −4 min −1 , respectively. Kinetic studies reveal that the desulphurization reaction is non-spontaneous in nature which is further supported by the negative value of ΔS and positive value of ΔG. Low frequency factors and negative values of ΔS suggest that desulphurization by electron transfer process is an associated reaction. Although the positive value of ΔH attributes the endothermicity of the desulphurization reaction which requires input of energy for effective desulphurization, but the energy liberated during the formation of ion-radicals is utilized for rupture of bonds in those organic sulphur compounds which contain relatively weak C–S as well as S–S bonds. Total desulphurization (summation of oxidative desulphurization and desulphurization by electron transfer process, in absence of naphthalene) of organic sulphur is found to be 27.38 wt% in feed coal and 28.45 wt% in Hg-treated coals. This suggests that the presence of Hg2+ ion and naphthalene has no significant influence on desulphurization. The results of this work have considerable technological interest.

A novel experiment was carried out for the removal of organic sulphur from high sulphur Indian coal using the electron transfer process. The process involves initial formation of naphthalene radical anion by the interaction of naphthalene, dissolved in ethanol, with a metal ion (Cu+, Co2+, Ni2+, Sn2+ or Sb3+) of variable valence state which subsequently transfers electron to organic sulphur compound. A mechanism is proposed in which cleavage of C–S bonds occur by the metal naphthalenide forming soluble metal–organic sulphur compounds. Maximum amount of leached out sulphur is found to be 9.4% of the total organic sulphur with Sb3+ ion (without naphthalene) revealing that a particular type of organic sulphur was removed by this process. Aliphatic sulphur compound is believed to have leached out from coal and was found to be effective with metal ions having highly negative oxidation potentials. In case of metal ions with low negative oxidation potentials, e.g. Cu+ and Sn2+, although organic sulphur is removed, however, these ions rapidly form insoluble metal sulphides. This work provides a novel breakthrough of desulphurization of organic sulphur from coal.

Microphase separation of block copolymer (BCPs) thin films has high potential as a surface patterning technique. However, the process times (during thermal or solvent anneal) can be inordinately long, and for it to be introduced into manufacturing, there is a need to reduce these times from hours to minutes. We report here BCP self-assembly on two different systems, polystyrene-b-polymethylmethacrylate (PS-b-PMMA) (lamellar- and cylinder-forming) and polystyrene-b-polydimethylsiloxane (PS-b-PDMS) (cylinder-forming) by microwave irradiation to achieve ordering in short times. Unlike previous reports of microwave assisted microphase segregation, the microwave annealing method reported here was undertaken without addition of solvents. Factors such as the anneal time and temperature, BCP film thickness, substrate surface type, etc. were investigated for their effect of the ordering behavior. The microwave technique was found to be compatible with graphoepitaxy, and in the case of the PS-b-PDMS system, long-range translational alignment of the BCP domains was observed within the topographic patterns. To demonstrate the usefulness of the method, the BCP nanopatterns were turned into an 'on-chip' resist by an initial plasma etch and these were used to transfer the pattern into the substrate.

The directed self-assembly (DSA) of block copolymer (BCP) thin films could enable a scalable, bottom-up alternative to photolithography for the generation of substrate features. The PS-b-PDMS (polystyrene-b-polydimethylsiloxane) system is attractive as it can be extended toward very small feature sizes as well as having two blocks that can be readily differentiated during pattern transfer. However, PS-b-PDMS offers a considerable challenge because of the chemical differences in the blocks which lead to poor surface-wetting, poor pattern orientation control, and structural instabilities. These challenges can be mitigated by careful definition of the interface chemistry between the substrate and the BCP. Here, we report controlled pattern formation in cylinder forming PS-b-PDMS system by use of a carefully controlled PDMS brush. Control of the brush was achieved using exposure to UV-O3 for varying time. It is demonstrated that this treatment enhances surface wetting and coverage of the BCP. The modified brushes also enable DSA of the BCP on topographically patterned substrates. UV-O3 exposure was also used to reveal the BCP structure and provide an in situ "hard mask" for pattern transfer to the substrate.

The use of block copolymer (BCP) thin films to generate nanostructured surfaces for device and other applications requires precise control of interfacial energies to achieve the desired domain orientation. Usually, the surface chemistry is engineered through the use of homo- or random copolymer brushes grown or attached to the surface. Herein, we demonstrate a facile, rapid, and tunable approach to surface functionalization using a molecular approach based on ethylene glycol attachment to the surface. The effectiveness of the molecular approach is demonstrated for the microphase separation of PS-b-PMMA and PS-b-PDMS BCPs in thin films and the development of nanoscale features at the substrate.