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1.
Sci Rep ; 10(1): 782, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31964925

RESUMO

Enhanced oil recovery (EOR) plays a significant role in improving oil production. Tertiary EOR, including surfactant flooding, can potentially mobilize residual oil after water flooding. Prior to the field deployment, the surfactant performance must be evaluated using site-specific crude oil at reservoir conditions. Core flood experiments are common practice to evaluate surfactants for oil displacement efficiency using core samples. Core flood experiments, however, are expensive and time-consuming and do not allow for pore scale observations of fluid-fluid interactions. This work introduces the framework to evaluate the performance of EOR surfactants via a Reservoir-on-a-Chip approach, which uses microfluidic devices to mimic the oil reservoir. A unique feature of this study is the use of chemically modified micromodels such that the pore surfaces are representative of carbonate reservoir rock. To represent calcium carbonate reservoir pores, the inner channels of glass microfluidic devices were coated with thin layers of calcium carbonate nanocrystals and the surface was modified to exhibit oil-wet conditions through a crude oil aging process. During surfactant screening, oil and water phases were imaged by fluorescence microscopy to reveal the micro to macro scale mechanisms controlling surfactant-assisted oil recovery. The role of the interfacial tension (IFT) and wettability in the microfluidic device was simulated using a phase-field model and compared to laboratory results. We demonstrated the effect of low IFT at the oil-water interface and wettability alteration on surfactant-enhanced oil displacement efficiency; thus providing a time-efficient and low-cost strategy for quantitative and qualitative assessment. In addition, this framework is an effective method for pre-screening EOR surfactants for use in carbonate reservoirs prior to further core and field scale testing.

2.
ACS Appl Mater Interfaces ; 12(5): 6699-6706, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31922389

RESUMO

The controlled and continuous production of nanoparticles (NPs) with functionalized surfaces remains a technological challenge. We present a multistage synthetic platform, consisting of 3D-printed miniature continuous stirred-tank reactor (CSTR) cascades, for the continuous synthesis and functionalization of SiO2 NPs. The use of the CSTR platform provides ideal and rapid mixing of precursor solutions, precise injection of additional reagents for multistep reactions, and facile operation when using viscous solutions and handling of syntheses with longer reaction times. To exemplify the use of such custom-designed CSTR cascades, amine- and carbohydrate-functionalized SiO2 NPs are chosen as model reaction systems. In particular, the intensified flow reactor units allowed for the reproducible formation of SiO2 NPs with diameters less than 100 nm and narrow size distributions (3-8%). Most importantly, by assembling various 3D-printed CSTR cascades, we synthesized gluconolactone-capped polyethylenimine-modified silica NPs in a fully continuous manner. The inherent control over NP surface charge, reactor scalability, and the significant shortening of processing times (less than 10 min) compared to batch methodologies (several days) strongly indicate the ability of the reactor technology to accelerate continuous nanomanufacturing. In general, it provides a simple route for the reproducible preparation of functionalized NPs, thus expanding the gamut of flow reactors for material synthesis.

3.
Adv Mater ; 31(21): e1900438, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30968473

RESUMO

Orthogonal functionalization of 2D materials by selective assembly at interfaces provides opportunities to create new materials with transformative properties. Challenges remain in realizing controllable, scalable surface-selective, and orthogonal functionalization. Herein, dynamic covalent assembly is reported that directs the functionalization of graphene surfaces at liquid-liquid interfaces. This process allows facile addition and segregation of chemical functionalities to impart Janus characteristics to graphenes. Specifically, dynamic covalent functionalization is accomplished via Meisenheimer complexes produced by reactions of primary amines with pendant dinitroaromatics attached to graphenes. Janus graphenes are demonstrated to be powerful surfactants that organize at water/organic, water/fluorocarbon, and organic/fluorocarbon liquid interfaces. This approach provides general access to the creation of diverse surfactant materials and promising building blocks for 2D materials.

4.
ACS Appl Mater Interfaces ; 9(34): 29380-29386, 2017 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-28792207

RESUMO

We introduce a novel and simple method to fabricate calcium carbonate (CaCO3) micromodels by in situ growing a thin layer of CaCO3 nanocrystals with a thickness of 1-2 µm in microfluidic channels. This approach enables us to fabricate synthetic CaCO3 reservoir micromodels having surfaces fully covered with calcite, while the dimensions and geometries of the micromodels are controllable on the basis of the original microfluidic channels. We have tuned the wettability of the CaCO3-coated microchannels at simulated oil reservoir conditions without introducing any chemical additives to the system; thus the resulting oil-wet surface makes the micromodel more faithfully resemble a natural carbonate reservoir rock. With the advantage of its excellent optical transparency, the micromodel allows us to directly visualize the complex multiphase flows and geochemical fluid-calcite interactions by spectroscopic and microscopic imaging techniques. The CaCO3-coated microfluidic channels provide new capabilities as a micromodel system to mimic real carbonate reservoir properties, which would allow us to perform a water-oil displacement experiment in small-volume samples for the rapid screening of candidate fluids for enhanced oil recovery (EOR). The immiscible fluid displacement process within carbonate micromodels has been demonstrated showing the water-oil-carbonate interactions at pore-scale in real time by fluorescence microscopic imaging.

5.
ACS Appl Mater Interfaces ; 9(15): 13111-13120, 2017 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-28291944

RESUMO

Environmental tracing applications require materials that can be detected in complex fluids composed of multiple phases and contaminants. Moreover, large libraries of tracers are necessary in order to mitigate memory effects and to deploy multiple tracers simultaneously in complex oil fields. Herein, we disclose a novel approach based on the thermal decomposition of polymeric nanoparticles comprised of styrenic and methacrylic monomers. Polymeric nanoparticles derived from these monomers cleanly decompose into their constituent monomers at elevated temperatures, thereby maximizing atom economy wherein the entire nanoparticle mass contributes to the generation of detectable units. A total of ten unique single monomer particles and three dual-monomer particles were synthesized using semicontinuous monomer starved addition polymerization. The pyrolysis gas chromatography-flame ionization detection/mass spectrometry (GC-FID/MS) behavior of these particles was studied using high-pressure mass spectrometry. The programmable nature of our methodology permits simultaneous removal of contaminants and subsequent identification and quantification in a single analytical step.

6.
Adv Mater ; 28(30): 6399-404, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27167214

RESUMO

The concept of a neutral hole-transporting polymer is realized for the first time, by integrating patterned Cl(-) -doped poly(3,4-dimethoxythiophene) thin films into organic solar cells through a vacuum-based polymer vapor printing technique. Due to this novel polymer's neutrality, high transparency, good conductivity, and appropriate energy levels, the solar-cell efficiency and lifetime are significantly enhanced.

7.
ACS Appl Mater Interfaces ; 8(13): 8511-9, 2016 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-26947400

RESUMO

Various electron and hole transport layers have been used to develop high-efficiency perovskite solar cells. To achieve low-temperature solution processing of perovskite solar cells, organic n-type materials are employed to replace the metal oxide electron transport layer (ETL). Although PCBM (phenyl-C61-butyric acid methyl ester) has been widely used for this application, its morphological instability in films (i.e., aggregation) is detrimental. Herein, we demonstrate the synthesis of a new fullerene derivative (isobenzofulvene-C60-epoxide, IBF-Ep) that serves as an electron transporting material for methylammonium mixed lead halide-based perovskite (CH3NH3PbI(3-x)Cl(x)) solar cells, both in the normal and inverted device configurations. We demonstrate that IBF-Ep has superior morphological stability compared to the conventional acceptor, PCBM. IBF-Ep provides higher photovoltaic device performance as compared to PCBM (6.9% vs 2.5% in the normal and 9.0% vs 5.3% in the inverted device configuration). Moreover, IBF-Ep devices show superior tolerance to high humidity (90%) in air. By reaching power conversion efficiencies up to 9.0% for the inverted devices with IBF-Ep as the ETL, we demonstrate the potential of this new material as an alternative to metal oxides for perovskite solar cells processed in air.

8.
Nano Lett ; 14(9): 5148-54, 2014 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-25141259

RESUMO

Advancements in the field of flexible high-efficiency solar cells and other optoelectronic devices will strongly depend on the development of electrode materials with good conductivity and flexibility. To address chemical and mechanical instability of currently used indium tin oxide (ITO), graphene has been suggested as a promising flexible transparent electrode but challenges remain in achieving high efficiency of graphene-based polymer solar cells (PSCs) compared to their ITO-based counterparts. Here we demonstrate graphene anode- and cathode-based flexible PSCs with record-high power conversion efficiencies of 6.1 and 7.1%, respectively. The high efficiencies were achieved via thermal treatment of MoO3 electron blocking layer and direct deposition of ZnO electron transporting layer on graphene. We also demonstrate graphene-based flexible PSCs on polyethylene naphthalate substrates and show the device stability under different bending conditions. Our work paves a way to fully graphene electrode-based flexible solar cells using a simple and reproducible process.

9.
Sci Rep ; 3: 1581, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23545570

RESUMO

The high transparency of graphene, together with its good electrical conductivity and mechanical robustness, enable its use as transparent electrodes in optoelectronic devices such as solar cells. While initial demonstrations of graphene-based organic photovoltaics (OPV) have been promising, realization of scalable technologies remains challenging due to their performance and, critically, poor device reproducibility and yield. In this work, we demonstrate by engineering the interface between graphene and organic layers, device performance and yield become close to devices using indium tin oxide. Our study confirms that the key issue leading to the poor performance or irreproducibility in graphene-based OPV originates from the graphene interface, and can be addressed by a simple interface modification method introduced in this work. We also show similar approach allows graphene to be used as cathode in inverted OPV geometry, thereby demonstrating the universal application of graphene as transparent conductors for both the anode and cathode.


Assuntos
Fontes de Energia Elétrica , Eletrodos , Grafite/química , Compostos Orgânicos/química , Energia Solar , Desenho de Equipamento , Análise de Falha de Equipamento , Teste de Materiais , Propriedades de Superfície
10.
Adv Mater ; 25(20): 2790-6, 2013 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-23440957

RESUMO

Vertical arrays of ZnO nanowires can decouple light absorption from carrier collection in PbS quantum dot solar cells and increase power conversion efficiencies by 35%. The resulting ordered bulk heterojunction devices achieve short-circuit current densities in excess of 20 mA cm(-2) and efficiencies of up to 4.9%.


Assuntos
Fontes de Energia Elétrica , Chumbo/química , Nanotubos/química , Nanotubos/efeitos da radiação , Pontos Quânticos , Compostos de Selênio/química , Energia Solar , Óxido de Zinco/química , Desenho de Equipamento , Análise de Falha de Equipamento , Chumbo/efeitos da radiação , Teste de Materiais , Compostos de Selênio/efeitos da radiação
11.
Nano Lett ; 13(1): 233-9, 2013 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-23205637

RESUMO

Growth of semiconducting nanostructures on graphene would open up opportunities for the development of flexible optoelectronic devices, but challenges remain in preserving the structural and electrical properties of graphene during this process. We demonstrate growth of highly uniform and well-aligned ZnO nanowire arrays on graphene by modifying the graphene surface with conductive polymer interlayers. On the basis of this structure, we then demonstrate graphene cathode-based hybrid solar cells using two different photoactive materials, PbS quantum dots and the conjugated polymer P3HT, with AM 1.5G power conversion efficiencies of 4.2% and 0.5%, respectively, approaching the performance of ITO-based devices with similar architectures. Our method preserves beneficial properties of graphene and demonstrates that it can serve as a viable replacement for ITO in various photovoltaic device configurations.

12.
Small ; 7(24): 3452-7, 2011 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-22052770

RESUMO

Optimization of pore diameter, the placement of nanoparticles, and the transmission of surface-enhanced Raman scattering (SERS) substrates are found to be very critical for achieving high SERS activity in porous alumina-membrane-based substrates. SERS substrates with a pore diameter of 355 nm incorporating silver nanoparticles show very high SERS activity with enhancement factors of 10(10) .


Assuntos
Nanoporos , Prata/química , Análise Espectral Raman , Eletricidade , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Nanoporos/ultraestrutura , Porosidade , Propriedades de Superfície
14.
Langmuir ; 27(6): 3198-205, 2011 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-21294559

RESUMO

We have demonstrated a nanoengineered substrate composed of micropatterned silver nanoparticles to be used for the label-free mapping of adsorbed biomolecules. We utilized surface-enhanced Raman scattering (SERS) phenomenon to monitor the known bioanalytes, protein A and human immunoglobulin G (IgG). The SERS substrate was composed of a poly(alylamine hydrochloride) (PAH)/poly(styrenesulfonate) (PSS) layer-by-layer (LbL) nanocoating micropatterned with silver nanoparticles confined to microscopic stripes. Selective adsorption of biomacromolecules is facilitated by the amine-terminated LbL nanocoating, which prevents the surface adsorption of positively charged protein A across the surface except on the patterned regions containing negatively charged silver nanoparticles. Furthermore, adsorption of IgG on predetermined regions is facilitated by the selective binding of the Fc region of IgG to protein A. This label-free SERS approach provides accurate, selective, and fast detection of protein A and IgG solutions with a nanomolar concentration, down to below 1 nM for IgG in solution. This method could also be utilized for the facile detection of proteins in field conditions as well as in clinical, forensic, industrial, and environmental laboratories.


Assuntos
Imunoglobulina G/química , Proteína Estafilocócica A/química , Nanopartículas Metálicas/química , Tamanho da Partícula , Prata/química , Análise Espectral Raman , Propriedades de Superfície
15.
ACS Appl Mater Interfaces ; 2(11): 3333-9, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21043524

RESUMO

We demonstrate the in situ growth of silver nanoparticles in porous alumina membranes (PAMs) for use as a surface-enhanced Raman scattering (SERS) detection substrate. This fabrication method is simple, cost-effective, and fast, while providing control over the size of silver nanoparticles through the entire length of the cylindrical nanopores with uniform particle density inside the pores unachievable by the traditional infiltration technique. The in situ growth of silver nanoparticles was conducted from electroless-deposited nanoscale seeds on the interior of the PAM and resulted in the formation of numerous hot spots, which facilitated significantly higher SERS enhancement for these substrates compared with previously reported porous substrates.

16.
Anal Chem ; 81(14): 5740-8, 2009 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-19518140

RESUMO

Monitoring trace amounts of peroxide-based molecules is challenging because of the lack of common optical signatures (fluorescence or absorption in UV-vis range) or chemical functionality easily detectable with common routines. To overcome this issue, we suggest a photochemical decomposition approach followed by the analysis of chemical fragments by a fast, sensitive, and reliable Raman spectroscopic method. To facilitate this approach, we employed a novel design of surface-enhanced Raman scattering (SERS)-active nanoporous substrate based on porous alumina membranes decorated with mixed nanoclusters composed of gold nanorods and nanoparticles. The detectable amount of HMTD below 2 pg demonstrated here is about 3 orders of magnitude lower than the current limit of detection. We suggest that laser-induced photocatalytic decomposition onto nanoparticle clusters is critical for achieving label-free detection of unstable and nonresonant organic molecules.


Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/análise , Substâncias Explosivas/análise , Membranas Artificiais , Nanoestruturas/química , Óxido de Alumínio/química , Compostos Bicíclicos Heterocíclicos com Pontes/química , Substâncias Explosivas/química , Radicais Livres/química , Nanopartículas Metálicas/química , Fotólise , Porosidade , Análise Espectral Raman , Coloração e Rotulagem , Propriedades de Superfície
17.
ACS Nano ; 3(1): 181-8, 2009 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-19206265

RESUMO

We report on the design of practical surface enhanced Raman scattering (SERS) substrate based upon 3D alumina membranes with cylindrical nanopores chemically modified with polyelectrolyte coating and loaded with gold nanoparticle clusters. These substrates allow for a molecular-level, label-free detection of common plastic explosive materials (TNT, DNT) down to 5-10 zeptograms or 15-30 molecules and a common liquid explosive (HMTD) down to 1 picogram. Such a sensitive detection of organic molecules by utilizing efficient SERS substrates opens the path for affordable and label-free detection of trace amount of practically important chemical compounds.


Assuntos
Técnicas de Química Analítica/métodos , Análise Espectral Raman/métodos , Óxido de Alumínio/química , Química Orgânica/métodos , Cristalização/instrumentação , Cristalização/métodos , Eletrólitos , Substâncias Explosivas , Ouro/química , Teste de Materiais/instrumentação , Teste de Materiais/métodos , Nanopartículas Metálicas/química , Nanotecnologia/instrumentação , Nanotecnologia/métodos , Tamanho da Partícula , Espalhamento de Radiação , Propriedades de Superfície , Tensoativos
18.
ACS Appl Mater Interfaces ; 1(1): 42-7, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20355751

RESUMO

Pattern transformation in periodic microporous elastoplastic solid coatings is caused by a buckling of the struts and a rotation of the nodes under compressive stresses. The results of a nonlinear numerical investigation confirm the critical role of the bifurcation of the periodic solid under compressive stresses. In striking contrast to the earlier observations of elastic instabilities in porous elastomeric solids, the elastic-plastic nature of the cross-linked periodic microstructure studied here provides the ability to lock in the transformed pattern with complete relaxation of the internal stresses. The study unveils a novel deformation mode in porous periodic solids in the form of organized buckling instability of weak strut elements.

19.
Phys Chem Chem Phys ; 10(28): 4093-105, 2008 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-18612511

RESUMO

We demonstrate that organized, porous, polymer microstructures with continuous open nanoscale pores and a sub-micron spacing obtained via interference lithography can be successfully utilized in a non-traditional field of ordered polymer microcomposites. The examples presented here include porous matrices for the fabrication of binary, glassy-rubbery microcomposites with intriguing mechanical properties with large energy dissipation and lattice-controlled fracturing.


Assuntos
Polímeros/química , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Porosidade , Estresse Mecânico
20.
Nanotechnology ; 19(43): 435302, 2008 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-21832689

RESUMO

A simple, scalable, and cost-effective technique for controlling the growth density of ZnO nanorod arrays based on a layer-by-layer polyelectrolyte polymer film is demonstrated. The ZnO nanorods were synthesized using a low temperature (T = 90 °C), solution-based method. The density-control technique utilizes a polymer thin film pre-coated on the substrate to control the mass transport of the reactant to the substrate. The density-controlled arrays were investigated as potential field emission candidates. The field emission results revealed that an emitter density of 7 nanorods µm(-2) and a tapered nanorod morphology generated a high field enhancement factor of 5884. This novel technique shows promise for applications in flat panel display technology.

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