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1.
Sci Rep ; 12(1): 9672, 2022 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-35690637

RESUMO

A fast response time (0.1 s) magnetic field sensor has been demonstrated utilizing a photonic crystal fiber with nano-size air holes infiltrated with polyethylene glycol based magnetic fluid. The effect of magnetic nanoparticles concentration in the fluid on the magneto-optical sensor performance and its dependence under varying magnetic-field loads was investigated in detail. In particular, the sensor response was analytically modelled with a Langevin function with a good fit (R[Formula: see text]0.996). A threshold sensing point as low as 20 gauss was recorded and a detection range of 0-350 gauss was demonstrated by means of optical transmission measurements. The experimental results were validated by theory using a waveguide light transmission model fed by finite-element method simulations of the principal guided modes in the infiltrated fiber sensor. The simple interrogation scheme, high sensitivity and quick response time makes the proposed hybrid fiber-optic magneto-fluidic probe a promising platform for novel biochemical sensing applications.

2.
ACS Appl Mater Interfaces ; 14(14): 16185-16196, 2022 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-35352950

RESUMO

Sufficient sunlight absorption and exciton generation are critical for developing efficient nonfullerene organic solar cells (OSCs). In this work, polyelectrolyte polystyrenesulfonate (PSS)-coated plasmonic gold nanorods (GNRs@PSS) were incorporated, for the first time, into the inverted nonfullerene OSCs as rear interfacial modifiers to improve sunlight absorption and charge generation via the near-field plasmonic and backscattering effects. The plasmonic GNRs effectively improved the sunlight absorption and enhanced the charge generation. Meanwhile, the negatively charged PSS shell ensured the uniform dispersion of the GNRs on the surface of the photoactive layer, optimized the interfacial contact, and further promoted the hole transport to the electrode. These concerted synergistic effects augmented the efficiency (10.11%) by nearly 20% relative to the control device (8.47%). Remarkably, the ultrathin (∼2.2 nm) organic layer on the surface of GNRs was closely examined by acquiring the carbon contrast image through energy-filtered transmission electron microscopy (EF-TEM), which clearly confirmed the coating uniformity from the side to end-cap of GNRs. The surface plasmon resonance (SPR) effect of the GNRs@PSS on the surface of the photoactive layer was unprecedentedly mapped by photoinduced force microscopy (PiFM) under the illumination of a tunable wavelength supercontinuum laser mimicking sunlight. Furthermore, investigations into the effect of size, surface coverage, and incorporation location of GNRs@PSS on the performance of OSCs revealed that the appropriate design and incorporation of the plasmonic nanostructures are crucial, otherwise the performance can be decreased, as evidenced in the case of front interface integration.

3.
Small Methods ; 6(1): e2100916, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-35041289

RESUMO

It is highly desired to develop advanced characterization techniques to explore the 3D nanoscale morphology of the complicated blend film of ternary organic solar cells (OSCs). Here, ternary OSCs are constructed by incorporating the nonfullerene acceptor perylenediimide (PDI)-diketopyrrolopyrrole (DPP)-PDI and their morphology is characterized in depth to understand the performance variation. In particular, photoinduced force microscopy (PiFM) coupled with infrared laser spectroscopy is conducted to qualitatively study the distribution of donor and acceptors in the blend film by chemical identification and to quantitatively probe the segmentation of domains and the domain size distribution after PDI-DPP-PDI acceptor incorporation by PiFM imaging and data processing. In addition, the energy-filtered transmission electron microscopy with energy loss spectra is utilized to visualize the nanoscale morphology of ultrathin cross-sections in the configuration of the real ternary device for the first time in the field of photovoltaics. These measurements allow to "view" the surface and cross-sectional morphology and provide strong evidence that the PDI-DPP-PDI acceptor can suppress the aggregation of the fullerene molecules and generate the homogenous morphology with a higher-level of the molecularly mixed phase, which can prevent the charge recombination and stabilize the morphology of photoactive layer.

4.
Angew Chem Int Ed Engl ; 60(47): 24833-24837, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34506067

RESUMO

Herein, we elucidate the photodegradation pathway of A-D-A-type non-fullerene acceptors for organic photovoltaics. Using IT-4F as a benchmark example, we isolated the photoproducts and proved them isomers of IT-4F formed by a 6-e electrocyclic reaction between the dicyanomethylene unit and the thiophene ring, followed by a 1,5-sigmatropic hydride shift. This photoisomerization was accelerated under inert conditions, as explained by DFT calculations predicting a triplet-mediated reaction path (quenchable by oxygen). Adding controlled amounts of the photoproduct P1 to PM6:IT-4F bulk heterojunction cells led to a progressive decrease in photocurrent and fill factor attributed to its poor absorption and charge transport properties. The reaction is a general photodegradation pathway for a series of A-D-A molecules with 1,1-dicyanomethylene-3-indanone termini, and its rate varies with the structure of the donor and acceptor moiety.

5.
Membranes (Basel) ; 10(11)2020 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-33202720

RESUMO

A stable and magnetic graphene oxide (GO) foam-polyethyleneimine-iron nanoparticle (GO-PEI-FeNPs) composite has been fabricated for removal of endocrine disruptors-bisphenol A, progesterone and norethisterone-from aqueous solution. The foam with porous and hierarchical structures was synthesized by reduction of graphene oxide layers coupled with co-precipitation of iron under a hydrothermal system using polyethyleneimine as a cross linker. The presence of magnetic iron nanoparticles facilitates the separation process after decontamination. The foam was fully characterized by surface and structural scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The foam exhibits a high adsorption capacity, and the maximum adsorption percentages are 68%, 49% and 80% for bisphenol A, progesterone and norethisterone, respectively. The adsorption process of bisphenol A is explained according to the Langmuir model, whereas the Freundlich model was used for progesterone and norethisterone adsorption.

6.
Sci Rep ; 10(1): 13612, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32788744

RESUMO

The integration of graphene materials into electrochemical biosensing platforms has gained significant interest in recent years. Bulk quantities of graphene can be synthesized by oxidation of graphite to graphite oxide and subsequent exfoliation to graphene oxide (GO). However, the size of the resultant GO sheets changes from the parent graphite yielding a polydispersed solution of sizes ranging from a few nanometers to tens of micrometers. Here, we investigate the direct effect of GO sheets sizes on biosensor performance. We separated different GO sheets sizes, and we characterized them via atomic force, scanning electron, Raman and X-ray photoelectron spectroscopies and solid state nuclear magnetic resonance (NMR). As proof of concept, the sensing performance of these GO samples was probed using a well-known ssDNA aptasensor against microcystin-LR toxin and an immunosensor against ß-lactoglobulin. The resulting aptasensors and immunosensors are fabricated by using covalent attachment and physical adsorption. We found that the aptasensors fabricated using physical adsorption, the binding signal variation was dramatically increased with increasing the GO sheet size. In contrast, for the aptasensor fabricated using covalent immobilization, the binding signal variation decreased with increasing GO sheet size. However, for the ß-lactoglobulin immunosensors, the optimum signals were observed at intermediate GO sheet size. GO sheet size could enhance or inhibit the sensitivity of the graphene-based electrochemical sensors. Our results demonstrate that controlling the size of GO sheets may have a profound impact in specific biosensing applications.

7.
Nanomaterials (Basel) ; 10(7)2020 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-32605210

RESUMO

Headed for developing minimalistic strategies to produce graphene@metal hybrids for electronics on a larger scale, we discovered that graphene oxide (GO)-metal oxide (MO) hybrids are formed spontaneously in water at room temperature in the presence of nothing else than graphene oxide itself and metal ions. Our observations show metal oxide nanoparticles decorating the surface of graphene oxide with particle diameter in the range of 10-40 nm after only 1 h of mixing. Their load ranged from 0.2% to 6.3% depending on the nature of the selected metal. To show the generality of the reactivity of GO with different ions in standard conditions, we prepared common hybrids with GO and tin, iron, zinc, aluminum and magnesium. By means of carbon-13 solid-state nuclear magnetic resonance using magic angle spinning, we have found that graphene oxide is also moderately reduced at the same time. Our method is powerful and unique because it avoids the use of chemicals and heat to promote the coprecipitation and the reduction of GO. This advantage allows synthesizing GO@MO hybrids with higher structural integrity and purity with a tunable level of oxidization, in a faster and greener way.

8.
Sensors (Basel) ; 20(6)2020 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-32192059

RESUMO

An ionization sensor based on suspended carbon nanotubes (CNTs) was presented. A suspended CNT beam was fabricated by a low-temperature surface micromachining process using SU8 photoresist as the sacrificial layer. Application of a bias to the CNT beam generated very high non-linear electric fields near the tips of individual CNTs sufficient to ionize target gas molecules and initiate a breakdown current. The sensing mechanism of the CNT ionization sensor was discussed. The sensor response was tested in air, nitrogen, argon, and helium ambients. Each gas demonstrated a unique breakdown signature. Further, the sensor was tested with gaseous mixtures. The sensor exhibited good long-term stability and had comparable performance to other reported CNT-based ionization sensors in literature, which use high-temperature vapor deposition methods to grow CNTs. The sensor notably allowed for lower ionization voltages due to its reduced ionization gap size.

9.
J Org Chem ; 85(1): 52-61, 2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31380639

RESUMO

The facile synthesis of a series of benzodithiophene (BDT)- and indacenodithiophene (IDT)-based A-D-A oligomers with different end groups is reported, and their properties are studied by optical spectroscopy, electrochemistry, and density functional theory calculations. The permutation of central and terminal units tunes the optoelectronic properties and photovoltaic device characteristics in a predictable way, aiding in the rational design of small molecule semiconducting materials. Among the three rhodanine-derived terminal groups, N-alkylthiazolonethione revealed the strongest electron-withdrawing character, resulting in the lowest band gap, the highest stability, and the best photovoltaic device performance. The crystallographic analysis of two IDT derivatives yielded a highly unusual three-dimensional packing of the conjugated backbone, which is likely responsible for the remarkable photovoltaic performance of such A-D-A semiconductors.

10.
Sensors (Basel) ; 19(3)2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30736455

RESUMO

A humidity sensor using suspended carbon nanotubes (CNTs) was fabricated using a low-temperature surface micromachining process. The CNTs were functionalized with carboxylic acid groups that facilitated the interaction of water vapor with the CNTs. The humidity sensor showed a response time of 12 s and a recovery time of 47 s, along with superior hysteresis and stable performance. The hysteresis curve area of the suspended structure is 3.6, a 3.2-fold reduction in comparison to the non-suspended structure. A comparative study between suspended and non-suspended devices highlights the advantages of using a suspended architecture.

11.
Small ; 15(7): e1804671, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30637957

RESUMO

High efficiency, excellent stability, and air processability are all important factors to consider in endeavoring to push forward the real-world application of organic solar cells. Herein, an air-processed inverted photovoltaic device built upon a low-bandgap, air-stable, phenanthridinone-based ter-polymer (C150 H218 N6 O6 S4 )n (PDPPPTD) and [6,6]-phenyl-C61 -butyric acid methyl ester (PC61 BM) without involving any additive engineering processes yields a high efficiency of 6.34%. The PDPPPTD/PC61 BM devices also exhibit superior thermal stability and photo-stability as well as long-term stability in ambient atmosphere without any device encapsulation, which show less performance decay as compared to most of the reported organic solar cells. In view of their great potential, solvent additive engineering via adding p-anisaldehyde (AA) is attempted, leading to a further improved efficiency of 7.41%, one of the highest efficiencies for all air-processed and stable organic photovoltaic devices. Moreover, the device stability under different ambient conditions is also further improved with the AA additive engineering. Various characterizations are conducted to probe the structural, morphology, and chemical information in order to correlate the structure with photovoltaic performance. This work paves a way for developing a new generation of air-processable organic solar cells for possible commercial application.

12.
J Refract Surg ; 35(1): 40-47, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30633786

RESUMO

PURPOSE: To assess the effectiveness of small incision lenticule extraction (SMILE) as a function of the astigmatism level and type. METHODS: A total of 102 right eyes were included in this study. Refractive astigmatism and corneal astigmatism measured with Scheimpflug technology were retrieved from the preoperative visit and the 3-month follow-up visit. Patients were split into three groups according to the preoperative refractive astigmatism (0.50, 0.75 to 1.25, and 1.50 diopters [D] or greater) and the effectiveness among each group was evaluated according to the with-the-rule (WTR), against-the-rule (ATR), and oblique classifications. The standard Alpins method was used for the analysis. RESULTS: Resultant astigmatism was not associated with its preoperative classification when the total sample was considered, but a significant association emerged between the presence of resultant astigmatism and its preoperative classification in the 1.50 D or greater group. The magnitude of error was significantly lower in the WTR (median: -0.30 D) than in the oblique and ATR astigmatism groups, resulting in a coefficient of adjustment of 1.13 for WTR astigmatism of 1.50 D or greater but not for the other types. CONCLUSIONS: Astigmatism correction with SMILE is predictable for astigmatism lower than 1.50 D without the need to apply a correction. However, higher undercorrection is present in WTR astigmatism of 1.50 D or greater. [J Refract Surg. 2019;35(1):40-47.].


Assuntos
Astigmatismo/cirurgia , Substância Própria/cirurgia , Cirurgia da Córnea a Laser/métodos , Miopia/cirurgia , Adulto , Astigmatismo/fisiopatologia , Córnea/fisiopatologia , Topografia da Córnea , Feminino , Humanos , Masculino , Microcirurgia , Pessoa de Meia-Idade , Miopia/fisiopatologia , Refração Ocular , Estudos Retrospectivos , Resultado do Tratamento , Acuidade Visual , Adulto Jovem
13.
Sensors (Basel) ; 18(5)2018 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-29786661

RESUMO

A room temperature microfabrication technique using SU8, an epoxy-based highly functional photoresist as a sacrificial layer, is developed to obtain suspended aligned carbon nanotube beams. The humidity-sensing characteristics of aligned suspended single-walled carbon nanotube films are studied. A comparative study between suspended and non-suspended architectures is done by recording the resistance change in the nanotubes under humidity. For the tests, the humidity was varied from 15% to 98% RH. A comparative study between suspended and non-suspended devices shows that the response and recovery times of the suspended devices was found to be almost 3 times shorter than the non-suspended devices. The suspended devices also showed minimal hysteresis even after 10 humidity cycles, and also exhibit enhanced sensitivity. Repeatability tests were performed by subjecting the sensors to continuous humidification cycles. All tests reported here have been performed using pristine non-functionalized nanotubes.

14.
ACS Appl Mater Interfaces ; 10(7): 6498-6504, 2018 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-29401370

RESUMO

Performance of bulk heterojunction polymer solar cells (PSCs) highly relies on the morphology of the photoactive layer involving conjugated polymers and fullerene derivatives as donors and acceptors, respectively. Herein, butylamine was found to be able to optimize the morphology of the donor/acceptor (D/A) film composed of a blend of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). Compared to the commonly used alkane dithiols and halogenated additives with high boiling points, butylamine has a much lower boiling point between 77 and 79 °C, and it is also much "greener". A specific interaction between butylamine and PCBM was demonstrated to account for the morphology improvement. Essentially, butylamine can selectively dissolve PCBM in the P3HT:PCBM blend and facilitate the diffusion of PCBM in the film fabrication processes. Atomic force microscopy and X-ray photoelectron spectroscopy investigations confirmed the formation of the P3HT-enriched top surface and the abundance of PCBM at the bottom side, i.e., the formation of vertical phase segregation, as a consequence of the specific PCBM-butylamine interaction. The D/A film with inhomogeneously distributed D and A components in the vertical film direction, with more P3HT at the hole extraction side and more PCBM at the electron extraction side, enables more efficient charge extraction in the D/A film, reflected by the largely enhanced fill factor. The power conversion efficiency of devices reached 4.03 and 4.61%, respectively, depending on the thickness of the D/A film, and these are among the best values reported for P3HT:PCBM-based devices. As compared to the devices fabricated without the introduction of butylamine under otherwise the same processing conditions, they represented 19.6 and 21.6% improvement in the efficiency, respectively. The discovery of butylamine as a new, effective additive in enhancing the performance of PSCs strongly suggests that the differential affinity of additives toward donors and acceptors likely plays a more important role in morphology optimization than their boiling point, different from what was reported previously. The finding provides useful information for realizing large-area PSC fabrication, where a "greener" additive is always preferred.

15.
ACS Appl Mater Interfaces ; 9(31): 26257-26267, 2017 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-28718290

RESUMO

Due to the practical applications of polymer solar cells (PSCs), their stability recently has received increasing attention. Herein, a new strategy was developed to largely enhance the long-term and thermal stability of PSCs in air with a relatively high humidity of 50-60% without any encapsulation. In this strategy, semiconductor PbS/CdS core/shell quantum dots (QDs) were incorporated into the photoactive blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). By replacing the initial ligands of oleic acid with halide ligands on the surface of PbS/CdS QDs via solution-phase ligand exchange, we were able to form unusual, continuous QD networks in the film of P3HT:PCBM, which effectively stabilized the photoactive layer. Air-processed PSCs based on the stabilized P3HT:PCBM film showed excellent long-term stability under high humidity, providing over 3% of power conversion efficiency (PCE) simultaneously. Around 91% of pristine PCE was retained after 30 days storage in high-humidity air without encapsulation. This constitutes a remarkable improvement compared to ∼53% retained PCE for the QD-free devices, which can be ascribed to the efficient suppression of both PCBM aggregation and oxidation of the thiophene ring in P3HT, thanks to the formation of robust QD networks. Furthermore, the presence of QD networks was able to enhance the stability of the P3HT:PCBM film against thermal stress/oxidation under high-humidity environment (50-60%) as well. The device kept 60% of pristine PCE after thermal treatment for 12 h at 85 °C in air, which is more than twice higher than that for the QD-free device. To the best of our knowledge, the work represents the first unambiguous demonstration of the formation of QD networks in the photoactive layer and of their important contribution to the stability of PSCs. This strategy is highly promising for other fullerene-based PSCs and opens a new avenue toward achieving PSCs with high PCE and excellent stability.

16.
Sci Total Environ ; 599-600: 1903-1911, 2017 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-28545217

RESUMO

Birds have been used intensively as biomonitors of halogenated flame retardants (HFRs), and several studies have reported elevated tissue concentrations and inter-individual variability for these contaminants. While diet is known to be an important exposure pathway for HFRs in birds, it has been suggested that exposure through air may represent an underestimated source of HFRs for certain species. However, a method was not available for measuring the atmospheric exposure of individual birds to HFRs or other semi-volatile contaminants. The goal of this study was to develop a bird-borne passive air sampler (PAS) enabling the determination of individual atmospheric exposure to gas- and particle-phase HFRs using the ring-billed gull (Larus delawarensis) nesting in the Montreal area (QC, Canada). The new miniaturized elliptical-shaped PAS (mean weight: 2.72g) was tested using two sorbent types during three exposure periods (one, two and three weeks). Results showed that PAS using polyurethane foam (PUF) combined with a glass fiber filter collected all major polybrominated diphenyl ethers (PBDEs) and exhibited better performance for collecting highly hydrophobic DecaBDE mixture congeners compared to the PAS using polydimethylsiloxane (PDMS). Emerging HFRs including hexabromobenzene, Dechlorane 604 Component B, and Dechlorane plus (DP) isomers also were sampled by the PUF-based PAS. Sampling rates for most HFRs were comparable between the three exposure periods. This novel bird-borne PAS provides valuable information on the non-dietary exposure of free-ranging birds to HFRs.


Assuntos
Poluentes Atmosféricos/análise , Charadriiformes , Monitoramento Ambiental/instrumentação , Retardadores de Chama/análise , Éteres Difenil Halogenados/análise , Animais , Quebeque
17.
Nanoscale ; 8(26): 12946-57, 2016 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-27304092

RESUMO

Semiconductor nanocrystals that show plasmonic resonance represent an emerging class of highly promising plasmonic materials with potential applications in diverse fields, such as sensing and optical and optoelectronic devices. We report a new approach to synthesizing homogeneous covellite CuS nanoplatelets in air and the almost complete disappearance of their plasmonic resonance once coupled with multiwalled carbon nanotubes (MWCNTs). These nanoplatelets were rapidly synthesized by a simple microwave-assisted approach at a relatively low reaction temperature in air, instead of under N2 as reported previously. These less severe synthesis conditions were enabled by appropriately selecting a Cu precursor and preparing a precursor sulfur solution (instead of using solid sulfur) and by using microwave radiation as the heat source. The advantages of utilizing microwave irradiation, including uniform and rapid heating, became clear after comparing the results of the synthesis with those achieved using a conventional oil-bath method under N2. The CuS nanoplatelets prepared in this way showed very strong plasmon resonance at c. 1160 nm as a result of their free charge carriers at the calculated density of nh = 1.5 × 10(22) cm(-3) based on the Drude model. With the aim of exploring their potential for near-infrared responsive optoelectronic devices, they were hybridized with functionalized MWCNTs. Their strong plasmon resonance almost completely disappeared on hybridization. Detailed investigations excluded the effect of possible structural changes in the CuS nanoplatelets during the hybridization process and a possible effect on the plasmon resonance arising from the chemical bonding of surface ligands. Charge transfer was considered to be the main reason for the almost complete disappearance of the plasmon resonance, which was further confirmed by terahertz (THz) time-domain spectrometry and THz time-resolved spectrometry measurements performed on the CuS-MWCNT nanohybrids. By extracting the rising and relaxation constants through fitting a single-exponential rising function and a bi-exponential relaxation function, in combination with the results of THz differential transmission as a function of the NIR pump fluence, it was found that hole injection changed the electronic properties of the MWCNTs only subtly on a short picosecond time scale, whereas the nature of the band structure of the MWCNTs remained largely unchanged. These findings aid our understanding of recently emerging semiconductor plasmonics and will also help in developing practical applications.

18.
Chemistry ; 22(17): 5849-52, 2016 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-26953926

RESUMO

Graphene oxide is regarded as a major precursor for graphene-based materials. The development of graphene oxide based derivatives with new functionalities requires a thorough understanding of its chemical reactivity, especially for canonical synthetic methods such as the Diels-Alder cycloaddition. The Diels-Alder reaction has been successfully extended with graphene oxide as a source of diene by using maleic anhydride as a dienophile, thereby outlining the presence of the cis diene present in the graphene oxide framework. This reaction provides fundamental information for understanding the exact structure and chemical nature of graphene oxide. On the basis of high-resolution (13) C-SS NMR spectra, we show evidence for the formation of new sp(3) carbon centers covalently bonded to graphene oxide following hydrolysis of the reaction product. DFT calculations are also used to show that the presence of a cis dihydroxyl and C vacancy on the surface of graphene oxide are promoting the reaction with significant negative reaction enthalpies.

19.
Annu Int Conf IEEE Eng Med Biol Soc ; 2016: 3002-3005, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28268944

RESUMO

Since the emergence of microfluidic platforms sensors integration has been a major challenge. With the advances in miniaturization of these platforms, there is a need for solutions to integrate various optical components in order to build sensors, which will offer different detection characteristics such as several emission and sensing wavelengths. Moreover, the integration of an electrochemical sensor including a transparent electrode that will be compatible with the optical sensor represents an additional challenge. In this perspective, organic optoelectronic devices combined with silver nanowire electrodes could be a solution. The integration of a fluorescent sensor and an electrochemical oxygen sensor into a microfluidic platform and the different characteristics, advantages and disadvantages that offer organic light-emitting diodes (OLED), organic photodetectors (OPD) and silver nanowire electrodes are discussed. Finally, an example of the integration of an optical and an electrochemical sensor into a microfluidic chip for water pollution detection will be described.


Assuntos
Técnicas Biossensoriais/instrumentação , Técnicas Eletroquímicas/instrumentação , Eletrônica , Microfluídica/instrumentação , Nanofios/química , Fenômenos Ópticos , Prata/química , Diurona/análise , Eletrodos , Herbicidas/análise , Nanofios/ultraestrutura , Espectrometria de Fluorescência , Poluição da Água/análise
20.
Nanoscale ; 7(22): 10039-49, 2015 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-25975363

RESUMO

Near infrared (NIR) PbS quantum dots (QDs) have attracted significant research interest in solar cell applications as they offer several advantages, such as tunable band gaps, capability of absorbing NIR photons, low cost solution processability and high potential for multiple exciton generation. Nonetheless, reports on solar cells based on NIR PbS/CdS core-shell QDs, which are in general more stable and better passivated than PbS QDs and thus more promising for solar cell applications, remain very rare. Herein we report high efficiency bulk heterojunction QD solar cells involving hydrothermally grown TiO2 nanorod arrays and PbS/CdS core-shell QDs processed in air (except for a device thermal annealing step) with a photoresponse extended to wavelengths >1200 nm and with a power conversion efficiency (PCE) as high as 4.43%. This efficiency was achieved by introducing a thin, sputter-deposited, uniform TiO2 seed layer to improve the interface between the TiO2 nanorod arrays and the front electrode, by optimizing TiO2 nanorod length and by conducting QD annealing treatment to enhance charge carrier transport. It was found that the effect of the seed layer became more obvious when the TiO2 nanorods were longer. Although photocurrent did not change much, both open circuit voltage and fill factor clearly changed with TiO2 nanorod length. This was mainly attributed to the variation of charge transport and recombination processes, as evidenced by series and shunt resistance studies. The optimal PCE was obtained at the nanorod length of ∼450 nm. Annealing is shown to further increase the PCE by ∼18%, because of the improvement of charge carrier transport in the devices as evidenced by considerably increased photocurrent. Our results clearly demonstrate the potential of the PbS/CdS core-shell QDs for the achievement of high PCE, solution processable and NIR responsive QD solar cells.

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