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1.
Phys Chem Chem Phys ; 21(41): 23187-23197, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31612872

RESUMO

Carotenoids in photosynthetic proteins carry out the dual function of harvesting light and defending against photo-damage by quenching excess energy. The latter involves the low-lying, dark, excited state labelled S1. Here "dark" means optically-forbidden, a property that is often attributed to molecular symmetry, which leads to speculation that its optical properties may be strongly-perturbed by structural distortions. This has been both explicitly and implicitly proposed as an important feature of photo-protective energy quenching. Here we present a theoretical analysis of the relationship between structural distortions and S1 optical properties. We outline how S1 is dark not because of overall geometric symmetry but because of a topological symmetry related to bond length alternation in the conjugated backbone. Taking the carotenoid echinenone as an example and using a combination of molecular dynamics, quantum chemistry, and the theory of spectral lineshapes, we show that distortions that break this symmetry are extremely stiff. They are therefore absent in solution and only marginally present in even a very highly-distorted protein binding pocket such as in the Orange Carotenoid Protein (OCP). S1 remains resolutely optically-forbidden despite any breaking of bulk molecular symmetry by the protein environment. However, rotations of partially conjugated end-rings can result in fine tuning of the S1 transition density which may exert some influence on interactions with neighbouring chromophores.


Assuntos
Carotenoides/química , Fenômenos Ópticos , Simulação de Dinâmica Molecular , Relação Estrutura-Atividade
2.
Chem Commun (Camb) ; 55(87): 13136-13139, 2019 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-31617550

RESUMO

We explore a facile approach to construct dipeptide-based building blocks containing π-conjugated bridges by using biocross-linkers. Well-defined nanostructures can be assembled and tuned by using different solvents. Compared to pristine units, such dipeptide-based assemblies exhibit structure-dependent and remarkably enhanced optoelectronic properties.


Assuntos
Dipeptídeos/química , Nanoestruturas/química , Estimulação Elétrica , Estrutura Molecular , Fenômenos Ópticos , Tamanho da Partícula , Solventes/química , Propriedades de Superfície
3.
Int J Nanomedicine ; 14: 7065-7078, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31507320

RESUMO

Background:  Metal-free, water-soluble and highly stable meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS4) has been studied for their singlet oxygen quantum yield. However, TPPS4 suffers from inherent shortcomings. To address these, TPPS4 was conjugated to ternary copper indium sulphide/ zinc sulphide (CuInS2/ZnS) quantum dots (QDs). Purpose:  We herein report for the first time the synthesis of TPPS4-CuInS/ZnS QDs conjugate as an improved photosensitizer. Methods:  Water-soluble TPPS4 was synthesized from tetraphenylporphyrin (TPPH2) after silica-gel purification. The CuInS/ZnS QDs were synthesized by hydrothermal method at a Cu:In ratio of 1:4. The porphyrin-QDs conjugate was formed via the daggling sulfonyl bond of the porphyrin and amine bond of the QDs. The effect of pH on the optical properties of TPPS4 was evaluated. The effect of Zn:Cu + In ratio on the ZnS shell passivation was examined to reduce structural defects on the as-synthesized QDs. Results : Various spectroscopic techniques were used to confirm the successful conversion of the organic TPPH2 to water-soluble TPPS4. The singlet oxygen generation evaluation shows an improved singlet oxygen quantum yield from 0.19 for the porphyrin (TPPS4) alone to 0.69 after conjugation (CuInS/ZnS-TPPS4) with an increase in the reaction rate constant (k (s-1)).


Assuntos
Cobre/química , Índio/química , Porfirinas/síntese química , Porfirinas/farmacologia , Pontos Quânticos/química , Sulfetos/síntese química , Compostos de Zinco/síntese química , Concentração de Íons de Hidrogênio , Fenômenos Ópticos , Fármacos Fotossensibilizantes , Porfirinas/química , Pontos Quânticos/ultraestrutura , Oxigênio Singlete/química , Espectroscopia de Infravermelho com Transformada de Fourier , Sulfetos/química , Temperatura Ambiente , Compostos de Zinco/química
4.
Opt Express ; 27(17): 24082-24092, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31510302

RESUMO

This paper investigates the performance of the neural network (NN) assisted motion detection (MD) over an indoor optical camera communication (OCC) link. The proposed study is based on the performance evaluation of various NN training algorithms, which provide efficient and reliable MD functionality along with vision, illumination, data communications and sensing in indoor OCC. To evaluate the proposed scheme, we have carried out an experimental investigation of a static indoor downlink OCC link employing a mobile phone front camera as the receiver and an 8 × 8 red, green and blue light-emitting diodes array as the transmitter. In addition to data transmission, MD is achieved using a camera to observe user's finger movement in the form of centroids via the OCC link. The captured motion is applied to the NN and is evaluated for a number of MD schemes. The results show that, resilient backpropagation based NN offers the fastest convergence with a minimum error of 10-5 within the processing time window of 0.67 s and a success probability of 100 % for MD compared to other algorithms. We demonstrate that, the proposed system with motion offers a bit error rate which is below the forward error correction limit of 3.8 × 10-3, over a transmission distance of 1.17 m.


Assuntos
Redes de Comunicação de Computadores , Movimento (Física) , Fenômenos Ópticos , Fotografação , Algoritmos
5.
Opt Express ; 27(14): 19369-19381, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31503697

RESUMO

Photoacoustic endomicroscopy (PAEM) is capable of imaging fine structures in digestive tract. However, conventional PAEM employs a tightly focused laser beam to irradiate the object, which results in a limited depth-of-field (DOF). Here, we propose a scanning-domain synthesis of optical beams (SDSOB) to optimize both transverse resolution and the DOF by synthetic effective focused beams in scanning domain for the PAEM. By utilizing the SDSOB technique, multiple defocused and scattered beams are refocused to synthesize virtual focuses covering a large range of depth. A transverse point spread function that is 5.7-time sharper, and a transverse spatial bandwidth that is 8.5-time broader than those of the conventional PAEM were simulatively obtained through SDSOB-PAEM at the defocus distance of 2.4 mm. We validated the transverse resolution improvement at both in- and out-focus positions via phantom experiments of carbon fibers. In addition, in vivo rabbit experiments were conducted to acquire vascular images over radial depth range of 900 µm. And further morphological analysis revealed that the SDSOB images were acquired with abundant vascular branches and nodes, large total-length and small average-length of blood vessels, which indicated that the SDSOB-PAEM achieved high-resolution imaging in distinct rectal layers. All these results suggest that the SDSOB-PAEM possesses high transverse resolution and extended DOF, which demonstrates the SDSOB-PAEM can provide more accurate information for clinical assessment.


Assuntos
Microscopia , Fenômenos Ópticos , Técnicas Fotoacústicas/métodos , Animais , Simulação por Computador , Feminino , Análise Numérica Assistida por Computador , Imagens de Fantasmas , Coelhos
6.
Appl Opt ; 58(23): 6268-6273, 2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31503769

RESUMO

In this paper, we have cultured normal epithelial cells (HaCaT) as analytes to detect the sensitivity of a biosensor based on Fano resonance metamaterials (FRMMs). The frequency shift Δf of the transmission spectrum was experimentally measured at three different concentrations (0.2×105, 0.5×105, and 5×105 cell/ml) of HaCaT cells. By employing the FRMMs-based biosensor, the detection concentration of HaCaT cells can approximately arrive at 0.2×105 cell/ml; further, the corresponding Δf is 25 GHz, which reaches the measurement limit of the THz-TDS system. Additionally, the increase of HaCaT cell concentration causes a different redshift of Δf from 24-50 GHz, and the maximum of Δf can reach 50 GHz when the HaCaT cell concentration is at 5×105 cell/ml. Similarly, the simulated results show that the Δf depends on the numbers of analytes with a semiball shape and the refractive index of analytes. The theoretical sensitivity was calculated to be 481 GHz/RIU. The proposed FRMMs-based biosensor paves a fascinating platform for biological and biomedical applications and may become a valuable complementary reference for traditional biological research.


Assuntos
Técnicas Biossensoriais , Células Epiteliais/citologia , Fenômenos Ópticos , Simulação por Computador , Humanos
7.
Opt Lett ; 44(16): 4063-4066, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31415547

RESUMO

Photo-mediated ultrasound therapy (PUT) is a novel, noninvasive antimicrovascular approach that can treat neovascularization with high precision. We developed a photoacoustic (PA) sensing (PAS) system for PUT and achieved real-time PAS-guided PUT. Experiments performed on a chicken yolk sac membrane model demonstrated that PAS could monitor the treatment effect in a microvessel during PUT. Vessel shrinkage induced a decrease in the PA signal amplitude, while vessel rupture induced an abrupt increase in the PA signal amplitude. The integrated PUT and PAS system can significantly improve the safety and effectiveness of PUT, and may assist with clinical translation of this novel antimicrovascular technique.


Assuntos
Técnicas Fotoacústicas , Terapia por Ultrassom/métodos , Fenômenos Ópticos , Razão Sinal-Ruído , Fatores de Tempo
8.
Analyst ; 144(18): 5373-5377, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31386702

RESUMO

Lipid droplets are known to play an important role in many cellular activities, as revealed by recent studies. Additionally, hexavalent chromium is considered extremely toxic because it readily passes through cellular membranes and easily accumulates in living cells. In this study, a novel lipid droplet-targeted fluorescent probe (Si-LDS) for recognition of Cr6+ in living cells was designed and synthesized using triphenylamine derivatives and organosiloxane. Si-LDS detected Cr6+ with high selectivity and sensitivity. The novel probe was successfully applied to cell imaging of exogenous Cr6+ in HeLa cells, and Si-LDS was able to localize mainly in the lipid droplets of HeLa cells. Si-LDS is the first lipid droplet-targeted fluorescent probe for monitoring Cr6+.


Assuntos
Aminas/química , Cromo/metabolismo , Corantes Fluorescentes/química , Gotículas Lipídicas/metabolismo , Imagem Óptica/métodos , Oxigênio/química , Silício/química , Corantes Fluorescentes/metabolismo , Células HeLa , Humanos , Fenômenos Ópticos , Bases de Schiff/química
9.
Int J Nanomedicine ; 14: 5147-5157, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31371953

RESUMO

Background: Kaempferol (K) is a recognized anticancer drug that can conjugate with small-size gold nanoclusters (AuNCs). Materials and methods: K-AuNCs were synthesized and their use as an anticancer drug was explored using A549 lung cancer cells. Colony formation and cell migration assays were carried out. The morphology of the K-AuNCs treated A549 cells was explored using bio-atomic force microscopy. Results: The K-AuNCs were 1-3 nm in diameter and emitted strong fluorescent at 650 nm following excitation at 550 nm. The stretching and bending nature of the K-AuNCs were analyzed by the Fourier transform infrared spectroscopy. The presence of kaempferol in the AuNCs were confirmed by the PL spectroscopy. Conclusion: The synthesized K-AuNCs mainly targeted and damaged the nuclei of the cancer cells. This composite nanocluster was less toxicity to the normal human cell and higher toxicity to the A549 lunch cancer cell and these material is potential for anticancer drug delivery and bio imaging applications.


Assuntos
Antineoplásicos/uso terapêutico , Ouro/química , Quempferóis/uso terapêutico , Neoplasias Pulmonares/tratamento farmacológico , Nanopartículas Metálicas/química , Células A549 , Antineoplásicos/química , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Núcleo Celular/efeitos dos fármacos , Núcleo Celular/patologia , Proliferação de Células/efeitos dos fármacos , Forma Celular/efeitos dos fármacos , Humanos , Quempferóis/farmacologia , Nanopartículas Metálicas/toxicidade , Nanopartículas Metálicas/ultraestrutura , Fenômenos Ópticos , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
10.
Opt Lett ; 44(17): 4119-4122, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31465343

RESUMO

Detailed assessment of skin conditions or the efficacy of skin treatments could greatly benefit from noninvasively assessing the distribution of cutaneous and subcutaneous structures and biomolecules. We considered ultrawideband raster scan optoacoustic mesoscopy with an extended wavelength range from visible to short-wave infrared and observed previously unseen high-resolution images of lipids colocalized with water, melanin, and hemoglobin distribution in human skin. Based on this contrast, the technique resolves subcutaneous fat, the pilosebaceous unit with complete hair strand and bulb, dermal microvasculature, and epidermal structures. We further visualize melanoidins that form via the Maillard reaction in the ultrathin stratum corneum layer, analyze their absorption spectrum, and separate them from the melanin layer. The suggested method may allow novel interrogation of skin conditions, possibly impacting diagnostics and medical and cosmetic treatments.


Assuntos
Raios Infravermelhos , Fenômenos Ópticos , Técnicas Fotoacústicas , Pele/diagnóstico por imagem , Tecido Adiposo/citologia , Hemoglobinas/metabolismo , Humanos , Metabolismo dos Lipídeos , Melaninas/metabolismo , Pele/citologia , Pele/metabolismo , Água/metabolismo
11.
Opt Lett ; 44(17): 4219-4222, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31465366

RESUMO

We describe the details of a multimodal retinal imaging system which combines adaptive optics (AO) with an integrated scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT) imaging system. The OCT subsystem consisted of a swept-source, Fourier-domain mode-locked (FDML) laser, with a very high A-scan rate (1.6 MHz), whose beam was raster scanned on the retina by two scanners-one resonant scanner and one galvanometer. The high sweep rate of the FDML permitted the SLO and OCT to utilize the same scanners for in vivo retinal imaging and, unlike existing multimodal systems, concurrently acquired SLO frames and OCT volumes with approximate en face correspondence at a rate of 6 Hz. The AO provided diffraction-limited cellular resolution for both imaging channels.


Assuntos
Fenômenos Ópticos , Retina/diagnóstico por imagem , Tomografia de Coerência Óptica/métodos , Humanos , Razão Sinal-Ruído , Tomografia de Coerência Óptica/instrumentação
12.
Ultrason Sonochem ; 59: 104728, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31421619

RESUMO

Ultra-sonication (US) at varying intensities (200 W, 300 W and 400 W) and hydrodynamic cavitation (HC) at increasing pressures (6 bar, 8 bar and 10 bar) on freshly extracted peanut milk as non-thermal processing of milk for enhanced quality. The effects of US and HC was investigated on physico-chemical properties of peanut milk, microbial inactivation (total plate count and yeasts and molds), microstructure by optical microscopy and particle size, ζ-potential, sedimentation index, rheology and color measurements. The high temperature short time (HTST) treated milk samples have shown 1.53 and 2 log reduction in TPC, yeast and molds respectively with highest protein hydrolysis of 15.7%. Among the non-thermal treatments HC has shown highest log reduction of TPC at around 1.2 for sample treated at 10 bar pressure, whereas the US treatment was most effective for yeast and mold at 400 W with log reduction of 0.9. A non-Newtonian flow behaviour was observed for all peanut milk samples. Viscosity determined by Herschel-Bulkley equation decreased significantly (p > 0.05) after both cavitation treatments. The US was found to be superior to HC and HTST with improved separation index and colour attributes. Therefore, the US and HC appear to be a remarkable non-thermal processing methods for peanut milk and or any dairy or non-dairy beverages.


Assuntos
Arachis/química , Bebidas/microbiologia , Fenômenos Químicos , Hidrodinâmica , Viabilidade Microbiana , Sonicação , Arachis/microbiologia , Cor , Concentração de Íons de Hidrogênio , Hidrólise , Fenômenos Ópticos , Tamanho da Partícula , Proteínas de Plantas/química , Solubilidade , Temperatura Ambiente
13.
J Mol Model ; 25(8): 223, 2019 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-31302811

RESUMO

Four novel ligands, namely N-benzhydryl benzamide, N, N-diphenethyl benzamide, N, N-dihexyl benzamide, and N, N-dioctyl benzamide (L1, L2, L3, and L4, respectively), based on the benzamide unit were designed and computed for their different properties, such as absorption spectrum, dipole moment, theoretically expected biological properties, and frontier molecular orbitals, by evaluating the HOMO/LUMO energy orbitals strength with DFT approaches and comparing these properties with the R benzamide properties available in literature. All molecules have a suitable frontier molecular orbital diagram and L1 exhibits maximum absorption at 246.8 nm due to the strong electron donating effect of the diphenylmethane ligand group. Moreover, strongly extended conjugated groups caused a redshift in absorption spectra. Newly designed molecules may show strong biological activities against cancer, bacterial diseases, and harmful fungal disorders. Graphical abstract Orbital energy, electron density and frontier molecular orbitals view of four designed novel benzamide derivates.


Assuntos
Benzamidas/química , Benzamidas/farmacologia , Teoria da Densidade Funcional , Benzamidas/síntese química , Linhagem Celular Tumoral , Simulação por Computador , Humanos , Ligantes , Conformação Molecular , Fenômenos Ópticos , Termodinâmica
14.
Int J Biol Macromol ; 138: 302-308, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31306700

RESUMO

During carcinogenesis, changes in the glycosylation can modulate many biological processes. Thus, the interest in exploring and understanding the roles of carbohydrates as cancer biomarkers has been increasing. Lectins have been applied as useful tools in glycobiology, especially when associated with fluorescent reporters. Therefore, to take advantage of the physicochemical properties of quantum dots (QDs), herein, we conjugated Cramoll, a lectin that recognizes glucose/mannose residues, with those nanoparticles. We applied the conjugates to investigate the glycocode of normal, fibroadenoma (FB), and invasive ductal carcinoma (IDC) human breast tissues. Additionally, we proposed a method to quantitatively evaluate the tissue labeling intensity by a fluorescence microplate assay (FMA). Conjugates showed intense fluorescence and specificity. The lectin activity and secondary structure were also preserved after the conjugation with QDs. Moreover, fluorescence images showed that ductal cells of normal and FB tissues were preferentially labeled by conjugates, whereas both cells and stroma were strongly labeled in IDC. FMA showed in a quantitative, practical, and sensitive way that the level of exposed glucose/mannose residues increased accordingly to the sample malignancy degree. In conclusion, QDs-Cramoll conjugates can be considered effective, specific, and versatile probes to evaluate glycan profiles in normal and transformed tissues, by fluorescence microscopy as well as FMA quantification. Furthermore, FMA showed to be a potential method that can be applied with other fluorescent conjugates.


Assuntos
Neoplasias da Mama/patologia , Fabaceae/química , Fenótipo , Lectinas de Plantas/química , Polissacarídeos/metabolismo , Pontos Quânticos/química , Pontos Quânticos/metabolismo , Neoplasias da Mama/metabolismo , Glicosilação , Humanos , Fenômenos Ópticos
15.
Rev Sci Instrum ; 90(6): 064102, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31254989

RESUMO

The rapid development of the optically pumped magnetometer (OPM) has offered a much more flexible method for magnetoencephalography (MEG). Without using liquid helium and its associated dewar device in the OPM detectors, the large and expensive magnetically shielded room (MSR) for traditional MEG systems could be replaced by a compact shield. In the present work, an economic and compact cylindrical shield was designed and built to meet the low-field working requirement of the OPM in detecting human brain neuronal activities. The performance of the compact shield was evaluated and further compared with that of a commercial MSR. Our results showed that the residual magnetic fields and background noise of the compact shield were lower than or comparable to those of the MSR. The remnant field in the shield is found to be 4.2 nT, a factor of 13 000 smaller than the geomagnetic field which is applied to the transverse direction of the shield, and the longitudinal shielding factors measured using a known alternating-current magnetic field are approximately 191, 205, and 3130 at 0.1 Hz, 1 Hz, and 10 Hz, respectively; in addition, the evoked dynamic waveforms in the human auditory cortex that were recorded separately in these two shields demonstrated consistency. Our findings suggested that a compact shield is feasible for OPM-based MEG applications with high performance and low cost.


Assuntos
Magnetoencefalografia/instrumentação , Magnetometria/instrumentação , Fenômenos Ópticos , Desenho de Equipamento
16.
Int J Biol Macromol ; 135: 752-759, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31152833

RESUMO

This paper reports on the fabrication of material comprised of chitosan stabilized silver nanoparticles on the carbon paste and its electro-catalytic reduction toward 4-nitroaniline. The synthesized material was obtained when AgNO3 was mixed with chitosan as a stabilizing agent and NaBH4 as a reducing agent. The developed Chitosan-AgNPs has been confirmed using UV-Vis spectroscopy, X-Ray diffraction analysis, scanning electron microscopy (SEM) and infrared spectroscopy. The synthesized chitosan-Ag NPs exhibit particle size around 51 nm. To build a voltammetric sensor (Chitosan-Ag NPs/CPE), a carbon paste electrode has immersed in the liquid suspension of chitosan-Ag NPs, thus, it could be employed for electro-catalytic reduction of 4-NA in 0.1 M Britton-Robinson buffer solution (B-R, pH 2). Therefore, the reduction over-potential of 4-NA shifted from -752.26 mV at CPE to -304 mV at chitosan-Ag NPs/CPE, and then showing a surface controlled process with the catalytic rate constant (Kcat) of 0.125 × 10-3 M-1 s-1 and a coefficient of diffusion (D) of 2.20 × 10-6 cm2 s-1 with an enhanced current response. Under optimized conditions, the electro-catalytic reduction peak current of 4-NA increased linearly with increasing of 4-NA concentration over the range of 1 µM to 0.5 mM (R2 = 0.9866) with a detection limit of 0.86 µM (3 × Sb/P).


Assuntos
Compostos de Anilina/química , Quitosana/química , Nanotecnologia , Prata/química , Catálise , Técnicas de Química Sintética , Eletroquímica , Eletrodos , Fenômenos Ópticos , Oxirredução
17.
Int J Biol Macromol ; 135: 647-658, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31150672

RESUMO

Active films were produced with sulphated polysaccharides "ulvan", extracted from the green seaweed Ulva lactuca with different extraction procedures, by varying the glycerol or sorbitol plasticizer concentration at 1% and 2% (w/v). The surface charge and glass transition temperature (Tg) of ulvans were carried out by zeta (ζ)-potential and DSC analysis, respectively. The investigation revealed that ulvans were anionic stable polymers and they had great Tg values. Regardless of the extraction procedure, ulvans can give successful films formulations. However, the optical, thermal, structural and antioxidant characteristics of ulvan films were strongly affected by extraction conditions and by the variation of the type and concentration of plasticizer. In general, as plasticizer concentration increased, ferrous chelating activity and compact structure increased as well, while, Tg, lightness and DPPH radical-scavenging activity decreased. Interestingly, the films plasticized with glycerol exhibited better compact structure, more negative temperature of transition, and greater free radical scavenging ability than with sorbitol. However, the films prepared with sorbitol had the highest L* values and chelating ability. The current study revealed a high correlation between zeta (ζ)-potential of ulvans and their Tg (R2 = 0.98), as well as with scavenging activity of ulvan films (R2 = 0.8-0.99).


Assuntos
Antioxidantes/química , Antioxidantes/isolamento & purificação , Fenômenos Ópticos , Plastificantes/química , Polissacarídeos/química , Polissacarídeos/isolamento & purificação , Temperatura Ambiente , Cor
18.
Int J Mol Sci ; 20(11)2019 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-31181732

RESUMO

Flexible transparent conductive films (FTCFs) composed of silver nanowires (AgNWs) have become an important research direction because of their potential in flexible electronic devices. The optoelectronic properties of FTCFs composed of AgNWs of different lengths were evaluated in this study. AgNWs, with an average diameter of about 25 nm and length of 15.49-3.92 µm were obtained by a sonication-induced scission process. AgNW-FTCFs were prepared on polyethylene terephthalate substrates using a Meyer bar and then dried in the ambient environment. The sheet resistance, non-uniformity factor of the sheet resistance, the root mean square roughness, and haze of the FTCFs increased as the length of AgNWs decreased. The transmittance of the films increased slightly as the length of AgNWs increased. AgNWs with a length of 15.49 µm provided an AgNW-FTCF with excellent properties including haze of 0.95%, transmittance of 93.42%, and sheet resistance of 80.15 Ω∙sq-1, without any additional post-treatment of the film. This work investigating the dependence of the optoelectronic properties of AgNW-FTCFs on AgNW length provides design guidelines for development of AgNW-FTCFs.


Assuntos
Nanopartículas Metálicas/química , Nanofios/química , Prata/química , Condutividade Elétrica , Fenômenos Ópticos , Polietilenotereftalatos/química , Sonicação
19.
Proc Inst Mech Eng H ; 233(9): 954-960, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31210622

RESUMO

The validity of conclusions drawn from pre-clinical tests on orthopaedic devices depends upon accurate characterisation of the support materials: frequently, polymer foam analogues. These materials often display anisotropic mechanical behaviour, which may considerably influence computational modelling predictions and interpretation of experiments. Therefore, this study sought to characterise the anisotropic mechanical properties of a range of commonly used analogue bone materials, using non-contact multi-point optical extensometry method to account for the effects of machine compliance and uneven loading. Testing was conducted on commercially available 'cellular', 'solid' and 'open-cell' Sawbone blocks with a range of densities. Solid foams behaved largely isotropically. However, across the available density range of cellular foams, the average Young's modulus was 23%-31% lower (p < 0.005) perpendicular to the foaming direction than parallel to it, indicating elongation of cells with foaming. The average Young's modulus of open-celled foams was 25%-59% higher (p < 0.05) perpendicular to the foaming direction than parallel to it. This is thought to result from solid planes of material that were observed perpendicular to the foaming direction, stiffening the bulk material. The presented data represent a reference to help researchers design, model and interpret tests using these materials.


Assuntos
Materiais Biomiméticos , Osso e Ossos , Força Compressiva , Teste de Materiais/métodos , Fenômenos Ópticos , Estresse Mecânico , Anisotropia , Fenômenos Biomecânicos , Módulo de Elasticidade , Distribuição de Poisson
20.
Int J Biol Macromol ; 136: 241-252, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31195048

RESUMO

In this work, sunflower oil cake (SOC) was identified as bio-sourced material for cellulose nanocrystals (CNC) production using chemical treatments followed by sulfuric acid hydrolysis. The hydrolysis was performed at 64% acid concentration, a temperature of 50 °C and at two different hydrolysis times, 15 min (CNC15) and 30 min (CNC30). It was found that CNC exhibited a diameter of 9 ±â€¯3 nm and 5 ±â€¯2 nm, a length of 354 ±â€¯101 nm and 329 ±â€¯98 nm, a crystallinity of 75% and 87%, a surface charge density of ~1.57 and ~1.88 sulfate groups per 100 anhydroglucose units and a zeta potential value of -25.6 and -30.7 mV, for CNC15 and CNC30, respectively. The thermal degradation under nitrogen atmosphere started at 225 °C (CNC15), which is relatively higher than the temperature for sulfuric acid hydrolyzed CNC from other sources. Due to a high importance of CNC application in aqueous systems, the rheological behaviour of CNC suspensions at various concentrations was evaluated by the steady shear viscosity measurements and the oscillatory dynamic tests. The results showed that the CNC suspensions exhibited a gel-like behaviour at very low CNC concentrations (0.1-1%) wherein a strong CNC entangled network is formed. Polymer nanoreinforcing capability of the newly produced CNC was also investigated in this study. CNC filled PVA nanocomposite films were produced at various CNC contents (1, 3, 5 and 8 wt%) and their mechanical and transparency properties were investigated, resulting in transparent nanocomposite materials with strong mechanical properties. The study suggested other possibilities to utilize agricultural wastes from SOC for CNC production with potential application as reinforcement in polymer nanocomposites.


Assuntos
Celulose/química , Celulose/isolamento & purificação , Fenômenos Químicos , Nanopartículas/química , Óleo de Girassol/química , Nanocompostos/química , Fenômenos Ópticos , Álcool de Polivinil/química , Propriedades de Superfície , Temperatura Ambiente
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