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1.
ACS Appl Mater Interfaces ; 12(18): 21057-21069, 2020 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-32289218

RESUMO

The reduction of bacteria and biofilm formation is important when designing surfaces for use in industry. Molybdenum disulfide surfaces (MoS2SUR) were produced using MoS2 particle (MoS2PAR) sizes of 90 nm, 2 µm, and 6 µm containing MoS2PAR concentrations of 5%, 10%, 15%, and 20%. These were tested to determine the efficacy of the MoS2SUR to impede bacterial retention and biofilm formation of two different types of bacteria, Staphylococcus aureus and Pseudomonas aeruginosa. The MoS2SUR were characterized using Fourier transform infrared spectroscopy, ion-coupled plasma atomic emission spectroscopy, scanning electron microscopy, optical profilometry, and water contact angles. The MoS2SUR made with the smaller 90 nm MoS2PAR sizes demonstrated smaller topographical-shaped features. As the size of the incorporated MoS2PAR increased, the MoS2SUR demonstrated wider surface features, and they were less wettable. The increase in MoS2PAR concentration within the MoS2SUR groups did not affect the surface topography but did increase wettability. However, the increase in MoS2PAR size increased both the surface topography and wettability. The MoS2SUR with the smaller topographical-shaped features influenced the retention of the S. aureus bacteria. Increased MoS2SUR topography and wettability resulted in the greatest reduction in bacterial retention, and the bacteria became more heterogeneously dispersed and less clustered across the surfaces. The surfaces that exhibited decreased bacterial retention (largest particle sizes, largest features, greatest roughness, and most wettable) resulted in decreased biofilm formation. Cytotoxicity testing of the surface using cell viability demonstrated that the MoS2SUR were not toxic against HK-2 cells at MoS2PAR sizes of 90 nm and 2 µm. This work demonstrated that individual surface variables (MoS2SUR topographic shape and roughness, MoS2PAR size, and concentration) decreased bacterial loading on the surfaces, which then decreased biofilm formation. By optimizing MoS2SUR properties, it was possible to impede bacterial retention and subsequent biofilm formation.

2.
Analyst ; 145(9): 3424-3430, 2020 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-32255110

RESUMO

Additive manufacturing is a promising technology for the rapid and economical fabrication of portable electroanalytical devices. In this paper we seek to determine how our bespoke additive manufacturing feedstocks act as the basis of an electrochemical sensing platform towards the sensing of manganese(ii) via differential pulse cathodic stripping voltammetry (DPCSV), despite the electrode comprising only 25 wt% nanographite and 75 wt% plastic (polylactic acid). The Additive Manufactured electrodes (AM-electrodes) are also critically compared to graphite screen-printed macroelectrodes (SPEs) and both are explored in model and real tap-water samples. Using optimized DPCSV conditions at pH 6.0, the analytical outputs using the AM-electrodes are as follows: limit of detection, 1.6 × 10-9 mol L-1 (0.09 µg L-1); analytical sensitivity, 3.4 µA V µmol-1 L; linear range, 9.1 × 10-9 mol L-1 to 2.7 × 10-6 mol L-1 (R2 = 0.998); and RSD 4.9% (N = 10 for 1 µmol L-1). These results are compared to screen-printed macroelectrodes (SPEs) giving comparable results providing confidence that AM-electrodes can provide the basis for useful electrochemical sensing platforms. The proposed electroanalytical method (both AM-electrodes and SPEs) is shown to be successfully applied for the determination of manganese(ii) in tap water samples and in the analysis of a certified material (drinking water). The proposed method is feasible to be applied for in-loco analyses due to the portability of sensing; in addition, the use of AM-printed electrodes is attractive due to their low cost.

3.
Biosensors (Basel) ; 10(3)2020 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-32204548

RESUMO

We demonstrate a facile methodology for the mass production of graphene oxide (GO) bulk-modified screen-printed electrodes (GO-SPEs) that are economical, highly reproducible and provide analytically useful outputs. Through fabricating GO-SPEs with varying percentage mass incorporations (2.5%, 5%, 7.5% and 10%) of GO, an electrocatalytic effect towards the chosen electroanalytical probes is observed, which increases with greater GO incorporated compared to bare/graphite SPEs. The optimum mass ratio of 10% GO to 90% carbon ink produces an electroanalytical signal towards dopamine (DA) and uric acid (UA) which is ca. ×10 greater in magnitude than that achievable at a bare/unmodified graphite SPE. Furthermore, 10% GO-SPEs exhibit a competitively low limit of detection (3σ) towards DA at ca. 81 nM, which is superior to that of a bare/unmodified graphite SPE at ca. 780 nM. The improved analytical response is attributed to the large number of oxygenated species inhabiting the edge and defect sites of the GO nanosheets, which are able to exhibit electrocatalytic responses towards inner-sphere electrochemical analytes. Our reported methodology is simple, scalable, and cost effective for the fabrication of GO-SPEs that display highly competitive LODs and are of significant interest for use in commercial and medicinal applications.

4.
Mikrochim Acta ; 187(2): 126, 2020 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-31938885

RESUMO

An electrochemical sensing platform based upon screen-printing electrodes (SPEs) modified with nanostructured lanthanide metal oxides facilitate the detection of the widely misused drugs acetaminophen (ACP) and tramadol (TRA). Among the metal oxides examined, Yb2O3 nanoplates (NPs) were found to give rise to an optimal electrochemical response. The electroanalysis of ACP and TRA individually, and within mixtures, was performed using cyclic and differential pulse voltammetry. The ACP and TRA exhibited non-overlapping voltammetric signals at voltages of +0.30 and + 0.67 V (vs. Ag/AgCl; pH 9) using Yb2O3-SPEs. Pharmaceutical dosage forms and spiked human fluids were analyzed in wide linear concentration ranges of 0.25-654 and 0.50-115 µmol.L-1 with limits of detection (LOD) of 55 and 87 nmol.L-1 for ACP and TRA, respectively. The Yb2O3-SPEs offer a sensitive and chemically stable enzyme-free electrochemical platform for ACP and TRA assay. Graphical abstractSchematic presentation of one-shot electrochemical analysis of misused drugs, tramadol (TRA) and acetaminophen (ACP) by utilizing ytterbium oxide nanoplates modified screen-printed electrodes (Yb2O3-SPEs). The Yb2O3-SPEs showed interesting responses for ACP and TRA within pharmaceutical formulations and human fluids.

5.
Arch Microbiol ; 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31915886

RESUMO

Burn infections caused by Pseudomonas aeruginosa pose a major complication in wound healing. This study aimed to determine the antimicrobial effect of metal ions, graphene (Gr), and graphene oxide (GO), individually and in combination, against the planktonic and biofilm states of two antimicrobially resistant clinical strains of P. aeruginosa each with different antibiotic resistance profiles. Minimum inhibitory, minimum bactericidal, and fractional inhibitory concentrations were performed to determine the efficacy of the metal ions and graphene composites individually and their synergy in combination. Crystal violet biofilm and XTT assays measured the biofilm inhibition and metabolic activity, respectively. Molybdenum, platinum, tin, gold, and palladium ions exhibited the greatest antimicrobial activity (MIC = 7.8-26.0 mg/L), whilst GO and Gr demonstrated moderate-to-no effect against the planktonic bacterial cells, irrespective of their antibiograms. Biofilms were inhibited by zinc, palladium, silver, and graphene. In combination, silver-graphene and molybdenum-graphene inhibited both the planktonic and biofilm forms of the bacteria making them potential candidates for development into topical antimicrobials for burns patients infected with antibiotic-resistant P. aeruginosa.

6.
Sci Rep ; 9(1): 15961, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31685906

RESUMO

Mono-, few-, and multilayer graphene is explored towards the electrochemical Hydrogen Evolution Reaction (HER). Careful physicochemical characterisation is undertaken during electrochemical perturbation revealing that the integrity of graphene is structurally compromised. Electrochemical perturbation, in the form of electrochemical potential scanning (linear sweep voltammetry), as induced when exploring the HER using monolayer graphene, creates defects upon the basal plane surface that increases the coverage of edge plane sites/defects resulting in an increase in the electrochemical reversibility of the HER process. This process of improved HER performance occurs up to a threshold, where substantial break-up of the basal sheet occurs, after which the electrochemical response decreases; this is due to the destruction of the sheet integrity and lack of electrical conductive pathways. Importantly, the severity of these changes is structurally dependent on the graphene variant utilised. This work indicates that multilayer graphene has more potential as an electrochemical platform for the HER, rather than that of mono- and few-layer graphene. There is huge potential for this knowledge to be usefully exploited within the energy sector and beyond.

7.
ACS Sens ; 4(10): 2838-2845, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31571480

RESUMO

This manuscript describes the production of molecularly imprinted polymer nanoparticles (nanoMIPs) for the cardiac biomarkers heart-fatty acid binding protein (H-FABP) and ST2 by solid-phase synthesis, and their use as synthetic antibodies in a multiplexed sensing platform. Analysis by surface plasmon resonance (SPR) shows that the affinity of the nanoMIPs is similar to that of commercially available antibodies. The particles are coated onto the surface of thermocouples and inserted into 3D-printed flow cells of different multiplexed designs. We demonstrate that it is possible to selectively detect both cardiac biomarkers within the physiologically relevant range. Furthermore, the developed sensor platform is the first example of a multiplex format of this thermal analysis technique which enables simultaneous measurements of two different compounds with minimal cross selectivity. The format where three thermocouples are positioned in parallel exhibits the highest sensitivity, which is explained by modeling the heat flow distribution within the flow cell. This design is used in further experiments and proof-of-application of the sensor platform is provided by measuring spiked fetal bovine serum samples. Because of the high selectivity, short measurement time, and low cost of this array format, it provides an interesting alternative to traditional immunoassays. The use of nanoMIPs enables a multimarker strategy, which has the potential to contribute to sustainable healthcare by improving the reliability of cardiac biomarker testing.

8.
Sci Rep ; 9(1): 12814, 2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31492903

RESUMO

The origin of electron transfer at Chemical Vapour Deposition (CVD) grown monolayer graphene using a polymer-free transfer methodology is explored through the selective electrodeposition of Molybdenum (di)oxide (MoO2). The electrochemical decoration of CVD monolayer graphene with MoO2 is shown to originate from the edge plane like- sites/defects. Edge plane decoration of MoO2 nanowires upon monolayer graphene is observed via electrochemical deposition over short time periods only (ca. -0.6 V for 1 second (vs. Ag/AgCl)). At more electrochemically negative potentials (ca. -1.0 V) or longer deposition times, a large MoO2 film is created/deposited on the graphene sheet, originating and expanding from the original nucleation points at edge plane like- sites/defects/wrinkles. Nanowire fabrication along the edge plane like- sites/defects of graphene is confirmed with Cyclic Voltammetry, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Raman Spectroscopy. Monitoring the electrochemical response towards [Ru(NH3)6]3+/2+ and comparing the heterogeneous electron transfer (HET) kinetics at CVD grown monolayer graphene prior and post nanowire fabrication reveals key understandings into the fundamental electrochemical properties of carbon materials. The HET kinetics ([Formula: see text]) at MoO2 nanowire decorated monolayer graphene sheets, when edge plane like- sites/defects have been coated/blocked with MoO2, are significantly reduced in comparison to the unmodified graphene alternative. Interestingly, MoO2 nucleation originates on the edge plane like- sites/defects of the graphene sheets, where the basal plane sites remain unaltered until the available edge plane like- sites/defects have been fully utilised; after which MoO2 deposition propagates towards and onto the basal planes, eventually covering the entire surface of the monolayer graphene surface. In such instances, there is no longer an observable electrochemical response. This work demonstrates the distinct electron transfer properties of edge and basal plane sites on CVD grown monolayer graphene, inferring favourable electrochemical reactivity at edge plane like- sites/defects and clarifying the origin of graphene electro-activity.

9.
Anal Chem ; 91(20): 12844-12851, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31535844

RESUMO

Herein, we report a complete additively manufactured (AM) electrochemical sensing platform. In this approach, a fully AM/3D-printed electrochemical system, using a conventional low-cost 3D printer (fused deposition modeling) fabricating both the conductive electrodes and the nonconductive/chemically inert electrochemical cell is reported. The electrodes (working, counter, and pseudo-reference) are AM using a conductive fused-filament comprised of a mixture of carbon black nanoparticles and polylactic acid (CB/PLA). AM components partially coated with silver ink presented a similar behavior to a conventional Ag/AgCl reference electrode. The performance of the AM working electrode was evaluated after a simple and fast polishing procedure on sandpaper and electrochemical activation in a NaOH solution (0.5 mol L-1). Following the electrochemical activation step, a considerable improvement in the electrochemical behavior (current intensity and voltammetric profile) was obtained for model analytes, such as dopamine, hexaammineruthenium(III) chloride, ferricyanide/ferrocyanide, uric acid, and ascorbic acid. Excellent repeatability (RSD = 0.4%, N = 10) and limit of detection (0.1 µmol L-1) were obtained with the all complete AM electrochemical system for dopamine analysis. The electrochemical performance of the developed system (after simple electrochemical activation of the working electrode) was similar or better than those obtained using commercial glassy carbon and screen-printed carbon electrodes. The results shown here represents a significant advance in AM (3D printing) technology for analytical chemistry.

10.
ACS Omega ; 4(11): 14439-14450, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31528797

RESUMO

The emergence of a new class of novel psychoactive substances, N-benzyl-substituted phenethylamine derivatives so-called "NBOMes" or "Smiles", in the recreational drug market has forced the development of new sensitive analytical methodologies for their detection and quantitation. NBOMes' hallucinogenic effects mimic those of the illegal psychedelic drug lysergic acid diethylamide (LSD) and are typically sold as LSD on blotter papers, resulting in a remarkable number of fatalities worldwide. In this article, four halide derivatives of NBOMe, namely, 2-(4-fluoro-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, 2-(4-chloro-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, 2-(4-bromo-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, and 2-(4-iodo-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, were detected and quantified simultaneously using a high-performance liquid chromatographic method, and two detection systems were compared: photodiode array detection (detection system I) and amperometric detection via a commercially available impinging jet flow-cell system incorporating embedded graphite screen-printed macroelectrodes (detection system II). Under optimized experimental conditions, linear calibration plots were obtained in the concentration range of 10-300 and 20-300 µg mL-1, for detection systems I and II, respectively. Detection limit (limit of detection) values were between 4.6-6.7 and 9.7-18 µg mL-1, for detection systems I and II, respectively. Both detectors were employed for the analysis of the four NBOMe derivatives in the bulk form, in the presence of LSD and adulterants commonly found in street samples (e.g. paracetamol, caffeine, and benzocaine). Furthermore, the method was applied for the analysis of simulated blotter papers, and the obtained percentage recoveries were satisfactory, emphasizing its advantageous applicability for the routine analysis of NBOMes in forensic laboratories.

11.
Sensors (Basel) ; 19(5)2019 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-30857285

RESUMO

The accurate detection of biological materials has remained at the forefront of scientific research for decades. This includes the detection of molecules, proteins, and bacteria. Biomimetic sensors look to replicate the sensitive and selective mechanisms that are found in biological systems and incorporate these properties into functional sensing platforms. Molecularly imprinted polymers (MIPs) are synthetic receptors that can form high affinity binding sites complementary to the specific analyte of interest. They utilise the shape, size, and functionality to produce sensitive and selective recognition of target analytes. One route of synthesizing MIPs is through electropolymerization, utilising predominantly constant potential methods or cyclic voltammetry. This methodology allows for the formation of a polymer directly onto the surface of a transducer. The thickness, morphology, and topography of the films can be manipulated specifically for each template. Recently, numerous reviews have been published in the production and sensing applications of MIPs; however, there are few reports on the use of electrosynthesized MIPs (eMIPs). The number of publications and citations utilising eMIPs is increasing each year, with a review produced on the topic in 2012. This review will primarily focus on advancements from 2012 in the use of eMIPs in sensing platforms for the detection of biologically relevant materials, including the development of increased polymer layer dimensions for whole bacteria detection and the use of mixed monomer compositions to increase selectivity toward analytes.


Assuntos
Técnicas Biossensoriais/métodos , Impressão Molecular/métodos , Polímeros/química , Proteínas/análise
12.
Mater Sci Eng C Mater Biol Appl ; 98: 256-265, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30813026

RESUMO

The cost-effective synthesis of novel functional nanomaterials has received significant attention in the physical and chemical sciences due to their improved surface area, high catalytic activity along with unique morphological features. This paper reports a facile and eco-friendly synthesis of spindle-like palladium nanostructures (PdSPs) on graphene oxide-cellulose microfiber (GO-CMF) composite for the first time. The GO-CMF/PdSPs composite was synthesized by an electrochemical method without the use of additional surfactants and capping agents. The synthesized materials were characterized and confirmed by using transmission electron microscopy, high-resolution scanning electron microscopy, X-ray diffraction spectroscopy, Raman spectroscopy and Fourier-transform infrared spectroscopy. As-synthesized GO-CMF/PdSPs composite modified electrode was used as a selective electrocatalyst for the oxidation of dopamine (DA). The electrochemical redox behaviors of DA were investigated using cyclic voltammetry (CV). The CV results revealed that the GO-CMF/PdSPs composite modified electrode has 10 folds enhanced oxidation current response to DA than GO, PdSPs and GO-CMF modified GCEs. Under optimized conditions, the GO-CMF/PdSPs composite sensor exhibits a linear response to DA in the concentration range from 0.3 to 196.3 µM with the lower detection limit of 23 nM. The nanocomposite electrode also shows promising features towards the reliable and selective detection of DA, which includes high stability, reproducibility and high selectivity towards the commonly interfering species such as ascorbic acid, uric acid, and dihydroxybenzene isomers. The sensor was successfully tested for the real-time detection of DA in the commercial DA injections and human serum samples.


Assuntos
Celulose/química , Dopamina/química , Grafite/química , Óxidos/química , Paládio/química , Técnicas Eletroquímicas , Eletroquímica , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Nanocompostos/química
13.
Talanta ; 198: 447-456, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30876585

RESUMO

Hypertension increases the risk of heart disease and stroke, is commonly known as a silent killer disease and considered as one of the key risk factor for premature death and disability over the world. Herein, we report for the first time a sensitive, costless and reproducible voltammetric method for individual determination of five antihypertensive drugs namely, propranolol (PRO), timolol (TIM), amlodipine (AML), amiloride (AMI) and triamterene (TRI) using differential pulse voltammetry at bare/unmodified screen-printed carbon electrodes (SPEs) in presence of sodium dodecyl sulfate (SDS). Each drug exhibits an electrochemical signal in aqueous media which is significantly enhanced in presence of optimized concentration of SDS due to accumulation of the protonated drug molecules and electrostatically interaction with negatively charged micellar structures. As a result, the spherical micellar orientation of SDS onto the graphitic surface of SPEs offered the analytically sensitive determination of the target drugs over a wide linear concentration range with nano-molar detection limits possible negating the need for any complicated surface modifications. Finally, the proposed voltammetric method was successfully utilized in the individual determination of the target antihypertensive drugs in pharmaceutical formulations and human urine samples.


Assuntos
Anti-Hipertensivos/análise , Técnicas Eletroquímicas , Impressão , Amilorida/análise , Anlodipino/análise , Avaliação Pré-Clínica de Medicamentos , Eletrodos , Humanos , Propranolol/análise , Timolol/análise , Triantereno/análise
14.
Mikrochim Acta ; 186(3): 200, 2019 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-30796537

RESUMO

The electroanalytical detection of the neurotransmitter dopamine (DA) in the presence of uric acid (UA) is explored for the first time using commercially procured nanodiamonds (NDs). These are electrically wired via surface modification upon screen-printed graphite macroelectrodes (SPEs). The surface coverage of the NDs on the SPEs was explored in order to optimize electroanalytical outputs to result in well-resolved signals and in low limits of detection. The (electro)analytical outputs are observed to be more sensitive than those achieved at bare (unmodified) SPEs. Such responses, previously reported in the academic literature have been reported to be electrocatalytic and have been previously attributed to the presence of surface sp2 carbon and oxygenated species on the surface of the NDs. However, XPS analysis reveals the commercial NDs to be solely composed of nonconductive sp3 carbon. The low/negligible electroconductivity of the NDs was further confirmed when ND paste electrodes were fabricated and found to exhibit no electrochemical activity. The electroanalytical enhancement, when using NDs electronically wired upon SPEs, is attributed not to the NDs themselves being electrocatalytic, as reported previously, but rather changes in mass transport where the inert NDs block the underlying electroactive SPEs and create a random array of graphite microelectrodes. The electrode was applied to simultaneous sensing of DA and UA at pH 5.5. Figures of merit include (a) low working potentials of around 0.27 and 0.35 V (vs. Ag/AgCl); and (b) detection limits of 5.7 × 10-7 and 8.9 × 10-7 M for DA and UA, respectively. Graphical abstract The electroanalytical enhancement of screen-printed electrodes modified with inert/non-conductive nanodiamonds is due to a change in mass transfer where the inert nanodiamonds facilitate the production of a random microelectrode array.

15.
Talanta ; 192: 471-477, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-30348420

RESUMO

Over the past decades, the synthesis of carbohydrate polymers incorporated graphene or reduced graphene oxide has received greater attention in different disciplines owing to their unique physicochemical properties. In this context, we report a facile electrochemical synthesis of cellulose microfibers supported reduced graphene oxide and its application towards enhanced and lower potential electrochemical detection of fenitrothion. The synthesized cellulose microfibers supported reduced graphene oxide composite was further characterized using Fourier-transform infrared spectroscopy, Raman spectroscopy and high resolution scanning electron microscopy. Cyclic voltammetry studies reveal that cellulose microfibers supported reduced graphene oxide composite modified screen-printed carbon electrode exhibits a superior electro-reduction ability and lower reduction potential towards fenitrothion compared to screen-printed carbon electrodes modified with graphene oxide, graphene oxide-cellulose microfibers, and reduced graphene oxide. Furthermore, cellulose microfibers supported reduced graphene oxide composite modified electrode showed 141 mV lower reduction potential towards fenitrothion than the chemically reduced graphene oxide- cellulose microfibers composite modified screen-printed carbon electrode. The effect of accumulation time, catalyst loading, scan rate and pH for the detection of fenitrothion has been studied and discussed. Differential pulse voltammetric studies show that the fabricated composite electrode can detect the fenitrothion in a wider linear response range up to 1.134 mM with a detection limit of 8 nM. To validate the proof of concept, the fabricated sensor was successfully applied for the detection of fenitrothion in different water samples.

16.
Colloids Surf B Biointerfaces ; 173: 303-311, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30308455

RESUMO

External bone fixation devices provide support and rehabilitation for severely damaged/broken bones, however, this invasive procedure is prone to infection. Zirconium nitride/silver (Ti-ZrN/Ag) coatings were characterised for surface topography, chemical composition, physicochemistry and antimicrobial efficacy (against Staphylococcus aureus and Staphylococcus epidermidis), in the presence of a blood conditioning film. The conditioning film altered the width of the microtopography of the surfaces however, the depth of the features remained relatively constant. The conditioning film also altered the coatings from hydrophobic to hydrophilic/partially hydrophilic surfaces. Following the MATH assay, the presence of a conditioning film reduced affinity towards the hydrocarbons for both microorganisms. The addition of a blood conditioning film reduced the antimicrobial efficacy of the Ti-ZrN/Ag coatings but also reduced the number of retained bacteria. This study suggests that the presence of a pre-defined blood conditioning film may result in surfaces with anti-adhesive properties, potentially leading to a reduction in bacterial retention. This, combined with the antimicrobial efficacy of the coatings, could reduce the risk of infection on biomaterial surfaces.


Assuntos
Antibacterianos/química , Células Sanguíneas/química , Materiais Revestidos Biocompatíveis/química , Plasma/química , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus epidermidis/efeitos dos fármacos , Zircônio/química , Antibacterianos/farmacologia , Aderência Bacteriana/efeitos dos fármacos , Interface Osso-Implante/microbiologia , Materiais Revestidos Biocompatíveis/farmacologia , Contagem de Colônia Microbiana , Fixadores Externos/microbiologia , Espaço Extracelular/química , Humanos , Microscopia de Força Atômica , Prata/química , Prata/farmacologia , Infecções Estafilocócicas/prevenção & controle , Staphylococcus aureus/crescimento & desenvolvimento , Staphylococcus epidermidis/crescimento & desenvolvimento , Propriedades de Superfície , Titânio/química , Titânio/farmacologia , Zircônio/farmacologia
17.
Carbohydr Polym ; 204: 152-160, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-30366526

RESUMO

In recent years, the carbohydrate polymers incorporated composite materials have shown significant interest in the bioanalytical chemistry due to their enhanced catalytic performances of various enzymes or mimics. This paper reports the fabrication of novel H2O2 biosensor using a hemin immobilized reduced graphene oxide-cellulose microfiber composite (hemin/RGO-CMF). The RGO-CMF composite was prepared by the reduction of GO-CMF composite using vitamin C as a reducing agent. Various physio-chemical methods have applied for the characterization of RGO-CMF composite. Cyclic voltammetry results revealed that the hemin/RGO-CMF composite shows a better redox electrochemical behavior than hemin/RGO and hemin/GO-CMF. Under optimized conditions, the hemin/RGO-CMF composite exhibit a linear response to H2O2 in the concentration range from 0.06 to 540.6 µM with the lower detection limit of 16 nM. The sensor also can able to detect the H2O2 in commercial contact lens solution and milk samples with functional recovery, which authenticates the potential ability in practical sensors.

18.
ACS Appl Mater Interfaces ; 10(50): 43669-43681, 2018 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-30489056

RESUMO

The transition-metal sulfide, CuS, is deemed a promising material for energy storage, mainly derived from its good chemisorption and conductivity, although serious capacity fading limits its advancement within reversible lithium storage. Learning from the gold extraction method utilizing the lime-sulfur-synthetic-solution, a CuS@S hybrid utilizing CaS x as both sulfur resource and reductant-oxidant is prepared, which is an efficient approach to apply the metallurgy for the preparation of electrode materials. Regulating the amount of CuCl2, the CuS@S is induced to reach a molecular-level hybrid. When utilized as an anode within a lithium-ion battery, it presents the specific capacity of 514.4 mA h g-1 at 0.1 A g-1 over 200 cycles. Supported by the analyses of pseudo-capacitive behaviors, it is confirmed that the CuS matrix with the suitable content of auxiliary sulfur could improve the durability of the CuS-based anode. Expanding the wider application within lithium-sulfur batteries, the synchronous growth of CuS@S exhibits stronger chemisorption with polysulfides than the mechanical mixture of CuS and S. A suite of in situ electrochemical impedance spectroscopy studies further investigates the stable resistances of the CuS@S within the charge/discharge process, corresponding to the reversible structure evolution. This systematic work may provide a practical fabricating route of metal sulfides for scalable energy storage applications.

19.
J Colloid Interface Sci ; 530: 37-45, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29960906

RESUMO

Over the past decades, the synthesis of inorganic and organic nanocomposites has received much attention in the range of fields including electroanalysis of organic chemicals. In this regard, we have prepared copper oxide nanoparticle (CuO NPs) decorated graphene/ß-cyclodextrin (GR-ß-CD) composites using a simple electrochemical methodology, where the CuO NPs are electrodeposited on GR-ß-CD composite modified electrodes. A stable GR-ß-CD composite was prepared by sonication of GR in ß-CD aqueous solution. As-prepared GR-ß-CD/CuO NPs composites were characterized by the high-resolution scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Cyclic voltammetry results reveal that the GR-ß-CD/CuO NPs composite modified electrode exhibits an excellent catalytic activity and lower reduction potential towards the electrochemical detection of metronidazole (MTZ) over other modified electrodes including GR, GR-ß-CD, and CuO NPs. Under optimized conditions, amperometry was used for the determination of MTZ using GR-ß-CD/CuO NPs composite modified electrodes. The response of MTZ using the composite electrodes was linear over the range from 0.002 to 210.0 µM. This sensor showed the lowest limit of detection of 0.6 nM and was much lower than the previously reported MTZ sensors. In addition, the sensor is highly sensitive, selective and durable in the presence of a range of potentially interfering electroactive compounds.


Assuntos
Antibacterianos/análise , Cobre/química , Grafite/química , Metronidazol/análise , Nanopartículas/química , beta-Ciclodextrinas/química , Técnicas Eletroquímicas/métodos , Eletrodos , Grafite/síntese química , Limite de Detecção , Nanopartículas/ultraestrutura , Nanotecnologia , Comprimidos , Difração de Raios X , beta-Ciclodextrinas/síntese química
20.
Phys Chem Chem Phys ; 20(30): 20010-20022, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30022207

RESUMO

We report the fabrication, characterisation (SEM/EDX, TEM, XRD, XPS and Raman spectroscopy) and electrochemical properties of graphite and graphene paste electrodes with varying lateral flake sizes. The fabricated paste electrodes are electrochemically analysed using both outer-sphere and inner-sphere redox probes, namely; hexaammineruthenium(iii) chloride, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), potassium ferrocyanide(ii) and ammonium ferrous(ii) sulphate. Upon comparison of different graphite paste electrodes, a clear correlation between the lateral flake sizes (La), ranging from 1.5 mm-0.5 µm, and electrochemical activity (heterogeneous electron transfer (HET) kinetics) is evident, where an improvement in the HET is observed at smaller lateral flake sizes. We infer that the beneficial response evident when employing laterally smaller flakes is due to an increased number of edge plane like-sites/defects available upon the electrode surface, facilitating electron transfer. Interestingly, given that the overall lateral flake sizes of the graphenes utilised (10.0-1.3 µm) were significantly smaller than those studied previously, an improvement in HET kinetics was also evident with the reduction of lateral flake size; the extent to which is redox-probe dependent. Improvements are observed up to a distinct point, termed the 'lateral size threshold' (ca. ≤2 µm) where the electrochemical reversible limit is approached. Further support is provided from density functional theory (DFT), exploring the electronic structure (i.e. HOMO-LUMO) as a function of flake size, which demonstrates that the coverage of edge plane like-sites/defects comprising the geometric structure of the relatively small graphene flakes is such that effectively the entire flake has become electrochemically active. In this study, the importance of lateral flake size with respect to electrochemical reactivity at carbon-based electrodes has been demonstrated alongside a structural relationship upon HET performance, a phenomenon that has not previously been described in the literature. Such work is both highly important and informative for the field of electrochemistry and electrode performance, with potential implications in a plethora of areas, ranging from novel renewable energy sources to electroanalytical sensing platforms.

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