Search

Fabrication of perovskite solar cells based on antisolvent treatment has attracted enormous attentions due to the great potential of achieving better crystallization and relatively high efficiency of the solar cells. Two main challenges to fabricating perovskite solar cells are hysteresis and their sensitivity to preliminary conditions, especially air moisture and oxygen. Here, we have investigated the dependency of different antisolvent effects including toluene, chloroform, chlorobenzene, dioxane, and isopropanol on the hysteresis of ambient-processed perovskite cells. The findings show that for fabrication of the cells in ambient conditions, efficient cells can be produced by using toluene antisolvent in comparison with the other ones, where the efficiency of this cell reached 12%. While the best hysteresis index occurs in the cells fabricated by employing chlorobenzene as antisolvent with the minimum value of 0.003, these findings shed light on the efficacy of different antisolvents in optimizing perovskite solar cell performance in ambient environments. [ABSTRACT FROM AUTHOR]

The development of an electrochemical aptasensor for the detection of CA125 as an ovarian cancer biomarker using gold nanostructures (GNs) modified electrodes is reported. The GNs were deposited on the surface of fluorine-doped tin oxide electrodes using a simple electrochemical method and the effects of pH and surfactant concentration on the topography and electrochemical properties of the resulting GNs modified electrodes were investigated. The electrodes were characterized using field-emission scanning electron microscopy and X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. The best electrode, in terms of the uniformity of the deposited GNs and the increase in electroactive surface area, was used for development of an aptasensor for CA125 tumor marker detection in human serum. Signal amplification was done by using aptamer-conjugated gold nanorods resulting in the detection limit of 2.6 U/ml and a linear range of 10 to 800 U/ml. The results showed that without the need for expensive antibodies, the developed aptasensor could specifically measure the clinically relevant concentrations of the tumor marker in human serum. [ABSTRACT FROM AUTHOR]

The core–shell non-enzymatic glucose sensors are generally fabricated by chemical synthesis approaches followed by a binder-based immobilization process. Here, we have introduced a new approach to directly synthesis the core–shell of Au@Cu and its Au@CuxO oxides on an FTO electrode for non-enzymatic glucose detection. Physical vapor deposition of Au thin film followed by thermal annealing has been used to fabricate Au nanocores on the electrode. The Cu shells have been deposited selectively on the Au cores using an electrodeposition method. Additionally, Au@Cu2O and Au@CuO have been synthesized via post thermal annealing of the Au@Cu electrode. This binder-free and selective-growing approach has the merit of high electrooxidation activity owing to improving electron transfer ability and providing more active sites on the surface. Electrochemical measurements indicate the superior activity of the Au@Cu2O electrode for glucose oxidation. The high sensitivity of 1601 μAcm−2 mM−1 and a low detection limit of 0.6 μM are achieved for the superior electrode. Additionally, the sensor indicates remarkable reproducibility and supplies accurate results for glucose detection in human serums. Moreover, this synthesis approach can be used for fast, highly controllable and precise fabrication of many core–shell structures by adjusting the electrochemical deposition and thermal treatment parameters. [ABSTRACT FROM AUTHOR]

We report on producing up to 403 W average power directly from an acousto-optically Q-switched Yb:YAG thin-disk laser (TDL). To achieve this power, it has theoretically and experimentally been shown that the laser stability border could be shifted toward higher repetition rates by engineering of the output coupler transmittance. This allows for stable operation of the laser at higher frequencies and a further increase in the power extraction from the active medium. Using an output coupler with 93% reflectivity, a maximum average power of 403 W at the repetition rate of 12.0 kHz has been recorded under the pump power of 1220 W. Furthermore, the maximum pulse energy of 57 mJ was produced at the repetition rate of 1.00 kHz and the pump power of 520 W. The characteristics of the laser at various Q-switching rates and the pump powers have been investigated. In addition, a numerical study for supporting the experimental results has been proposed here. To the best of our knowledge, the achieved average power and the pulse energy are the highest values reported to date from a Q-switched Yb:YAG TDL. The results pave the way to further power scaling of solid-state Q-switched oscillators. [ABSTRACT FROM AUTHOR]

A facile and sensitive approach is introduced to precisely determine trace amounts of prostate specific antigen (PSA) by gold nanostructures deposited on fluorine-doped tin oxide (FTO) electrodes. The gold electrode fabrication is carried out by integration of two techniques of vacuum-deposition and electrochemical growth. The electrode was successfully used as a label-free immunosensor for PSA determination in human serum samples. The dependency of the biosensor performance on various fabrication parameters have been investigated and the optimized fabrication rout has been specified. This label-free immunosensor presents a noticeable performance with a large range of linearity from 0.05 to 30 ng/mL, a low detection limit of 5.7 pg/mL, and a long-term stability of 4 weeks. The obtained results for PSA determination in real samples show a good agreement with ELISA results with less than 10% deviation. [ABSTRACT FROM AUTHOR]

Label-free detection of biomarkers has been recently noticed and optical biosensors showed great potential to be the method of choice in such situation. Here, we used glancing angle deposition (GLAD) method in which silver nano-columns stabilized by a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (MUA) and 6-mercaptohexanol to investigate the capability of localized surface plasmon resonance (LSPR)–based silver nanochips to detect prostate-specific antigen (PSA). Using different standard solutions of PSA, limit of detection (LOD) of the nano-sensors has been calculated to be 850 pg/ml. The selectivity of the nano-sensors has also been evaluated. We showed that these nano-sensors could detect PSA in clinically acceptable sensitivity and specificity without any complicated laboratory equipment. [ABSTRACT FROM AUTHOR]

A bimetallic nanostructure of Co/Cu for the non-enzymatic determination of glucose is presented. The heterostructure includes cobalt thin film on a porous array of Cu nanocolumns. Glancing angle deposition (GLAD) method was used to grow Cu nanocolumns directly on a fluorine-doped tin oxide (FTO) substrate. Then a thin film of cobalt was electrodeposited on the Cu nanostructures. Various characterization studies were performed in order to define the optimum nanostructure for the determination of glucose. The results showed remarkable boosting of the electrocatalytic activity of Co/Cu bimetallic structure compare to the responses achieved by the monometallic structures of Co or Cu. The sensor showed two linear response ranges for the determination of glucose at 0.55 V in 0.1 M NaOH, from 5 μM–1 mM and 2–9 mM. The sensitivity was 1741 (μA mM−1 cm−2) and 626 (μA mM−1 cm−2), respectively, while the detection limit for a signal-to-noise ratio of 3 was found to be 0.4 μM. The sensor exhibited excellent selectivity and was successfully applied to the determination of glucose in real human blood serum samples. [ABSTRACT FROM AUTHOR]

A new approach has been developed to improve sensing performances of electrochemically grown Au nanostructures (AuNSs) based on the pre-seeding of the electrode. The pre-seeding modification is simply carried out by vacuum thermal deposition of 5 nm thin film of Au on the substrate followed by thermal annealing at 500 °C. The electrochemical growth of AuNSs on the pre-seeded substrates leads to impressive electrochemical responses of the electrode owing to the seeding modification. The dependence of the morphology and the electrochemical properties of the AuNSs on various deposition potentials and times have been investigated. For the positive potentials, the pre-seeding leads to the growth of porous and hole-possess networks of AuNSs on the surface. For the negative potentials, AuNSs with carved stone ball shapes are produced. The superior electrode was achieved from AuNSs developed at 0.1 V for 900 s with pre-seeding modification. The sensing properties of the superior electrode toward glucose detection show a high sensitivity of 184.9 µA mM−1 cm−2, with a remarkable detection limit of 0.32 µM and a wide range of linearity. The excellent selectivity and reproducibility of the sensors propose the current approach as a large-scale production route for non-enzymatic glucose detection. [ABSTRACT FROM AUTHOR]

Metal-enhanced fluorescence (MEF) phenomenon has shown a promising potential in the field of fluorescence-based biological sensing. In this study, we optimized the electroless metal deposition method to fabricate silver dendritic nanostructures as effective MEF active substrates. Then, an aptasensor was developed for thrombin detection using the established surfaces. For this purpose, thiolated 29-mer thrombin-binding aptamers (TBA29 (12T) SH) as capturing aptamer were immobilized on the surface of silver dendritic nanostructures, then thrombin was sandwiched between the capturing aptamer and Cy5-labeled 15-mer thrombin aptamer (TBA15-Cy5). Quantitative analysis was performed through fluorescence signal measurement. The established aptasensor presented satisfactory sensitivity and selectivity and exhibited a limit of detection (LOD) as low as 32 pM. This aptasensor was also able to detect thrombin in the human serum at picomolar levels. Furthermore, the ease and relatively low-cost of fabrication of this platform introduce it as a tool with great potential for the clinical diagnosis of diseases and also for improving sensitivity of a variety of technologies which exploit fluorescent dyes for analyte detection, at ultra-trace levels, in complex matrices. [ABSTRACT FROM AUTHOR]

We report on remarkable improvement of photoelectrochemical (PEC) properties of TiO2 nanotubes by loading of Ag nanoparticles into them. The silver nanoparticles were loaded on the nanotubes by sequential chemical bath deposition (S-CBD) with different number of deposition cycles. Various characterizations including field emission scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis (EDX), all confirm that the silver nanoparticles were deposited inside and outside of TiO2 nanotubes. In addition, the PEC properties of the samples were investigated using linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The PEC analyses clearly show that the photo-electrochemical activity of the Ag-loaded samples are considerably higher than the bare TiO2 nanotubes (about 3 times). This mostly originates from the improvement of light absorption due to the plasmonic effects in addition to better separation and transport of electron-hole pairs in the Ag-loaded samples relative to the bare TiO2 nanotubes. All results indicate that the maximum efficiency were obtained for the 8-cycle of S-CBD Ag-loading on the bare TiO2 nanotubes. [ABSTRACT FROM AUTHOR]

Although glancing angle deposited silver substrates offer an excellent figures for surface enhanced Raman scattering (SERS) sensing, the chemical instability issues of silver substrates upon exposure to the aqueous solutions is still challenging and limits their application in SERS-based biosensors. In this context, we applied and compared two different strategies including sodium citrate as a self-assembled monolayer (SAM), and thermal deposition of gold at different thicknesses to stabilize the silver chevron arrays deposited by the glancing angle deposition method. Although optical characterization confirms good stabilization in both strategies, intact morphological features can only be detected after gold coating compared to sodium citrate coating which makes a homogenous monolayer on the surface. Furthermore, the SERS intensity of Rhodamine B increases after these coating processes, which might be due to the less oxidation and deformation of the nanostructures on the substrate or improved attachment of the analyte to the substrates. This research can extend our knowledge for the development of stable and reproducible SERS substrates in the field of biological sensing. [ABSTRACT FROM AUTHOR]

Chemical adsorption and sensing reactions of liquid petroleum gas over the surface and between grain boundaries of nanostructured zinc oxide thin films were investigated and monitored under the influence of various post-synthesis thermal annealing and target gas concentration conditions. Prior to sensing tests, zinc oxide thin films were synthesized in three steps: at first, zinc oxide nanoparticles were synthesized by a sol-gel method using zinc acetate dihydrate, ethanol and monoethanolamine as precursor, solvent and stabilizing agent, respectively. Then, untreated zinc oxide thin films were prepared from zinc oxide sol through spin coating procedure and finally, thermal post-annealing treatment with different temperatures was performed to yield heated thin films. The formation of the synthesized nanoparticles, morphology, crystalline size, porosity and transparency of final thin films were characterized by field emission-scanning electron microscopy, X-ray diffraction and ultraviolet-visible spectroscopy techniques. Sensing tests showed the dependence of the liquid petroleum gas detection on the thermal annealing process and gas concentration and indicated a maximum response of 75 % at the operation temperature of 300 °C for the zinc oxide film pre-annealed at 600 °C and 1,000 ppm gas. Moreover, the results exhibit excellent sensitivity for the sensor via short response and recovery times of 34 and 220 s, respectively. [ABSTRACT FROM AUTHOR]