Self-healing 2D/3D perovskite for efficient and stable p-i-n perovskite solar cells.

Beyond the p-i-n perovskite solar cell's high-power conversion efficiency (PCE), its moisture instability is the most challenging factor in its commercialization. Recently, the innovative use of three and two-dimensional multi-structures, by creating a barrier against the penetration of moisture and oxygen, has played a very influential role in improving the PSC's long-term stability. Here, a new strategy, the anti-solvent quenching method, is used to construct multi-structure perovskite by involving cetyltrimethylammonium bromide (CTAB) as an active agent. The solar cell efficiency is significantly improved during the perovskite formation on the substrate by creating a multidimensional (2D/3D) heterojunction perovskite. The synergistic role of using 2D/3D heterojunction perovskite structures led to the 29.2% improvement (14.58-18.84) in the PCE. The attractive ability of the 2D/3D active layer in self-healing has increased the perovskite's long-term stability under harsh environmental conditions.

Ultrasensitive electrochemical molecularly imprinted sensor based on AuE/Ag-MOF@MC for determination of hemoglobin using response surface methodology.

Considering the importance of determining the levels of hemoglobin (Hb) as a vital protein in red blood cells, in this work a highly sensitive electrochemical sensor was developed based on a gold electrode (AuE) modified with Ag metal-organic framework mesoporous carbon (Ag-MOF@MC) and molecularly imprinted polymers (MIPs). To that end, the MIP layer was formed on the Ag-MOF@MC by implanting Hb as the pattern molecule during the polymerization. The modified electrode was designed using electrochemical approaches including differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Using a response level experimental design method, the most important parameters affecting the reaction of the sensing system including pH, incubation time, and scanning rate were optimized. Following the same route, the Hb concentration, pH, temperature, and elution times were optimized to prepare the imprinted polymer layer on the Ag-MOF@MC surface. By exploiting DPV techniques based on the optimal parameters, the electrochemical response of the AuE/Ag-MOF@MC-MIPs for Hb determination was recorded in a wide linear dynamic range (LDR) of 0.2 pM to 1000 nM, with a limit of detection (LOD) of 0.09 pM. Moreover, the Ag-MOF@MC-MIP sensing system showed good stability, high selectivity, and acceptable reproducibility for Hb determination. The sensing system was successfully applied for Hb determination in real blood samples, and the results were compared with those of the standard methods for Hb determination. Acceptable recovery (99.0%) and RDS% (4.6%) confirmed the applicability and reliability of the designed Hb sensing system.

Ultra-sensitive and selective electrochemical biosensor with aptamer recognition surface based on polymer quantum dots and C60/MWCNTs- polyethylenimine nanocomposites for analysis of thrombin protein.

In this study, an ultra-sensitive and selective Thrombin biosensor with aptamer-recognition surface is introduced based on carbon nanocomposite. To prepare the this biosensor, screen-printed carbon electrodes (SPCE) were modified with a nanocomposite made from fullerene (C60), multi-walled carbon nanotubes (MWCNTs), polyethylenimine (PEI) and polymer quantum dots (PQdot). The unique characteristics of each component of the C60/MWCNTs-PEI/PQdot nanocomposite allow for synergy between nanoparticles while polymer quantum dots resulted in characteristics such as high stability, high surface to volume ratio, high electrical conductivity, high biocompatibility, and high mechanical and chemical stability. The large number of amine groups in C60/MWCNTs-PEI/PQdot nanocomposite created more sites for better covalent immobilization of amino-linked aptamer (APT) which improved the sensitivity and stability of the aptasensor. Differential Pulse Voltammetry (DPV) method with probe solution was used as the measurment method. Binding of thrombin protein to aptamers immobilized on the transducer resulted in reduced electron transfer at the electrode/electrolyte interface which reduces the peak current (IP) in DPV. The calibration curve was drawn using the changes in the peak current (ΔIP),. The proposed aptasensor has a very low detection limit of 6 fmol L-1, and a large linear range of 50 fmol L-1 to 20 nmol L-1. Furthermore, the proposed C60/MWCNTs-PEI/PQdot/APT aptasensor has good reproducibility, great selectivity, low response time and a good stability during its storage. Finally, the application of the proposed aptasensor for measuring thrombin on human blood serum samples was investigated. This aptasensor can be useful in bioengineering and biomedicine applications as well as for clinical studies.

Novel synthesis of a dual fluorimetric sensor for the simultaneous analysis of levodopa and pyridoxine.

Herein, a fluorimetric sensor was fabricated based on molecularly imprinted polymers (MIPs) with two types of carbon dots as fluorophores. The MIPs produced had similar excitation wavelengths (400 nm) and different emission wavelengths (445 and 545 nm). They were used for the simultaneous analysis of levodopa and pyridoxine. First, two types of carbon dots, i.e. nitrogen-doped carbon dots (NCDs) with a quantum yield of 43%, and carbon dots from o-phenylenediamine (O-CDs) with a quantum yield of 17%, were prepared using the hydrothermal method. Their surfaces were then covered with MIPs through the reverse microemulsion method. Finally, a mixture of powdered NCD@MIP and O-CD@MIP nanocomposites was used for the simultaneous fluorescence measurement of levodopa and pyridoxine. Under optimal conditions using response surface methodology and Design-Expert software, a linear dynamic range of 38 to 369 nM and 53 to 457 nM, and detection limits of 13 nM and 25 nM were obtained for levodopa and pyridoxine, respectively. The capability of the proposed fluorimetric sensor was investigated in human blood serum and urine samples. Graphical Abstract Schematic representation of nitrogen-doped carbon dots (NCDs), carbon dots from o-phenylenediamine (O-CDs), NCDs coated with imprinted polymers (NCD@MIPs), and O-CDs coated with imprinted polymers (O-CD@MIPs) in the presence and absence of levodopa and pyridoxine.

Preparation and comparison of molecularly imprinted polymer fluorimetric nanoprobe based on polymer dots and carbon quantum dots for determination of acetamiprid using response surface method.

In this study molecularly imprinted polymers (MIP) based on carbon quantum dots (CQDs) and polymer dots (PDs) are developed for selective determination of acetamiprid using fluorometry. The measurement is based on the fluorescence quenching of CQDs and PDs in the presence of acetamiprid. PDs were prepared using a one-step aqueous synthesis method from ascorbic acid and diethylenetriamine at room temperature. CQDs were prepared from the same materials using the hydrothermal method at 180 °C. These particles were characterized using field emission scanning electron microscopy (FE-SEM), FTIR, dynamic light scattering (DLS), X-ray diffraction (XRD), UV-Vis, and fluorescence. The quantum yield was 47% for PDs and 8% for CQDs. Then, molecularly imprinted polymers (MIP) were prepared based on PDs and CQDs using reverse microemulsion method. The fluorescence quenching of CQD@MIPs and PD@MIPs was investigated at an excitation wavelength of 350 nm and emission wavelength of 440 nm in the presence of a template. Other variables affecting the fluorescence peaking were optimized using design expert software. The results illustrate that the use of PD@MIPs had a wide dynamic range 0.08-109 nmol L-1, good accuracy and detection limit of 0.02 nmol L-1, while using CQD@MIPs led to a lower dynamic range 0.36-64 nmol L-1, and detection limit of only 0.11 nmol L-1. The responses of the optical nanoprobe for acetamiprid in water (recovery 92-102%) and apple (recovery 92-103%) were also investigated. Graphical abstract Schematic representation of preparation polymer dots (PDs), carbon quantum dots (CQDs), PDs coated with imprinted polymers (PD@MIPs), and CQDs coated with imprinted polymers (CQD@MIPs) in the presence and absence of acetamiprid.

Design a fluorometric aptasensor based on CoOOH nanosheets and carbon dots for simultaneous detection of lysozyme and adenosine triphosphate.

Simultaneous detection of biomarkers and biomolecules with great analytical performance still is challenging. A simple fluorometric dual-functional aptasensor was designed to detect Lysozyme (LYS) and adenosine triphosphate (ATP) as models of a protein and a small molecule simultaneously. The sensing principle of the aptasensor is based on the interactions between cobalt oxyhydroxide CoOOH nanosheets as fluorescence quencher and carbon dots (CDs) as fluorophores. The aptamer labeled with CDs was able to assemble on CoOOH nanosheets and consequently, the fluorescence signal was quenched. With addition target analytes to the system, the aptamers folded around of targets with a strong and specific affinity. Therefore, the labeled aptamer with CDs was detached from CoOOH nanosheets and the fluorescence signal was restored. The fluorescence spectral overlap of these two CDs is the main limitation for the simultaneous analysis. The least squared support vector machine (LS-SVM) was applied to resolve this problem. Under optimal conditions, when LS-SVR was used, detection limits were found 4.0 and 1.8 nmol L-1 for ATP and LYS. The parallel biosensor is capable of monitoring ATP and LYS levels in the biological samples with satisfactory results.

Sensitive imprinted optical sensor based on mesoporous structure and green nanoparticles for the detection of methamphetamine in plasma and urine.

Methamphetamine (MA), a psychoactive substance with many medicinal applications in different countries, has destructive impacts on the nervous system and brain and can lead to addiction. The optimal system for MA determination must be able to measure the tiny amount of MA in complex matrixes accurately. In the current work, a simple and biocompatible sensitive optical probe was developed based on molecularly imprinted polymers (MIPs) technique and by using green CQDs and mesoporous structured imprinting microspheres (SiO2@CQDs@ms-MIPs). CQDs (ФF = 33%) were synthesized via the hydrothermal method using natural chewing gum as carbon source. SiO2 nanoparticles were used as the backup substrate for the placement of CQDs. In spite of biocompatibility, porosity and having high specific area are the unique features of SiO2 nanoparticles. When MA is present, the fluorescence response of MIPs enhances. This is caused by the passivation and adjustment of active clusters that are present on the surface of CQDs. By this optical sensor, the favorable linear dynamic range (5.0-250 µM) and the detection limit (1.6 µM) were obtained. The applicability of the advanced sensor was studied in real samples such as human urine and human blood plasma. Acceptable results were obtained and recovery amounts were in the 92-110% interval.

The investigation of Amido black 10B adsorption-photocatalytic degradation using the synergistic effect of Cr-doped ZnO/CDs nanocomposite under solar light.

In this work, the modification of ZnO nanoparticles with green synthesized carbon dots and Cr yielded a nanocomposite named Cr-doped ZnO/CDs. Further, 0.48 g/L of this nanocomposite was able to remove (95 ± 1) % of 25 mg/L Amido black 10B (AB10B) from a solution, by adsorption process less than 5 min. The photocatalytic property of Cr-doped ZnO/CDs was able to improve the removal efficiency of AB10B to 99% during irradiation of sunlight within 15 min. The maximum adsorbent capacity of Cr-doped ZnO/CDs nanocomposite was 152.4 mg/g. Unmodified ZnO nanoparticles (0.48 g/L) were able to remove only 30% of the dye within 60 min of irradiation. Its modification showed coupling the absorption and photocatalytic process dramatically increased the dye removal efficiency. Adsorption isotherm investigation indicated that the experimental data were fitted satisfactorily by the Langmuir model. This method is an economical method because the Cr-doped ZnO/CDs synthesis was easy and inexpensive, the dye removal time was very short, and infinite sunlight is required to remove the dye with high efficiency. Graphical abstract.

An ultrasensitive electrochemical anti-lysozyme aptasensor with biorecognition surface based on aptamer/amino-rGO/ionic liquid/amino-mesosilica nanoparticles.

In this work, a novel method based on aptamers is proposed for electrochemical measurement of lysozyme. To this end, screen-printed carbon electrode (SPCE) was modified with a nanocomposite made from amino-reduced graphene oxide (Amino-rGO) synthesized from natural graphite powder, an ionic liquid (IL), and amino-mesosilica nanoparticles (Amino-MSNs). The composition of the nanocomposite (Amino-rGO/IL/Amino-MSNs) results in high thermal and chemical stability, conductivity, surface-to-volume ratio, cost efficiency, biocompatibility, and great bioelectrocatalysis characteristics. Presence of numerous amino groups, as well as remaining oxygen defects in rGO, provides a suitable site for immobilization of aptamers. Furthermore, use of this nanocomposite leads to considerable enhancement of the electrochemical signal and improved method sensitivity. Covalent coupling of aptamer's amino groups with that of the nanocomposite using glutaraldehyde (GLA) as a linker helps immobilize amino-linked lysozyme aptamers (Anti-Lys aptamers) on nanocomposite. The modified electrode was characterized using electrochemical methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The immobilized aptamer selectively adsorbs lysozyme (Lys) on the electrode interface, leading to increased Charge Transfer Resistance (RCT) in EIS and decrease in the DPV peak currents which are used as analytical signals. Two separate calibration curves were drawn using the data acquired from EIS and DPV. The prepared anti-Lys aptasensor has two very low LODs equal to 2.1 and 4.2 fmol L-1 with wide detection ranges of 10 fmol L-1 to 200 nmol L-1, and 20 fmol L-1 to 50 nmol L-1 for EIS and DPV calibration curves, respectively. The SPCE/Amino-rGO/IL/Amino-MSNs/APT also showed high reproducibility, specificity, sensitivity, and rapid response to Lys which has various applications in fields of bioengineering and biomedicine.

Manufacturing of a Sensitive and Selective Optical Sensor Based on Molecularly Imprinted Polymers and Green Carbon Dots Synthesized from Cedrus Plant for Trace Analysis of Propranolol.

In this article, a new optical sensor was developed using a molecularly imprinted polymers layer coated with new green carbon dots (CDs) for the determination of propranolol. First, the CDs were synthesized for the first time from Cedrus plant through the hydrothermal method. Then, a nanolayer molecularly imprinted polymer (MIP) was applied on the CDs (MIP-CDs) in the presence of propranolol as a template using a reverse microemulsion technique. Afterward, propranolol was removed from MIP-CDs nanocomposites using a mixture of ethanol and acetonitrile, and the obtained nanocomposite was used as a fluorescence sensor for propranolol determination. Under the optimal conditions, the sensor response was linear in the range of 0.8 - 65.0 nmol L-1 with a detection limit of 0.2 nmol L-1. The results confirmed that the sensor has some advantages such as cost-effectiveness, rapid response, high sensitivity and selectivity for propranolol determination.

Application of coated green source carbon dots with silica molecularly imprinted polymers as a fluorescence probe for selective and sensitive determination of phenobarbital.

Herein, a selective and sensitive fluorescence sensor was developed for the detection of phenobarbital, an epilepsy drug, using molecularly imprinted polymers (MIPs) coated on the surface of green source carbon dots (GSCDs). First, GSCDs were synthesized through a hydrothermal method using Cedrus as a carbon source. Then, a MIPs-GSCDs as a fluorescence probe was obtained by coating a thin film of silica on the surface of the GSCDs using a reverse micro emulsion method. In this step, phenobarbital, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were applied as a template, a functional monomer, and cross linker, respectively. The fluorescence signal of MIPs-GSCDs was selectively quenched by phenobarbital rebinding with MIP cavities. The fluorescence quenching signal was applied for phenobarbital sensing at the pH = 8 without the interference of other materials. After optimizing the factors affecting the sensor's response, a linear range between 0.4 and 34.5 nmol L-1 with a detection limit of 0.1 nmol L-1 was obtained. The sensor's capability in the real sample analysis was investigated by phenobarbital determination in a human blood plasma samples.

An ultrasensitive and selective electrochemical aptasensor based on rGO-MWCNTs/Chitosan/carbon quantum dot for the detection of lysozyme.

An aptamer-based method is described for the electrochemical determination of lysozyme. A glassy carbon electrode was modified with a nanocomposite composed of reduced graphene oxide (rGO), multi-walled carbon nanotubes (MWCNTs), chitosan (CS), and a synthesized carbon quantum dot (CQD) from CS. The composition of the nanocomposite (rGO-MWCNT/CS/CQD) warrants a high surface-to-volume ratio, high conductivity, high stability, and great electrocatalytic activity. This nanocomposite provides a suitable site for better immobilization of aptamers due to the existence of many amino and carboxyl functional groups, and remaining oxygen-related defects properties in rGO. In addition, this nanocomposite allows considerable enhancement of the electrochemical signal and contributes to improving sensitivity. The amino-linked lysozyme aptamers were immobilized on the nanocomposite through covalent coupling between the amino groups of the aptamer and the amino groups of the nanocomposite using glutaraldehyde (GLA) linker. The modified electrode was characterized by electrochemical methods including differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). In the presence of lysozyme, the immobilized aptamer selectively caught the target lysozyme on the electrode interface that leads to a decrease in the DPV peak current and an increase in Charge Transfer Resistance (Rct) in EIS as an analytical signal. Using the obtained data from DPV and EIS techniques, two calibration curves were drawn. The anti-lysozyme aptasensor proposed has two very low LODs. These measures are 3.7 and 1.9 fmol L-1 within the wide detection ranges of 20 fmol L-1 to 10 nmol L-1, and 10 fmol L-1 to 100 nmol L-1 for DPV and EIS calibration curves, respectively. The GCE/rGO-MWCNT/CS/CQD showed sensitivity, high reproducibility, specificity and rapid response for lysozyme which can be used in biomedical fields.

Lysozyme aptasensor based on a glassy carbon electrode modified with a nanocomposite consisting of multi-walled carbon nanotubes, poly(diallyl dimethyl ammonium chloride) and carbon quantum dots.

An aptamer-based method is described for electrochemical determination of lysozyme. A glassy carbon electrode was modified with a nanocomposite composed of multi-walled carbon nanotubes, poly(diallyl dimethyl ammonium chloride), and carbon quantum dots. The composition of the nanocomposite (MWCNT/PDDA/CQD) warrants good electrical conductivity and a high surface-to-volume ratio. The lysozyme-binding aptamers were immobilized on the nanocomposite via covalent coupling between the amino groups of the aptamer and the carboxy groups of the nanocomposite. The modified electrode was characterized by electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The use of this nanocomposite results in a considerable enhancement of the electrochemical signal and contributes to improving sensitivity. Hexacyanoferrate was used as an electrochemical probe to study the dependence of the peak current on lysozyme concentration. In the presence of lysozyme, the interaction of lysozyme with immobilized aptamer results in a decrease of the peak current, best measured at +0.15 V vs. Ag/AgCl. A plot of peak current changes versus the logarithm of the lysozyme concentration is linear in the 50 fmol L-1 to 10 nmol L-1 concentration range, with a 12.9 fmol L-1 detection limit (at an S/N ratio of 3). The method is highly reproducible, specific and sensitive, and the electrode has a rapid response. It was applied to the determination of lysozyme in egg white, serum, and urine. Graphical abstract Schematic of a nanocomposite composed of multi-walled carbon nanotubes (MWCNTs), poly(diallyldimethyl ammonium chloride) (PDDA), and carbon quantum dots (CQDs) for use in a lysozyme aptasensor. The aptamer was immobilized on the surface, and bovine serum albumin (BSA) was applied to block the surface. The changes of peak current for the electrochemical probe hexacyanoferrate (Fe(CN)63-/4-) in the presence and absence of lysozyme was traced.

Determination of losartan and triamterene in pharmaceutical compounds and urine using cathodic adsorptive stripping voltammetry.

A square-wave voltammetric procedure for the electroanalytical determination of losartan and triamterene in Britton-Robinson buffer (pH 3.0, 0.1 mol L(-1)) as a supporting electrolyte containing 30 ng mL(-1) of copper ions was developed. Opposite to the case of triamterene, losartan can not be reduced at a mercury electrode alone, but a new peak appears at -0.25 V in the presence of copper due to the formation of a complex between copper(II) and losartan. An accumulation potential of -0.30 V during 80 s for the prior adsorption of losartan-copper(II) and triamterene on the electrode surface was used. The response of the system was found to be linear in the range of 30.0 - 270.0 nmol L(-1) for losartan and two linear dynamic ranges containing 0.5-200.0 and 200.0-400.0 nmol L(-1) of triamterene. The limits of detections were 9.7 and 0.3 nmol L(-1) for losartan and triamterene, respectively. The relative standard deviations for five replicate analyses of 100.0 and 10.0 nmol L(-1) losartan and triamterene were 5.5%. Applicability to assay the drugs in urine and pharmaceutical formulations was illustrated with satisfactory results. The direct-current polarography of triamterene indicates that the reduction of a related drug is strongly dependent on the pH of the solution. A linear segment was found with slope value of -63.6 mV pH(-1) in the pH range of 2.0 - 6.0. The stoichiometry and complex formation constant (beta) for losartan-Cu(II), number of transfer electrons (n), transfer coefficients (alpha) and number of proton transfers were also estimated.

Flow-injection determination of ascorbic acid and cysteine simultaneously with spectrofluorometric detection.

A simple and sensitive spectrofluorometric method was developed for the simultaneous determination of ascorbic acid and cysteine by a flow-injection system. This method is based on the reduction of Tl(III) with ascorbic acid or cysteine in acidic media, producing fluorescence reagent, TlCl3(2-) (lambdaex = 227 nm, lambdaem = 419 nm). The injected sample solution was divided into two separate streams. The first stream was treated with Tl(III) at pH 3.0 and then passed through a 270 cm reaction coil to the flow cell of the spectrofluorometer, where the fluorescence intensity was measured. This signal is related to ascorbic acid and cysteine concentration. The second part of the injected sample solution was treated with Tl(III) in HCl solution and then passed through a 50 cm reaction coil to the flow cell and the fluorescence intensity was measured. This signal is related only to cysteine. Thus, the ascorbic acid content was determined directly by the difference according to the calibration curve. Ascorbic acid and cysteine can be determined in the range of 1 x 10(-6) to 5.0 x 10(-5) M, at a rate of 16 samples per hour. The limits of detection (S/N = 3) were 8 x 10(-7) M for ascorbic acid and 7 x 10(-7) M for cysteine. The influence of potential interfering substances was studied. The proposed method was successfully applied to the simultaneous determination of both analytes in real samples.

Flow injection determination of formaldehyde by its catalytic effect on the oxidation of sulfonazo III by bromate with spectrophotometric detection.

A simple and sensitive flow injection method with spectrophotometric detection was developed for the determination of formaldehyde. The method is based on the catalytic effect of formaldehyde on the oxidation of sulfonazo III with bromate in acidic media. The decrease in absorbance of the reaction mixture was measured at 566 nm. The calibration graph was linear in the range of 0.005 to 2.80 microg ml(-1) formaldehyde at a rate of 38 +/- 4 samples h(-1). The limit of detection was 4 ng ml(-1). The relative standard deviations for ten replicate measurements of 0.20, 0.50 and 1.00 microg ml(-1) formaldehyde were 1.3, 0.8 and 0.7%, respectively. The method was applied to the determination of formaldehyde in river water, shampoo and melamine-formaldehyde resin.

Simultaneous spectrophotometric determination of nitrite and nitrate by flow injection analysis.

A new catalytic spectrophotometric method is reported for the simultaneous determination of nitrite and nitrate by flow injection analysis, based on the catalytic effect of nitrite on the redox reaction between pyrogallolsulfonephthalein and potassium bromate in acidic media. Nitrate can also be on-line reduced to nitrite with a modified copper-coated cadmium reduction column. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of pyrogallolsulfonephthalein at 465 nm. Various analytical parameters such as effects of acidity, reagent concentrations, flow rates, sample sizes, lengths of the reaction coil and temperatures were studied and were optimized. Under the optimized conditions, the calibration graph was linear for 2.4 to 160 ng ml(-1) of nitrite and 4.0 to 100 ng ml(-1) of nitrate. The influences of potential interfering cations and anions for nitrite and nitrate determination were studied. The method is successfully applied for food and water samples. Up to ten samples can be analyzed per hour.

Silver(I)-selective coated-wire electrode based on an octahydroxycalix[4]arene derivative.

The performance of octahydroxycalix[4]arene derivative used as a neutral carrier for silver polymeric membrane electrode was studied. The sensor gave a good Nernstian response of 58 +/- 1 mV per decade for silver ion in the activity range 3.3 x 10(-6) to 3.3 x 10(-2) M Ag+. The limit of detection reached 2.1 x 10(-6) M Ag+ and exhibited high selectivity for silver ion against the alkali, alkaline earth and transition metal ions. The sensor can be used in wide pH range from 1.5 to 6.5. The response time of the sensor is less than 20 s. The potentiometric sensor was used as the indicator electrode in the titration of Ag+ ions by sodium chloride solution.