Advanced Nanomaterial-Based Biosensors for N-Terminal Pro-Brain Natriuretic Peptide Biomarker Detection: Progress and Future Challenges in Cardiovascular Disease Diagnostics.

Cardiovascular diseases (CVDs) represent a significant challenge in global health, demanding advancements in diagnostic modalities. This review delineates the progressive and restrictive facets of nanomaterial-based biosensors in the context of detecting N-terminal pro-B-type natriuretic peptide (NT-proBNP), an indispensable biomarker for CVD prognosis. It scrutinizes the escalation in diagnostic sensitivity and specificity attributable to the incorporation of novel nanomaterials such as graphene derivatives, quantum dots, and metallic nanoparticles, and how these enhancements contribute to reducing detection thresholds and augmenting diagnostic fidelity in heart failure (HF). Despite these technological strides, the review articulates pivotal challenges impeding the clinical translation of these biosensors, including the attainment of clinical-grade sensitivity, the substantial costs associated with synthesizing and functionalizing nanomaterials, and their pragmatic deployment across varied healthcare settings. The necessity for intensified research into the synthesis and functionalization of nanomaterials, strategies to economize production, and amelioration of biosensor durability and ease of use is accentuated. Regulatory hurdles in clinical integration are also contemplated. In summation, the review accentuates the transformative potential of nanomaterial-based biosensors in HF diagnostics and emphasizes critical avenues of research requisite to surmount current impediments and harness the full spectrum of these avant-garde diagnostic instruments.

Two-Dimensional CuMn-Layered Double Hydroxides: A Study of Interlayer Anion Variants on the Electrochemical Sensing of Trichlorophenol.

Despite their diverse application profile, aromatic organochlorides such as 2,4,6-trichlorophenol (TP) are widely renowned for creating a negative toll on the balance of the ecosystem. Strict regulatory regimes are required to limit exposure to such organic pollutants. By deployment of a straightforward detection scheme, electrochemical sensing technology offers a competitive edge over the other techniques and practices available for pollutant monitoring. Here, we present a streamlined hydrothermal approach for synthesizing copper-manganese layered double hydroxide (CuMn-LDH) rods to be employed as electrocatalysts for detecting TP in various media. With a focused intention to leverage the full potential of the prepared CuMn-LDHs, the interlamellar region is configured using a series of intercalants. Further, a thorough comparative analysis of their structures, morphologies, and electrochemical performance is accomplished using various analytical techniques. The electrocatalytic oxidation ability of the CuMn-LDH toward TP molecules is markedly altered by incorporating various anions into the gallery region. The dynamic attributes of the developed sensor, such as a wide linear response (0.02-289.2 µM), a low detection limit (0.0026 µM), and good anti-interfering ability, acclaim its superior viability for real-time detection of TP with exceptional tolerance to the presence of foreign moieties. Hence, this work manifests that the nature of intercalants is a vital aspect to consider while designing LDH-based electrochemical probes to detect priority pollutants.

Unlocking Catalytic Potential: Exploring the Impact of Thermal Treatment on Enhanced Electrocatalysis of Nanomaterials.

In the evolving field of electrocatalysis, thermal treatment of nano-electrocatalysts has become an essential strategy for performance enhancement. This review systematically investigates the impact of various thermal treatments on the catalytic potential of nano-electrocatalysts. The focus encompasses an in-depth analysis of the changes induced in structural, morphological, and compositional properties, as well as alterations in electro-active surface area, surface chemistry, and crystal defects. By providing a comprehensive comparison of commonly used thermal techniques, such as annealing, calcination, sintering, pyrolysis, hydrothermal, and solvothermal methods, this review serves as a scientific guide for selecting the right thermal technique and favorable temperature to tailor the nano-electrocatalysts for optimal electrocatalysis. The resultant modifications in catalytic activity are explored across key electrochemical reactions such as electrochemical (bio)sensing, catalytic degradation, oxygen reduction reaction, hydrogen evolution reaction, overall water splitting, fuel cells, and carbon dioxide reduction reaction. Through a detailed examination of the underlying mechanisms and synergistic effects, this review contributes to a fundamental understanding of the role of thermal treatments in enhancing electrocatalytic properties. The insights provided offer a roadmap for future research aimed at optimizing the electrocatalytic performance of nanomaterials, fostering the development of next-generation sensors and energy conversion technologies.

The Fabrication of a La2Sn2O7/f-HNT Composite for Non-Enzymatic Electrochemical Detection of 3-Nitro-l-tyrosine in Biological Samples.

Reactive oxygen and nitrogen species (RONS), including 3-nitro-l-tyrosine, play a dual role in human health, inducing oxidative damage and regulating cellular functions. Early and accurate detection of such molecules, such as L-tyrosine in urine, can serve as critical biomarkers for various cancers. In this study, we aimed to enhance the electrochemical detection of these molecules through the synthesis of La2Sn2O7/f-HNT nanocomposites via a simple hydrothermal method. Detailed structural and morphological characterizations confirmed successful synthesis, consistent with our expected outcomes. The synthesized nanocomposites were utilized as nanocatalysts in electrochemical sensors, showing a notable limit of the detection of 0.012 µM for the real-time detection of 3-nitro-l-tyrosine. These findings underscore the potential of nanomaterial-based sensors in advancing early disease detection with high sensitivity, furthering our understanding of cellular oxidative processes.

Nanoengineered disposable sensor fabricated with lanthanum stannate nanocrystallite for detecting animal feed additive: Ractopamine.

Ractopamine (RA) has been at the forefront of feed additives as a nutrient repartitioning mediator that recuperates the growth rate, decreases animal fat, and guarantees food safety. However, inappropriate and abusive usage of RA to enhance economic efficiency can negatively impact the environment-animal-human interactions. Therefore, the call for monitoring and quantifying RA is highly desired. In this work, the potentiality of La2Sn2O7 as an electrode modifier on the surface of the portable screen-printed carbon electrode (SPCE) was examined for its precision, disposability, and ability to detect RA. The superior electrocatalytic activity of the fabricated La2Sn2O7/SPCE fortifies its standpoints by displaying a wide linear working range of 0.01-501.2 µM, an enhanced sensitivity, a better stability, a lower LOD of 0.86 nM, and an increased selectivity toward the detection of RA. Furthermore, the investigation of the constructed electrochemical sensor with real-time food samples underpins its practicality and feasibility.

Fabrication of Praseodymium Vanadate Nanoparticles on Disposable Strip for Rapid and Real-Time Amperometric Sensing of Arsenic Drug Roxarsone.

Nanomaterials have versatile properties owing to their high surface-to-volume ratio and can thus be used in a variety of applications. This work focused on applying a facile hydrothermal strategy to prepare praseodymium vanadate nanoparticles due to the importance of nanoparticles in today's society and the fact that their synthesis might be a challenging endeavor. The structural and morphological characterizations were carried out to confirm the influence of the optimizations on the reaction's outcomes, which revealed praseodymium vanadate (PrVO4) with a tetragonal crystal system. In this regard, the proposed development of electrochemical sensors based on the PrVO4 nanocatalyst for the real-time detection of arsenic drug roxarsone (RXS) is a primary concern. The detection was measured by amperometric (i-t) signals where PrVO4/SPCE, as a new electrochemical sensing medium for RXS detection, increased the sensitivity of the sensor to about ∼2.5 folds compared to the previously reported ones. In the concentration range of 0.001-551.78 µM, the suggested PrVO4/SPCE sensor has a high sensitivity for RXS, with a detection limit of 0.4 nM. Furthermore, the impact of several selected potential interferences, operational stability (2000 s), and reproducibility measurements have no discernible effect on RXS sensing, making it the ideal sensing device feasible for technical analysis. The real-time analysis reveals the excellent efficiency and reliability of the prosed sensor toward RXS detection with favorable recovery ranges between ±97.00-99.66% for chicken, egg, water, and urine samples.

Construction of ANbO3 (A= Na, K)/f-carbon nanofiber composite: Rapid and real-time electrochemical detection of hydroxychloroquine in environmental samples.

Hydroxychloroquine (HCQ) is a significant viral resistant drug widely acknowledged for its immunomodulatory and anti-inflammatory activities. To minimize the impact of HCQ residues on environmental pathways, exploring control measures is vital. In this regard, electrochemical sensing of HCQ using well-structured functional materials is advantageous. This work aims to provide an economical and sustainable route for the synthesis of ANbO3 (A = Na,K) perovskites via a thymol-menthol-based natural deep eutectic solvent. The as-synthesized NaNbO3 and KNbO3 are pinned to functionalized carbon nanofibers (f-CNF) via an ultrasonication approach. Benefitting from the synergistic effect of rapid electron transfer and improved surface area, enhanced electrochemical activity for NaNbO3@f-CNF/GCE is achieved. The fabricated NaNbO3@f-CNF displays a LOD (DPV = 0.01 µM, i-t = 0.007 µM), wide dynamic range (DPV = 0.09-22.5 µM, i-t = 0.006-35 µM), outstanding selectivity, and reproducibility, proving feasible in real-time analysis with good recovery rates (±97.67-99.81%). The NADES-mediated preparation of perovskites evades the incorporation of traditional toxic solvents and yields atom-efficient ANbO3 (A = Na,K) associated with green solvent templates. This validates the sustainable fabrication of electrode materials with reduced energy stipulations for detecting hazardous drug pollutants in the ecosystem.

In Situ Synthesis of a Bismuth Vanadate/Molybdenum Disulfide Composite: An Electrochemical Tool for 3-Nitro-l-Tyrosine Analysis.

The quantification of 3-nitro-l-tyrosine (NO2-Tyr), an in vivo biomarker of nitrosative stress, is indispensable for the clinical intervention of various inflammatory disorders caused by nitrosative stress. By integrating the unique features of BiVO4 and MoS2 with matching bandgap energies, electrode materials with amplified response signals can be developed. In this regard, we introduce a hydrothermally synthesized bismuth vanadate sheathed molybdenum disulfide (MoS2@BiVO4) heterojunction as a highly sensitive electrode material for the determination of NO2-Tyr. Excellent electrochemical behavior perceived for the MoS2@BiVO4 augments the performance of the sensor and allows the measurement of NO2-Tyr in biological media without any time-consuming pretreatments. The synergistic interactions between BiVO4 and MoS2 heterojunctions contribute to low resistance charge transfer (Rct = 159.13 Ω·cm2), a reduction potential Epc = -0.58 V (vs Ag/AgCl), and a good response range (0.001-526.3 µM) with a lower limit of detection (0.94 nM) toward the detection of NO2-Tyr. An improved active surface area, reduced charge recombination, and high analyte adsorption contribute to the high loading of the biomarker for improved selectivity (in the presence of 10 interfering compounds), operational stability (1000 s), and reproducibility (six various modified electrodes). The proposed sensor was successfully utilized for the real-time determination of NO2-Tyr in water, urine, and saliva samples with good recovery values (±98.94-99.98%), ascertaining the reliability of the method. It is noteworthy that the electrochemical activity remains unaffected by other redox interferons, thus leading to targeted sensing applications.

Surfactant-Assisted Synthesis of Praseodymium Orthovanadate Nanofiber-Supported NiFe-Layered Double Hydroxide Bifunctional Catalyst: The Electrochemical Detection and Degradation of Diphenylamine.

Physiological storage disorders are caused by ineffective post-harvest handling of horticultural crops, particularly fruits. To address these post-harvest concerns, diphenylamine (DPAH•+) is widely used as a preservative to prevent fruit degradation and surface scald during storage around the world. Humans are negatively affected by the use of high concentrations of DPAH•+ because of the various health complications related to its exposure. As a result, accurate detection and quantification of DPAH•+ residues in treated fruits are critical. Rare earth metal orthovanadates, which have excellent physical and chemical properties, are potential materials for electrochemical sensors in this area. Herein, we present a simple and direct ultrasonication technique for the surfactant-assisted synthesis of praseodymium orthovanadate (PrVO4 or PrV) loaded on nickel iron layered double hydroxide (NiFe-LDH) synthesized with deep eutectic solvent assistance, as well as its application as an effective catalyst in the detection and degradation of DPAH•+ in fruits and water samples. The current work presents supreme electrochemical features of a PrV@NiFe-LDH-modified screen-printed carbon electrode (SPCE) where cetyltrimethylammonium bromide (CTAB) surfactant-driven fabrication of PrV directs the formation of highly qualified engineered structures and the deep eutectic solvent based green synthesis of NiFe-LDH creates hierarchical lamellar structures following the principles of green chemistry. PrV and NiFe-LDH combine to produce a synergistic effect that improves the number of active sites, charge transfer kinetics, and electronic conductivity. Differential pulse voltammetry analysis of PrV@NiFe-LDH/SPCE reveals a dynamic working range (0.005-226.26 µM), increased sensitivity (133.13 µA µM-1 cm-2), enhanced photocatalytic activity, and low detection limit (0.001 µM), which are considered significant when compared with the former reported electrodes in the literature for the determination of DPAH+ for its real-time applications.

Well-Designed Construction of Yttrium Orthovanadate Confined on Graphitic Carbon Nitride Sheets: Electrochemical Investigation of Dimetridazole.

Antibiotics are the most important drugs for people and animals to fight bacterial illnesses. Overuse of antibiotics has had unintended consequences, such as antibiotic resistance and ecosystem eradication owing to toxic chemical discharge, which have a negative influence on the biome. Herein, we report the synthesis of a hollow ellipsoid-shaped yttrium vanadate/graphitic carbon nitride (YVO4@CN) nanocomposite by a hydrothermal approach followed by a sonochemical method for the effective detection of dimetridazole (DMZ). The synergic and coupling effect between both the phases offer non-linear cumulative ramifications which can positively enhance the individual properties of the materials under consideration. This positive hybrid effect increases the conductivity, shortens the ion-diffusion pathway, enhances the electron/ion transportation, and provides more active sites and electron-conducting channels. The accurate optimization of the experimental conditions proposes good electrocatalytic activity for the YVO4@CN catalyst, exhibiting a good response toward DMZ detection. It reveals an extensive linear concentration range (0.001-153.3 and 176.64-351.6 µM), a low detection limit (0.8 nM), higher sensitivity (4.98 µA µM-1 cm-2), appreciable selectivity, increased operational stability (2200 s), and good cycle stability (60 cycles). The electrochemical performance of YVO4@CN indicates its practical application in real-time sample analysis of several families of nitroimidazole drugs.

Toward the Development of Disposable Electrodes Based on Holmium Orthovanadate/f-Boron Nitride: Impacts and Electrochemical Performances of Emerging Inorganic Contaminants.

Rare-earth metal orthovanadates have great technological relevance in the family of rare-earth compounds owing to their excellent physical and chemical properties. A significant number of studies have been carried out on this class of compounds to exploit their electrochemical properties in virtue of variable oxidation states. But holmium vanadate (HoV) and its morphology selective synthesis have not been considered, which can have potential applications similar to the rest of the family. In this work, we propose the synthesis of superior architectures of HoV with a functionalized boron nitride (f-BN) nanocomposite. The synergistic effect between HoV and f-BN can have a positive effect on the physical characteristics of the nanocomposite, which can be explored for its electrochemical capacity. Here, HoV incorporated with f-BN is explored for the electrochemical detection of Hg2+ ions, which is known for its toxicity-induced environmental health hazards. The structural and compositional revelation reveals higher conductivity and faster electron transfer in the composite, which facilitates a wide working range (0.02-53.8 and 64.73-295.4 µM), low limit of detection (5 nM), higher sensitivity (66.6 µA µM-1 cm-2), good selectivity over 10-fold higher concentration of other interfering compounds compared to Hg2+ ion concentration, and good cycles stability (30 segments) toward Hg2+ ion detection. This also envisages the morphology selective synthesis and utilization of other rare-earth metals, whose electrochemical capacities are unexplored.

Synergy of the LaVO4/h-BN Nanocomposite: A Highly Active Electrocatalyst for the Rapid Analysis of Carbendazim.

In the field of agriculture fungicides are vital, providing the most important ecosystem service for food production. The widespread use of these chemicals can significantly lead to various ecotoxicological threats with adverse effects, such as environmental changes, microbial resistance, and phytotoxicity. Electrochemical sensors offer enormous potential for the identification and monitoring of hazardous substances in accordance with their constructive characteristics, namely, precision, accuracy, sensitivity, and selectivity, over traditional analytical techniques. Here, we thus report the synthesis of the lanthanum vanadate/hexagonal boron nitride (LaV/h-BN) composite for the electrochemical determination of carbendazim (CZ), which is a widely used fungicide for disease management with critical risks associated with its overexposure. The combination of LaV and h-BN accelerates the formation of active sites, facilitating faster charge transfer and higher electronic conductivity. The synergistic effects greatly improve the preference of the modified electrode with increased sensitivity, a lower limit of detection, and wide linear responses toward CZ detection. The existence of variable oxidation states in the orthovanadate together with the unique properties of h-BN mark LaV/h-BN as an advanced material for specific applications in the family of rare-earth metal orthovanadate. Also, the deep eutectic solvent-assisted synthesis of the material creates an environmentally efficient system with reduced energy requisites to allow for applications in effective environmental monitoring.

Integration of samarium vanadate/carbon nanofiber through synergy: An electrochemical tool for sulfadiazine analysis.

Antibiotic pollution causes worldwide concern due to its more apparent consequences, namely antibiotic resistance and destruction of the environment. Extensive use of antibiotics in human and veterinary drugs releases a significant amount of toxins into the sphere of living matter, causing adverse ecological impacts. This requires the design of new analytical protocols for the effective mitigation and monitoring of hazardous pharmaceutical products to reduce the environmental burden. Therefore, we present here the hydrothermal synthesis of samarium vanadate/carbon nanofiber (SmV/CNF) composite for the determination of sulfadiazine (SFZ). The synergistic effect arising from the combination of SmV and CNF accelerates charge transfer kinetics along with the creation of more surface-active sites that benefit effective detection. The structural and compositional disclosure indicates the high purity and superior attributes of the composite material that possesses the ability to improve catalytic performance. The proposed SmV/CNF sensor exhibits important static characteristics such as wide linear response ranges, low detection limit, high sensitivity and selectivity, and increased stability. To the best of our knowledge, this is the first report on the electrochemical performance of SmV/CNF, establishing its potential application in real-time analysis of environmentally hazardous contaminants.

Cobalt molybdate nanorods decorated on boron-doped graphitic carbon nitride sheets for electrochemical sensing of furazolidone.

A nanorod-like structured CoMoO4 embedded on boron doped-graphitic carbon nitride composite (CoMoO4/BCN) has been developed by a simple sonochemical method for electrochemical detection of furazolidone (FUZ). Interestingly, the impedance of CoMoO4/BCN fabricated screen-printed carbon electrode (SPCE) possesses a lower resistance charge transfer (Rct), which favors superior electrochemical detection of FUZ. Such CoMoO4/BCN/SPCE exhibits an ultralow detection limit of 1.6 nM with a concentration range of 0.04-408.9 µM, and high sensitivity of 11.6 µA µM-1 cm-2 by DPV method. In addition, biological and water samples were used for demonstration of practical application of CoMoO4/BCN/SPCE towards electrochemical detection of FUZ, and the result exhibits a satisfactory recovery.Graphical abstract.

Highly sensitive determination of cancer toxic mercury ions in biological and human sustenance samples based on green and robust synthesized stannic oxide nanoparticles decorated reduced graphene oxide sheets.

This work proposes the conventional sonochemical synthesis of nanoparticles of tin (IV) oxide on reduced graphene oxide (rGOS@SnO2) influencing the formation of a composite with enhanced properties. The combination of SnO2 nanoparticles with rGOS weakens the accumulation in layered structures of the latter system, which leads to better exposure of SnO2 active sites and thus increases the conductivity of rGOS@SnO2 composite. This validates the improved electro-catalytic activity of the composite based on previous reports for its successful utilization in the electrochemical determination of toxic contaminants. The quantitative determination of mercury ions, through the use of the electrochemical sensor based on rGOS@SnO2 manifests several advantages such as simple operator, promptness, cost effectiveness and time independency when compared to other traditional techniques. The fabricated sensor displays two wide linear responses in the range of 0.25-705.3 µM for mercury ions, with a rapid response time about 1 s, and with a high sensitivity of 10.18 µA µM-1 cm-2 under optimized conditions. The accumulation of traces of mercury in the bodies of fish in the marine eco system marks the significance of its detection in real samples. The satisfactory results of the proposed sensor establish the supreme efficacy of layered nanomaterials in conjunction with nanoparticles for the simple, rapid and efficient detection of pollutants in food and biological samples.

Deep eutectic solvent-based manganese molybdate nanosheets for sensitive and simultaneous detection of human lethal compounds: comparing the electrochemical performances of M-molybdate (M = Mg, Fe, and Mn) electrocatalysts.

Potentially hazardous chemical contaminants endanger the environment and human well-being, challenging scientists and policy makers to develop holistic alternative approaches for remediation. The addition or accumulation of these chemicals can have a series of far-reaching consequences and have direct and indirect effects at multiple levels of ecological organization. Therefore, the development of a sensitive tool for the comprehensive evaluation of chemical concentrations is highly relevant. Herein, we thus report the simultaneous electrochemical detection of highly toxic hydroquinone (HQ), Hg2+, and nitrite (NO2-) compounds using nanostructured metal molybdate (M = Mg, Fe and Mn) catalysts. These functional nanomaterials are synthesized using a deep eutectic solvent (DES) modified hydrothermal method that provides sustainable aspects and energy efficient synthesis strategies. Choline chloride (ChCl)-urea DES used in this study exhibits an all-in-one behaviour by simultaneously acting as a template, reducing agent, and homogeneous means for stabilizing metal ions. This stimulates the fabrication of hierarchical structures of metal molybdates with high surface activities that cause their remarkable properties with minimal waste generation. The structural, morphological, catalytic, and electrochemical capacities of the as-synthesized MgMoO4, Fe2(MoO4)3, and MnMoO4 materials are explored through various techniques and comparatively, MnMoO4 presents superior characterization features such as a reduced particle size, increased surface area and hierarchical architectures. Owing to the exceptional physicochemical attributes, the MnMoO4 modified glassy carbon electrode (GCE) demonstrates superior electrochemical activities towards the individual and simultaneous detection of HQ, Hg2+, and NO2-. Well-defined and separate peaks are observed for the simultaneous detection of HQ, Hg2+, and NO2- which is influenced by the binding energies of these pollutants. Furthermore, the modified electrode exhibits a high sensitivity of 23.8, 17.7 and 10.2 µA µM-1 cm-2 with a limit of detection (LOD) of 0.026, 0.05, and 0.01 µM for HQ, Hg2+, and NO2- respectively under ideal conditions. Also, the reproducibility and anti-interference ability reinforce the application potential of the MnMoO4 modified electrode for the simultaneous electrochemical detection of HQ, Hg2+, and NO2- in real samples with better recoveries, thus assessing the effect of these hazardous chemicals on humanity.

Novel sonochemical synthesis of Fe3O4 nanospheres decorated on highly active reduced graphene oxide nanosheets for sensitive detection of uric acid in biological samples.

In this study, a super-active Iron (II, III) oxide nanospheres (Fe3O4 NPs) decorated reduced graphene oxide (rGOS) nanocomposite was developed. Fe3O4 NPs were stabilized on rGOS through electrostatic interactions in the aqueous medium. This process involves an ultrasound assisted reduction reaction of the GOS. The as-synthesized Fe3O4 NPs@rGOS was characterized through the HRTEM, SEM, XRD, Raman, elemental mapping and EDX analysis. The Fe3O4 NPs@rGOS modified GCE was developed for the determination of biomarker. Uric acid is important biomarker based on gout and kidney stone with high adverse effect in human body. The results obtained showed that the modified electrode Fe3O4 NPs@rGOS shows good electrochemical reduction peak compared to bare electrode and control electrodes. The Fe3O4 NPs@rGOS modified sensor linear range 0.02-783.6 µM was observed with nanomolar LOD 0.12 nM. In addition, the modified Fe3O4 NPs@rGOS/GCE sensor has been applied to determination of uric acid concentration in urine and blood serum samples. Furthermore, advantages of the modified sensor are high stability, repeatability and reproducibility.

The co-optimization of floral display and nectar reward.

In most insect-pollinated flowers, pollinators cannot detect the presence of nectar without entering the flower. Therefore, flowers may cheat by not producing nectar and may still get pollinated. Earlier studies supported this 'cheater flower' hypothesis and suggested that the cost saving by cheater flowers could be the most predominant selective force in the evolution of nectarless flowers. Previous models as well as empirical studies have addressed the problem of optimizing the proportion of nectarless and nectarful flowers. However, there has been no attempt to optimize the investment in nectar production along with that in floral display. One of the key questions that arises is whether the floral display will evolve to be an honest indicator of nectar reward. We use a mathematical model to cooptimize the investments in nectar and floral display in order to achieve maximum reproductive success. The model assumes that pollinators rely on a relative rather than an absolute judgement of reward. A conspicuous floral display attracts naive pollinators on the one hand and enhances pollinator learning on the other. We show that under these assumptions, plant-pollinator co-evolution leads to honest signalling, i.e. a positive correlation between display and reward.