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As a significant biomarker during the apoptosis process, cytochrome c (Cyt c) is considered as a critical component in the inherent apoptotic pathway, but the simple and portable detection still remains challengeable. In this work, a portable and visual sensing platform for Cyt c was developed based upon the fluorescence quenching of graphene quantum dots (GQDs), which could be finished within a few seconds. Herein, the absorption spectrum of Cyt c matched the emission spectrum of GQDs well, which could cause the fluorescence quenching of GQDs via the inner filter effect (IFE) in the range of 1–50 μg/mL with the limit of detection as low as 0.1 μg/mL. Furthermore, the intracellular Cyt c was imaged to observe the apoptosis process of cancer cells induced by staurosporine. To achieve the portable and visual detection of Cyt c, GQDs were deposited on the filter paper to form the solid platform, which displayed a gradual fluorescence quenching when different concentrations of Cyt c were present. Compared to the conventional methods, the proposed assay is low-cost, fast, portable, and visual, which will be useful for the investigation of mitochondrial dysfunction and apoptotic cell death. [ABSTRACT FROM AUTHOR]

In this work, a new paper-based device (PAD) was developed for the colorimetric detection of multiple heavy metals. The sensing principle of this PAD is based on the analyte-regulated photocatalytic activity of quantum dots (QDs) to certain substrates. The PAD consisted of three filter paper layers, defining a sample area, three channels, and three testing areas. Three photocatalytic reactions between different QDs and their corresponding substrates could be performed in one device, achieving the simultaneous detection of Cu(II), Mn(II), and Hg(II). The detection limits are 7.3 nM for Cu(II), 5.4 nM for Mn(II), and 8.1 nM for Hg(II), respectively. This PAD was applied to analyze real samples and the results were consistent with those obtained by inductively coupled plasma-optical emission spectrometer. This approach may provide a promising colorimetric sensing platform for multi-target analysis.

The rapid discrimination of bacteria is currently an emerging trend in the fields of food safety, medical detection, and environmental observation. Traditional methods often require lengthy culturing processes, specialized analytical equipment, and bacterial recognition receptors. In response to this need, we have developed a paper-based fluorescence sensor array platform for identifying different bacteria. The sensor array is based on three unique carbon quantum dots (CQDs) as sensing units, each modified with a different antibiotic (polymyxin B, ampicillin, and gentamicin). These antibiotic-modified CQDs can aggregate on the bacterial surface, triggering aggregation-induced fluorescence quenching. The sensor array exhibits varying fluorescent responses to different bacterial species. To achieve low-cost and portable detection, CQDs were formulated into fluorescent ink and used with an inkjet printer to manufacture paper-based sensor arrays. A smartphone was used to collect the responses generated by the bacteria and platform. Diverse machine learning algorithms were utilized to discriminate bacterial types. Our findings showcase the platform's remarkable capability to differentiate among five bacterial strains, within a detection range spanning from 1.0 × 103 CFU/mL to 1.0 × 107 CFU/mL. Its practicality is further validated through the accurate identification of blind bacterial samples. With its cost-effectiveness, ease of fabrication, and high degree of integration, this platform holds significant promise for on-site detection of diverse bacteria. [ABSTRACT FROM AUTHOR]

Fluorescent sensors with single reading are generally subject to unpredictable disturbs from environmental and artificial factors. In order to overcome this barrier of detection reliability, a paper-based optical sensor with proportional fluorescence was established and further combined with a smartphone for visual, on-site and quantitative detection of Fe3+, which affects the color, smell and taste of water, and endangers the health of plants and animals. The ratio fluorescent probe was fabricated by rhodamine B and carbon quantum dots derived from xylan. The red fluorescence of rhodamine B was inert to Fe3+, which was referred to as background. And blue emitting carbon quantum dots functioned as signal report units, which would be quenched by Fe3+ and make the fluorescence of the ratio probe change from purple to red. The quantitative detection of Fe3+ was conducted by investigating the RGB value of fluorescent images with a smartphone. With the increase of Fe3+ concentration, the R/B (red/blue) value of the fluorescent paper gradually increased. The linear detection range was 10–180 μM, and the limit of detection was 198.2 nM. The application of ratio fluorescent paper with a smartphone provides a facile method for the rapid detection of ions. [ABSTRACT FROM AUTHOR]

BACKGROUND: This work proposes the use of a simple, inexpensive method for the hydrothermal synthesis of fluorescent carbon dot nanoparticles (CDs) from rice starch aimed at the determination of Hg2+ in water. The proposed method involved using a paper‐based analytical device coupled to a 3D plate, with a UV‐LED chamber and a smartphone for the acquisition and analysis of the fluorescence digital images of the CDs. RESULTS: The size of the carbon dots ranged from 0.5 to 3 nm, with an average particle size of ~1 nm. The functionalization of carbon dots with methimazole allowed a high selective for Hg2+ determination. The results obtained showed a linear response R2 of 0.997 and Hg2+ concentration in the range of 0.5–45.0 μmol L−1 with a limit of detection and limit of quantitation of 0.23 and 0.62 μmol L−1, respectively. The results of the study show that there were no significant differences, at 95% confidence level, between the data obtained from the application of the proposed method and the reference method. CONCLUSION: The proposed method is in line with the principles of green chemistry, as it involves the use of renewable sources for starch extraction and a hydrothermal synthesis process that does not employ toxic reagents. In addition, the method employs only 15 μL reagent/sample. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Microfluidic based sensors are one of the emerging alternatives for bringing solutions studies on paper platforms. Microfluidic paper assisted platform was developed over here through a simple, easy, cost effective and instrument free process. The self‐same method of waxing through crayoning, was estimated thoroughly on different paper platforms. Varied parameter including type of crayoning, way of patterning, color effect, wicking rate and channel optimization was performed on paper milieus. Optimized time of baking for obtaining controlled penetration ranges from 2 min to 8 min depending on the type of paper used. Wax crayoning was preferred over oil pasteling for making hydrophobic barriers uniformly, solid as well fully penetrated within paper inner layers. Fabrication through this easy cost‐effective route allows a formation of hydrophilic reaction or sensing zone of 0.25 cm2 with sufficient reactive area. Further sensing of dopamine on paper platform was carried using paper chip adsorbed with fluorescent modified graphene quantum dots as sensing material. The patterned paper showed advantage as only few microliter (5 μl to 10 μl) range of sample volume was required for testing. Fluorescence quenching with increase of concentration was witnessed where around 25–75 μM dopamine concentration was positively tested through naked eye; which for the first time was demonstrated here via robust wax crayoning method for developing paper based biosensor. [ABSTRACT FROM AUTHOR]

Handling and storing the immense amounts of data native to the information age is a major challenge in terms of technological sustainability and energy demand. To date, tape storage remains the most widespread method for data archiving, while DNA data storage appears to offer the best data density and long-term stability in the future. However, DNA data storage is still in its infancy primarily due to economic and accessibility challenges. This emphasizes the need for more practical and readily available alternatives. We present a method for data storage utilizing inkjet printable quantum dots on paper with photoluminescence (PL) readout. Our proof of principle study showcases the ability to print and stack multiple bits of data on a single spot by exploiting the unique PL properties of quantum dots. This approach utilizes easily accessible resources, including a consumer-grade printer and paper as the substrate. Additionally, we perform initial stability tests, investigate scalability by controlling emission intensity, and evaluate the potential data density achievable by our approach.

A highly selective solid-state fluorescent sensor based on N-doped carbon quantum dots (N-CQDs) and cotton fiber paper (CFP) is reported for the determination of trace mercury (II)(Hg2+). The N-doped carbon quantum dots on cotton fiber paper (N-CQDs@CFP) was synthesized using a facile one-step microwave hydrothermal method. Multiple approaches were employed to fully investigate the morphology and chemical structure of the paper-based fluorescent sensor. The N-CQDs were chemically bonded onto the CFP, which offers good reproducibility and stability of the sensor. The N-CQDs@CFP showed high-intensity blue emission in dark-field imaging, and the fluorescence was quenched by Hg2+. The Hg2+ in aqueous samples was easily determined and visually monitored. There was good linearity from 0 to 250 μM, and the limit of detection was 34 nM. The paper-based fluorescent sensor provided accurate and rapid determination of Hg2+ upon comparison with flame atomic absorption spectrophotometry (FAAS). The simple preparation, rapid detection (< 5 min), low cost, and easy-handling illustrate that the reported sensor has a significant value in environmental monitoring. [ABSTRACT FROM AUTHOR]

Paper‐based photodetectors have emerged as reliable candidates for wearable electronics due to their low‐cost, degradability and excellent bending properties. However, the application of quantum dots (QDs) to paper‐based devices remains a challenge due to the low carrier mobility. In this work, lead sulfide (PbS) QDs are successfully applied to paper‐based devices by constructing the amorphous indium gallium zinc oxide (a‐IGZO)/PbS QDs‐EDT heterojunction to enhance the photoconductive gain of the QDs film. The effect of different paper substrates are investigated on device performance and demonstrate that the heterojunction is not suitable for the fiber‐like paper substrate. Heterojunction devices based on Senyan paper and glass paper exhibit stable detection performance with detectivity of 1.71 × 1010 and 3.19 × 1011 Jones, respectively. Benefit from the unique micro‐morphology, the Senyan paper‐based device exhibits excellent bending resistance and remained stable after 1000 bends. [ABSTRACT FROM AUTHOR]

Rapid, simple, and sensitive analysis of relevant proteins is crucial in many research areas, such as clinical diagnosis and biomarker detection. In particular, clinical data on cancer biomarkers show great promise in forming reliable predictions for early cancer diagnostics, although the current analytical systems are difficult to implement in regions of limited recourses. Paper-based biosensors, in particular, have recently received great interest because they meet the criteria for point-of-care (PoC) devices; the main drawbacks with these devices are the low sensitivity and efficiency in performing quantitative measurements. In this work, we design a low-cost paper-based nanosensor through plasmonic calligraphy by directly drawing individual plasmonic lines on filter paper using a ballpoint pen filled with gold nanorods (AuNR) as the colloidal ink. The plasmonic arrays were further successively coated with negatively and positively charged polyelectrolyte layers employed as dielectric spacers to promote the enhancement of the emission of carboxyl-functionalized quantum dots (QD)—previously conjugated with specific antibodies—for indirect detection of the carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5). The efficiency, sensitivity, as well as the specificity of our portable nanosensor were validated by recording the luminescence of the QD@Ab complex when different concentrations of CEACAM5 were added dropwise onto the calligraphed plasmonic arrays.

The design of light‐responsive color switching systems (LCSs) is essential to the implementation of rewritable paper and oxygen detection. Previous LCSs rely on metal‐based semiconductor photocatalysts which are expensive and pose metal‐leaking risk. To solve the issue, for the first time, nitrogen‐doped carbon quantum dots (N‐CQDs) are reported as metal‐free photocatalyst for visible photoprinting and oxygen sensing. On N‐CQD surface, the decorated amino and hydroxyl groups act as hole scavengers and thus realize visible‐light‐responsive single and multiple color switching, after mixing with redox‐sensitive dyes. Combined with polymeric substrates, LCS rewritable papers can be fabricated and exhibit rapid decoloration performances under 420 nm light irradiation, due to the reduction of dye by photogenerated electrons from N‐CQDs. After the decoloration, efficient color reversion can be realized by the oxidization of dye in ambient air (O2). By taking advantage of the controlled recoloration kinetics, an oxygen sensor can be attained for visual quantitative analysis of atmospheric conditions with color variations. These results assist the future development of nonmetal color switching systems for superior functional design of photoprintable papers and colorimetric oxygen sensors. [ABSTRACT FROM AUTHOR]

"Waste" is "wealth": the transformation of biomass waste into high value-added substances holds significant environmental and economic importance. In our work, orange peel was effectively transformed into valuable fluorescent carbon quantum dots (CQDs) by solvothermal treatment. The resultant CQDs displayed favorable dispersion and a mean particle size of 3.14 ± 0.71 nm. Moreover, these CQDs exhibited a characteristic excitation-dependent fluorescence behavior, which can produce the maximum emission wavelength at 506 nm with excitation at 400 nm. Upon the introduction of permanganate (MnO4−), the fluorescence intensity of CQDs diminished gradually caused by the inner filter effect (IFE) as well as the static quenching effect (SQE). The results revealed that the CQDs can serve as a fluorescent probe, which possessed high performance in terms of sensitivity for quantitative analysis of MnO4−, boasting a low detection limit of 3.31 μM. Subsequently, the application of this fluorescent probe in actual water samples was further explored, resulting in a recovery rate between 98.18% and 101.69%, with relative standard deviations (RSDs) ranging from 1.85% to 2.68%, which was highly satisfactory. The portable paper-based sensor, fabricated by depositing CQDs onto filter paper, is capable of quantitatively and visually detecting MnO4− in combination with a smartphone, thus providing a rapid on-site detection tool for MnO4−. As far as we know, this study provides the inaugural account of a smartphone-based portable sensor for visual determination of MnO4− by using biomass waste based CQDs, suggesting its immense potential for real-time monitoring applications. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots (CQDs) and rhodamine B (RhB) were physically mixed to construct a highly selective and sensitive ratiometric fluorescent sensor (CQDs@RhB) for the quantitative and visual detection of Hg2+. After adding Hg2+, the emission peak of CQDs at 445 nm was quenched and the peak of RhB at 575 nm remained unchanged; the ratio of the two emission peaks had a linear relationship with the Hg2+ concentration. The CQDs@RhB had a detection range of 0–15 µM and the limit of detection (LOD) is 65.93 nM and a color change from blue to pink was visible to the naked eye under ultraviolet light. The study revealed a static quenching mechanism of CQDs@RhB. The established method was successfully applied to the detection of Hg2+ in real water and rice samples with satisfactory results. In addition, a portable fluorescent paper-based sensor platform was developed using computer software assistance. The relationship with Hg2+ concentration was constructed by converting the pictures obtained under ultraviolet light to RGB color mode for visualization and quantitative detection of Hg2+. This study provides a valuable strategy for constructing a rapid detection system for Hg2+ in the field. [ABSTRACT FROM AUTHOR]

Abstract Halide perovskite quantum dots (PQDs) are promising materials for diverse applications including displays, light‐emitting diodes, and solar cells due to their intriguing properties such as tunable bandgap, high photoluminescence quantum yield, high absorbance, and narrow emission peaks. Despite the prosperous achievements over the past several years, PQDs face severe challenges in terms of stability under different circumstances. Currently, researchers have overcome part of the stability problem, making PQDs sustainable in water, oxygen, and polar solvents for long‐term use. However, halide PQDs are easily degraded under continuous irradiation, which significantly limits their potential for conventional applications. In this study, an oleic acid/oleylamine (traditional surface ligands)‐free method to fabricate perovskite quantum dot papers (PQDP) is developed by adding cellulose nanocrystals as long‐chain binding ligands that stabilize the PQD structure. As a result, the relative photoluminescence intensity of PQDP remains over ≈90% under continuous ultraviolet (UV, 16 W) irradiation for 2 months, showing negligible photodegradation. This proposed method paves the way for the fabrication of ultrastable PQDs and the future development of related applications.

Abstract Perovskite quantum dots (PQDs) are a competitive candidate for next‐generation display technologies as a result of their superior photoluminescence, narrow emission, high quantum yield, and color tunability. However, due to poor thermal resistance and instability under high energy radiation, most PQD‐based white light‐emitting diodes (LEDs) show only modest luminous efficiency of ≈50 lm W−1 and a short lifetime of

Traces of mercury ions in environmental water can harm humans and animals. Paper-based visual detection methods have been widely developed for the rapid detection of mercury ions; however, existing methods are not sensitive enough to be used in real environments. Here, we developed a novel, simple and effective visual fluorescent sensing paper-based chip for the ultrasensitive detection of mercury ions in environmental water. CdTe-quantum-dots-modified silica nanospheres were firmly absorbed by and anchored to the fiber interspaces on the paper's surface to effectively avoid the unevenness caused by liquid evaporation. The fluorescence of quantum dots emitted at 525 nm can be selectively and efficiently quenched with mercury ions, and the ultrasensitive visual fluorescence sensing results attained using this principle can be captured using a smartphone camera. This method has a detection limit of 2.83 µg/L and a fast response time (90 s). We successfully achieved the trace spiking detection of seawater (from three regions), lake water, river water and tap water with recoveries in the range of 96.8–105.4% using this method. This method is effective, low-cost, user-friendly and has good prospects for commercial application. Additionally, the work is expected to be utilized in the automated big data collection of large numbers of environmental samples. [ABSTRACT FROM AUTHOR]

Carbonaceous materials, especially with graphite‐layers structure, as anode for potassium‐ion batteries (PIBs), are the footstone for industrialization of PIBs. However, carbonaceous materials with graphite‐layers structure usually suffer from poor cycle life and inferior stability, not to mention freestanding and flexible PIBs. Here, a freestanding and flexible 3D hybrid architecture by introducing carbon dots on the reduced graphene oxide surface (CDs@rGO) is synthesized as high performance PIBs anode. The CDs@rGO paper has efficient electron and ion transfer channels due to its unique structure, thus enhancing reaction kinetics. In addition, the CDs provide abundant defects and oxygen‐containing functional groups, which can improve the electrochemical performance. This freestanding and flexible anode exhibits the high capacity of 310 mAh g−1 at 100 mA g−1, ultra‐long cycle life (840 cycles with a capacity of 244 mAh g−1 at 200 mA g−1), and excellent rate performance (undergo six consecutive currents changing from 100 to 500 mA g−1, high capacity 185 mAh g−1 at 500 mA g−1), outperforming many existing carbonaceous PIB anodes. The results may provide a starting point for high‐performance freestanding and flexible PIBs and promote the rapid development of next‐generation flexible batteries. [ABSTRACT FROM AUTHOR]

Pesticide residues are a serious problem towards agriculture, environment and food safety, so it is highly desirable to develop a swift, efficient and portable pesticide detection method. A fluorescence visual sensing method for glyphosine based on a nitrogen-doped biomass carbon quantum dot (N-CQD) paper-based sensor was developed. The fluorescence signal was quenched by Fe3+ in a static quenching process, and then the fluorescence of N-CQDs was recovered after adding glyphosine. Under the optimal experimental conditions and when tested with a fluorescence spectrofluorometer, the detection of glyphosine showed a two-stage linear pattern in the range of 0.1–0.6 μM and 0.6–1.6 μM with a detection limit of 0.075 μM. Then, the RGB values of different concentrations of glyphosine on the filter paper chip were detected by the software of the smartphone-color identifier. The logarithm of the glyphosine concentration was linearly related to the G value of RGB in the range of 0.25–10.00 mM and with a detection limit of 0.15 mM. The method was applied to measuring glyphosine-spiked juice and flour samples, and the recovery rates were 87.60–112.69% and 93.27–105.83%, respectively. The proposed N-CQDs/Fe3+ system had wide applications, and it was expected to be fast and effective at detecting pesticide residues. [ABSTRACT FROM AUTHOR]

Cellulose paper specimens with and without surface modification were compared in order to study their physicochemical compatibility with quantum dots (QDs) for biochemical sensing applications. Silane and chitosan modification methods were applied. The distribution of QDs deposited on untreated paper and papers modified with silane and chitosan were investigated in order to understand the interaction between QDs and fibre. Modified papers were shown to significantly reduce the undesirable redistribution of QDs during paper drying. The retention ability and thermal resistance of QDs to the loss of fluorescence on modified papers were also studied for the purpose of determining the most suitable paper surface modification for developing QD-Paper-based analytical devices (QD-PADs). Furthermore, chitosan-modified paper was used to design QD-PADs to quantify glucose concentration in aqueous samples; the quenching effect of the enzymatic product on the fluorescent emission of QDs was used as the indicator system. The change of fluorescence of QDs was measured by a simple in-house constructed fluorescence imaging system. The detection limit of glucose was 5 mg/dL, which is comparable with other reported paper sensors for detection of glucose.

To establish rapid, high-sensitive, quantitative detection of ACP residues in vegetables. A 1G2 cell clone was selected as the most sensitive for anti-ACP antibody production following secondary immunization, cell fusion, and screening. The affinity of the 1G2 antibody to each of the four coating agents (imidacloprid–bovine serum albumin [BSA], thiacloprid–BSA, imidaclothiz–BSA, and ACP-BSA) was determined using a 20 min enzyme-linked immunosorbent assay (ELISA). The half maximal inhibitory concentration (IC50) was 0.51–0.62 ng/mL, showing no significant difference in affinity to different antigens. However, we obtained IC50 values of 0.58 and 1.40 ng/mL on the linear regression lines for 1G2 anti-ACP antibody/imidacloprid–BSA and 1G2 anti-ACP antibody/thiacloprid–BSA, respectively, via quantum dot (QD)-based immunochromatography. That is, the 1G2 antibody/imidacloprid–BSA pair (the best combination) was about three times more sensitive than the 1G2 antibody/thiacloprid–BSA pair in immunochromatographic detection. The best combination was used for the development of an 8 min chromatographic paper test. With simple and convenient sample pretreatment, we achieved an average recovery of 75–117%. The coefficient of variation (CoV) was

With the continuous development of electronic skin (e-skin), multifunctional e-skin is approaching, and in some cases even surpassing, the capabilities of real human skin, which has garnered increasing attention. Especially, if e-skin processes eye's function, it will endow e-skins more powerful advantages, such as the vision reparation, enhanced security, improved adaptability and enhanced interactivity. Here, we first study the photodetector based on CsPbBr3 quantum dots film and the pressure sensor based on PEDOT: PSS-coated cellulose paper, respectively. On the base of these two kinds of sensors, a light/pressure bifunctional sensor was successfully fabricated. Finally, flexible bifunctional sensors were obtained by using a flexible interdigital electrode. They can simultaneously detect light and pressure stimulation. As e-skin, a high photosensitivity with a switching ratio of 168 under 405 nm light at a power of 40 mW/cm2 was obtained and they can also monitor human motions in the meantime. Our work showed that the strategy to introduce perovskite photodetectors into e-skins is feasible and may open a new way for the development of flexible multi-functional e-skin. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based point-of-care assays are a highly valuable technology with many promising applications in public health and environmental monitoring. High-sensitivity detection of certain trace substances is one of the critical important considerations for practical usage of microfluidic point-of-care techniques. Over the past decade, luminescence nanoprobes have been increasingly emerged as powerful toolboxes to achieve exceptional sensitivity and low detection limits for many chemical sensors. In this Review, we provide an overview of the fundamental principles underlying paper-based microfluidic point-of-care detection. We highlight various luminescence nanoprobes, including nano-diamonds, upconversion luminescent nanoparticles, inorganic quantum dots, and carbon dots, along with their corresponding sensing mechanisms. In subsequent sections, we emphasize the requisite utilization of specialized readout equipment for the effective implementation of fluorescence detection. Moreover, we summarize key microfluidic design strategies capable of achieving enhanced precision in the detection processes. We also discuss future research directions and the main challenges to be addressed for fluorescence nanoprobes-inspired paper-based microfluidic point-of-care technology. • Microfluidic point-of-care paper-based Luminescence assays. • Luminescence nanoprobes and corresponding mechanism. • Portable devices for signal readout and diagnosis. [ABSTRACT FROM AUTHOR]

Rapid detection of pesticides in fruits is an ongoing challenge. The objective of the present study was to develop novel fluorescent microfluidic paper chips for specific recognition and sensitive detection of the pesticide 2,4-D through the electron-transfer-induced fluorescence quenching mechanism. CdTe quantum dots (QDs) were deposited onto cellulose paper (base material) to yield imprinted paper chips (paper@QDs@MIPs). This method allows the transferability of the molecularly imprinted fluorescence sensor from the liquid phase to the solid phase (paper base) for rapid and portable analysis. The resultant imprinted paper chips were effectively characterized, and they exhibited ideal ordered spatial network structure, chemical stability, and fluorescence property. The paper@QDs@MIPs showed that 2,4-D binding significantly reduced the fluorescence intensity within less than 18 min, and it achieved satisfactory linearity in the range of 0.83–100 μM and high detectability of 90 nM. The recognition specificity for 2,4-D relative to its analogues was shown, and the imprinting factor was 2.13. In addition, the recoveries of the spiked bean sprouts at three concentration levels ranged within 94.2–107.0%, with a relative standard deviation of less than 5.9%. Collectively, the device provided an effective platform for rapid recognition, convenience, and detection of trace food pollutants in complex matrices, thereby ensuring food safety and further promoting surface imprinting studies. [ABSTRACT FROM AUTHOR]

• A QD-based colorimetric sensing system with high selectivity was developed. • A ternary colorimetric probe combining aptamer recognition with a QD-based photocatalytic reaction was created. • Automatic data readout through smartphones was achieved. • The system is convenient, universal, and multi-target sensing available. Quantum dots colorimetric sensing systems (QDs-CSSs) are promising tools for on-site monitoring or point-of-care testing, owing to their high sensitivity, low cost, and direct visual readout. Despite these advantages, a notable challenge hindering their practical applications lies in the limited selectivity. To date, scant attention has been devoted to addressing this issue. In this study, we designed a ternary colorimetric probe integrating aptamer recognition with a QDs-based photocatalytic reaction. The target can specifically modulate the photocatalytic oxidation of o -phenylenediamine through its specific aptamer, thereby triggering a color change within the probe. We fabricated a multi-layer paper chip to load the probe and perform multi-target detection. We manufactured a multi-functional smartphone-based device to support the chip and provide automatic readout of the colorimetric sensing results. By putting these elements together, we obtained a QDs-CSS with high selectivity, good reproducibility, and low consumption. To prove its practical performance, this system was used for the simultaneous sensing of Pb(II), As(III), and Cd(II). A nM level detection limit was achieved and the testing results in actual samples agreed with those from the standard method. The proposed system opens up a new avenue to develop QDs-CSSs with high selectivity. Moreover, it shows promising prospects to be a general sensing system for various targets. [ABSTRACT FROM AUTHOR]

A simple microfluidic device based on the use of a paper platform modified with AuNPs was developed. The ALP-like CeO 2 nanozyme first converts p-nitrophenyl phosphate (pNPP) to PNP. Fluorescence detection of Tau-441 was proposed based on the inner filter effect (IFE) of n-doped graphene quantum dots (NGQDs) and p-nitrophenol (PNP). [Display omitted] • A novel device based on the use of a paper platform modified with AuNPs was developed. • Fluorescence detection of Tau protein (Tau-441) was proposed based on the inner filter effect (IFE) of n-doped graphene quantum dots (NGQDs). • The ALP-like CeO 2 nanozyme first converts p-nitrophenyl phosphate (pNPP) to p-nitrophenol (PNP) for the rapid analysis of Tau-441 content in human serum samples. The advancement of Alzheimer's disease (AD) is directly correlated to the phosphorylation damage of Tau protein (Tau-441), which is considered the most reliable indicator for early detection of AD. Nevertheless, the concentration of Tau-441 in human serum remains considerably low. To address this issue, a paper-based fluorescence immunosensor based on internal filter effect (IFE) was developed for the detection Tau-441. The microfluidic paper-based channel was prepared and modified with a gold layer to attach primary antibodies and increase the sensitivity of the sensor. All at once, Au@CeO 2 nanorods was employed as a fluorescence probe to hydrolyze p-nitrophenyl phosphate (pNPP), which generates hydrolyzed product p-nitrophenol (PNP) can reduce or quench the fluorescence intensity of N-doped graphene quantum dots (NGQDs). The immunosensor was designed to detect an increase in the amount of Tau-441 collected as the fluorescence intensity of NGQDs decreased. The developed sensor demonstrated satisfactory results in clinical serum samples, offering a promising concept for an immunoassay tagged with nanozymes for early detection of AD. Overall, this microfluidic paper-based fluorescent immunosensor has the potential to improve early diagnosis of AD. [ABSTRACT FROM AUTHOR]

Rapid, simple, and sensitive analysis of relevant proteins is crucial in many research areas, such as clinical diagnosis and biomarker detection. In particular, clinical data on cancer biomarkers show great promise in forming reliable predictions for early cancer diagnostics, although the current analytical systems are difficult to implement in regions of limited recourses. Paper-based biosensors, in particular, have recently received great interest because they meet the criteria for point-of-care (PoC) devices; the main drawbacks with these devices are the low sensitivity and efficiency in performing quantitative measurements. In this work, we design a low-cost paper-based nanosensor through plasmonic calligraphy by directly drawing individual plasmonic lines on filter paper using a ballpoint pen filled with gold nanorods (AuNR) as the colloidal ink. The plasmonic arrays were further successively coated with negatively and positively charged polyelectrolyte layers employed as dielectric spacers to promote the enhancement of the emission of carboxyl-functionalized quantum dots (QD)—previously conjugated with specific antibodies—for indirect detection of the carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5). The efficiency, sensitivity, as well as the specificity of our portable nanosensor were validated by recording the luminescence of the QD@Ab complex when different concentrations of CEACAM5 were added dropwise onto the calligraphed plasmonic arrays. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel route to carbon quantum dots (CQDs) of customized surface functionality. • CQDs with amine functionality obtained from modified paper precursors. • Amine functionalized CQDs demonstrated as efficient probes for DNA binding studies. We report a novel synthesis route for preparing carbon quantum dots (CQDs) of customized surface functionality from readily available precursors. The synthetic strategy is based on the chemical modification of paper precursors prior to preparing CQDs from them. The pre-synthesis modification of paper precursors with (3-Aminopropyl) triethoxy silane (APTES) enabled us to synthesize CQDs with amine functional groups on the surface. The silane coupling via condensation between the ethoxy group of APTES and the cellulose hydroxyl group on the paper resulted in the tethering of amine groups on the paper substrates, which are retained as surface-bound species during the synthesis of CQDs from the modified paper. Amine functionalization on the surface of CQDs helped us use them in applications such as DNA binding. We analyzed the interaction of CQDs with calf thymus DNA (CT-DNA), and the results imply their propensity as an efficient biological probe. The synthetic strategy presented here can also be extended to other functional groups. [ABSTRACT FROM AUTHOR]

Tungsten disulfide quantum dots (WS2 QDs) embedded lab on genochip based analytical device (PAD) was developed for the specific DNA detection of Meningitis, a life threatening disease. This paper-based lab on genochip was designed by grafting the two electrodes onto the surface of paper using conductive ink. The WS2 QDs were characterized by X-ray diffraction technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Following this, specific oligonucleotide sequence of DNA (capture probe) was immobilized over the surface of WS2 QDs/PAD electrode. The ssDNA/WS2QDs/PAD device was characterized electrochemically by cyclic voltammetry. The device was employed for detection of target DNA (by hybridization) by employing methylene blue (MB) as an indicator. The biosensor exhibited a wide linear response in the range 1 nM-100 µM towards the target DNA. The limit of detection (LOD) of target DNA of the proposed device is 1 nM. The advantageous features of this device than the existing biosensors include cheaper analysis cost, tiny sample requirements and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • N-BPQD was synthesized through a solvothermal method using formamide as N source and solvent. • The N-BPQD exhibit a bright blue fluorescence with high quantum yield of 73.7%. • N-BPQD on fPAD was used as a visual fluorescent sensing platform for detection of bilirubin. • The fluorescent sensor shows high sensitivity and selectivity to bilirubin. • N-BPQD was a good fluorescent probe for cellular imaging. A facile top down producing approach for synthesis and doping of a nitrogen doped black phosphorus quantum dots (N-BPQD) in one-pot was developed by solvothermal method with formamide as a nitrogen source and solvent. The nitrogen atoms had introduced into BPQD structure and exhibit a bright blue photoluminescent with a high quantum yield of 73.7 %. The morphology and chemical structure of N-BPQD was characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. A fluorescent paper analysis device (fPAD) was applied in rapid and cost-effective detection of biomarker bilirubin with naked eyes. The fPAD sensor present a high selectivity, stability and sensitive response to bilirubin in a wide linear range of 10 to 150 µM with a limit of detection limit as 26 nM (S/N = 3) and limit of quantitation as 86 nM (S/N = 10). The principles-based density functional theory, calculations on doping and binding energy of N-BPQD were analyzed via the density functional theory (DFT) simulations. Moreover, N-BPQD showed extremely low cytotoxicity, which is a promising as a good fluorescent probe for stem cell imaging application. This work provide a new platform for diagnosis of jaundice disease. [ABSTRACT FROM AUTHOR]

• MIPs were synthesized as a macromolecule to extract histamine from canned tuna. • Carbon quantum dots were functioned as the fluorescent probe. • A microfluidic paper device was developed. • This assay achieved the limit of detection of 14.04 mg/kg of histamine in canned tuna. • The entire test could be completed in 45 min including sample preparation. We reported the development of a smartphone-integrated microfluidic paper-based optosensing platform for in-situ detection and quantification of histamine in canned tuna. Molecularly imprinted polymers were synthesized via precipitation polymerization and utilized as dispersive solid phase extraction sorbent to selectively extract histamine from canned tuna. Carbon quantum dots functioning as a fluorescent probe were synthesized and introduced onto the microzones of the microfluidic paper device. This facilitated a noticeable fluorescence color change from dark red to vivid blue upon the addition of histamine. The change in fluorescence on the paper device was converted into specific RGB values using a portable UV light box combined with a smartphone. This assay achieved the limit of detection of 14.04 mg/kg with the linear range from 20 to 100 mg/kg of histamine in canned tuna. The entire molecular imprinting-microfluidic optosensing test could be completed in 45 min including sample preparation. [ABSTRACT FROM AUTHOR]

The synthesis of carbon quantum dots (CQDs) from biomass through a "bottom-up" method has attracted a great deal of interest because of its outstanding environmental and economic advantages. However, the yield of biomass-based CQDs is still low due to the high polymerization of biochar. In this study, we propose a new approach for harvesting high-yield biomass-based CQDs by integrating mechanochemistry and strong chemical oxidation. Ball milling can reduce the particle size and resistance of biochar and increase the contents of C C, while the powerful oxidant HOO- produced by alkaline hydrogen peroxide can break C C to generate biomass-based CQDs. Using this two-step process, the yields of biomass-based CQDs reached 57.75% for blue-green algae, 65.8% for straw, 47.9% for corn protein meal, and 45.35% for Typha angustifolia. Based on the excellent sensitivity and selectivity for Fe3+ of biomass-based CQDs, CQDs paper-based sensors were prepared for expedient and precise detection of Fe3+ in surface water, wastewater treatment plant effluent, and tap water. When the Fe3+ content is between 0 and 60 μM, the R2 of Fe3+ detection by blue-green algae CQDs can reach 0.9956. This work provides a new and reliable method for the large-scale preparation of biomass-based CQDs and expands their environmental applications. [Display omitted] • A method was proposed to improve the yield of biomass-based carbon quantum dot (CQD). • Ball milling can reduce the resistance of biochar and increase the contents of C C. • This scalable method is applicable to other biomass wastes. • The CQDs has excellent sensitivity and selectivity for Fe3+. • The paper-based CQD sensors are applicable in different water bodies. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots (CQDs) and rhodamine B (RhB) were physically mixed to construct a highly selective and sensitive ratiometric fluorescent sensor (CQDs@RhB) for the quantitative and visual detection of Hg2+. After adding Hg2+, the emission peak of CQDs at 445 nm was quenched and the peak of RhB at 575 nm remained unchanged; the ratio of the two emission peaks had a linear relationship with the Hg2+ concentration. The CQDs@RhB had a detection range of 0–15 µM and the limit of detection (LOD) is 65.93 nM and a color change from blue to pink was visible to the naked eye under ultraviolet light. The study revealed a static quenching mechanism of CQDs@RhB. The established method was successfully applied to the detection of Hg2+ in real water and rice samples with satisfactory results. In addition, a portable fluorescent paper-based sensor platform was developed using computer software assistance. The relationship with Hg2+ concentration was constructed by converting the pictures obtained under ultraviolet light to RGB color mode for visualization and quantitative detection of Hg2+. This study provides a valuable strategy for constructing a rapid detection system for Hg2+ in the field. [ABSTRACT FROM AUTHOR]

Nasal ions environment plays a crucial role in maintaining nasal physiology and supports olfactory transmission. Addressing the limited research on nasal ion levels and their association with olfactory function, paper-based sensors were developed for determination of sodium, potassium, calcium and chloride in the nasal mucus of healthy volunteers and patients with olfactory dysfunction. Multi-walled carbon nanotubes and carbon quantum dots from beetroot were incorporated into paper substrate where sensors were designed with ion association complexes for sodium, potassium, calcium and chloride enhancing the recognition sensing capabilities. The sensors composition was optimized, including ion-exchange materials and plasticizers, to enhance sensitivity and selectivity. The performance of the sensors is evaluated based on Nernstian slope, dynamic range, detection limit and response time. Selectivity of the sensors was tested and the results demonstrated high selectivity for the target ions. The sensors were successfully determined sodium, potassium, calcium and chloride levels in nasal mucus of healthy volunteers and patients with olfactory dysfunction. The results revealed elevated calcium levels in patients with olfactory dysfunction, highlighting associated diagnostic implications. This suggests that the proposed sensors could serve as a diagnostic tool for olfactory evaluation, particularly in resource-constrained settings where access to advanced diagnostic tools is limited. [Display omitted] • Develop paper sensors for precise ion detection in nasal mucus. • Optimize sensors with nanoparticles to enhance sensitivity and selectivity. • Investigate the diagnostic potential for efficiently assessing olfactory dysfunction. [ABSTRACT FROM AUTHOR]

The use of papers as substrates in the process of manufacturing flexible electronic components is urgently required to obtain cost-effective products as well as to expand the potential applications of such components. This study aimed to examine the suitability of three different types of paper for sensor applications using an inkjet printing process. Three types of paper (denoted as Types 1, 2, and 3) designed for specific applications in printed electronics were selected and entirely characterized in terms of microscopic and macroscopic properties, such as internal fibers structure, cross-sectional layer structure, surface roughness, and hardness. Dot arrays were printed on these three types of paper to determine how the papers absorb silver ink and which one is the best substrate for manufacturing printed electronic components. After a comprehensive analysis, the paper that exhibited the best feature was further studied as a substrate for printing interdigitated electrodes to develop a humidity sensor. The Type 2 paper-based sensor demonstrated the variation in capacitance in the range from 9.4 to 10.6 pF while changing the relative humidity (RH) from 40 to 90%. Thus, Type 2 has the great potential for application in flexible sensors, suggesting the possibility of industrial scalability and mass production of inexpensive, biodegradable, and conformable electronic components. [ABSTRACT FROM AUTHOR]

The nanoLED, an electroluminescent device utilizing quantum dots (QDs), is expected to be a promising candidate for the next‐generation display. This paper presents a newly developed QD protection technology for cadmium‐free nanoLEDs that enables simultaneous achievement of high‐efficiency electroluminescence (EL) and long lifetime. The device which was prototyped by applying ZnSeTe blue QDs to an emissive layer demonstrated a maximum external quantum efficiency (EQE) of 21.0% and a luminance half‐lifetime (LT50) of 128,000 hours at 100 nits. These results indicate that cadmium‐free nanoLEDs can meet the requirements for display application in terms of both EL efficiency and reliability. [ABSTRACT FROM AUTHOR]

In this paper the photolithgraphic patterning approaches of quantum dots in electroluminescent devices and demoes were summerized. Photolithograpy process meets the requirements for QLED mass production, including high pixel density, large‐area process and low cost. We summerized three approaches of quantum dot photolithographic procrsses, including direct photolithography, photolithography with lift‐off process and sacrificial layer assisted patterning (SLAP). [ABSTRACT FROM AUTHOR]

The current state of ozone layer depletion caused by ultraviolet (UV) radiation and its impacts on human health and the environment make eco-friendly UV-blocking materials highly important. The present study reports an efficient, biodegradable film using polyvinyl alcohol (PVA) functionalized with cellulose nanocrystals (CNCs) and carbon dots (CDs) that exhibits outstanding UV-blocking capabilities through blue light conversion. This study demonstrated an effective way for the clean and improved utilisation of waste paper by extracting CNCs from it and a green hydrothermal method employed for synthesising CDs from CNCs. The film composed of PVA blended with CNCs and CDs used in this work successfully blocked 99.7 UV-C, 98.5 UV-B, and 92.1% UV-A while transmitting 80.1% visible light. Furthermore, this film converted UV rays into blue light, indicating its sunlight conversion properties. High UV resistance, UV-to-blue light conversion capabilities, and excellent visible light transmission of these films make them a new contender among PVA-based UV-shielding and sunlight conversion materials. [ABSTRACT FROM AUTHOR]

On‐paper microsupercapacitors (MSCs) are a key energy storage component for disposable electronics that are anticipated to essentially address the increasing global concern of electronic waste. However, nearly none of the present on‐paper MSCs combine eco‐friendliness with high electrochemical performance (especially the rate capacity). In this work, highly reliable conductive inks based on the ternary composite of poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS), graphene quantum dots and graphene are developed for scalable inkjet printing of compact (footprint area ≈ 20 mm2) disposable MSCs on commercial paper substrates. Without any post treatment, the printed patterns attain a sheet resistance as low as 4 Ω ▫−1. The metal‐free all‐solid‐state MSCs exhibit a maximum areal capacitance > 2 mF cm−2 at a high scan rate of 1000 mV s−1, long cycle life (>95% capacitance retention after 10 000 cycles), excellent flexibility, and long service time. Remarkably, the "totally metal‐free" MSC arrays are fully inkjet printed on paper substrates and also exhibit high rate performance. The life cycle assessment indicates that these printed devices have much lower eco‐toxicity and global warming potential than other on‐paper MSCs. [ABSTRACT FROM AUTHOR]

Synthesis of nitrogen and sulfur-doped graphene quantum dots via pyrolysis method using citric acid as a carbon source and L-cysteine as a sulfur and nitrogen source, for the detection of catechol and tryptophol on paper-based electrodes. [Display omitted] • N,S-GQDs is synthesized by pyrolysis in one step. • The detection of catechol and tryptophol is based on a paper-based ECL sensor using N,S-GQDs. • Establishing a Catechol Detection System in Wastewater. • Determination of the Quorum Sensing Molecule (Tryptophol) in Candida albicans. In this study, Nitrogen and Sulfur co-doped Graphene Quantum Dots (N, S-GQDs) were synthesized via a pyrolysis approach, utilizing citric acid as the carbon source and L-cysteine as the nitrogen and sulfur sources. These N, S-GQDs were used to develop a novel paper-based electrochemiluminescence (ECL) sensor for the detection of catechol (CC) and tryptophol, two potentially hazardous substances in the environment. Screen printing technology was utilized to construct the ECL sensor on filter paper, incorporating a hydrophobic layer, working and counter electrodes, and a reference electrode. The presence of CC and tryptophol was found to result in a decrease in the ECL intensity of the quantum dots (QDs), this quenching phenomenon is attributed to the oxidation of these substances within the electrochemical system and the subsequent electron transfer from the excited state of the QDs to the oxidation products. The sensor demonstrated a linear detection range for CC and tryptophol from 0.01 to 1000 μM, with detection limits of 0.0082 μM and 0.0066 μM, respectively, and exhibited excellent selectivity, stability, and repeatability. This cost-effective and efficient monitoring technique holds significant promise for environmental and health safety by facilitating the detection of CC and tryptophol, thereby mitigating their potential adverse impacts. [ABSTRACT FROM AUTHOR]

The rapid detection of insecticides such as parathion-methyl (PM) requires methods with high sensitivities and selectivities. Herein, a dual catalytic amplification strategy was developed using Fe3O4 nanozyme-supported carbon quantum dots and silver terephthalate metal–organic frameworks (Fe3O4/C-dots@Ag-MOFs) as current amplification elements. Based on this strategy, a novel electrochemical microfluidic paper-based chip was designed to detect PM. Fe3O4/C-dots@Ag-MOFs were synthesised by a hydrothermal method, and a molecularly imprinted polymer (MIP) was then synthesised on the surface of Fe3O4/C-dots@Ag-MOFs using PM as a template molecule. Finally, the reaction zone of a chip was modified with MIP/Fe3O4/C-dots@Ag-MOFs. PM from a sample introduced into the reaction zone was captured by the MIP, which generated a reduction current response at − 0.53 V in a three-electrode system embedded in the chip. Simultaneous catalysis by Fe3O4/C-dots and Ag-MOFs significantly enhanced the signal. The chip had a detection limit of 1.16 × 10−11 mol L−1 and was successfully applied to the determination of PM in agricultural products and environmental samples with recovery rates ranging from 82.7 to 109%, with a relative standard deviation (RSD) of less than 5.0%. This approach of combining a dual catalytic amplification strategy with an MIP significantly increased the sensitivity as well as selectivity of chips and can potentially be used to detect a wide variety of target analytes using microfluidic paper-based chips. [ABSTRACT FROM AUTHOR]

Paper-based biosensors featuring immunoconjugated gold nanoparticles have gained extraordinary momentum in recent times as the platform of choice in key cases of field applications, including the so-called rapid antigen tests for SARS-CoV-2. Here, we propose a revision of this format, one that may leverage on the most recent advances in materials science and data processing. In particular, we target an amplifiable DNA rather than a protein analyte, and we replace gold nanospheres with anisotropic nanorods, which are intrinsically brighter by a factor of ~ 10, and multiplexable. By comparison with a gold-standard method for dot-blot readout with digoxigenin, we show that gold nanorods entail much faster and easier processing, at the cost of a higher limit of detection (from below 1 to 10 ppm in the case of plasmid DNA containing a target transgene, in our current setup). In addition, we test a complete workflow to acquire and process photographs of dot-blot membranes with custom-made hardware and regression tools, as a strategy to gain more analytical sensitivity and potential for quantification. A leave-one-out approach for training and validation with as few as 36 sample instances already improves the limit of detection reached by the naked eye by a factor around 2. Taken together, we conjecture that the synergistic combination of new materials and innovative tools for data processing may bring the analytical sensitivity of paper-based biosensors to approach the level of lab-grade molecular tests. [ABSTRACT FROM AUTHOR]

Simple and visual quantitative detection of foodborne pathogens can effectively reduce the outbreaks of foodborne diseases. Herein, we developed a simple and sensitive quantum dot (QD)-based paper device for visual and quantitative detection of Escherichia coli (E. coli) O157:H7 based on immunomagnetic separation and nanoparticle dissolution-triggered signal amplification. In this study, E. coli O157:H7 was magnetically separated and labeled with silver nanoparticles (AgNPs), and the AgNP labels can be converted into millions of Ag ions, which subsequently quench the fluorescence of QDs in the paper strip, which along with the readout can be visualized and quantified by the change in length of fluorescent quenched band. Owing to the high capture efficiency and effective signal amplification, as low as 500 cfu mL−1 of E. coli O157:H7 could be easily detected by naked eyes. Furthermore, this novel platform was successfully applied to detect E. coli O157:H7 in spiked milk samples with good accuracy, indicating its potential in the detection of foodborne pathogens in real samples. [ABSTRACT FROM AUTHOR]

Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min. [ABSTRACT FROM AUTHOR]

[Display omitted] • M-GQDs exhibit excellent performance in distinguishing and detecting antibiotics. • Special phenomena are presented when various kinds of antibiotics are added with different mechanisms. • The probe shows low LOD for DOX, PEF and LEV of 39.3 nM, 48.6 nM and 35.1 nM. • A 3D μPAD-based platform is proposed for real-time monitoring antibiotics. For antibiotics misuse since the global outbreak of COVID 19, a novel strategy for discriminating and detecting antibiotics is proposed based on the graphene quantum dots with multi-doped heteroatoms including F, N and P (M-GQDs), which exhibit blue emission (419.0 nm) under the excitation of 336.0 nm. Specifically, the fluorescence of M-GQDs is quenched by tetracyclines (TCs) owing to inner filter effect (IFE) and enhanced by alkane-modified fluoroquinolones (AFQs), which is attributed to restricted conformational rotation based on π-π stacking, hydrogen-bonding and electrostatic interactions. Meanwhile, the electron-accepting property of oxazine ring in oxazine-modified fluoroquinolones (OFQs) increases emission peak at 498.0 nm and decreases emission peak at 419.0 nm as the color changes from blue to cyan. Moreover, a cascade system integrated with 3D microfluidic paper‐based analytical device (3D-μPAD) is applied successfully for visually distinguishing three antibiotics, which shows great potential and versatility of M-GQDs for food safety monitoring. [ABSTRACT FROM AUTHOR]

Nanoscale integration is difficult on rough surfaces despite their ubiquity and usefulness. Paper is an emerging material system because it is renewable, flexible, and lightweight. However, owing to the rough surface of paper, it is difficult to use conventional nanoscale integration methods. Herein, nanoscale printing of CdSe/ZnS quantum dots on paper using a 3D printing method with surface adaptive control of the femtoliter meniscus is demonstrated. The approach allows the direct integration of light‐emitting materials on the intact surface of paper with nanoscale lateral confinement. The 3D‐printed nanostructures can be treated as a planar pattern of the nanoscale dots when viewed from the top. The individually addressable nature of the 3D printing method enables the equalization of the printed heights, which is essential for practical use in general planar systems. This method can be used in many areas that require paper such as paper electronics, security printing, biomedical engineering, and possibly other material systems with rough surfaces. [ABSTRACT FROM AUTHOR]

One of the micro‐LED direct view display major challenges is to find ways of drastically dropping the cost, for instance, by reducing the micro‐LED size, simplifying the assembly process and improving the assembly yield. In this paper, we present Aledia's GaN‐on‐Si nanowire (NW) LED technology made on standard 8 "Si wafers, scalable to 12" wafers. We will present two components using our NW technology and their use case for the manufacturing of micro‐LED direct view fine pitch display: NWs RGB three color chips obtained using quantum dot (QD) color conversion at chip level. The RGB chips can then be transferred on PCB or glass or TFT substrates for panel manufacturing.The integration within the same chip of a three color RGB chip together with its CMOS driving electronics. Those chips allow to obtain an active‐matrix architecture on any passive backplane without the use of TFT. [ABSTRACT FROM AUTHOR]