Near-infrared-emitting two-dimensional codes based on lattice-strained core/(doped) shell quantum dots with long fluorescence lifetime

Recent Advances in Construction Strategies for Fluorescence Sensing Films

A year ago, film-based fluorescent sensors (FFSs) were recognized in the "IUPAC Top Ten Emerging Technologies in Chemistry 2022" due to their extensive application in detecting hidden explosives, illicit drugs, and volatile organic compounds. These sensors offer high sensitivity, specificity, immunity to light scattering, and noninvasiveness. The core of FFSs is the construction of high-performance fluorescent sensing films, which are dependent on the processes of "energy transfer" and "mass transfer" in the active layer and involve complex interactions between sensing molecules and analytes. This Perspective focuses on the latest strategies in constructing these films, emphasizing the design of sensing molecules with various innovative features and structures that enhance the mass transfer efficiency. Additionally, it discusses the ongoing challenges and potential advancements in the field of FFSs.

Photoswitch-Based Fluorescence Encoding of Microspheres in a Limited Spectral Window for Multiplexed Detection

Fluorescence barcoding with multicolor fluorophores is limited by spectral crowding. Herein, we propose a fluorescence encoding method in a single-color channel with photoswitches. The photochromic naphthopyran was used to mediate the fluorescence of polystyrene microspheres through resonance energy transfer. The initial fluorescence intensity (F₀) and the fluorescence after UV light activation (F/F₀) were combined to generate hundreds of 2-dimensional barcodes. The coding capacity was further expanded with the different chemical kinetics of the photoswitches. The photoswitch-based fluorescence barcodes were applied to simultaneously and selectively detect the DNA sequences of COVID-19 (with related mutations) as a proof-of-concept for real applications. The compatibility with the state-of-the-art fluorescence microscopes and simple encoding and decoding make the method very attractive for multiplexed and high-throughput analyses.

A facile fabrication of conjugated fluorescent nanoparticles and micro-scale patterned encryption via high resolution inkjet printing

Conjugated fluorescent materials are getting more and more attention in the biomedical arena due to their high fluorescence intensity, non-bleaching and good biocompatibility. However, conjugated fluorescent materials are still not widely used in the field of anti-counterfeiting and pattern encryption due to their extremely low solubility and enormous difficulties in processing. Here, we use a facile approach to fabricate conjugated polymer fluorescent nanoparticles through a classic micro-emulsion method to address these issues. The particle size, loading materials and fluorescence intensity can be tuned as demanded. Later, these particles are transformed into invisible inks for inkjet printers to achieve micro-scale pattern encryption. These patterns show an ultra-high accuracy of around 30 micrometres. They can be used as QR codes for information encryption with 3 times more information encryption and great anti-counterfeiting ability. Finally, we establish an identification recognition system to check their validity. The scenario is the patient identification system of a hospital. The results show that these tags can be read in less than 3 seconds and they can last for 12 months at least. This facile approach holds great potential and bright prospects in the field of privacy protection, information encryption and anti-counterfeiting.

Functional Micro-/Nanomaterials for Multiplexed Biodetection

When analyzing biological phenomena and processes, multiplexed biodetection has many advantages over single-factor biodetection and is highly relevant to both human health issues and advancements in the life sciences. However, many key problems with current multiplexed biodetection strategies remain unresolved. Herein, the main issues are analyzed and summarized: 1) generating sufficient signal to label targets, 2) improving the signal-to-noise ratio to ensure total detection sensitivity, and 3) simplifying the detection process to reduce the time and labor costs of multiple target detection. Then, available solutions made possible by designing and controlling the properties of micro- and nanomaterials are introduced. The aim is to emphasize the role that micro-/nanomaterials can play in the improvement of multiplexed biodetection strategies. Through analyzing existing problems, introducing state-of-the-art developments regarding relevant materials, and discussing future directions of the field, it is hopeful to help promote necessary developments in multiplexed biodetection and associated scientific research.

Anodic near-infrared electrochemiluminescence from Cu-doped CdTe quantum dots for tetracycline detection

A sensitive anodic near-infrared electrochemiluminescence (ECL) immunosensor for the detection of tetracycline, based on Cu-doped CdTe quantum dots, was fabricated for the first time in this work. We have synthesized Cu-doped CdTe quantum dots by co-precipitation. The emission spectrum of the Cu-doped CdTe quantum dots could reach the near-infrared region at 730 nm in a short reflux time. More importantly, the ECL intensity of the CdTe quantum dots was enhanced by 2 fold after Cu element doping, which was attributed to the Cu d-orbital mixed with the conduction band and valence band of the host CdTe quantum dots. Inspired by the strong anodic ECL intensity of Cu-doped CdTe quantum dots, the anodic near infrared ECL sensor was constructed to detect tetracycline by competitive immunoassay. The detection range of the developed biosensor was 0.01-10 ng mL-1 and the detection limit was 0.0030 ng mL-1. In addition, the biosensor showed outstanding selectivity, long-term stability and high reproducibility, which has great potential in the field of analysis and detection.

Functionalization of Metal and Carbon Nanoparticles with Potential in Cancer Theranostics

Cancer theranostics is a new concept of medical approach that attempts to combine in a unique nanoplatform diagnosis, monitoring and therapy so as to provide eradication of a solid tumor in a non-invasive fashion. There are many available solutions to tackle cancer using theranostic agents such as photothermal therapy (PTT) and photodynamic therapy (PDT) under the guidance of imaging techniques (e.g., magnetic resonance-MRI, photoacoustic-PA or computed tomography-CT imaging). Additionally, there are several potential theranostic nanoplatforms able to combine diagnosis and therapy at once, such as gold nanoparticles (GNPs), graphene oxide (GO), superparamagnetic iron oxide nanoparticles (SPIONs) and carbon nanodots (CDs). Currently, surface functionalization of these nanoplatforms is an extremely useful protocol for effectively tuning their structures, interface features and physicochemical properties. This approach is much more reliable and amenable to fine adjustment, reaching both physicochemical and regulatory requirements as a function of the specific field of application. Here, we summarize and compare the most promising metal- and carbon-based theranostic tools reported as potential candidates in precision cancer theranostics. We focused our review on the latest developments in surface functionalization strategies for these nanosystems, or hybrid nanocomposites consisting of their combination, and discuss their main characteristics and potential applications in precision cancer medicine.

Lifetime-Engineered Carbon Nanodots for Time Division Duplexing

Optical multiplexing attracts considerable attention in the field of information encryption, optical probe, and time-resolved bioimaging. However, the optical multiplexing based on rare-earth nanoparticles suffers from heavy metal elements and relatively short lifetimes; sophisticated facilities are thus needed. Herein, time division duplexing based on eco-friendly carbon nanodots (CNDs) with manipulative luminescence lifetimes is demonstrated. In a single green color emission channel, the luminescence lifetimes of the CNDs can be manipulated from nanosecond level to second level by introducing water, while the lifetime of the CNDs confined by a silica shell stays. Time division duplexing based on the CNDs and CNDs@silica with distinct lifetimes is realized and spatio-temporal overlapping information is thus resolved. High-level information encryption using the time division duplexing technology is realized. This work may promise the potential applications of CNDs in multi-lifetime channels biological imaging, high-density information storage, and anti-counterfeiting.

Lanthanide-Based Optical Probes of Biological Systems

The unique photophysical properties of lanthanides, such as europium, terbium, and ytterbium, make them versatile molecular probes of biological systems. In particular, their long-lived photoluminescence, narrow bandwidth emissions, and large Stokes shifts enable experiments that are infeasible with organic fluorophores and fluorescent proteins. The ability of these metal ions to undergo luminescence resonance energy transfer, and photon upconversion further expands the capabilities of lanthanide probes. In this review, we describe recent advances in the design of lanthanide luminophores and their application in biological research. We also summarize the latest detection systems that have been developed to fully exploit the optical properties of lanthanide luminophores. We conclude with a discussion of remaining challenges and new frontiers in lanthanide technologies. The unprecedented levels of sensitivity and multiplexing afforded by rare-earth elements illustrate how chemistry can enable new approaches in biology.

Near Infrared (NIR) imaging: Exploring biologically relevant chemical space for lanthanide complexes

Near Infrared (NIR) imaging agents are extensively used in the biological or preclinical treatment and diagnosis of a wide range of diseases including cancers and tumors. The current arsenal of NIR compounds are most constituted by organic dyes, polymers, inorganic nanomaterials, whereas Ln molecular complexes explore an alternative approach to design NIR probes that are potentially bring new molecular toolkits into the biomedicine. In this review, NIR imaging agents are categorized according to their molecular sizes, constitution and the key properties and features of each class of compounds are briefly defined wherever possible. To better elucidate the features of Ln complexes, we provide a succinct understanding of sensitization process and molecular Ln luminescence at a mechanistic level, which may help to deliver new insights to design NIR imaging probes. Finally, we used our work on NIR ytterbium (Yb³⁺) probes as an example to raise awareness of exploring biologically relevant chemical space for lanthanide complexes as chemical entities for biological activity.

Nanomedicines for Near-Infrared Fluorescent Lifetime-Based Bioimaging

Nanomedicines refer to the application of nanotechnology in disease diagnosis, treatment, and monitoring. Bioimaging provides crucial biological information for disease diagnosis and treatment monitoring. Fluorescent bioimaging shows the advantages of good contrast and a vast variety of signal readouts and yet suffers from imaging depth due to the background noise from the autofluorescence of tissue and light scattering. Near-infrared fluorescent lifetime bioimaging (NIR- FLTB) suppresses such background noises and significantly improves signal-to-background ratio. This article gives an overview of recent advances in NIR- FLTB using organic compounds and nanomaterials as contrast agent (CA). The advantages and disadvantages of each CA are discussed in detail. We survey relevant reports about NIR-FLTB in recent years and summarize important findings or progresses. In addition, emerging hybrid bioimaging techniques are introduced, such as ultrasound-modulated FLTB. The challenges and an outlook for NIR- FLTB development are discussed at the end, aiming to provide references and inspire new ideas for future nanomedicine development.

An invisible private 2D barcode design and implementation with tunable fluorescent nanoparticles

The popularity of 2D barcodes is playing a key role in simplifying people's daily life activities, such as identification, quick payment, checking in and checking out, etc. However, relevant issues have emerged as their popularity has soared. The most urgent and representative problem is decryption, which may lead to serious information leakage and substantial damage to organizations, such as governments and international enterprises. This issue is mainly due to the visibility of 2D barcodes. In order to prevent potential privacy violation and sensitive information leakage through easy access of those visible 2D barcodes, we have designed and fabricated invisible 2D barcodes that will only be visible under UV illumination. This approach provides a promising solution to address the previous problem by transferring 2D barcodes into an invisible state. We have employed a typical micro-emulsion method to fabricate polystyrene (PS) fluorescent nanoparticles due to its simplicity. The invisible patterns can and will only be accessed and recognized under UV light illumination to protect personal private information. These invisible 2D barcodes provide a feasible solution for personal information protection and fit with a patient's privacy protection scenario very well, as we have demonstrated.

AIEgens Barcodes Combined with AIEgens Nanobeads for High-sensitivity Multiplexed Detection

Suspension arrays based on optical encoded microspheres have attracted great attention for multiplexed detection in gene analysis, protein profiling, early disease diagnosis, treatment monitoring and so on. However, the fluorescence stability of barcodes and detection sensitivity require further improvement to meet the increasing demands of “precision diagnosis”. Methods: This work reports a novel suspension array platform based on extremely stable AIEgens (AIE33 and AIE NIR800) microbeads as barcodes and AIEgens (1,1,2,3,4,5-Hexaphenyl-1H-silole, HPS) nanobeads as fluorescent signal reporter coupled with flow cytometry for multiplexed detection. Results: Due to the excellent fluorescent signal amplification effect of the HPS nanobeads, our multiplex assay showed enhanced detection sensitivity, compared to multiplex assay using QDs nanobeads (up to 3-fold improvement) and commercial organic dye of phycoerythrin (up to 5-fold improvement) as the fluorescent signal reporters. Conclusion: Furthermore, validating experiments showed similar detection performance to the clinical gold-standard method of ImmunoCAP for allergen detection in patient serum samples, demonstrating the suspension array platform based on AIEgens microbeads with excellent fluorescence stability and AIEgens nanobeads with strong signal amplification ability is promising for high-sensitivity multiplexed bioassay applications.

Cu-doped quantum dots: a new class of near-infrared emitting fluorophores for bioanalysis and bioimaging

Transition metal ion-doped quantum dots (QDs) exhibit unique optical and photophysical properties that offer significant advantages over undoped QDs, such as larger Stokes shift to avoid self-absorption/energy transfer, longer excited-state lifetimes, wider spectral window, and improved chemical and thermal stability. Among the doped QDs emitters, Cu is widely introduced into the doped QDs as novel, efficient, stable, and tunable optical materials that span a wide spectrum from blue to near-infrared (NIR) light. Their unique physical and chemical characteristics enable the use of Cu-doped QDs as NIR labels for bioanalysis and bioimaging. In this review, we discuss doping mechanisms and optical properties of Cu-doped QDs that are capable of NIR emission. Applications of Cu-doped QDs in in vitro biosensing and in in vivo bioimaging are highlighted. Moreover, a prospect of the future of Cu-doped QDs for bioanalysis and bioimaging are also summarized.

Fluorescence lifetime imaging of upper gastrointestinal pH in vivo with a lanthanide based near-infrared τ probe

Lanthanide complex was successfully applied in the design of pH-responsive NIR τ probe for quantitative in vivo imaging.

Time-resolved fluorescence lifetime imaging (FLIM) in the near-infrared region of 900–1700 nm not only allows a deep tissue penetration depth but also offers the unique benefit of the quantitative visualization of molecular events in vivo and is independent of local luminescence intensity and fluorophore concentration. Herein, we report the design of a wide-range pH sensitive molecular probe based on Yb³⁺ porphyrinate. The Yb³⁺ probe shows increasing NIR emission and lifetime with pK_a values of ca. 6.6 from pH 9.0 and 5.0 and also displays an elongated lifetime from ca. 135 to 170 μs at lower pH values (5.0–1.0) due to aggregation and reduced exposure to water at low pH values. Importantly, the probe is able to monitor a wide range of in vivo gastrointestinal pH values in mice models and the potential applications in imaging-guided gastrointestinal diagnostics and therapeutics were revealed. This study shows that lifetime contrast is important for preclinical imaging; lanthanide complexes could be successfully used in the design of stimuli-responsive NIR τ probes for advanced in vivo imaging.

Conformational Details of Quantum Dot-DNA Resolved by Förster Resonance Energy Transfer Lifetime Nanoruler

DNA-nanoparticle conjugates are important tools in nanobiotechnology. Knowing the orientation, function, and length of DNA on nanoparticle surfaces at low nanomolar concentrations under physiological conditions is therefore of great interest. Here, we investigate the conformation of a 31 nucleotides (nt) long DNA attached to a semiconductor quantum dot (QD) via Förster resonance energy transfer (FRET) from Tb-DNA probes hybridized to different positions on the QD-DNA. Precise Tb-to-QD distance determination from 7 to 14 nm along 26 nt of the peptide-appended QD-DNA was realized by time-resolved FRET spectroscopy. The FRET nanoruler measured linear single-stranded (ssDNA) and double-stranded (dsDNA) extensions of ∼0.15 and ∼0.31 nm per base, reflecting the different conformations. Comparison with biomolecular modeling confirmed the denser conformation of ssDNA and a possibly more flexible orientation on the QD surface, whereas the dsDNA was fully extended with radial orientation. The temporally distinct photoluminescence decays of the different DNA-FRET configurations were used for prototypical DNA hybridization assays that demonstrated the large potential for extended temporal multiplexing. The extensive experimental and theoretical analysis of 11 different distances/configurations of the same QD-DNA conjugate provided important information on DNA conformation on nanoparticle surfaces and will be an important benchmark for the development and optimization of DNA-nanobiosensors.

A proof-of-concept application of water-soluble ytterbium(iii) molecular probes in in vivo NIR-II whole body bioimaging

Lanthanide complexes are firstly applied for in vivo NIR-II high resolution whole body bioimaging.

Single-Nanoparticle Cell Barcoding by Tunable FRET from Lanthanides to Quantum Dots

Fluorescence barcoding based on nanoparticles provides many advantages for multiparameter imaging. However, creating different concentration‐independent codes without mixing various nanoparticles and by using single‐wavelength excitation and emission for multiplexed cellular imaging is extremely challenging. Herein, we report the development of quantum dots (QDs) with two different SiO₂ shell thicknesses (6 and 12 nm) that are coated with two different lanthanide complexes (Tb and Eu). FRET from the Tb or Eu donors to the QD acceptors resulted in four distinct photoluminescence (PL) decays, which were encoded by simple time‐gated (TG) PL intensity detection in three individual temporal detection windows. The well‐defined single‐nanoparticle codes were used for live cell imaging and a one‐measurement distinction of four different cells in a single field of view. This single‐color barcoding strategy opens new opportunities for multiplexed labeling and tracking of cells.

Impurity Location-Dependent Relaxation Dynamics of Cu:CdS Quantum Dots

Various types of 2% Cu-incorporated CdS (Cu:CdS) quantum dots (QDs) with very similar sizes have been prepared via a water soluble colloidal method. The locations of Cu impurities in CdS host nanocrystals have been controlled by adopting three different synthetic ways of doping, exchange, and adsorption to understand the impurity location-dependent relaxation dynamics of charge carriers. The oxidation state of incorporated Cu impurities has been found to be +1 and the band-gap energy of Cu:CdS QDs decreases as Cu2S forms at the surfaces of CdS QDs. Broad and red-shifted emission with a large Stokes shift has been observed for Cu:CdS QDs as newly produced Cu-related defects become luminescent centers. The energetically favored hole trapping of thiol molecules, as well as the local environment, inhibits the radiative recombination processes of Cu:CdS QDs, thus resulting in low photoluminescence. Upon excitation, an electron is promoted to the conduction band, leaving a hole on the valence band. The hole is transferred to the Cu+ d-state, changing Cu+ into Cu2+, which then participates in radiative recombination with an electron. Electrons in the conduction band are ensnared into shallow-trap sites within 52 ns. The electrons can be further captured on the time scale of 260 ns into deep-trap sites, where electrons recombine with holes in 820 ns. Our in-depth analysis of carrier relaxation has shown that the possibilities of both nonradiative recombination and energy transfer to Cu impurities become high when Cu ions are located at the surface of CdS QDs.

Engineering Quantum Dots with Different Emission Wavelengths and Specific Fluorescence Lifetimes for Spectrally and Temporally Multiplexed Imaging of Cells

In this work, a proof-of-concept study was performed to examine the potential of spectrally and temporally multiplexed imaging of cells by using quantum dots (QDs). The CdSe and ZAIS QDs with different emission wavelengths and well-separated fluorescence lifetimes were prepared to provide 2-dimensional information. After incubation with cells, the same type of QDs with different emission wavelengths were distinguishable in spectral imaging while different types of QDs with similar emission wavelengths but well-separated fluorescence lifetimes were resolvable in fluorescence lifetime imaging. For cells co-stained with dye and different types of QDs, the fluorescence lifetime imaging microscopy (FLIM) images showed spatially separated patterns that can be split into channel images by using the software-based time gates. Overall, the results demonstrate the feasibility of combining the 2-dimensional encoded QDs for spectrally and temporally multiplexed imaging. This method can be extended to other QDs and organic dyes to maximize the number of measurable species in multiplexed imaging and sensing applications.

Versatile design and synthesis of nano-barcodes

This review provides a critical discussion on the versatile designing and usage of nano-barcodes for various existing and emerging applications.

Gold-Quantum Dot Core-Satellite Assemblies for Lighting Up MicroRNA In Vitro and In Vivo

A high yield DNA-driven gold-quantum dot core-satellite is developed for miRNA detection in vitro and vivo. In the presence of the target miRNA, the DNA hairpin between core and satellite is ruined, resulting in the recovery of fluorescence. The limit of detection for miRNA-21 detection in living cells reaches 296 copies per cell.

Four-Dimensional Screening Anti-Counterfeiting Pattern by Inkjet Printed Photonic Crystals

A four-dimensional screening anti-counterfeiting QR code composed of differently shaped photonic crystal (PC) dots has been fabricated that could display four images depending on different lighting conditions. By controlling the rheology of poly(dimethylsiloxane) (PDMS), three kinds of PC dots could be sequentially integrated into one pattern using the layer-by-layer printing strategy. The information can be encoded and stored in shapes and read out by the difference in optical properties.

Living Cell Multilifetime Encoding Based on Lifetime-Tunable Lattice-Strained Quantum Dots

A series of functional quantum dots (QDs) with widely tunable near-infrared fluorescence emission (620-750 nm) and lifetime (30-160 ns) were synthesized via lattice strain and showed excellent photo, colloid, pH, and lifetime stabilities. The well-defined targeting QDs were first developed for a living cell multilifetime encoding strategy to track and recognize specified tumor cell clusters dependent on lifetime distribution using fluorescence lifetime imaging microscopy.

Tunable fluorescence lifetime of Eu-PMMA films with plasmonic nanostructures for multiplexing

A method to tune fluorescence lifetime of Eu-PMMA films is proposed, which consists of self-assembled gold nanorods on glass substrate covered by Eu-PMMA shell. The fluorescence lifetime is tunable in a wide range, and depends on aspect ratio and mutual distance of gold nanorods. In a single red color emission channel, more than six distinct fluorescence lifetime populations ranging from 356 to 513 μs are obtained. Through theoretical calculation, we attribute tunable fluorescence lifetime to the change of radiative and nonradiative decay rate and density of photon states. In addition, we use these as-prepared Eu-PMMA films for security data storage to demonstrate optical multiplexing applications. The optical multiplexing experiments show an interesting pseudo-information "8" and conceal the real messages "2" and "6".

Wide-Range Tunable Fluorescence Lifetime and Ultrabright Luminescence of Eu-Grafted Plasmonic Core-Shell Nanoparticles for Multiplexing

Wide-range, well-separated, and tunable lifetime nanocomposites with ultrabright fluorescence are highly desirable for applications in optical multiplexing such as multiplexed biological detection, data storage, and security printing. Here, a synthesis of tunable fluorescence lifetime nanocomposites is reported featuring europium chelate grafted onto the surface of plasmonic core-shell nanoparticles, and systematically investigated their optical performance. In a single red color emission channel, more than 12 distinct fluorescence lifetime populations with high fluorescence efficiency (up to 73%) are reported. The fluorescence lifetime of Eu-grafted core-shell nanoparticles exhibits a wider tunable range, possesses larger lifetime interval and is more sensitive to separation distance than that of ordinary Eu-doping core-shell type. These superior performances are attributed to the unique nanostructure of Eu-grafed type. In addition, these as-prepared nanocomposites are used for security printing to demonstrate optical multiplexing applications. The optical multiplexing experiments show an interesting pseudo-information "a rabbit in a well" and conceal the real message "NKU."

Tuning the Upconversion Luminescence Lifetimes of KYb2 F7 :Ho(3+) Nanocrystals for Optical Multiplexing

Conventional luminescent color coding is limited by spectral overlap and the interference of background fluorescence, thus restricting the number of distinguishable identities that can be used in practice. Here, we demonstrate the possibility of generating diverse time-domain codes, specially designed for a single emission band, using lanthanide-doped upconversion nanocrystals. Based on the knowledge of concentration quenching, the upconversion luminescence kinetics of KYb2 F7 : Ho(3+) nanocrystals can be precisely controlled by modifying the dopant concentration of Ho(3+) ions, resulting in a tunable emission lifetime from 75.8 to 1944.5 μs, which suggests the practicality of these time-domain codes for optical multiplexing.

Suspension arrays based on nanoparticle-encoded microspheres for high-throughput multiplexed detection

Spectrometrically or optically encoded microsphere based suspension array technology (SAT) is applicable to the high-throughput, simultaneous detection of multiple analytes within a small, single sample volume. Thanks to the rapid development of nanotechnology, tremendous progress has been made in the multiplexed detecting capability, sensitivity, and photostability of suspension arrays. In this review, we first focus on the current stock of nanoparticle-based barcodes as well as the manufacturing technologies required for their production. We then move on to discuss all existing barcode-based bioanalysis patterns, including the various labels used in suspension arrays, label-free platforms, signal amplification methods, and fluorescence resonance energy transfer (FRET)-based platforms. We then introduce automatic platforms for suspension arrays that use superparamagnetic nanoparticle-based microspheres. Finally, we summarize the current challenges and their proposed solutions, which are centered on improving encoding capacities, alternative probe possibilities, nonspecificity suppression, directional immobilization, and "point of care" platforms. Throughout this review, we aim to provide a comprehensive guide for the design of suspension arrays, with the goal of improving their performance in areas such as multiplexing capacity, throughput, sensitivity, and cost effectiveness. We hope that our summary on the state-of-the-art development of these arrays, our commentary on future challenges, and some proposed avenues for further advances will help drive the development of suspension array technology and its related fields.

Long-decay near-infrared-emitting doped quantum dots for lifetime-based in vivo pH imaging

Long-decay near-infrared-emitting doped quantum dots were synthesized for lifetime-based in vivo pH imaging.