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Surface engineering is a critical step in the functionalization of nanomaterials to improve their optical and electrochemical properties. However, this process remains a challenge in II-VI magic-size clusters (MSCs) due to their high sensitivity to the environment. Herein, we developed a general surface modification strategy to design all-inorganic MSCs by using certain metal salts (cation = Zn

All-inorganic nanocrystals (NCs) are of great importance in a range of electronic devices. However, current all-inorganic NCs suffer from limitations in their optical properties, such as low fluorescence efficiencies. Here, we developed a general surface treatment strategy to obtain intensely luminescent all-inorganic NCs (ILANs). The absolute photoluminescence quantum yields (PLQYs) of red-, green- and blue-emitting ILANs in polar solvents are 97%, 80% and 72%, respectively, which are the highest among inorganically functionalized NCs. Further study revealed that the passivated Lewis basic sites of ILANs by metal cations boosts the efficiency of radiative recombination of electron-hole pairs. While the passivation of Lewis basic sites leads to a high PLQY of ILANs, the exposed Lewis acidic sites provide the opportunities for directly optically patterning of functional NCs with high-resolution. Our studies provide a new surface engineering approach to design functional NCs and create a versatile platform for patterning NCs.

All-inorganic nanocrystals (NCs) are of great importance in a range of electronic devices. However, current all-inorganic NCs suffer from limitations in their optical properties, such as low fluorescence efficiencies. Here, we develop a general surface treatment strategy to obtain intensely luminescent all-inorganic NCs (ILANs) by using designed metal salts with noncoordinating anions that play a dual role in the surface treatment process: (i) removing the original organic ligands and (ii) binding to unpassivated Lewis basic sites to preserve the photoluminescent (PL) properties of the NCs. The absolute photoluminescence quantum yields (PLQYs) of red-emitting CdSe/ZnS NCs, green-emitting CdSe/CdZnSeS/ZnS NCs and blue-emitting CdZnS/ZnS NCs in polar solvents are 97%, 80% and 72%, respectively. Further study reveals that the passivated Lewis basic sites of ILANs by metal cations boost the efficiency of radiative recombination of electron-hole pairs. While the passivation of Lewis basic sites leads to a high PLQY of ILANs, the exposed Lewis acidic sites provide the possibility for in situ tuning of the functions of NCs, creating opportunities for direct optical patterning of functional NCs with high resolution.

Luminescent nanoclusters (NCs), with their easy preparation, ultrafine size, low toxicity, and excellent photostability have recently emerged as novel electrochemiluminescence (ECL) emitters. However, relatively low quantum yield (QY) in both aqueous and organic media has impeded their application in ECL emitter evolution. In this mini-review, we discuss the recent development of NCs in ECL with particular focus on their optical properties. We first classify the NCs according to composition and structure, and then summarize four aspects that affect QY, including environment effects, construction, valence state effects and aggregation-induced ECL. The ECL mechanisms based on NCs are elucidated as well. Finally, we briefly discuss the potential applications of NCs in tumor markers test, immunoassay and serum test. This review aims to provide a comprehensive summary of the progress of NCs in ECL, which will motivate researchers to develop NC chemistry and explore their future applications in ECL.

Glutathione (GSH) serves vital functions in biological systems and associates with various human diseases. In this work, a versatile electrochemiluminence (ECL) and a photoelectrochemical (PEC) "signal on" biosensing platform were developed for a sensitive assay of GSH by a Mn2+-powered DNAzyme amplification strategy combined with DNA-walker-triggered allosteric conversion. First, MnO2 nanosheets were reduced to Mn2+ by GSH; then, Mn2+ as a substitute target triggered DNAzyme-assisted cleavage-cycling amplification to generate numerous DNA output (s3). Meanwhile, the DNA molecular machine was introduced to bridge signal probes for versatile biosensing, which included hairpin DNA as a track and an arm as a walker. The presence of DNA output (s3) activated the swing arm to hybridize with hairpin DNA and then cut it by Nt.BbvCI, which initiated autonomous walking of the arm for forming a large number of streptavidin (SA) aptamers. Thus, a large number of CdS:Mn-SA tags as versatile signal probes was linked to the electrode by specific SA-aptamer binding, generating highly enhanced ECL and PEC signals for sensitive detection of the target. The present biosensing system take advantage of metal ion-based DNAzyme amplification, a DNA walker machine, multi-signals of QDs, and specificity of aptamers, which can provide a universal and efficient biosensing method for detecting various targets. The designed strategy demonstrated good performance for a GSH assay in human serum samples, showing more promising applications than other reported methods.

In this work, we designed a new strategy for ultrasensitive detection of CEA based on efficient electrochemiluminescence (ECL) quenching of Ru(bpy)32+-doped SiO2 nanocomposite by ferrocene using target recycling amplification technique. A large number of Ru@SiO2 ECL signal probe were firstly assembled on the novel magnetic core−shell Fe3O4@Au nanoparticles (NPs), then the ferrocene-labeled ECL quenching probe (Fc-probe) was linked to the magnetic NPs. Finally, numerous DNA1 sequences were produced by target CEA-triggered multiple recycling amplification and displaced the Fc-probe on the magnetic NPs, leading to significantly enhanced ECL signal for CEA detection. Because of the designed cascade signal amplification strategy, the newly developed method achieved a wide linear range of 10 fg/mL to 10 ng/mL with a low detection limit of 3.5 fg/mL. Furthermore, taking advantages of the magnetic Fe3O4@Au NPs for carring abundant signal probes, sensing target and ECL detection, the developed ECL strategy is convenient, rapid and displayed high sensitivity for CEA detection, which has great potential for analyzing the clinical samples in practical disease diagnosis applications.

Glutathione (GSH) serves vital functions in biological systems and associates with various human diseases. In this work, a versatile electrochemiluminence (ECL) and a photoelectrochemical (PEC) "signal on" biosensing platform were developed for a sensitive assay of GSH by a Mn

In this work, a new 3D DNA nanosphere was ingeniously designed and fabricated, which was used to combine with multiple enzyme-free amplification strategy to develop a photoelectrochemical (PEC) biosensing platform for ultrasensitive detection of carcinoembryonic antigen (CEA). The 3D DNA nanostructure was self-assembled by base complementary pairing in a few minutes and rolling circle amplification (RCA) reaction. The intense photocurrent derived from Au NPs/ZnSe QDs can be effectively decreased by 3D DNA nanospheres assembled on the electrode, making photoelectric signal present “off” state. The specific binding of target CEA with its hairpin (HP1) aptamer opens HP1 structure, which initiated multiple enzyme-free strand displacement amplification (SDA) reaction and generated a large number of single strands DNA S1. Then S1 competitively binds to capture DNA on the electrode to release 3D DNA nanospheres, thus the photocurrent signal became “on” state for achieving amplified assay of target CEA. The proposed PEC biosensor exhibits excellent performance with a wide linear range of 1.0 fg/mL to 10 ng/mL and a low detection limit of 0.12 fg/mL for CEA, which was successfully applied for the assay of real serum samples with good precision. The reported strategy opens a new simple way for PEC biosensor using DNA nanostructure, showing huge potential in clinical application research.

Herein, a new multifunctional DNA nanotube (DNANT) was self-assembled and used to load Ru(phen)32+ and methylene blue (MB) as amplified signal probes for versatile electrochemiluminescence (ECL) and electrochemical (EC) “on–off” assays of Dam methylase (MTase) and aflatoxin B1 (AFB1). The DNA nanotube as a carrier could immobilize numerous MB or Ru(phen)32+ species in the double-stranded DNA (dsDNA) to significantly amplify signals, which enabled highly sensitive ECL and electrochemical detection of dual targets. The target Dam MTase first catalyzed the methylation of hairpin DNA (H1), and then the methylated DNA was cleaved by endonuclease DpnI to expose a single-strand DNA. After the Ru(phen)32+-DNANT or MB-DNANT signal probes were assembled to the electrode by hybridization, remarkable “signal on” states for amplified ECL or EC assays of MTase were obtained. Furthermore, in the presence of the target AFB1, the structure of DNANTs collapsed due to the specific binding of AFB1 to aptamer S2 in NTs, which...

A multifunctional DNA nanocage containing CdTe quantum dots (QDs) was prepared. It was applied to the fluorometric detection of human 8-oxoG DNA glycosylase 1 (hOGG1) by exonuclease-assisted cycling amplification technique. When loaded with the cancer drug doxorubicin (Dox), the nanocage is also a versatile probe for fluorescence imaging of cancer cells, and drug delivery to them. The presence of hOGG1 leads to the division of DNA HP1 (containing 8-oxo-dG) and formation of DNA fragments 1 and 2. Then, HP2 is added to hybridize with DNA 1 and produced lots of trigger DNA (containing nucleolin aptamer) by Exo III-aided cycling amplification. The DNA nanocage was fabricated by linking the trigger DNA to multiple specific DNA strands, and the fluorescent CdTe QDs were further conjugated to the DNA nanocage for sensitive detection of hOGG1 activity. After Dox is incorporated into the DNA nanocage, the fluorescence of Dox is turned off. Once the DNA nanocage enters the MCF-7 cells, the Dox is released and its fluorescence (measured at excitation/emission wavelengths of 480/560 nm) is turned on. The DNA nanocage containing fluorescent QDs and Dox was successfully applied to the fluorometric detection of hOGG1, fluorescence imaging, and therapy of cancer cells, which has great promise in clinical application and treatment of cancer. Graphical abstract A multifunctional DNA nanocage containing CdTe quantum dots and acting as a signalling probe was prepared. It was applied to fluorometric determination of human 8-oxoG DNA glycosylase 1 using cycling amplification technique. It also enables drug delivery to cancer cells if loaded with doxorubicin.

In this work, we designed a new strategy for ultrasensitive detection of CEA based on efficient electrochemiluminescence (ECL) quenching of Ru(bpy)

In the present work, we designed a unique enzyme-aided multiple amplification strategy for sensitive electrochemiluminescence (ECL) detection of DNA by using the amplified gold nanoparticles (GNPS)-polyamidoamine (PAMAM)-CdSe quantum dots (QDs) signal probe. Firstly, the novel GNPS-PAMAM dendrimers nanostructure with good biocompatibility and electroconductibility contains many amino groups, which can load a large number of CdSe QDs to develop amplified ECL signal probe. Then, the presence of target DNA activated the enzyme-assisted polymerization strand-displacement cycling reaction, and a large number of the hairpin template was opened. Subsequently, the opened stem further interacted with the capture hairpin (HP) DNA on the electrode, and the GNPS-PAMAM-CdSe signal probe hybridized with the exposed stem of the HP to trigger the second new polymerization reaction. Meanwhile, the first cycle was generating abundant DNA triggers which could directly open the template. As a result of the cascade amplification technique, a large number of CdSe QDs signal probe could be assembled on the electrode, generating much amplified ECL signal for sensitive detection of target DNA. Thus, this novel QDs-based amplified ECL strategy holds great promise for DNA detection and can be further exploited for sensing applications in clinical diagnostics.