Surface Ligands Research Articles

Multi‐Factor Modulated Organic Bulk Heterojunction Synaptic Transistor Enabled by Ligand Engineering for Centrosymmetric In‐Sensor Computing

AbstractEfficient in‐sensor computing necessitates linear, bidirectional, and centrosymmetric photoresponse weight updates; however, the realization of these attributes poses a persistent challenge, with most photosensor devices achieving linear analog weight updates while falling short of accomplishing bidirectional and centrosymmetric characteristics. Here, the development of a quantum dot (QD)–based bulk heterojunction synaptic transistor (QBST) with multi‐factor modulation through surface ligand engineering of blend QDs is reported. By controlling the charge transmission between QDs and the semiconductor, the QBST device enables tunable fading memory, which transforms linear weight updates in short‐chain devices into linear, bidirectional, and unprecedented centrosymmetric optical synaptic responses in long‐chain devices. Moreover, through the synergy of chemical and electric factors, the convolutional kernel of QBSTs‐based convolutional neural network realizes enhanced recognition for complex noisy fashion‐costume images, achieving an impressive 90.3% accuracy in the long‐chain device, highlighting the efficiency of centrosymmetric weight updates. The results demonstrate that surface ligand engineering offers a promising approach for customizable synaptic modulation, facilitating energy‐ and time‐efficient in‐sensor computing.

Colloidal synthesis of functionalized CdSe/CdS@ZnO nanoplatelets and their potential application as sensors

Atomically precise two-dimensional semiconductor nanoplatelets (NPLs) have attracted enormous attention due to their low-cost solution processing and outstanding optoelectronic properties. However, the challenges in organic-inorganic interfaces between surface ligands and NPLs are the poor passivation effect, limited charge translation, and low working stability in the active layer. Herein, the functionalized CdSe/CdS@ZnO NPLs were constructed with the inorganic ZnO sol by a facile solution process. We demonstrated that the introduction of inorganic sol to passivate surface defects and improve the optical stability of NPLs. Meanwhile, the inorganic ZnO hosts could effectively enhance the electroconductibility of NPLs film, thus boosting the charge transport capacity in active layer. Besides, the CdSe/CdS@ZnO NPLs as the active layer exhibited the obvious optical response for electric current signal. The emission intensity of NPLs layer was reduced to below ∼50% of their initial intensity with increasing driving current. These results suggest that the functionalized surface with inorganic sol is feasible and can pave the way for future commercial applications of all-inorganic NPLs in next-generation optoelectronic sensors.

Classifying the Role of Surface Ligands on the Passivation and Stability of Cs2NaInCl6 Double Perovskite Quantum Dots.

Cs2NaInCl6 double perovskites, which have excellent photoelectric conversion properties and are non-toxic and lead-free, have recently gained significant attention. In particular, double-perovskite quantum dots (QDs) are viewed as a promising material for optoelectronic device applications. Ligands such as oleic acid (OA) and oleylamine (OAm) are essential for the synthesis of perovskite QDs, but their specific roles in double-perovskite QDs remain unclear. In this study, we have investigated the binding of OA and OAm to Cs2NaInCl6 QDs through FTIR and NMR and their effects on the surface defect reduction and stability improvement for Cs2NaInCl6 QDs. We found that only OAm was bound to the QD surfaces while OA was not. The OAm has a significant effect on the photoluminescence quantum yield (PLQY) improvement by passivating the QD surface defects. The stability of the QDs was also evaluated, and it was observed that OA played a significant role in the stability of the QDs. Our findings provide valuable insights into the roles of ligands in influencing the photophysical properties and stability of lead-free double-perovskite QDs.

Blue-Emissive ZnSeTe Quantum Dots and Their Electroluminescent Devices.

Over the last two decades, quantum-dot light-emitting diodes (QLEDs), also known as quantum dot (QD) electroluminescent devices, have gained prominence in next-generation display technologies, positioning them as potential alternatives to organic light-emitting diodes. Nonetheless, challenges persist in enhancing key device performances such as efficiency and lifetime, while those of blue QLEDs lag behind compared with green and red counterparts. In this Perspective, we discuss key factors affecting the photoluminescence characteristics of environmentally benign blue-emissive ternary ZnSeTe QDs, including composition, core/shell heterostructure, and surface ligand. Notably, we highlight the recent progress in breakthrough strategies to enhance blue QLED performance, examining the effects of the ZnSeTe QD attribute and device architecture on device performance. This Perspective offers insights into integrated aspects of QD material and device structure in overcoming challenges toward a high-performance blue ZnSeTe QLED.

Oligomeric Zinc Thiolates Tethering Multidentate Carboxylates for Nondestructive Aqueous Phase Transfer of Quantum Dots.

Functionalization of quantum dots (QDs) via ligand exchange is prone to debase their photoluminescence quantum yield (PL QY) owing to the unavoidable surface damage by excess reactants, and even worse in aqueous medium. Herein, the oligomeric zinc thiolate as the multidentate hydrophilic ligand featuring facile synthetic protocol is proposed. A simple reaction between ZnCl2 and 3-mercaptopropionic acid produces oligomeric ligands containing 3-6 zinc thiolate units, where the terminal moieties provide multidentate anchoring to the surface as well as hydrophilicity. 2D proton nuclear Overhauser effect spectroscopy (2D 1H NOESY) and X-ray photoelectron spectroscopy (XPS) reveal that the oligomeric zinc thiolate ligands adsorb on the surface via multidentate metal carboxylate bindings without destruction of molecular structure, regardless of partial dissociation of thiolate branches in aqueous phase. Enhanced binding affinity granted by the multidentate nature allows for the effective exchange of original surface ligands without considerable surface deterioration. The zinc thiolate-capped Cd-free aqueous QDs exhibit a high photoluminescence quantum yield of ≈90% and extended stability against long-term storage and photochemical stress.

Electrocatalytic Effects of Au Nanoclusters in Its Electrochemiluminescence Enhanced by Coreactant Tertiary Amines

AbstractAtomically precise metal nanoclusters are increasingly exploited in electrocatalysis such as water electrolysis and CO2 reduction. The catalytic effects are generally evaluated by conventional electrochemical methods or end‐product analysis. Herein, near infrared electrochemiluminescence (ECL) of the nanoclusters is introduced as a new signaling mechanism to complement classical voltammetric analysis for elucidating essential electrocatalytic parameters. Coreactant ECL from an aqueous soluble Au22 nanocluster (NCs) enhanced by a common pH buffer materials 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid (HEPES) and by a piperazine drug hydroxyzine (HDZ) is studied under oxidative reduction pathways. Foot of the wave analysis on voltametric features and the kinetics profiles in potential‐step experiments are studied in different nanocluster and coreactant concentrations. Benchmark parameters such as rate constants are determined under EC (Electron‐transfer‐Chemical‐reaction) mechanism as feasibility validations. Because the luminescence properties of AuNCs are sensitive to the surface ligands or adsorbents, ECL is proposed as a new signal readout for operando studies providing insights for governing reaction mechanism and kinetics during catalytic reactions. Retrospectively, mechanistic understanding of the complex multi‐step reactions during ECL generation can provide guidance for the evaluation and optimization of ECL property for better quantitative applications.

Development of a Dual Fluorescence Signal-Enhancement Immunosensor Based on Substrate Modification for Simultaneous Detection of Interleukin-6 and Procalcitonin.

High-sensitivity detection of biomarkers is of great significance to improve the accuracy of disease diagnosis and the rate of occult disease diagnosis. Using a substrate modification and two-color quantum dot (QD) nanobeads (QBs), we have developed a dual fluorescence signal-enhancement immunosensor for sensitive, simultaneous detection of interleukin 6 (IL-6) and procalcitonin (PCT) at low volumes (∼20 μL). First, the QBs compatible with QDs with different surface ligands were prepared by optimizing surfactants based on the microemulsion method. Through the use of a fluorescence-linked immunosorbent assay (FLISA), the feasibility of a dual signal-enhancement immunosensor was verified, and a 5-fold enhancement of fluorescence intensity was achieved after the directional coating of the antibodies on sulfhydryl functionalization (-SH) substrates and the preparation of QBs by using a polymer and silica double-protection method. Next, a simple polydimethylsiloxane (HS-PDMS) immunosensor with a low volume consumption was prepared. Under optimal conditions, we achieved the simultaneous detection of IL-6 and PCT with a linear range of 0.05-50 ng/mL, and the limit of detection (LOD) was 24 and 32 pg/mL, respectively. The result is comparable to two-color QBs-FLISA with a sulfhydryl microplate, even though only 20% of its volume was used. Thus, the dual fluorescence signal-enhancement HS-PDMS immunosensor offers the capability of early microvolume diagnosis of diseases, while the detection of inflammatory factors is clinically important for assisting disease diagnosis and determining disease progression.

Ligand Exchange of Quantum Dots: A Thermodynamic Perspective.

Colloidal quantum dots (QDs) consist of an inorganic core and organic surface ligands. Surface ligands play a dominant role in maintaining the colloidal stability of QDs and passivating the surface defects of QDs. However, the original ligands introduced in the synthetic process of QDs cannot meet the requirements for diverse applications; therefore, ligand exchanges with functional ligands are mandatory. Understanding the ligand exchange process requires a comprehensive combination of the concepts and techniques of surface chemistry. In this Perspective, the ligand exchange process is discussed in detail. Specifically, we elaborate on the thermodynamics that can reveal the feasibility and mechanism of ligand exchange. It depicts a critical physical picture of the surface of QDs along with the following ligand exchange.

Fast Organic Cation Exchange in Colloidal Perovskite Quantum Dots toward Functional Optoelectronic Applications.

Colloidal quantum dots with lower surface ligand density are desired for preparing the active layer for photovoltaic, lighting, and other potential optoelectronic applications. In emerging perovskite quantum dots (PQDs), the diffusion of cations is thought to have a high energy barrier, relative to that of halide anions. Herein, we investigate the fast cross cation exchange approach in colloidal lead triiodide PQDs containing methylammonium (MA+) and formamidinium (FA+) organic cations, which exhibits a significantly lower exchange barrier than inorganic cesium (Cs+)-FA+ and Cs+-MA+ systems. First-principles calculations further suggest that the fast internal cation diffusion arises due to a lowering in structural distortions and the consequent decline in attractive cation-cation and cation-anion interactions in the presence of organic cation vacancies in mixed MA+-FA+ PQDs. Combining both experimental and theoretical evidence, we propose a vacancy-assisted exchange model to understand the impact of structural features and intermolecular interaction in PQDs with fewer surface ligands. Finally, for a realistic outcome, the as-prepared mixed-cation PQDs display better photostability and can be directly applied for one-step coated photovoltaic and photodetector devices, achieving a high photovoltaic efficiency of 15.05% using MA0.5FA0.5PbI3 PQDs and more precisely tunable detective spectral response from visible to near-infrared regions.

Colloidal Synthesis of P-Type Zn3As2 Nanocrystals.

Zinc pnictides, particularly Zn3As2, hold significant promise for optoelectronic applications owing to their intrinsic p-type behavior and appropriate bandgaps. However, despite the outstanding properties of colloidal Zn3As2 nanocrystals, research in this area is lacking because of the absence of suitable precursors, occurrence of surface oxidation, and intricacy of the crystal structures. In this study, a novel and facile solution-based synthetic approach is presented for obtaining highly crystalline p-type Zn3As2 nanocrystals with accurate stoichiometry. By carefully controlling the feed ratio and reaction temperature, colloidal Zn3As2 nanocrystals are successfully obtained. Moreover, the mechanism underlying the conversion of As precursors in the initial phases of Zn3As2 synthesis is elucidated. Furthermore, these nanocrystals are employed as active layers in field-effect transistors that exhibit inherent p-type characteristics with native surface ligands. To enhance the charge transport properties, a dual passivation strategy is introduced via phase-transfer ligand exchange, leading to enhanced hole mobilities as high as 0.089 cm2 V-1 s-1. This study not only contributes to the advancement of nanocrystal synthesis, but also opens up new possibilities for previously underexplored p-type nanocrystal research.

Enzyme-Responsive Modular Peptides Enhance Tumor Penetration of Quantum Dots via Charge Reversal Strategy.

Quantum dots (QDs) are colloidal semiconductor nanoparticles acting as fluorescent probes for detection, disease diagnosis, and photothermal and photodynamic therapy. However, their performance in cancer treatment is limited by inadequate tumor accumulation and penetration due to the larger size of nanoparticles compared to small molecules. To address this challenge, charge reversal nanoparticles offer an effective strategy to prolong blood circulation time and achieve enhanced endocytosis and tumor penetration. In this study, we leveraged the overexpressed γ-glutamyl transpeptidase (GGT) in many human tumors and developed a library of modular peptides to serve as water-soluble surface ligands of QDs. We successfully transferred the QDs from the organic phase to the aqueous phase within 5 min. And through systematic tuning of the peptide sequence, we optimized the fluorescent stability of QDs and their charge reversal behavior in response to GGT. The resulting optimal peptide stabilized QDs in aqueous solution with a high fluorescent retention rate of 93% after three months and realized the surface charge reversal of QDs triggered by GGT in vitro. The binding between the peptide and QD surface was investigated by using saturation transfer differential nuclear magnetic resonance (STD NMR). Thanks to its charge reversal ability, the GGT-responsive QDs exhibited enhanced cellular uptake in GGT-expressing cancer cells and deeper penetration in the 3D multicellular spheroids. This enzyme-responsive modular peptide can lead to specific tumor targeting and deeper tumor penetration, holding great promise to enhance the treatment efficacy of QD-based theranostics.

Multi-Species Surface Reconstruction for High-Efficiency Perovskite Nanocrystal Light-Emitting Diodes.

Although colloidal perovskite nanocrystal (PNC) solution has exhibited near-unity photoluminescence quantum yield (PLQY), the luminance would be severely quenched when the PNC solution is assembled into thin films due to the agglomeration and fusion of NCs caused by the exfoliation of surface ligands and non-radiative Förster resonance energy transfer (FRET) from small to large particle sizes, which seriously affected the performances of light-emitting diodes (LEDs). Here, we used Guanidine thiocyanate (GASCN) and Sodium thiocyanate (NaSCN) to achieve effective CsPbI3 PNC surface reconstruction. Due to the strong coordination ability of these small molecules with the anions and cations on the surface of the PNCs, they can provide strong surface protection against PNC fusion during centrifugal purification process and repair the surface defects of PNCs, so that the original uniform size distribution of PNCs can be maintained and FRET between close-packed PNC films is effectively suppressed, which allows the emission characteristics of the films to be preserved. As a result, highly oriented, smooth and nearly defect-free high-quality PNC thin films are obtained, with PLQY as high as 95.1 %, far exceeding that of the original film, and corresponding LEDs exhibit a maximum external quantum efficiency of 24.5 %.

Multi‐Species Surface Reconstruction for High‐Efficiency Perovskite Nanocrystal Light‐Emitting Diodes

AbstractAlthough colloidal perovskite nanocrystal (PNC) solution has exhibited near‐unity photoluminescence quantum yield (PLQY), the luminance would be severely quenched when the PNC solution is assembled into thin films due to the agglomeration and fusion of NCs caused by the exfoliation of surface ligands and non‐radiative Förster resonance energy transfer (FRET) from small to large particle sizes, which seriously affected the performances of light‐emitting diodes (LEDs). Here, we used Guanidine thiocyanate (GASCN) and Sodium thiocyanate (NaSCN) to achieve effective CsPbI3 PNC surface reconstruction. Due to the strong coordination ability of these small molecules with the anions and cations on the surface of the PNCs, they can provide strong surface protection against PNC fusion during centrifugal purification process and repair the surface defects of PNCs, so that the original uniform size distribution of PNCs can be maintained and FRET between close‐packed PNC films is effectively suppressed, which allows the emission characteristics of the films to be preserved. As a result, highly oriented, smooth and nearly defect‐free high‐quality PNC thin films are obtained, with PLQY as high as 95.1 %, far exceeding that of the original film, and corresponding LEDs exhibit a maximum external quantum efficiency of 24.5 %.

Amino Acid Double-Passivation-Enhanced Quantum Dot Coupling for High-Efficiency FAPbI3 Perovskite Quantum Dot Solar Cells.

Formamidinium lead triiodide (FAPbI3) perovskite quantum dot has outstanding durability, reasonable carrier lifetime, and long carrier diffusion length for a new generation of highly efficient solar cells. However, ligand engineering is a dilemma because of the highly ionized and dynamic characteristics of quantum dots. To circumvent this issue, herein, we employed a mild solution-phase ligand-exchange approach through adding short-chain amino acids that contain amino and carboxyl groups to modify quantum dots and passivate their surface defects during the purification process. As a result, the photoelectric conversion efficiency of FAPbI3 perovskite quantum dot solar cells (PQDSCs) increased from 11.23 to 12.97% with an open-circuit voltage of 1.09 V, a short-circuit current density of 16.37 mA cm-2, and a filling factor of 72.13%. Furthermore, the stability of the device modified by amino acids retains over 80% of the initial efficiency upon being exposed to 20-30% relative humidity for 240 h of aging treatment. This work may offer an innovative concept and approach for surface ligand treatment to improve the photovoltaic performance of PQDSCs toward large-scale manufacture.

Chitosan-initiated gold nanoparticles with enhanced fluorescence for unique Fe3+/PPi sensing and photothermal therapy

The design of surface ligands is crucial for ligand-protected gold nanoparticles (AuNPs). Herein, following the principle of green synthesis, environmentally friendly gold nanoparticles (AuNPs@His@CC, AuHC) were fabricated based on dual ligands of histidine and carboxylated chitosan. AuHC showed the advantages of low toxicity, good photoluminescent stability and ideal biocompatibility. Compared with single histidine-coated gold nanoclusters (AuNCs@His, AuH), AuHC presented enhanced fluorescence attributed to the addition of chitosan. The blue-emitting AuHC has a unique response to Fe3+ with detection limits as low as 9.51 nM. Interestingly, the quenched fluorescence of AuHC–Fe3+ system could be restored through the introduction of PPi with a detection limit of 10.6 μM. So an “on-off-on” fluorescence sensing platform was achieved. Apart from good optical properties and sensing, the designed AuHC demonstrated outstanding photothermal conversion efficiency (27.8 %), which made it ideal material for thermal ablation of tumor. To be specific, after laser irradiation (660 nm, 0.78 W cm−2, 10 min) of AuHC, the survival rate of HeLa cells as a tumor cell model decreased to 12.7 %, indicating that AuHC has a significant tumor inhibition effect in vitro. Besides, AuHC also could be a befitting candidate for overcoming drug-resistant tumor cells such as MCF-7/ADR cells. Notably, AuHC can markedly ablate solid tumors in 4T1 tumor-bearing mice after laser irradiation (660 nm, 0.78 W cm−2, 10 min). Hence this work provides insight into the design of multifunctional AuNPs platform for simultaneously integrating the ion sensing and photothermal therapy of cancer.

Colloidal InAs Quantum Dot-Based Infrared Optoelectronics Enabled by Universal Dual-Ligand Passivation.

Solution-processed low-bandgap semiconductors are crucial to next-generation infrared (IR) detection for various applications, such as autonomous driving, virtual reality, recognitions, and quantum communications. In particular, III-V group colloidal quantum dots (CQDs) are interesting as nontoxic bandgap-tunable materials and suitable for IR absorbers; however, the device performance is still lower than that of Pb-based devices. Herein, a universal surface-passivation method of InAs CQDs enabled by intermediate phase transfer (IPT), a preliminary process that exchanges native ligands with aromatic ligands on the CQD surface is presented. IPT yields highly stable CQD ink. In particular, desirable surface ligands with various reactivities can be obtained by dispersing them in green solvents. Furthermore, CQD near-infrared (NIR) photodetectors are demonstrated using solution processes. Careful surface ligand control via IPT is revealed that enables the modulation of surface-mediated photomultiplication, resulting in a notable gain control up to ≈10 with a fast rise/fall response time (≈12/36ns). Considering the figure of merit (FOM), EQE versus response time (or -3dB bandwidth), the optimal CQD photodiode yields one of the highest FOMs among all previously reported solution-processed nontoxic semiconductors comprising organics, perovskites, and CQDs in the NIR wavelength range.

Ligand-Nondestructive Direct Photolithography Assisted by Semiconductor Polymer Cross-Linking for High-Resolution Quantum Dot Light-Emitting Diodes.

The photolithographic patterning of fine quantum dot (QD) films is of great significance for the construction of QD optoelectronic device arrays. However, the photolithography methods reported so far either introduce insulating photoresist or manipulate the surface ligands of QDs, each of which has negative effects on device performance. Here, we report a direct photolithography strategy without photoresist and without engineering the QD surface ligands. Through cross-linking of the surrounding semiconductor polymer, QDs are spatially confined to the network frame of the polymer to form high-quality patterns. More importantly, the wrapped polymer incidentally regulates the energy levels of the emitting layer, which is conducive to improving the hole injection capacity while weakening the electron injection level, to achieve balanced injection of carriers. The patterned QD light-emitting diodes (with a pixel size of 1.5 μm) achieve a high external quantum efficiency of 16.25% and a brightness of >1.4 × 105 cd/m2. This work paves the way for efficient high-resolution QD light-emitting devices.

Surface defect passivation by ligand in polymeric melt encapsulated CsPbBr3 perovskite nanocrystals/PP composite with high X-ray imaging performance

In-situ growth method has been widely used in the preparation of metal halide perovskite nanocrystals/polymer composites. However, the ligand-free process tends to bring surface defects which always deteriorate the photoluminescence. The passivation effect of surface ligands on the defects of nanocrystals, which is of benefit to promote the photoluminescence performance of the composites, is often neglected in the preparation of perovskite nanocrystals/polymers. Here, we report a facile post-passivation treatment of CsPbBr3/polypropylene (PP) composite film with octylamine solution, and surface engineering of CsPbBr3 nanocrystals in PP molecular chain by swelling effect to passivate the surface defects of nanocrystals. The composite film achieves a significant photoluminescence enhancement by 27 times under UV light. In addition, when used as a scintillator material, the passivated CsPbBr3/PP composite film has a enhanced significant light response to X-ray, and the X-ray imaging ability of the metal spring in the capsule is preliminarily realized. Moreover, this post-treatment passivation strategy is easy to apply and expected to be applied to the performance improvement of other perovskite nanocrystals/polymer composites. Overall, this approach has the potential to design a new generation of perovskite nanocrystals/polymer-based scintillator materials.

Enhancing Liver Delivery of Gold Nanoclusters via Human Serum Albumin Encapsulation for Autoimmune Hepatitis Alleviation.

Peptide-protected gold nanoclusters (AuNCs), possessing exceptional biocompatibility and remarkable physicochemical properties, have demonstrated intrinsic pharmaceutical activity in immunomodulation, making them a highly attractive frontier in the field of nanomedicine exploration. Autoimmune hepatitis (AIH) is a serious autoimmune liver disease caused by the disruption of immune balance, for which effective treatment options are still lacking. In this study, we initially identified glutathione (GSH)-protected AuNCs as a promising nanodrug candidate for AIH alleviating in a Concanavalin A (Con A)-induced mice model. However, to enhance treatment efficiency, liver-targeted delivery needs to be improved. Therefore, human serum albumin (HSA)-encapsulated AuNCs were constructed to achieve enhanced liver targeting and more potent mitigation of Con A-induced elevations in plasma aspartate transaminase (AST), alanine transaminase (ALT), and liver injury in mice. In vivo and in vitro mechanism studies indicated that AuNCs could suppress the secretion of IFN-γ by Con A-stimulated T cells and subsequently inhibit the activation of the JAK2/STAT1 pathway and eventual hepatocyte apoptosis induced by IFN-γ. These actions ultimately protect the liver from immune cell infiltration and damage caused by Con A. These findings suggest that bio-protected AuNCs hold promise as nanodrugs for AIH therapy, with their liver targeting capabilities and therapeutic efficiency being further improved via rational surface ligand engineering.

Bright silicon quantum dot synthesis and LED design: insights into size–ligand–property relationships from slow- and fast-band engineering

Abstract Multicolor, bright silicon quantum dots (SiQDs)—SiQDs with photoluminescence in a range of colors and quantum yields (PLQYs) of >90%—are promising heavy-metal-free light sources for full-color displays, lighting, and biomedical imaging. Colloidal SiQDs can be used to manufacture devices via printing and roll-to-roll processing. Furthermore, the in vivo use of biodegradable SiQDs and Si nanomaterials, for imaging cancer cells and as drug delivery systems, has been demonstrated. However, a large body of research demonstrates that the photoluminescence (PL) wavelength and PLQY of colloidal SiQDs are dependent not only on the SiQD particle size but also on the methods and/or procedures and chemical reagents used to synthesize them. This is because SiQDs are quite sensitive to both the intrinsic properties of Si and external factors. These intrinsic and external factors can be respectively linked to different PL mechanisms: the quantum confinement effect, which produces a slow-decaying “S”-band PL signal, and surface ligand effects, corresponding to fast-decaying “F”-band PL. This review focuses on mechanistic insights into the relationships linking the structures, ligands, and optical properties of SiQDs. Synthesis methods and the application performance of bright multicolor colloidal SiQDs, based on excellent state-of-the-art experimental and theoretical studies, are also reviewed.