Surface Passivation Agent Research Articles

Facile Synthesis of Carbonized Polymer Dots and their Applications in Security Inks, Sensing, Light Emitting Diodes, and UV Shielding Films

AbstractCarbonized polymer dots (CPDs) have received much attention in recent years owing to their cost‐effective synthesis, high resistance to photobleaching, environmental friendliness, and excellent biocompatibility. However, the aggregation‐induced fluorescence quenching is a great obstacle to its applications. In this work, the highly fluorescent CPDs are prepared by a facile hydrothermal method assisted by polyethylene glycol (PEG) as the surface passivation agent, where phthalic acid and ethylenediamine are used as carbon and nitrogen source, respectively. Meanwhile, five types of PEG species are applied to prepare five CPDs to investigate PEG on optical properties of the resultant CPDs, among which the best quantum yield reaches 57.0 %. The promising applications of CPDs as fluorescent inks, sensors, light emitting diodes, and UV shielding films have been demonstrated. Overall, our contribution here develops a facile and accessible route for the synthesis of CPDs and further demonstrates its versatile applications.

Functionalized Green Carbon dots for Specific Detection of Copper in Human Serum Samples and Living Cells.

Intracellular copper ion (Cu2+) is irreplaceable and essential in regulation of physiological and biological processes, while excessive copper from bioaccumulation may cause potential hazards to human health. Hence, effective and sensitive recognition is urgently significant to prevent over-intake of copper. In this work, a novel highly sensitive and green carbon quantum dots (Green-CQDs) were synthesized by a low-cost and facile one-step microwave auxiliary method, which utilized gallic acid, carbamide and PEG400 as carbon source, nitrogen source and surface passivation agent, respectively. The decreased fluorescence illustrated excellent linear relationship with the increasing of Cu2+ concentration in a wide range. Substantial surface amino and hydroxyl group introduced by PEG400 significantly improved selectivity and sensitivity of Green-CQDs. The surface amino chelation mechanism and fluorescence internal filtration effect were demonstrated by the restored fluorescence after addition of EDTA. Crucially, the nanosensor illustrated good cell permeability, high biocompatibility and recovery rate, significantly practical application in fluorescent imaging and biosensing of intracellular Cu2+ in HepG-2 cells, which revealed a potential and promising biological applications in early diagnosis and treatment of copper ion related disease.

Reinforcement of Positive Electrode-Electrolyte Interface without Using Electrolyte Additives Through Thermoelectrochemical Oxidation of LiPF6 for Lithium Secondary Batteries.

Owing to the limited electrochemical stability window of carbonate electrolytes, the initial formation of a solid electrolyte interphase and surface film on the negative and positive electrode surfaces by the decomposition of the electrolyte component is inevitable for the operation of lithium secondary batteries. The deposited film on the surface of the active material is vital for reducing further electrochemical side reactions at the surface; hence, the manipulation of this formation process is necessary for the appropriate operation of the assembled battery system. In this study, the thermal decomposition of LiPF6 salt is used as a surface passivation agent, which is autocatalytically formed during high-temperature storage. The thermally formed difluorophosphoric acid is subsequently oxidized on the partially charged high-Ni positive electrode surface, which improves the cycleability of lithium metal cells via phosphorus- and fluorine-based surface film formation. Moreover, the improvement in the high-temperature cycleability is demonstrated by controlling the formation process in the lithium-ion pouch cell with a short period of high-temperature storage before battery usage.

Interfacial modification of LiF-incorporated MnO2 mixed P3HT:PC60BM-based organic photoactive layer

Interfacial charge transfer in the photoactive layer plays an essential role in determining device performance in organic photovoltaics. Recently, numerous studies have reported interfacial modification by incorporating inorganic nanostructures into the bulk heterojunction photoactive layer, with the aim of increasing the interfacial area to improve charge transfer efficiency. However, there is limited understanding of in-depth defect analysis and the charge transfer mechanism. In this report, different weight percentages of LiF were incorporated into MnO2 (LMO) mixed photoactive layers. The robust relationship between charge transport dynamics and defect density of the device in the presence of LiF is elucidated. The results show that the photoactive layer with 10.0 wt% LMO exhibited a 41% improvement in device performance compared to that of pristine P3HT:PC60BM, with a power conversion efficiency (PCE), open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) of 2.43%, 0.52 V, 9.77 mA/cm2, and 0.48, respectively. The photovoltaic performance improvement can be attributed to (i) the efficient charge transfer properties in the 10.0 wt% LMO, as evidenced by the suppressed S 2p and intensified O=C in X-ray photoelectron spectroscopy (XPS) analysis, and (ii) the low carrier recombination due to the success of LiF as a surface passivation agent, as indicated by 53% photoluminescence quenching. This report provides a fundamental understanding and offers an alternative solution for designing high-efficiency organic photovoltaics in the near future.

Li0.5La0.5TiO3 as an Ionic Conducting Additive Enhancing the High-Voltage Performance of LiNi0.8Mn0.1Co0.1O2 Cathodes in Lithium-Ion Batteries.

Although high-voltage (e.g., >4.3 VvsLi) operation can increase specific capacity and energy of Ni-rich NMC cathodes, it accelerates the oxidative decomposition of electrolytes and surface degradation of NMC cathodes, leading to rapid capacity fading. This work presents a novel approach that employs Li0.5La0.5TiO3 (LLTO) solid-electrolyte as a Li-ion conductor and surface passivation agent to stabilize the cathode/electrolyte interphase (CEI) layer of the LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode and enhance its high-voltage performances. The LLTO particles improve Li-ion transportation across the CEI layer, as evidenced by its reduced impedance in Nyquist plots. Furthermore, passivation of CEI by LLTO mitigates parasitic reactions (e.g., transition metal dissolution) that occur on the graphite solid electrolyte interphase layer during extended cycles of pouch-cells. As a result, pouch-cells with the 1 or 5 wt % LLTO-blended NMC811 cathodes can deliver 19-23% increase in specific capacity and improved cycle life (1000 cycles) at high voltages (up to 4.4 V), comparing to bare NMC811 cathodes. Post-mortem characterization of pouch-cells quantitatively identified the degradation sources of NMC811 cathode at high-voltages, which highlighted the improvement mechanisms of LLTO blended-cathodes.

A functionalized phosphorous tetrabenzotriazacorrole dye as a novel passivating agent of high-performance planar perovskite solar cells

Surface passivation is a crucial strategy to manage the film characteristics of solution-processed perovskite absorber layers, which greatly impact the photovoltaic properties of perovskite solar cells (PSCs). However, designing and synthesizing suitable passivating agents with required functional groups and solution-processability is challenging due to their complex molecular structure. In this study, we demonstrate a facile passivation technique using a functionalized phosphorous tetrabenzotriazacorrole dye (PTBC) for p-i-n PSCs. The tetrabenzotriazacorrole dye has amines and ether linkages that can closely interact with the undercoordinated Pb2+ with halogen vacancies through Lewis acid-base interactions, leading to a pinhole-free perovskite absorber layer with reduced trap density. Moreover, the central phosphorus of PTBC is functionalized with dimethoxy groups, which can provide a more hydrophobic surface in the perovskite absorber layer. Consequently, high-quality perovskite films (CsFAPbI3) prepared with PTBC exhibit improved optical, electrical, and morphological properties, as well as superior carrier transportation/recombination kinetics, boosting the power conversion efficiency of PSCs from 17.64 % to 20.08 %, with over 75 % of initial efficiency preserved after 1000 h of aging under ambient conditions. These results highlight PTBC as an effective surface passivation agent for perovskite absorber layers and emphasize the importance of suitable passivating agents in optimizing PSC performance.

Suppressing the Ion Migration in Halide Perovskite Wafers for Current-Drift Free X-ray Detectors

Metal halide perovskites have been demonstrated as potential X-ray detection materials due to their high defect tolerance, large diffusion length, and high attenuation efficiency. X-ray detectors based on hot-pressed perovskite wafers are investigated intensively recently because of the convenience of scalable fabrication. However, in spite of the large crystal size within wafers, the prepared detectors usually suffer from severe ion migration and current drift under both dark and bright states. In this work, ethylenediamine dihydroiodate (EDDI) was introduced as a strong surface passivation agent, which compensated for the surface iodide vacancy successfully. The ion migration in optimal MAPbI3@EDDI wafer is significantly suppressed, which is manifested by increased migration activation energy and stable current under high bias for 10 h. Moreover, the introduction of EDDI also reduced the dark current, contributing a high on–off ratio and a champion sensitivity of 8291.22 μC Gyair–1 cm–2. A low detection limit of 340 nGyair s–1 is also obtained, which is much lower than that of commercial X-ray detectors. Besides, the as-fabricated X-ray detector can endure long-term operation with flat current under a high bias of 20 V. This work provides a route for the performance improvement of perovskite wafer-based X-ray detectors.

High quantum yield carbon quantum dots as selective fluorescent turn-off probes for dual detection of Fe2+/Fe3+ ions

Carbon quantum dots (CQDs) are fluorescent nanoparticles that have great potential for use as nontoxic fluorescent probes. However, synthesizing CQDs with high photoluminescence quantum yield (QY) in a rapid and facile way from commonly available and low-cost reagents is still challenging. In this work, Tween®80 was used as a surface passivation agent along with citric acid/urea in a one-step microwave procedure to make extremely blue luminous nitrogen doped CQDs. When excited at 350 nm, these CQDs had a fluorescent quantum yield of 75.5 %. The significant high quantum yield and stability of these CQDs are attributed to the high aromatic sp2 domain size within the CQD core and improved carbon and oxygen functional groups at the CQDs surface. We employed the CQDs as a fluorescent probe to detect Fe2+ and Fe3+ ions and could establish a linear relationship between photoluminescence quenching efficiency (F0-F/F0) and ion concentration with a detection limit of 6.5 µM and 2.5 µM for Fe2+ and Fe3+, respectively. Our studies suggest that the highly selective detection of iron ions is a result of partial transfers of excited electrons from the CQDs to the d orbital of the iron ions, instead of contributing to radiative relaxation that induces photoluminescence quenching of the CQDs. Other reported carbon dots for this application have a substantially lower quantum yield and only detect Fe3+ ions. Therefore, our CQDs have considerable benefits over similar probes. Subsequent research may adapt them to other areas due to the high quantum yield and stability.

Highly stable aqueous phase black phosphorus quantum dots with enhanced fluorescence property

Black phosphorus quantum dots (BPQDs) are a kind of outstanding optical material due to the tunable band structure. However, their fluorescence property and stability are obviously weakened in the aqueous phase, which extremely restricts the development of BPQDs. Here, we propose a new method to prepare stable BPQDs in an aqueous solution directly with high absolute fluorescence quantum yield. Aqueous phase BPQDs are synthesized by liquid exfoliation and hydrothermal with NH2-polyethylene glycol (PEG)-NH2 as the modification agent to protect the BPQDs, which have high stability more than six months. In addition, NH2-PEG-NH2 is also a surface passivation agent to enhance the emission of BPQDs by forming P–N bonds, which is confirmed by an absolute fluorescent quantum yield of 11.5%. Moreover, BPQDs show excellent resistance to a strong acid environment and high ionic strengths except for Fe3+. Therefore, the BPQDs are a kind of highly selective and linear response fluorescence probe for Fe3+. Considering the good biocompatibility of BPQDs, they are employed as cell fluorescent label probes and show excellent fluorescence imaging contrast. Based on the unique structural stability and fluorescence performance in the aqueous phase, BPQDs are potential candidates for Fe3+ detection and optical bio-imaging.

Efficient NIR Perovskite Light-Emitting Diodes Enabled by Incorporating an Anthracene Derivative as a Bifunctional Electron Transport Layer

Exploring multifunctional charge transport materials with well-matched energy-levels alignment and compatible interfaces is deemed a potential approach toward high-performance perovskite light-emitting diodes (PeLEDs). Herein, an anthracene derivative, 1-[4-(10-[1,1′-biphenyl]-4-yl-9-anthracenyl)phenyl]-2-ethyl-1H-benzimidazole (BAEBi), is demonstrated as an efficient electron tranport layer (ETL) as well as an effective surface passivation agent for near-infrared (NIR) quasi two-dimensional (Q-2D) PeLEDs. Owing to the promising electron injection and transport capability of BAEBi, an improved charge-carrier balance is attained in rather hole-dominant PeLEDs. Meanwhile, BAEBi assisted to significantly mitigate the perovskite/ETL interfacial defects, rendering a pinhole-free smooth film with quite low roughness and ameliorated exciton lifetime. Consequently, BAEBi-containing NIR Q-2D PeLEDs manifested a low turn-on voltage of 2.5 V with a decent external quantum efficiency (EQE) of 9.2% and a peak radiance of 127 W sr–1 m–2; these values are, respectively, ∼1.5- and 15-fold higher compared to that of a commonly used ETL, 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi). Importantly, the BAEBi-incorporating champion PeLED exhibited significantly curtailed efficiency roll-off and prolonged operational stability. These findings reveal an ingenious solution to address the charge imbalance issue and suppress the interfacial defects in PeLEDs that would spur further development of this emerging technology toward efficient solid-state lighting and high-resolution displays.

Ultrasensitive Graphene-Based Nanobiosensor for Rapid Detection of Hemoglobin in Undiluted Biofluids.

Detection of hemoglobin (Hb), a critical part of the biological system that is responsible for oxygen transportation, is of great significance on clinical diagnosis of various diseases. Particularly, time-efficient Hb detection under nanomole levels has drawn much attention in recent years. Herein, we present a graphene field effect transistor (GFET)-based aptameric nanobiosensor for rapid detection of Hb in undiluted biofluids including serum and urine and for the first time use polyethylenimine (PEI), a kind of comparatively low-cost polymer consisting of numerous amino groups, which can be directly linked with the anchor molecule without any pretreatment as the graphene surface passivation agent. Experimental results indicate the PEI-modified graphene aptameric nanobiosensor can respond to the Hb concentration change in a few minutes (6-8 min) with estimated detection limits of 10.6 fM in 1× PBS, 14.2 fM in undiluted serum, and 11.9 fM in undiluted urine, respectively. Further, considering the potential use of our sensor for implantable and wearable applications, we also examine the sensing performance of the sensor fabricated on an ultrathin flexible polyethylene terephthalate (PET) substrate. The Hb detection results are almost invariable even after 100 cycles of cyclic extension by 120% or 100 cycles of bending with a radius of 1 mm. Hence, our sensor holds great potential for accurate monitoring of nanomole levels of Hb in clinical applications.

A pseudohomogeneous nanocarrier based on carbon quantum dots decorated with arginine as an efficient gene delivery vehicle

A pseudohomogeneous carrier as an emerging term refers to subnanometric carbon-based vehicle with a high ability to interact with genetic materials to form stable carboplex and successfully transfer them into the cell which will result in inhibiting or expressing of therapeutic genes. Chitosan is a non-toxic polyaminosaccharide used as a precursor in the presence of citric acid to produce carbon quantum dots (CQDs), which decorated with arginine as a surface passivation agent with high amine density in hydrothermal methodology. The Arginine-CQDs are comprehensively characterized by Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet–visible spectroscopy (UV–vis), Atomic force microscopy (AFM), field emission scanning electron microscope (FE-SEM), Energy-dispersive X-ray (EDX) mapping, fluorescence, High-resolution transmission electron microscopy (HR-TEM), zeta potential and X-ray powder diffraction (XRD). In this regard, for the first time, carboplex are formed by electrostatic conjugating of Arginine-CQDs with DNA to protect it from enzymatic degradation. Moreover, the carboplex, like the chitosan precursor, has not shown toxicity against AGS cell line. Interestingly, the Arginine-CQDs have exhibited an excellent ability to overcome cell barriers to deliver into cells compared to chitosan at the same weight ratio. The Arginine-CQDs/pEGFP (W/W) nanocomplex, not only lead to transfection with a relatively higher efficiency than PEI polymer, which is the “golden standard”, but carboplex also demonstrates no significant toxicity. Indeed, the EGFP expression level has reached to 2.4 ± 0.2 via Arginine-CQDs carboplex at W/W 50 weight ratio. To the best of our knowledge, this is the first report includes chitosan-based CQDs functionalized by arginine which is applied to serve as a pseudohomogeneous vehicle for gene transfection.

Green Synthesis of Self-Passivated Fluorescent Carbon Dots Derived from Rice Bran for Degradation of Methylene Blue and Fluorescent Ink Applications

Recently, natural products are the powerful carbon source to synthesize carbon dots (CDs) with interesting physical and chemical properties. In this present work, we report a facile hydrothermal synthesis method for preparing fluorescent carbon dots using a biogenic precursor of rice bran without any surface passivation agent. The synthetic methodology was easy, simple, environmental friendly and convenient. Structural and optical properties of the RB-CDs have been studied by UV-visible, Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Fluorescence spectra and X-ray photoelectron spectroscopy (XPS) techniques. The prepared RB-CDs exhibited green emission upon irradiation with UV light and the calculated fluorescence quantum yield (QY) was found to be 7.4%. The morphological features of the synthesized RB-CDs were characterized by High-Resolution Transmission Electron Microscopy (HR-TEM), the average size of the RB-CDs was found to be 2.96nm. The synthesized RB-CDs were beneficially applied as a catalyst for the catalytic degradation of methylene blue (MB) dye using NaBH4 as the reducing agent in the ambient conditions. The degradation of MB dye under light illumination was 89.20% in 30min. Further, the obtained highly fluorescent RB-CDs were efficiently utilized as a fluorescent ink for luminescent pattern printing (patterning agent) in the anti-counterfeiting applications.

High-quality borophene quantum dot realization and their application in a photovoltaic device

High-quality and stable borophene quantum dots (BQDs) are first introduced as a surface passivation agent on the TiO2 layer in CsPbI2Br solar cells. The efficiencies of solar cells with and without BQDs modified are15.31% and 14.40%, respectively.

Effect of thioglycolic acid molecules on luminescence properties of $$\hbox {Ag}_2$$S quantum dots

For monoclinic $$\hbox {Ag}_2$$S nanocrystals (quantum dots, $$\hbox {Ag}_2$$S/TGA QDs), the correlation between their luminescence properties and aspects of their passivation by thioglycolic acid (TGA) molecules is considered. The features of quantum confinement effect in the QDs absorption and photoluminescence spectra are analyzed for $$\hbox {Ag}_2$$S QDs with an average size of 1.7–3.1 nm. We show that, in various conditions of passivation of QDs interfaces, the luminescence mechanism of $$\hbox {Ag}_2$$S/TGA QDs is switched from recombination luminescence in the 870–1000 nm region to exciton luminescence with a band maximum at 620 nm. By means of FTIR spectra, two major types of interactions between TGA molecules and $$\hbox {Ag}_2$$S QDs, arising due to changing the [$$\hbox {Ag}^+$$]:[$$\hbox {S}^{2-}$$] ratio from 1:0.9 to 1:1.43, are determined. Exciton luminescence (620 nm) occurs in case of using TGA as the sulfur source in $$\hbox {Ag}_2$$S crystallization and the interface passivation agent, with [$$\hbox {Ag}^+$$]:[$$\hbox {S}^{2-}$$] = 1:1. The analysis of the FTIR spectra indicates bonding of TGA with the $$\hbox {Ag}_2$$S surface by both thiol and carboxylic groups in this case. With increasing the sulfur concentration in the synthesis of $$\hbox {Ag}_2$$S/TGA QDs, the exciton luminescence is suppressed. The employment of $$\hbox {Na}_2$$S as the sulfur source in $$\hbox {Ag}_2$$S crystallization with TGA acting as the surface passivation agent promotes the formation of recombination centers for IR luminescence. In this case, analysis of the FTIR spectra indicates passivation of $$\hbox {Ag}_2$$S QDs by TGA molecules due to adsorption of thiol groups. It is found that the photodegradation or IR luminescence of $$\hbox {Ag}_2$$S/TGA QDs upon exposure to exciting radiation is due to the photolysis of $$\hbox {Ag}_2$$S nanocrystals with formation of luminescence quenching centers as well as due to photodestruction of TGA molecules.

Correction to: Differential Immunomodulatory Effect of Carbon Dots Influenced by the Type of Surface Passivation Agent.

In the Published article, the article title shows "Differential Immunomodulatory Effect of Carbon Dots Influenced". It should be "Differential Immunomodulatory Effect of Carbon Dots Influenced by the Type of Surface Passivation Agent".

Differential Immunomodulatory Effect of Carbon Dots Influenced by the Type of Surface Passivation Agent.

Carbon nanodots (CDs) are often synthesized from natural sources including honey, molasses, fruits, and foods, and plant extracts simply through caramelization. They have wide biological applications especially as drug delivery vehicles and bioimaging agent due to their small size and biocompatibility. This article details the synthesis of carbon dots from carob and its derivatives by surface passivation with polyethylene glycol (PEG), polyvinyl alcohol (PVA), and alginate (ALG). We investigated the immune response against CDs and evaluated the effect of surface passivation agents on their immunomodulatory functions. CDPVA had strong anti-inflammatory activities, whereas CDALG were pro-inflammatory. CDPEG had mild anti-inflammatory activities suggesting that these CDs can be used in the drug delivery studies as inert carriers. These results showed that depending on the type of activated groups dominated on the surface, CDs exerted differential effects on the inflammatory potential of the macrophages by changing the pro-inflammatory TNFα and IL6 production levels.

Novel mulberry silkworm cocoon-derived carbon dots and their anti-inflammatory properties

Mulberry silkworm cocoon (MSC) carbonisata has been used for the treatment of inflammatory diseases for hundreds of years; however, after years of research efforts, little information is available on its anti-inflammatory components and underlying mechanism. We developed novel carbon dots (CDs) derived from MSC carbonisata (MSC-CDs), for the first time, with an average diameter of 2.26–9.35 nm and a quantum yield (QY) of 6.32%. The MSC-CDs were prepared using a modified pyrolysis method, and no further modification and external surface passivation agent was required. With abundant surface groups, MSC-CDs showed distinct solubility and bioactivity. In this study, we innovatively used three classical experimental models of inflammation to evaluate the anti-inflammatory bioactivity of MSC-CDs. The results indicated that MSC-CDs exhibited marked anti-inflammatory bioactivity which was likely mediated by inhibition of the expression of interleukin-6 and tumour necrosis factor-α. These results suggest that MSC-CDs possess a remarkable anti-inflammatory property, which provides evidence to support further investigation of the considerable potential and effective material basis of this traditional Chinese medicine.

Application of PEGylated graphene quantum dots in cell imaging

Polyethylene glycol (PEG) functionalized graphene quantum dots (GQDs-PEG) with average particle size of 2.1 nm were successfully prepared by hydrothermal method with PEG as surface passivation agent. The quantum yield (QY) of GQDs-PEG was 3.7%and its physiological stability was significantly better than that of GQDs. The cell viability assay results showed that GQDs-PEG display no obvious toxicity to cells. The results of cell fluorescence imaging showed that GQDs-PEG could enter the whole cell with high fluorescence recognition.

Fluorescent Carbon Dots from Nerium oleander: Effects of Physical Conditions and the Extract Types.

In this original research, the synthesis of carbon nanodots (CDs) from two different solvent extracts of Nerium oleander by the thermal method was investigated under various physical conditions such as pH, reaction temperature, ionic strength, and surface passivation agent (polyethylene glycol, PEG) presence in the reaction media. The effects of extract types and physical conditions on CDs formation were characterized by UV-Visible spectrophotometry, fluorescence spectrophotometry, Fourier transform infrared spectroscopy and dynamic light scattering analysis. Fluorescent CDs were obtained from PEG included reaction media. Additionally, the enhanced fluorescence intensity correlated with ascending reaction temperature was reported. The hydrodynamic particle size of CDs in aqueous solution was determined between ~1 and 235nm with negative surface potential in the range of -6mV and -28mV. Moreover, CDs synthesized from aqueous extract mostly resulted in smaller size than that of ethanol extract based ones. The impact of surface passivation with PEG on the fluorescence feature of CDs was verified. For the relevant extracts of Oleander, CDs synthesized from PEG included formulations at pH5 and NaCl free reaction media found as better alternatives than CDs synthesized under other conditions taking account their effect on fluorescence feature, hydrodynamic size and etc. Graphical Abstract.