Localized Surface Research Articles

Tunable optical properties of graphene wrapped ZnO@Ag spherical core-shell nanoparticles

In this paper, we studied theoretically and numerically the material’s response to incident electromagnetic wave of graphene wrapped zinc-oxide/silver (g − ZnO@Ag) core–shell spherical nanoparticles embedded in a dielectric host matrix. As the nanoparticles size is ∼30 nm, a size much smaller than the wavelength of light, the quasi-static approximation is utilized to obtain analytical expressions for the electric polarizability and the corresponding extinction cross-section. It is found that the spectra of the extinction cross-section of g − ZnO@Ag nanoparticles exhibit two sets of localized surface resonance peaks in the visible and near infra-red (NIR) spectral regions. The first set of peaks observed below ∼900 nm are due to the coupling of the energy gap of the ZnO core with the local surface plasmon resonances of Ag shell, and the second set of graphene-assisted narrow peaks located in the NIR region (above ∼900 nm) are attributed to the plasmons excited at the Ag/graphene interface. It is found that the intensity of the extinction cross-section as well as the positions of the resonance wavelengths are interesting that the graphene-assisted narrow peaks are strongly dependent on the number of layers (N g ) and the chemical potential (μ) of graphene. It means that the response of ZnO@Ag core–shell nanoparticles to electromagnetic fields are greatly enhanced when it is wrapped with graphene and can also be tuned in the therapeutic NIR spectral region by varying N g and μ. The results may be used for possible application in the medical fields, especially for cancer detection and drug delivery.

SOA: Seed point offset attention for indoor 3D object detection in point clouds

Three-dimensional object detection plays a pivotal role in scene understanding and holds significant importance in various indoor perception applications. Traditional methods based on Hough voting are susceptible to interference from background points or neighboring objects when casting votes for the target’s center from each seed point. Moreover, fixed-size set abstraction modules may result in the loss of structural information for large objects. To address these challenges, this paper proposes a three-dimensional object detection model based on seed point offset attention. The objective of this model is to enhance the model’s resilience to voting noise interference and alleviate feature loss for large-scale objects. Specifically, a seed point offset tensor is first defined, and then the offset tensor self-attention network is employed to learn the weights between votes, thereby establishing a correlation between the voting semantic features and the object structural information. Furthermore, an object surface perception module is introduced, which incorporates detailed features of local object surfaces into global feature representations through vote backtracking and surface mapping. Experimental results indicate that the model achieved excellent performance on the ScanNet-V2 (mAP@0.5, 60.3%) and SUN RGB-D (mAP@0.5, 64.0%) datasets, respectively improving by 2.6% (mAP@0.5) and 5.4% (mAP@0.5) compared to VoteNet.

Visual tracking of real-time freshness of fish using an agar hydrogel colorimetric indicator containing CuNPs/NCQDs

A simple, selective, and affordable dual fluorescence-colorimetric indicator for hydrogen sulfide was developed based on a complex of copper nanoparticles and N-doped carbon quantum dots (CuNPs/NCQDs). Real-time and visual freshness tracking of fish was done using a colorimetric indicator by incorporating CuNPs/NCQDs into agar hydrogel (AH-CuNPs/NCQDs). The fluorescence response of the CuNPs/NCQDs solution is quenched upon exposure to H2S. The field-emission scanning electron microscopy image of the AH-CuNPs/NCQDs film revealed a unified structure. The prepared indicator exhibited a good and irreversible response to H2S, with a LOD of 91.36 and a LOQ of 276.86 μM, based on the localized surface plasmon resonance (LSPR) mechanism. The X-ray photoelectron spectrometer and Fourier transform infrared spectrometer results confirmed the formation of a CuS bond in the colorimetric indicator exposed to fish spoilage. The prepared indicator demonstrated good stability and remained unaffected by pH or other volatile compounds. Notably, there was a strong correlation between ΔΕ and fish freshness parameters (pH, TV-BN, and TVC). Light green, pale yellow, and dark yellow colors, respectively, indicated freshness, semi-freshness, and spoilage of fish during storage in the refrigerator. Overall, the prepared indicator can be effectively used for detecting spoilage in meat products as a highly sensitive freshness indicator.

Colorimetric sensing of lead ion using gold nanorod with enhanced sensitivity via catalytic etching

AbstractLead, a prevalent heavy metal, poses significant risks to human health through various exposure pathways. Herein, we propose an extremely sensitive assay toward lead ion (Pb2+) using gold nanorods (GNRs) as probes based on its catalytic activity on etching gold in the presence of 2‐mercaptoethanol and sodium thiosulfate. In the presence of Pb2+, etching predominantly occurs at the two ends of GNRs, leading to the reduction of aspect ratio and the corresponding blueshift of the localized surface plasmon resonance (LSPR). With increasing Pb2+ concentration over the range of 0–50 μM, the color of GNR solution lightens, ultimately becoming colorless. The wavelength shift (Δλ) of LSPR is highly dependent on Pb2+ concentration, with a linear regression equation of Δλ = 10.05ln[Pb2+] + 9.59 and an R2 = 0.995. The assay demonstrates high selectivity for Pb2+ over other potentially interfering ions such as Cu2+ because of its special catalytic activity in the etching of GNRs and the complexing ability of 2‐mercaptoethanol and sodium thiosulfate. Validation of the assay was accomplished by analyzing several forest‐derived food samples, affirming the accuracy in real‐world scenarios. The assay we developed holds promise for many applications in environmental protection and food safety.

Mesoporous platinum@copper selenide-based NIR-II photothermal agents with photothermal conversion efficiency over 80% for photoacoustic imaging and targeted cancer therapy

Elevating photothermal conversion efficiency (PCE) is the key to enhance curative efficacy during photothermal therapy. Nevertheless, current functionalized or synthetic methods for preparing photothermal agents with high PCE are too complicated, greatly hindering the development of photothermal therapy. In this study, we developed a tumor-targeting flower-like nanocomposite termed mesoporous platinum nanoparticles@Cu2-xSe-AS1411 (MPNPs@Cu2-xSe-AS1411, denoted as MPCSA) with remarkable PCE for high-resolution PA imaging guided photothermal/chemodynamic therapy for tumor ablation. We discovered that MPNPs served as carriers for delivering photoacoustic (PA) contrast agents. Cu2-xSe nanosheets emerged as promising near-infrared-II (NIR-II) PA imaging and photothermal/chemodynamic therapy agents owing to their strong localized surface plasmon resonance property in the NIR-II region. The amine-modified AS1411 aptamer, which is connected to the surface of the flower-like MPNPs@Cu2-xSe can target the nucleolar protein on the surface of 4 T1 cells, achieving the accumulation of MPCSA at the tumor site in mice. Notably, these MPCSA nano-flowers exhibited an excellent PCE up to 82.33 % under 1064 nm laser irradiation, resulting in highly efficient cancer cell ablation and greatly hindering in vivo tumor growth. This study has paved the way for imaging-guided accurate cancer diagnosis and targeted cancer therapy.

Enhanced light harvesting ability in hollow Pt/TiO2 nanoreactor for boosting tetracycline photodegradation

Utilizing solar energy to decompose tetracycline (TC) is a green strategy to treat wastewater. Herein, a heterogeneous hollow structured TiO2 decorated Pt nanoparticles were successfully designed and synthesized via hard-template approach and photo-deposition process toward TC photodegradation. The Pt nanoparticles loaded on the surface of hollow structured TiO2 can increase the visible light absorption due to the local surface plasmon resonance (LSPR) effect. Furthermore, owing to the tough electron oscillation of the LSPR excitation, the plasmonic hot holes on the surface of Pt nanoparticles can capture the electrons of TiO2, effectively facilitating the separation of photo-excited charge carriers because of the formation of Schottky junction constructed between Pt and TiO2. Combined the natural merits of shorten conveying path of charge carriers and physical structural stability for hollow structure, the optimal Pt/TiO2 hetero-junction hybrid showed superior photocatalytic activity and durability for TC photodegradation with the degradation efficiency of 93.8 ​% after 30 ​min and the rate constant of 0.09196 min−1 under 300 ​W Xe lamp irradiation. This work displays a heterogeneous hybrids catalyst based on eco-friendly metal and semiconductor materials which can be used in the fields including without limitation TC photodegradation.

Advanced bionic inverted coral solar evaporator: Enhancing sustainable water utilization with efficient and salt-resistant evaporation

Interfacial solar-driven steam generation technology shows great potential in addressing desalination and wastewater purification. However, there is a lack of advanced evaporators with high evaporation efficiency and salt tolerance, which is an obstacle to its widespread application. Drawing inspiration from marine coral structures, we develop a bionic inverted coral-type 3D solar evaporator with an array structure using structural engineering design. The microscopically porous vertical channel structure within the overall skeleton enhances the longitudinal reflux of salt ions and water evaporation, while macroscopic gaps in the bionic coral branching facilitate lateral advection–diffusion of salt ions. Numerical simulations confirm that this bionic coral structure design improves the diffusion rate of concentrated brine. Due to the localized surface plasma resonance and the Marangoni effect, the evaporator achieves remarkable water evaporation performance (evaporation rate: 2.72 kg m−2h−1, energy efficiency: 95.8 %) and operates reliably even under 20 % brine concentration (evaporation rate: 2.65 kg m−2h−1) without significant salt crystallization. Furthermore, it exhibits good wettability and robust mechanical properties, capable of withstanding a wide range of temperatures. The efficient and salt-resistant evaporation makes it valuable for applications including desalination, various wastewater treatments, and agricultural irrigation, thereby promoting the sustainable utilization of water resources.

Reverse Transcriptase Loop-mediated Isothermal Amplification Assisted with Localized Surface Plasmon Resonance of Gold Nanorods for Viability Assessment of Lactobacillus acidophilus in Yogurt

In light of the growing production and consumption of functional foods, it is crucial to develop new methods to assess the authenticity of these products and prevent fraud and mislabeling. In this research, by integrating reverse transcription loop-mediated isothermal amplification (RT-LAMP) and the localized surface plasmon resonance (LSPR) effect of gold nanorods (GNRs), the viability of the probiotic bacteria has been evaluated. The RT-LAMP-GNR method effectively amplifies and identifies bacterial 16S-rRNA within 60 minutes. The efficiency of the RT-LAMP method was assessed by its implementation using RNA isolated from Lactobacillus acidophilus strain (L. acidophilus) and commercial probiotic yogurts. The method's limit of detection (LoD) was 104 bacterial cells per ml, and its sensitivity was 10-5 ng/ml RNA.

Control of the size distribution of AuNPs for colorimetric sensing by pulsed laser ablation in liquids

Gold nanoparticles (AuNPs) are extensively employed in colorimetric sensing, taking advantage of their optical properties to detect variables via observable color changes. These properties are primarily driven by localized surface plasmon resonance (LSPR), particularly pronounced in AuNPs within the visible spectrum. In this study, AuNPs were synthesized via pulsed laser ablation in liquids (PLAL) with a laser pulse energy (Ep) ranging from 25 mJ to 75 mJ. Size distributions, hydrodynamic diameters, polydispersity indices (PDI), absorbance intensity, and LSPR were characterized. Spherical AuNPs with FCC structure were synthesized, exhibiting a maximum absorption peak centered at approximately 529 nm wavelength and a size range between 50 nm and 178 nm, easily adjustable depending on the laser pulse energy used in the synthesis process. An anomalous behavior was noted at Ep=50 mJ, exhibiting three peaks in size distribution, high PDI, low absorbance intensity, and indistinct LSPR. By extending the ablation time from 10 min to 30 min, particle size decreased alongside lower PDI. Size distributions transitioned from three to two peaks, absorbance increased, and LSPR became readily identifiable. These findings underscore the size control over AuNP characteristics achievable through PLAL synthesis parameters, promising significant implications for the optimization of colorimetric sensor design and development.

Efficient evaporation of seawater desalination by novel double-interface evaporator: Photothermal conversion, water transfer and salt-resistant

Interfacial solar-driven water evaporation emerged as an established eco-friendly method for seawater desalination to combat water scarcity, yet the low evaporation rate and cost-effectiveness limit the practicable application. Herein, we presented a double-interface evaporator with a bilayer structure (BCCu@FC). The upper layer was constructed using carbonized copper-doped biochar (BCCu), which exhibited broadband sunlight absorption and effective photothermal conversion capability for the localized surface plasmon resonance (LSPR) effect. Meanwhile, the lower layer was constructed by felt fabric (FC), which featured a large spatial network structure, guaranteeing sufficient water transportation. Therefore, BCCu@FC exhibited a high photothermal conversion efficiency of 87.05 % with a 1.571 kg m−2 h−1 water evaporation rate under 1 sun illumination. Moreover, BCCu@FC further exhibited high stability and salt resistance, showing no significant salt crust formation after continuous operation for 24 h under 3.5 wt% brine. Especially, BCCu@FC could stably work under 21 % brine, and the salt crust re-dissolved within 4 h after the cessation of illumination. This facile and universal strategy was anticipated to pave the way for future designs and fabrication of diverse, more efficient, and cost-effective photothermal conversion devices.

Photoelectrochemical sensor consisting of sulfhydryl-borate ester modified A1/B1 type Pillar[5]arene-functionalized gold NPs

Recognition of mitochondrial reactive oxygen species (ROS) in cells is essential for understanding the critical roles of different ROS in biology reaction processes. In this study, an ultrasensitive and specific photoelectrochemical (PEC) sensor is constructed and applied for the capture and identification of H2O2 in cells. For the targeted detection of H2O2 in cells containing similar groups, such as •OH and O2•-, a new sulfhydryl-borate ester modified A1/B1 type pillar[5]arene (BP5) with a specific borate group is designed as a specific recognition molecule, and Au nanoparticles (Au NPs) are synthesized as the photoactive material. Specifically, the localized surface plasmon resonance (LSPR) of the Au NPs and host-guest interaction between BP5 and H2O2 increase the photocurrent signal. At the same time, specific groups on BP5 react with H2O2 to specifically recognize it. The Au@BP5/GCE shows strong photoelectrochemical response for the detection of H2O2 with limit of detection (0.33 pM, S/N=3), an extended linear range (1–60 pM), high specificity, good stability and excellent reproducibility.

Photovoltaic enhancement in OSCs based on PM6:Y7 when doping the active layer withAg2Snanoparticles

Herein, silver sulfide (Ag2S) nanoparticles (NPs) with an average size of 31 nm ± 4 nm were synthesized using a simple, economic, and eco-friendly method assisted by ultrasonic bathing; the reaction was carried out in a non-polluting aqueous medium. These Ag2S NPs were suspended in ethanol and used to dope the active layer of Organic Solar Cells (OSCs) based on PM6 (donor) and Y7 (acceptor) by adding 2 v/v % of a suspension to the PM6:Y7 solution in chlorobenzene (CB). The entire fabrication process and testing was carried out under normal atmospheric conditions. Field’s metal (FM) was used as the top electrode of the OSCs, which is a eutectic alloy of bismuth, indium, and tin (Bi 32.5%, In 51%, and Sn 16.5%) with a melting point above 62 ºC deposited by free evaporation techniques. The average Power Conversion Efficiency (PCE) for the reference and doped OSCs were 9.19 % (9.43 % the best) and 10.31 % (10.77 % the best), respectively; representing an increase of more than 14 % in the PCE value when Ag2S NPs are added to the active layer. It can be attributed to different optical phenomena, among which could be the enhance in the internal light reflection processes (scattering) and the Local Surface Plasmon Resonance (LSPR) effect.

Synthesis of ZrN–SiO2 core–shell particles by a sol–gel process and use as particle‐based structured coloring material

AbstractZrN–SiO2 core–shell particles were prepared, where the ZrN core nanoparticles and SiO2 shell were designed to exhibit localized surface plasmon resonances (LSPRs) and structural coloring. The heating of ZrO2 nanoparticles with Mg3N2 under a nitrogen gas flow produced ZrN nanoparticles with a diameter in the range of 10–20 nm. The dispersion of ZrN nanoparticles in water exhibited an absorption maximum at approximately 700 nm owing to LSPRs. An SiO2 shell was formed on the ZrN nanoparticles using a sol–gel process. Scanning transmission electron microscopy confirmed the formation of ZrN–SiO2 core–shell particles containing ZrN particles with a diameter of approximately 10 nm. The SiO2 shell thickness was controlled by varying the reaction time to form SiO2. The use of particles as a structural component of a structural color material owing to the high uniformity of the size of obtained core–shell particles was investigated. The obtained ZrN–SiO2 core–shell particles were arrayed on a glass substrate using a layer‐by‐layer method. The particle‐stacked film of the ZrN–SiO2 core–shell particles exhibited the maximum reflection depending on the particle size of the SiO2 shell.

Locally Varying Surface Binding Affinity on Pd-Au Nanocrystals Enhances Electrochemical Ethanol Oxidation Activity.

Noble metal nanocrystals face challenges in effectively catalyzing electrochemical ethanol oxidation reaction (EOR)-represented multistep, multielectron transfer processes due to the linear scaling relationship among binding energies of intermediates, impeding independent optimization of individual elemental steps. Herein, we develop noble metal nanocrystals with a range of local surface binding affinities in close proximity to overcome this challenge. Experimentally, this is demonstrated by applying tensile strain to a Pd surface and decorating it with discrete Au atoms, forming a diversity of binding sites with varying affinities in close proximity for guest molecules, as evidenced by CO probing and density functional theory calculations. Such a surface enables reaction intermediates to migrate between different binding sites as needed for each elemental step, thereby reducing the energy barrier for the overall EOR when compared to reactions at a single site. On these tailored surfaces, we attain specific and mass activities of 32.7 mA cm-2 and 47.8 A mgPd-1 in EOR, surpassing commercial Pd/C by 10.9 and 43.8 times, respectively, and outperforming state-of-the-art Pd-based catalysts. These results highlight the promise of this approach in improving a variety of multistep, multielectron transfer reactions, which are crucial for energy conversion applications.

Localized Surface Doping Induced Ultralow Contact Resistance between Metal and (Bi,Sb)2Te3 Thermoelectric Films.

Micro thermoelectric devices are expected to further improve the cooling density for the temperature control of electronic devices; nevertheless, the high contact resistivity between metals and semiconductors critically limits their applications, especially in chip cooling with extremely high heat flux. Herein, based on the calculated results, a low specific contact resistivity of ∼10-7 Ω cm2 at the interface is required to guarantee a desirable cooling power density of micro devices. Thus, we developed a generally applicable interfacial modulation strategy via localized surface doping of thermoelectric films, and the feasibility of such a doping approach for both n/p-type (Bi,Sb)2Te3 films was demonstrated, which can effectively increase the surface-majority carrier concentration explained by the charge transfer mechanism. With a proper doping level, ultralow specific contact resistivities at the interfaces are obtained for n-type (6.71 × 10-8 Ω cm2) and p-type (3.70 × 10-7 Ω cm2) (Bi,Sb)2Te3 layers, respectively, which is mainly attributed to the carrier tunneling enhancement with a narrowed interfacial contact barrier width. This work provides an effective scheme to further reduce the internal resistance of micro thermoelectric coolers, which can also be extended as a kind of universal interfacial modification technique for micro semiconductor devices.

Prediction of forming accuracy in incremental sheet forming using artificial neural networks on local surface representations

While incremental sheet metal forming offers the potential for producing sheet metal parts in small lot sizes, the relatively low forming accuracy prevents widespread industrial use. For improving the forming accuracy, research institutes are using machine learning techniques to predict the geometric accuracy and modify the toolpath based on the prediction. A critical challenge is it to ensure the generalizability of the prediction model as only a small amount of process data is available to train the model due to the lack of industrial collaborations. This publication presents a highly transferable feature engineering approach where surface representations of the part’s geometry around each toolpath point are transferred into a standardized coordinate system. Several artificial neural networks were trained and used for predicting the forming accuracy and modifying the toolpath. During the validation experiments, the forming errors of parts which were independent of the training process were reduced by up to 68.5 %. The framework for computing the surface representations alongside with several pre-trained artificial neural networks is publicity available for download.

Dynamic responses and damage/element composition analysis of thermoplastic polyamide reinforced epoxy composites exposed to HCI environment

AbstractThe present study aimed to examine how the corrosive environment affected the low‐velocity impact (LVI) characteristics and damage mechanisms of thermoplastic polyamide fiber‐reinforced polymer (PFRP) composites. In this regard, composite specimens were subjected to corrosive environment containing 10 wt.% diluted HCl for one week and one month before LVI tests. To investigate the hostile effects of the corrosive environment on the composites, scanning electron microscope (SEM) coupled with energy‐dispersive X‐ray system (EDX) analyses were carried out, and thus variations in the elemental composition and damage mechanisms for the composites were determined. According to the examinations, it was discovered that the degradation in LVI responses, such as contact stiffness, bending stiffness, and peak force, increased with longer aging time, as expected. Furthermore, when the aging effect was assessed based on absorbed energy, the specimens exposed to a corrosive environment for one month exhibited the highest energy absorption compared to the control and 1‐week‐immersed ones. The degrading effect of the HCI environment appeared as higher damage severity on the composites, which was also detected from the SEM images. According to the SEM analyses, matrix cracks, corrosion pits, and local surface imperfections caused by ion exchange are detected in 1‐week‐immersed specimens, while more serious damage mechanisms such as fiber breakage and fiber pull‐out are noted in specimens exposed to corrosive environment for 1 month. Furthermore, approximately 6.33 wt.% CI was identified in the composites after 1 month of aging, which was associated with the hydrolysis triggered by rise in the composite's damage severity.Highlights Aging effects in mechanical properties of PFRP composites were investigated LVI tests were conducted to determine dynamic responses of aged composites Longer aging time led to more severe damages such fiber rupture, delamination etc. PFRP composites absorbed at least 68% of impact energy.

Plasmon-enhanced fluorescence for biophotonics and bio-analytical applications.

Fluorescence spectroscopy serves as an ultrasensitive sophisticated tool where background noises which serve as a major impediment to the detection of the desired signals can be safely avoided for detections down to the single-molecule levels. One such way of bypassing background noise is plasmon-enhanced fluorescence (PEF), where the interactions of fluorophores at the surface of metals or plasmonic nanoparticles are probed. The underlying condition is a significant spectral overlap between the localized surface plasmon resonance (LSPR) of the nanoparticle and the absorption or emission spectra of the fluorophore. The rationale being the coupling of the excited state of the fluorophore with the localized surface plasmon leads to an augmented emission, owing to local field enhancement. It is manifested in enhanced quantum yields concurrent with a decrease in fluorescence lifetimes, owing to an increase in radiative rate constants. This improvement in detection provided by PEF allows a significant scope of expansion in the domain of weakly emitting fluorophores which otherwise would have remained unperceivable. The concept of coupling of weak emitters with plasmons can bypass the problems of photobleaching, opening up avenues of imaging with significantly higher sensitivity and improved resolution. Furthermore, amplification of the emission signal by the coupling of free electrons of the metal nanoparticles with the electrons of the fluorophore provides ample opportunities for achieving lower detection limits that are involved in biological imaging and molecular sensing. One avenue that has attracted significant attraction in the last few years is the fast, label-free detection of bio-analytes under physiological conditions using plasmonic nanoparticles for point-of-care analysis. This review focusses on the applications of plasmonic nanomaterials in the field of biosensing, imaging with a brief introduction on the different aspects of LSPR and fabrication techniques.

Plasmonic cross-reactive sensing noses and tongues.

The advancements in the capabilities of artificial sensory technologies, such as electronic/optical noses and tongues, have significantly enhanced their ability to identify complex mixtures of analytes. These improvements are rooted in the evolving manufacturing processes of cross-reactive sensor arrays (CRSAs) and the development of innovative computational methods. The potential applications in early diagnosis, food quality control, environmental monitoring, and more, position CRSAs as an exciting area of research for scientists from diverse backgrounds. Among these, plasmonic CRSAs are particularly noteworthy because they offer enhanced capabilities for remote, fast, and even real-time monitoring, in addition to better portability of instrumentation. Specifically, the synergy between the localized surface plasmon resonance (LSPR) of nanoparticles (NPs) and CRSAs introduces advanced techniques such as surface plasmon resonance (SPR), metal-enhanced fluorescence (MEF), surface-enhanced infrared absorption (SEIRA), surface-enhanced Raman scattering (SERS), and surface-enhanced resonance Raman scattering (SERRS) spectroscopies. This review delves into the importance and versatility of optical-CRSAs, especially those based on plasmonic materials, discussing recent applications and potential new research directions.

Formation mechanism and control of a kind of pit-shaped defect in Cf53 rolled products

Aiming at the frequent issue of pit-shaped surface defects in S-bearing and Al-killed steel products and the related poor castability due to submerged entry nozzle (SEN) clogging, the melting and casting process of a popular auto steel Cf53 has been studied based on in-situ investigation and experimental analysis. To clarify the generation of the pit-shaped defects, the local surface chemistry, evolution of steel inclusions throughout the melting process, SEN clogging substances, and the internal relationship among them were systematically analyzed. The results show that this type of defect in the Cf53 rolled products is caused by the large-sized composite inclusions rich in CaS, which originate from the molten steel during the refining process, gradually accumulate on the inner wall of the SEN during casting, and finally lead to SEN clogging. The loose structure of clogging inclusions makes them prone to fall off into the mold and get trapped by solidifying steel shell. The formation mechanism of the inclusions was studied through FactSage software calculation. The results show that the increase in total sulfur and total calcium content, and the decrease in total oxygen content and temperature in steel will lead to CaS inclusion formation, which agrees reasonably well with experimental results. An optimized refining process to reduce calcium addition into molten steel is proposed accordingly, which achieves a remarkably alleviation in casting SEN clogging and an elimination of the pit-shaped defects on the final rolled products as well.