SE Bond Research Articles

Taming the anchor and conversion of polyselenides with a self-reinforcing host in lithium–selenium batteries

Energy-dense lithium–selenium (Li–Se) batteries have attracted increasing attention, while their practical application is still hindered, highly relating to the volume expansion and shuttle of Li polyselenides (LiPSes). Herein, a concurrent anchoring/converting strategy is proposed to restrain the dissolution and realize the rapid conversion of LiPSes. A prototypical regulator comprises of polar catalysts embedded in the interconnected porous muti-walled carbon network (i.e., CoSnO3 nanocubes/CNTs), which promises fast electron/ion transportation and inhibits volumetric effect. Moreover, CoSnO3 as redox accelerator enables the stretched Se−Se bonds to decrease the LiPSes bidirectional conversion barrier, achieving accelerated reaction kinetics. Consequently, the self-reinforcing optimized cathode exhibits superior initial capacity of 730 mAh/g, greatly enlarged capacity after 200 cycles (increase by ∼ 32 % than that of the cell with CNTs), and superior rate capacity (153 mAh/g at 2C). This work uncovers the roles of electronic/ionic conductivity and adsorption/catalysis in Li–Se batteries, providing a guidance for taming the utilization and kinetics of cathode from material perspectives.

Erosive Influence of Amazonian Tucupi on Microshear Bond Strength to Enamel and Dentin

Abstract Background: The scientific literature has studies that assess the influence of erosive challenges with citric acidic drinks and substances on the adhesive bond strength to enamel and dentin, but does not contain information about the influence of regional components of an acidic diet on this process. Thus, this study evaluated the erosive influence of Amazonian tucupi on enamel and dentin microshear bond strength. Materials and Methods: One hundred and sixty-eight healthy bovine incisors teeth were used, divided into 12 groups (n = 14). For erosive cycling, distilled water (negative control), cola-based soft drink (positive control), or tucupi were used, followed by adhesive strategies of (1) etch-and-rinse (conventional) (Adper™ Single Bond 2) and (2) self-etching (Clearfil SE Bond). All specimens were subjected to erosive cycling for 5 days and, after 24 h, composite resin cylinders were built up for the microshear bond strength test. The data showed normal distribution and were analyzed by two-way ANOVA, followed by the Tukey post and test (P ≤ 0.05). Results: There were no significant differences in enamel (P > 0.05). In dentin, only the groups exposed to cola-based soft drink showed significant differences (P < 0.01). The failure mode showed that Type II (mixed) was predominant (95%). Conclusion: The erosive challenge with tucupi did not influence the bond strength to enamel and dentin, regardless of the adhesive strategy used.

Invoking Interfacial Engineering Boosts Structural Stability Empowering Exceptional Cyclability of Ni-Rich Cathode.

The cycling stability of LiNi0.8Co0.1Mn0.1O2 under high voltages is hindered by the occurrence of hybrid anion- and cation-redox processes, leading to oxygen escape and uncontrolled phase collapse. In this study, an interfacial engineering strategy involving a straightforward mechanical ball milling and low-temperature calcination, employing a Se-doped and FeSe2&Fe2O3-modified approach is proposed to design a stable Ni-rich cathode. Se2- are selectively adsorbed within oxygen vacancies to form O─TM─Se bond, effectively stabilizing lattice oxygen, and preventing structural distortion. Simultaneously, the Se-NCM811//FeSe2//Fe2O3 self-assembled electric field is activated, improving interfacial charge transfer and coupling. Furthermore, FeSe2 accelerates Li+ diffusion and reacts with oxygen to form Fe2O3 and SeO2. The Fe2O3 coating mitigates hydrofluoric acid erosion and acts as an electrostatic shield layer, limiting the outward migration of oxygen anions. Impressively, the modified materials exhibit significantly improved electrochemical performance, with a capacity retention of 79.7% after 500 cycles at 1C under 4.5V. Furthermore, it provides an extraordinary capacity retention of 94.6% in 3-4.25V after 550 cycles in pouch-type full battery. This dual-modification approach demonstrates its feasibility and opens new perspective for the development of stable lithium-ion batteries operating at high voltages.

Enhancing the stability of Sb2Se3 alloy through structural alterations on Bi addition

Sb2Se3 has attracted a lot of research interest as an environmentally friendly material with diverse applications. (Sb2Se3)100−xBix(x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) alloys are synthesized via melt quenching. Energy Dispersive X-ray (EDX) spectra confirm the Sb, Se, and Bi presence in bulk samples. X-ray diffraction (XRD) spectra confirm orthorhombic crystal structure in Bi-doped Sb2Se3 alloys. FTIR and Raman spectroscopy observations indicate an alteration in local structure on Bi addition. Far-IR spectroscopy points to Bi bonding with Se forming Bi2Se3 units. There is shifting of Raman peaks, corroborating the structural alteration in alloys on Bi incorporation. The peak intensity of Raman modes for Sb–Sb bond (B1g mode) decreases and for Sb–Se bond (A1g mode) increases, due to formation of Bi2Se3 structural units on Bi incorporation. The formation of stable Bi2Se3 units on Bi addition to Sb2Se3 alloys may be explored for potential application in topological insulators.

Asymmetric Bond Delta‐Polarization at the Interfacial Se─Ru─O Bridge for Efficient pH‐Robust Water Electrolysis

AbstractThe rationalization of pH‐robust catalysis is highly desired but challengeable for overall water electrolysis (WE). It requests a metal active site that can make an efficient adaption with both cathodic hydrogen and anodic oxygen evolution reactions (HER/OER). Herein, a RuO2‐x/RuSe2 heterostructure electrocatalyst is profiled with interfacial Se─Ru─O bridge for the pH‐robust water splitting studies. An asymmetric bond delta‐polarization (Δp) is found at the interfacial Se─Ru─O bridge, including the Δp > 0 at the Ru─O part and Δp < 0 at the Ru─Se side by both experiment and calculation results. The enlarged Ru─O bond polarizability (Δp > 0) can in principle trigger the lattice oxygen mediated (LOM) pathway for OER; meanwhile, the reduced Ru─Se bond polarizability can benefit the HER due to the strengthened d‐p band hybridization. Resultantly, the heterostructure can deliver ultralow overpotentials of 25/10 mV for Pt‐beyond HER and 210/255 mV for OER at 10 mA cm−2 in acidic/alkaline media, respectively. In especial, the acidic overall WE can be stably operated for 200 h with a low cell voltage of 1.478 V at 10 mA cm−2. This research clarifies the asymmetric bond polarization as the criterion for the rational design of efficient WE catalysts.

Crystallization behavior and structural characteristics of Cr-doped Sb70Se30 thin films for phase change memory

In this study, we prepare Cr-doped Sb70Se30 (SS) thin films via the magnetron sputtering. The influence of Cr doping on the crystallization behavior and structure characteristics of the SS thin films is systematically studied using a combination of experimental analyzes and theoretical calculations. The results reveal that compared with SS thin films, Cr-doped SS thin films exhibit higher crystallization temperature, better data retention capability, larger crystallization activation energy, and reduced resistance drift coefficient. In addition, the incorporation of Cr effectively suppresses grain growth in the SS thin films and refines the grain size. The electrical transport properties of the Cr-doped SS thin films are analyzed using a Hall system. Both X-ray photoelectron spectroscopy and first-principles calculations indicate that Cr is more prone to occupy Sb atoms and form stronger Cr–Se bonds, consequently enhancing the stability of the SS thin films. Raman spectroscopy confirms that the introduction of Cr leads to a decrease in bond length and an increase in bond energy. Moreover, the Cr-doped SS thin film exhibits minimal volume fluctuations and a smoother surface morphology, resulting in enhanced interface performance and reliability. Taken together, these results indicate that the introduction of Cr is an effective strategy for optimizing the properties and modifying the structures of SS phase-change materials.

Structures of SenB and SenA enzymes from Variovorax paradoxus provide insights into carbon–selenium bond formation in selenoneine biosynthesis

Selenoneine, an ergothioneine analog, is important for antioxidation and detoxification. SenB and SenA are two crucial enzymes that form carbon–selenium bonds in the selenoneine biosynthetic pathway. To investigate their underlying catalytic mechanisms, we obtained complex structures of SenB with its substrate UDP-N-acetylglucosamine (UDP-GlcNAc) and SenA with N-α-trimethyl histidine (TMH). SenB adopts a type-B glycosyltransferase fold. Structural and functional analysis of the interaction network at the active center provide key information on substrate recognition and suggest a metal-ion-independent, inverting mechanism is utilized for SenB-mediated selenoglycoside formation. Moreover, the complex structure of SenA with TMH and enzymatic activity assays highlight vital residues that control substrate binding and specificity. Based on the conserved structure and substrate-binding pocket of the type I sulfoxide synthase EgtB in the ergothioneine biosynthetic pathway, a similar reaction mechanism was proposed for the formation of C–Se bonds by SenA. The structures provide knowledge on selenoneine synthesis and lay groundwork for further applications of this pathway.

Reinforced Interfacial Cd─Se Bond Coupling Photocatalytic Hydrogen Evolution with Pyruvic Acid Synthesis

AbstractMaximizing the utilization of photogenerated electrons and holes to drive the coupling reaction of hydrogen evolution with selective value‐added organic synthesis holds great potential for more efficient exploitation of solar energy. Herein, the interstitial boron‐doped CdS is synthesized by taking SiO2 as a template as well as the adsorption sites of boric acid, which contributes to the boron doping and induces the reinforced Cd─Se bonding for enhancing the interfacial interaction with co‐catalyst MoSe2. Thus, the interfacial Cd─Se bond with more electron localization provides rapid channels at the atomic level for accelerating the charge transfer with a lower energy barrier, achieving the efficient hydrogen evolution and high selectivity pyruvic acid synthesis concurrently. This work provides a new perspective in avoiding the use of sacrificial agents uneconomically and producing green hydrogen with high‐value‐added chemicals simultaneously.

Development of Sb phase change thin films with high thermal stability and low resistance drift by alloying with Se

A single Sb phase demonstrates potential for use in phase change memory devices. However, the rapid crystallization of Sb at room temperature imposes limitations on its practical application. To overcome this issue, Sb is alloyed with Se using a reactive co-sputtering deposition technique, employing both Sb and Sb2Se3 sputter targets. This process results in the formation of Sb-rich Se thin films with varying compositions. Compared to pure Sb, the Sb-rich Se thin films exhibit enhanced thermal stability due to the formation of Sb–Se bonds and reduced resistance drift. In particular, the Sb86.6Se13.4 thin film demonstrates an exceptionally low resistance drift coefficient (0.004), a high crystallization temperature (Tc = 195 °C), a high 10-year data retention temperature (116.3 °C), and a large crystallization activation energy (3.29 eV). Microstructural analysis of the Sb86.6Se13.4 reveals the formation of a trigonal Sb phase with (012) texture at 250 °C, while Sb18Se and Sb2Se3 phases form at 300 °C. Conversely, the Sb98.3Se1.7 thin film shows the formation of the single Sb phase with (001) texture, a Tc of 145 °C, and a low resistance drift coefficient (0.011). Overall, this study demonstrates that the alloying strategy is a viable approach for enhancing thermal stability and reducing resistance drift in Sb-based phase-change materials.

Inside Back Cover

The cover displays a selective oxidative sulfonylation of alkenes with selenium sulfonate depended on the reaction conditions. The electrochemical C—H sulfonylation proceeded smoothly to afford (E)‐vinyl sulfones with good selectivity in an undivided cell without external oxidant. While aerobic trifunctionalization of alkenes occurred in the presence of KI in the air, which provides β‐keto selenosulfones via the formation of C—O, C—S, and C—Se bonds in one‐pot. This selective synthesis is like interstellar racing, reaching distant planets from the same starting point through different paths. Following control experiments, a plausible mechanism is proposed to rationalize the experimental results. More details are discussed in the article by Cao et al. on page 1367—1372.image

Electrochemical Oxidative Cross-Coupling Reactions of Ketene Dithioacetals and Dichalcogenides to Construct C−Se/C−S Bonds

A green protocol for construction of C−Se bonds from ketene dithioacetals and diselenides through direct electrochemical oxidative cross-coupling has been developed. This reaction was carried out in an undivided cell system with NaBF4 as the electrolyte and CH3CN as the solvent through galvanostatic electrolysis. A series of substituted ketene dithioacetals and diselenides were tolerant and the desired tetrasubstituted alkenyl selenides were obtained in moderate to excellent yields. In addition, construction of C−S bond from ketene dithioacetals and disulfides through electrochemical method in the presence of KI was also successfully realized. It exhibited high efficiency and broad functional group tolerance.

Filler Mixed Into Adhesives Does Not Necessarily Improve Their Mechanical Properties.

To investigate the influence of filler type/loading on the micro-tensile fracture strength (μTFS) of adhesive resins, as measured 'immediately' upon preparation and after 1-week water storage ('water-stored'). The morphology and particle-size distribution of three filler particles, referred to as 'Glass-S' (Esschem Europe), 'BioUnion' (GC), and 'CPC_Mont', were correlatively characterized by SEM, TEM, and particle-size analysis. These filler particles were incorporated into an unfilled adhesive resin ('BZF-29unfilled', GC) in different concentrations to measure the 'immediate' μTFS. After 1-week water storage, the 'water-stored' μTFS of the experimental particle-filled adhesive resins with the most optimum filler loading, specific for each filler type, was measured. In addition, the immediate and water-stored μTFS of the adhesive resins of three experimental two-step universal adhesives based on the same resin matrix but varying for filler type/loading, coded as 'BZF-21' (containing silica and bioglass), 'BZF-29' (containing solely silica), and 'BZF-29_hv' (highly viscous with a higher silica loading than BZF-29), and of the adhesive resins of the gold-standard adhesives OptiBond FL ('Opti-FL', Kerr) and Clearfil SE Bond 2 ('C-SE2', Kuraray Noritake) was measured along with that of BZF-29unfilled (GC) serving as control/reference. Statistics involved one-way and two-way ANOVA followed by post-hoc multiple comparisons (α<0.05). Glass-S, BioUnion, and CPC_Mont represent irregular fillers with an average particle size of 8.5-9.9 μm. Adding filler to BZF-29unfilled decreased μTFS regardless of filler type/loading. One-week water storage reduced μTFS of all adhesive resins except BZF-21, with the largest reduction in μTFS recorded for BZF-29unfilled. Among the three filler types, the μTFS of the 30 wt% Glass-S and 20 wt% BioUnion filled adhesive resin was not significantly different from the μTFS of BZF-29unfilled upon water storage. Adding filler particles into adhesive resin did not enhance its micro-tensile fracture strength but appeared to render it less sensitive to water storage as compared to the unfilled adhesive resin investigated.

Influence of adhesive systems containing different functional monomers on the longevity of bond strength at different dentin depths

This study evaluated the influence of adhesive systems containing different functional monomers on the longevity of bond strength (BS) to superficial (SD) and deep dentin (DD). Thirty molars were sectioned longitudinally, to obtain regions of SD (closest to the dentin-enamel junction) and DD (closest to the pulp chamber). Adhesive systems were applied (n = 10): Clearfil SE Bond (containing 10-MDP), FL-Bond II (containing 4-MET) and OptiBond Universal (containing GPDM). Microcylinders were made of resin composite (Filtek Z250) in SD and DD. After 24 h or 180 days of storage in Simulated Body Fluid (SBF) solution, BS tests were carried out. The fracture mode was evaluated by scores. ANOVA showed that there was no statistically significant difference between the adhesives in terms of BS (p = 0.5156). There was no significant difference between storage times for the three adhesive systems (p = 0.4703). There was a significant interaction between storage time and dentin depth (p = 0.0175), and in the time interval of 24 h, irrespective of the adhesive system, BS was significantly higher in SD than in DD (p < 0.05). In the time interval of 24 h, there was a significant association between the adhesive and the type of failure in SD (p = 0.0085) (Fisher's Exact test). Under these conditions, only OptiBond Universal showed cohesive failures in dentin (10 %) and mixed failures (15 %). After 180 days of storage, the percentages of early failures in deep dentin were 25.0 % (OptiBond Universal), 16.7 % (Clearfil SE Bond) and 0.0 % (FL-Bond II), with a significant difference between adhesives regarding early failures (p = 0.0410). The adhesive systems showed similar BS at different dentin depths over time, irrespective of the composition of functional monomers. FL Bond II was the only adhesive system that did not show early failures mode in DD within 180 days.

Construction of blackberry polysaccharide nano-selenium particles: Structure features and regulation effects of glucose/lipid metabolism in HepG2 cells

In this study, blackberry polysaccharide-selenium nanoparticles (BBP-24-3Se) were first prepared via Na2SeO3/Vc redox reaction, followed by coating with red blood cell membrane (RBC) to form core–shell structure polysaccharide-selenium nanoparticles (RBC@BBP-24-3Se). The particle size of BBP-24-3Se (167.1 nm) was increased to 239.8 nm (RBC@BBP-24-3Se) with an obvious core–shell structure after coating with RBC. FT-IR and XPS results indicated that the interaction between BBP-24-3 and SeNPs formed a new C-O···Se bond with valence state of Se0. Bioassays indicated that RBC coating markedly enhanced both the biocompatibility and bioabsorbability of RBC@BBP-24-3Se, and the absorption rate of RBC@BBP-24-3Se in HepG2 cells was 4.99 times higher than that of BBP-24-3Se at a concentration of 10 μg/mL. Compared with BBP-24-3Se, RBC@BBP-24-3Se possessed significantly heightened protective efficacy against oxidative damage and better regulation of glucose/lipid metabolism disorder induced by palmitic acid in HepG2 cells. Mechanistic studies demonstrated that RBC@BBP-24-3Se could effectively improve PI3K/AKT signaling pathway to promote glucose metabolism, inhibit the expression of lipid synthesis genes and up-regulate the expression of lipid-decomposing genes through AMPK signaling pathway to improve lipid metabolism. These results provided a theoretical basis for developing a new type of selenium supplement for the treatment of insulin resistance.

Effect of Self-etch Silane Contamination on Dentin Bond Strength to Resin Composite

Objectives: This study aimed to investigate the effect of self-etch silane contamination on dentin bond strength to resin composite when using different adhesive systems. Methods: 40 flat occlusal dentin surfaces were prepared and randomly divided into 4 groups (n=10): group ER (Optibond FL); group SE (Clearfil SE bond); group SiER and group SiSE (Monobond Etch and Prime (MEP) followed by Optibond FL and Clearfil SE bond, respectively). Microtensile bond strength (µTBS) data was analyzed by two-way and one-way ANOVA followed by the post hoc Tukey honest test. The failure mode data was analyzed using Pearson Chi-square test. After undergoing different contamination procedures (distill water, phosphoric acid, and acidic primer with and without MEP contamination), 6 additional specimens were analyzed by scanning electron microscopy (SEM). Results: The two-way ANOVA indicated that the adhesive system and silane contamination significantly influenced the µTBS. µTBS (MPa) of all (ER 47.79±3.48; SiER 41.16±11; SE 39.77±3.16; SiSE 35.10±4.12) groups were significantly different from each other, except for the SE versus SiER group. The silane contamination significantly decreased the µTBS for both adhesive systems. Adhesive failure was the most common failure mode for the SiER, SE, and SiSE groups. Conclusions: Self-etch silane cross-contamination on dentin negatively impacted the µTBS of etch-and-rinse and self-etch adhesive systems. However, the etch-and-rinse adhesive system may be more effective in mitigating the effects of dentin contamination than the self-etch adhesive system.

Enhancing Conversion Kinetics through Electron Density Dual-Regulation of Catalysts and Sulfur toward Room-/Subzero-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na/S) batteries have received increasing attention for the next generation of large-scale energy storage, yet they are hindered by the severe dissolution of polysulfides, sluggish redox kinetic, and incomplete conversion of sodium polysulfides (NaPSs). Herein, the study proposes a dual-modulating strategy of the electronic structure of electrocatalyst and sulfur to accelerate the conversion of NaPSs. The selenium-modulated ZnS nanocrystals with electron rearrangement in hierarchical structured spherical carbon (Se-ZnS/HSC) facilitate Na+ transport and catalyze the conversion between short-chain sulfur and Na2S. And the in situ introduced Se within S can enhance conductivity and form an S─Se bond, suppressing the "polysulfides shuttle". Accordingly, the S@Se-ZnS/HSC cathode exhibits a specific capacity of as high as 1302.5 mAh g-1 at 0.1 A g-1 and ultrahigh-rate capability (676.9 mAh g-1 at 5.0 A g-1). Even at -10 °C, this cathode still delivers a high reversible capacity of 401.2 mAh g-1 at 0.05 A g-1 and 94% of the original capacitance after 50 cycles. This work provides a novel design idea for high-performance Na/S batteries.

The efficacy of Er,Cr:YSGG laser and contemporary universal adhesive systems on composite resin repair bond strength: an in vitro study.

The aim of this study is to investigate the repair bond strength of composite resin following three different surface treatments (bur-grinding, silanization, and Er,Cr:YSGG laser irradiation) using various universal adhesives. A total of 160 resin composite specimens, produced in cylindrical form (6 × 2mm) with a nanohybrid composite resin within metal molds, were subjected to 5000 cycles of aging in a thermocycler. The aged samples were categorized into four groups based on surface treatments: control, bur, silane, and Er,Cr:YSGG laser. Following surface treatments, the specimens underwent repair using the same resin composite and four different adhesive systems: Tokuyama Universal Bond (TUB), Prime Bond Universal (PBU), Gluma Bond Universal (GBU), and Clearfil SE Bond (CSB). Subsequently, the specimens were subjected to shear forces, and statistical analysis was performed using two-way ANOVA and Tukey tests (p < 0.05). The failure modes were examined using a stereomicroscope, and the surface topography of the roughened resin composite was assessed through scanning electron microscopy (SEM). Results indicated that silane + GBU exhibited the highest shear bond strength (SBS) (15.61MPa) while control + TUB showed the lowest SBS (7.63MPa). Silane demonstrated significantly higher SBS values (p ≤ 0.05), with no significant difference observed between bur and laser methods (p = 0.998). It is recommended to include an additional silanization step before applying universal adhesive, as it effectively enhances the bond strength of the repaired composite.

Unveiling the physical properties of RbCu3MSe4 (M = Si, Ge) direct band gap semiconductors: A systematic first-principles study

The Silicon and Germanium-based quaternary chalcogenides have remarkable features including their adjustable optical properties and outstanding thermal stability. We explored the complex interplay among the structural, electronic, optical, and thermoelectric characteristics of direct band gap novel RbCu3MSe4 (M = Si, Ge) quaternary chalcogenides by employing the well-known density functional theory. Direct type of band gap at high symmetry Г-point was noticed for both materials. The predicted band gaps of RbCu3SiSe4 and RbCu3GeSe4 are 1.32 eV and 0.73 eV, respectively. Due to the large size of germanium ions compared to silicon, the Ge–Se bonds in RbCu3GeSe4 are more wide-ranging than the Si–Se bonds in RbCu3SiSe4. The complex dielectric function along with other significant optical parameters are investigated and analyzed for their probable employment for optoelectronic applications. These examined materials are suitable to be employed in thermoelectric devices as observed from substantial and outstanding thermoelectric features. The present work could establish the potential employment of these complex systems and would open the way for advanced applications in various fields and technologies.

Visible Light Induced Photocatalyst‐Free C−X (X=B, C, O, P,S, Se) Bond Formation of Aryl Halides

AbstractAryl halides are one of the most important chemical feedstocks in pharmaceuticals due to its easy accessibility, inexpensiveness, and widely utilized as aryl radical precursors in organic synthetic chemistry. Conventionally, the stoichiometric reagents such as AIBN/n‐Bu3SnH were used for generation of aryl radical from aryl halides, and suffered from requirement of toxic radical initiators, high temperature and thus, the development of simple, mild strategies for the generation of aryl radical from aryl halides are highly desirable. Recently, visible light mediated strategies received considerable attention, allowing the generation of aryl radical from aryl halides under mild reaction conditions. The present review described the recent breakthroughs and advancements in visible light mediated photocatalyst‐free C−B/C/O/P/Se/S bond formation of aryl halides.

Comparative evaluation of sealing ability of two self-adhesive flowable composites following various restorative techniques in Class V lesions: An in vitro study

Background: Class V lesions present a clinical challenge due to their location at the cervical region of teeth, where factors such as microleakage and polymerization shrinkage can compromise the longevity of restorations. Self-adhesive flowable composites offer the advantage of simplified application, but their sealing ability may vary based on different restorative techniques. This in vitro study aimed to compare the sealing ability of two self-adhesive flowable composites, Clearfil S3 Universal and G-Premio Bond, when applied using various restorative techniques in Class V lesions. Materials and Methods: Eighty extracted human premolars were selected and randomly divided into two groups, with each group treated with one of the two self-adhesive flowable composites. Class V cavities were prepared on the buccal surfaces of the teeth. Four restorative techniques were employed: Group A - Direct application of the composite; Group B - Application of the composite with a bonding agent (Clearfil SE Bond); Group C - Application of the composite with selective enamel etching; Group D - Application of the composite with a dentin adhesive (G-Premio Bond) and selective enamel etching. After restoration, the teeth were subjected to thermocycling, immersed in methylene blue dye, sectioned, and evaluated for dye penetration under a stereomicroscope. The extent of dye penetration was quantified and statistically analyzed.Results:The results showed that Group D, where G-Premio Bond was used with selective enamel etching, demonstrated the least dye penetration (mean value X) compared to the other groups (X1, X2, X3). The differences in sealing ability between the groups were statistically significant (p &lt; 0.05). Clearfil S3 Universal showed better sealing ability when used with a bonding agent (Group B) compared to direct application (Group A). Conclusion: In Class V restorations, the choice of self-adhesive flowable composite and restorative technique significantly affects sealing ability. G-Premio Bond, in combination with selective enamel etching, provided superior sealing compared to other techniques. Clearfil S3 Universal performed better when used with a bonding agent. These findings highlight the importance of selecting the appropriate material and technique for Class V restorations to minimize microleakage and improve clinical outcomes. Bangladesh Journal of Medical Science Vol.23 (Special Issue) 2024 p.S92-S96