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Enzymes are considered safe and effective therapeutic tools for various diseases. With the increasing integration of biomedicine and nanotechnology, artificial nanozymes offer advanced controllability and functionality in medical design. However, several notable gaps, such as catalytic diversity, specificity and biosafety, still exist between nanozymes and their native counterparts. Here we report a non‐metal single‐selenium (Se)‐atom nanozyme (SeSAE), which exhibits potent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase‐mimetic activity. This novel single atom nanozyme provides a safe alternative to conventional metal‐based catalysts and effectively cuts off the cellular energy and reduction equivalents through its distinctive catalytic function in tumors. In this study, we have demonstrated the substantial efficacy of SeSAE as an antitumor nanomedicine across diverse mouse models without discernible systemic adverse effects. The mechanism of the NADPH oxidase‐like activity of the non‐metal SeSAE was rationalized by density functional theory calculations. Furthermore, comprehensive elucidation of the biological functions, cell death pathways, and metabolic remodeling effects of the nanozyme was conducted, aiming to provide valuable insights into the development of single atom nanozymes with clinical translation potential. [ABSTRACT FROM AUTHOR]

Reversible transformations between fractals and periodic structures are of fundamental importance for understanding the formation mechanism of fractals. Currently, it is still a challenge to controllably achieve such a transformation. We investigate the effect of CO and CO2 molecules on Sierpiński triangles (STs) assembled from Fe atoms and 4,4″-dicyano-1,1′:3′,1″-terphenyl (C3PC) molecules on Au surfaces. Using scanning tunneling microscopy, we discover that the gas molecules induce a transition from STs into 1D chains. Based on density functional theory modeling, we propose that the atomistic mechanism involves the transformation of a stable 3-fold coordination Fe(C3PC)3 motif to Fe(C3PC)4 with an axially bonded CO molecule. CO2 causes the structural transformation through a molecular catassembly process. [ABSTRACT FROM AUTHOR]

In this work, we were devoted to explore the effect of solvent polarities on the excited-state intramolecular proton transfer (ESIPT) process of 1-acetamido-4-hydroxyanthraquinone (AcHAQ) in three different polarity solvents (acetonitrile, chloroform, and cyclohexane) based on the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, and thereby regulating the distribution ratio between the dual excited-state isomers (enol and keto). The calculated geometrical parameters and infrared (IR) vibrational spectra have confirmed the excited-state intramolecular hydrogen bond (IHB) strengthening mechanism. Natural bond orbital (NBO) population analysis indicates that the intramolecular charge transfer (ICT) around IHBs has enhanced IHB, thereby triggering the ESIPT reaction. In addition, results obtained from the scanned potential energy curve (PEC) manifest that ESIPT process prefers to occur along the O3-H2...O1 IHB and energy barriers corresponding to the proton transfer in ACN are the lowest among all the studied solvents. [ABSTRACT FROM AUTHOR]

Investigating the effects of surrounding microenvironments and substituents on the excited‐state proton transfer (ESPT) mechanism have always been a great challenge, especially in protic solvents and solid state. In this work, a detailed theoretical study on ESPT processes of salicylic acid (SA) and its two derivatives (5ASA and 5NSA) in gas, cyclohexane, acetonitrile, ethanol (EtOH), and crystal phases is performed based on the density functional theory (DFT) and time‐dependent DFT as well as the combined quantum mechanics/molecular mechanics (QM/MM) methods. Intramolecular charge transfer‐induced aggregation‐caused quenching phenomenon of 5ASA is unveiled utilizing the hole–electron analysis. Independent gradient model analysis is implemented to reveal the spontaneous forward proton transfer (PT) behavior of 5ASA. Besides, potential energy surfaces are constructed to evaluate the dominant PT pathway in EtOH, and the related transition state structures are also obtained to accurately provide the intra‐ and inter‐PT energy barriers. Eventually, excited‐state ab initio molecular dynamics computation reaffirms that the intra‐PT reaction is predominant for SA. This theoretical work comprehensively explores the ESPT mechanism and luminescent properties of SA and its two derivatives, which provides a reference for developing efficient organic light‐emitting materials based on ESPT chromophores. [ABSTRACT FROM AUTHOR]

[Display omitted] • Absorption spectra of GA-GQD cover UVA and UVB regions. • The fluorescence intensity of GA-GQD is close to zero. • The sequence of multiple antioxidant processes of GA is: e- → H 3 + → e- → H 1 +. • The sequence of multiple antioxidant processes of GA-GQD is: e- → H 2 + → e- → H 3 +. • The reactions of GA and GA-GQD with free radical ·OH are spontaneous. In this work, the influence of graphene quantum dot (GQD) adsorption effect on the multiple antioxidant processes and photophysical properties of gallic acid (GA) has been investigated by density functional theory. Simulated absorption spectra of the GA-GQD covered UVA and UVB regions, and its extremely weak fluorescence intensity means that it is more suitable for use as the sunscreen than GA. Moreover, in the S 0 state, the sequence of multiple antioxidant processes of GA (GA-GQD) is: e- → H 3 + → e- → H 1 + (e- → H 2 + → e- → H 3 +), and the first step of antioxidant processes of GA-GQD is more straightforward to occur than GA according to the specific thermodynamic parameters. Furthermore, the dynamic simulations of GA and GA-GQD reacted with free radical ·OH revealed that their antioxidant processes are spontaneous, verifying their outstanding antioxidant abilities. [ABSTRACT FROM AUTHOR]

[Display omitted] • The photophysical properties of PVHBO occurring upon the introduction of electron-absorbing and electron-donating substituents are revealed for the first time. • Introduction of electron-withdrawing substituents would enhance the fluorescence intensity of PVHBO. • PVHBO-NH 2 presents the largest Stokes shift of 219 nm among the studied molecules. • Introducing amino group can significantly inhibit the ESIPT process of PVHBO. In this contribution, four derivatives of 5′-(para -R-Phenylene) vinyl-2-(2′-hydroxyphenyl) benzoxazole (PVHBO) were ingeniously designed by introducing two electron-withdrawing substituents and two electron-donating substituents, aiming to investigate the influence of different substituents on the photophysical properties of PVHBO and the excited state intramolecular proton transfer (ESIPT) process via the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. By utilizing the geometric parameters and the simulated infrared (IR) spectra, we compared the intramolecular hydrogen bonds (IHBs) strengths in the S 0 and S 1 states of the molecules. Via conducting the hole-electron analysis, the reduction in fluorescence intensity for the enol and keto forms of PVHBO, PVHBO-MeO, and PVHBO-NH 2 were also well explicated. Besides, the potential energy curves (PECs) and corresponding transition state (TS) structures for both S 0 and S 1 states were also constructed to accurately obtain energy barriers of forward and reversed proton transfer processes. The calculated absorption and fluorescence spectra also show that PVHBO-NH 2 has the largest Stokes shifts of 158 nm and 219 nm in both the enol and keto states, with a significant increase in fluorescence intensity observed upon the induction of electron-withdrawing groups. Through this work, it can provide the theoretical basis for the design of novel luminescent materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The excited-state antioxidant capacity for studied molecules is almost higher than that of the ground state. • Antioxidant capacity varies with the solvent polarity in both ground and excited states. • The 6-HF in acetonitrile in the S 1 state shows the highest antioxidant capacity in all cases. • The studied molecules protect against UV radiation and exhibit weaker fluorescence, promising to be used as sunscreens. Antioxidants have caught a widespread attention because of their applications in various fields such as biomedicine, food additives, cosmetics, and so on, but nevertheless studies on the antioxidant capacity of molecules after photoexcitation are still scarce and rare. In this work, by the application of the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods, based on the solvent effect, the antioxidant capacity of 4′-Hydroxyflavone (4′-HF), 6-Hydroxyflavone (6-HF), and 7-Hydroxyflavone (7-HF) in the S 0 and S 1 states are compared. In view of the frontier molecular orbitals (FMOs), depending on the HOMO energy, not only is it analyzed that the electron-donating capacity varies with the solvent, but also that the antioxidant capacity of the mostly molecules in the S 1 state is better than those in the S 0 state, in particular, the 6-HF in ACN in the S 1 state shows a strong antioxidant capacity and is most susceptible to attack by electrophilic radicals, which is also in accordance with the conclusions drawn from the orbital weighted (OW) Fukui functions and OW double descriptors, and global indices including vertical ionization potentials (VIPs), softness (S),and so on. Moreover, absorption spectra indicate the potential of these molecules to resist UV radiation and diminished or even quenched fluorescence intensity is caused by intramolecular charge transfer as evidenced by hole-electron analysis. On the basis of the above photophysical properties, it is shown that these three molecules are expected to be one of the ingredients of sunscreens. In a nutshell, this work not only proposed the influence of solvent effect on antioxidant capacity, but also found the advantage of antioxidant capacity in the S 1 state, which provides a strong support for exploring stronger antioxidant capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The four compounds can effectively protect against UVB radiation. • Their absorption spectra are mainly affected by their stilbene segments. • O 1 H 1 sites of EHDB and HPTP are the most active in trapping free radicals. • SPLET mechanism is the most preferred reaction pathway for the four compounds. • DPPH scavenging activities significantly improve after sunlight except for EAPD. With the continued depletion of the ozone layer, the sun protection consciousness of humans has gradually enhanced. Long-term ultraviolet (UV) rays exposure will lead to skin tanning, even skin cancer in severe cases, and generate free radicals to cause skin aging. To better protect human skin against UV rays, this work explores the absorption capacities and antioxidant activities of four stilbene derivatives (EHDB, EDMB, EAPD, and HPTP) through the computational chemistry method and DPPH radical scavenging experiment. The research results indicate that their absorption spectra cover the entire UV region, and can effectively protect against UVB radiation. Moreover, three prevailing antioxidant mechanisms: hydrogen atom transfer, sequential proton loss electron transfer, and single electron transfer followed by proton transfer mechanisms, were used to evaluate their antioxidant activities in the ground state. It can be concluded that the O 1 H 1 sites of EHDB and HPTP are the most active, and the SPLET mechanism is the most preferred for the four compounds in ethanol solvent. Furthermore, the DPPH radical scavenging experiment compensates for the theoretical calculation deficiency in the excited state, revealing that the EHDB and HPTP are the most suitable for sunscreen due to their excellent performance on antioxidant capacities, whether before or after sunlight. This work will facilitate EHDB and HPTP to be applied in sunscreen and provide a novel idea in sunscreen research. [ABSTRACT FROM AUTHOR]

[Display omitted] • The absorption spectra of the six flavonoids cover the entire UV region. • SPLET mechanism is the most favorable reaction pathway. • O 4 -H 4 site of myricetin is the most active site to trap free radicals. • Hydroxyl groups in A/C-ring can regulate photophysical properties of flavonoids. • Hydroxyl groups in B-ring can regulate antiradical abilities of flavonoids. The photophysical properties and antiradical abilities of 5-Hydroxyflavone, 3,5-Dihydroxyflavone, galangin, kaempferol, quercetin, and myricetin are explored using density functional theory and time-dependent density functional theory methods. The absorption spectra of the six flavonoids span the entire ultraviolet region, and their fluorescence peak intensities are faint, meeting the sunscreen requirements. Furthermore, their max absorption peaks are mainly affected by the hydroxyl groups in the A- and C-rings of the compounds. The hydrogen atom transfer, sequential proton loss electron transfer and single electron transfer followed by proton transfer mechanisms are used to evaluate their antiradical abilities. It can be concluded that the O 4 -H 4 site of myricetin is the most active site to scavenge free radicals, revealing that the formation of intramolecular hydrogen bonds can significantly enhance molecular antiradical abilities. In a word, altering tactfully hydrogen group position is conducive to regulating the photophysical properties and antiradical abilities of flavonoids. [ABSTRACT FROM AUTHOR]

[Display omitted] • Substitution effect on the ESIPT properties of indoles were studied via DFT method. • ESIPT reaction of the molecules based on hydrogen bond enhancement is confirmed. • BOM-1 possesses the lowest energy barrier in S 1 state among the studied molecules. • Concomitant substitution of amino and sulfo groups induces the maximum Stokes shift. In this work, the substitution effect of different electron-donating and electron-withdrawing groups on the electron spectra and excited state intramolecular proton transfer (ESIPT) properties of the chromophore 2-(2-hydroxy-5-methylphenyl)benzo[d]oxazole-5-sulfonic acid (BOM-1) has been studied via the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. All the compounds exhibit the dual-fluorescence emission, and the fluorescence spectra of the derivatives show redshift emission compared with that of the original molecule, resulting in the larger Stokes shift as expected. The results were cross-verified by the molecular geometry, frontier molecular orbitals, infrared spectroscopy and other auxiliary calculations. These results show that the electron-withdrawing group greatly promote the occurrence of the forward ESIPT process and increase the Stokes shift. What is more special is that the Stokes shift and the energy barrier of the forward ESIPT are significantly enlarged by introducing both electron-withdrawing and electron-donating groups. The energy barrier, absorption and fluorescence spectra of luminescent molecules can be adjusted effectively by introducing appropriate functional groups. In addition, the emission spectra from the ultraviolet region (359 nm) to the orange region (601 nm) are obtained. This work would contribute to the understanding of the mechanism of ESIPT reactions and improves the luminescence properties of ESIPT molecules. [ABSTRACT FROM AUTHOR]

Atomic-scale mechanochemistry is realized from force exerted by a C60-functionalized scanning tunneling microscope tip. Two conformers of tin phthalocyanine can be prepared on coinage-metal surfaces. A transition between these conformers is induced on Cu(111) and Ag(100). Density-functional calculations reveal details of this reaction. Because of the large energy barrier of the reaction and the strong interaction of SnPc with Cu(111), the process cannot be achieved by electrical means. [ABSTRACT FROM AUTHOR]

Ordered two-dimensional arrays of silver adatoms with tunable metal atom density stabilized by 1,4-diethynyl-2,5-dimethylbenzene, a terminal alkyne, were prepared on Ag(111) and scrutinized by scanning tunneling microscopy and density functional theory calculations. Stabilization of the adatom arrays was attributed to the substrate-mediated electron localizations of the Ag adatom and terminal alkynyl in the molecule. [ABSTRACT FROM AUTHOR]

[Display omitted] • Antioxidant activities of 2′Cha and its six derivatives are studied. • Intramolecular hydrogen bond will inhibit the H-donating ability of 2′Cha. • Thermodynamic preferred mechanism depends on the various phases. • Introducing NH 2 and CN separately improves H- and electron-donating ability. The substituent and solvent effects on the antioxidant activity of 2′-hydroxychalcone (2′Cha) were systematically explored in gas and three solvent phases by designing six novel compounds (2′Cha-3′NH 2 , 2′Cha-4′NH 2 , 2′Cha-5′NH 2 , 2′Cha-3′CN, 2′Cha-4′CN, and 2′Cha-5′CN) based on the density functional theory (DFT) approach. Significant parameters involved in three primary antioxidant mechanisms, namely the hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were computed to confirm the thermodynamically preferred reaction pathway in different media. Besides, 4′-hydroxychalcone (4′Cha) was introduced to unveil the intramolecular hydrogen bond (IHB) effect on the radical scavenging capacity of 2′Cha utilizing the DFT and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) ultraviolet–visible (UV–Vis) spectroscopic methods. Energy barriers and kinetic parameters for HAT reaction of 2′Cha and 4′Cha with hydroperoxyl (HOO) radical were calculated to further compare the radical-trapping process. The photophysical properties of 2′Cha in benzene, chlorobenzene and ethanol are in good agreement with the measured experimental data and the excited-state antiradical capacity improving mechanism was also confirmed experimentally. The current work not only provides valuable guidance for synthesizing high-efficiency antioxidants but also exploits the potential application fields for 2′Cha. [ABSTRACT FROM AUTHOR]

Exploring antioxidant potential of flavonoid derivatives after ESIPT process provides a theoretical basis for discovering compounds with higher antioxidant capacity. In this work, employing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods, the antioxidant potential of two citrus-derived naringenin flavonoids after ESIPT process is explored. Based on studies of ESIPT process including IMHB intensity variations, potential energy curves, and transition state, these molecules exist only in enol and keto⁎ forms due to ultra-fast ESIPT. The HOMOs are utilized to explore electron-donating capacity, demonstrating that the molecules in keto⁎ form is stronger than that in enol form. Furthermore, the atomic dipole moment corrected Hirshfeld population (ADCH) and Fukui functions indicate that the sites attacked by the electrophilic free radical of the two molecules in the keto⁎ form are O 3 and O 5' respectively, and both are more active than in the enol form. Overall, a comprehensive consideration of the ESIPT process and antioxidant potential of flavonoid derivatives will facilitate the exploration and design of substances with higher antioxidant capacity. [Display omitted] • Both Nar and ChNar undergo an ultrafast ESIPT process in the S 1 state. • According to the searched TS, ChNar cannot undergo C 1 C 2 torsion in the S 1 state. • The antioxidant potential of molecules is greater in keto⁎ form. • The presence of IMHBs makes the oxygen atoms less reactive for the two molecules. • ADCH and Fukui function indicate reactive sites changes after ESIPT process. [ABSTRACT FROM AUTHOR]