Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

DANGLING BONDS IN HYDROXYLATED AND AMINATED NANODIAMONDS: APPLICATION OF THE GLOBAL OPTIMIZATION ALGORITHM
Šarūnas Masys^a, Valdas Jonauskas^a, and Zilvinas Rinkevicius^b
^aInstitute of Theoretical Physics and Astronomy, Faculty of Physics, Vilnius University, Saulėtekio 3, 10257 Vilnius, Lithuania
^bDepartment of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-10691 Stockholm, Sweden
Email: sarunas.masys@tfai.vu.lt

Received 10 December 2025; revised 29 April 2026; accepted 30 April 2026

The geometric configuration of dangling bonds (DBs) – one of the most abundant paramagnetic defects in nanodiamonds (NDs) – is investigated by applying the global optimization algorithm (GOAT). A total of more than five million geometry optimization runs are carried out to search for the lowest-energy conformers of DBs introduced into hydroxylated and aminated NDs. An analysis of over 3,000 electronic g-tensor calculations performed for the obtained structures shows that only three unique DB types are present in octahedrally shaped C₃₅(OH)₃₆ and C₃₅(NH₂)₃₆ nanoparticles, enabling future studies on similar NDs with fully functionalized surfaces to consider a relatively small number of DBs and thereby save computational time and resources. It is also revealed that the arithmetically averaged isotropic g-shifts from the geometries of the standard optimization agree well with the GOAT results, although the behaviour of individual DBs is not properly captured.
Keywords: nanodiamonds, dangling bonds, geometry optimization, electronic g-tensor

NEKOMPENSUOTIEJI RYŠIAI HIDROKSILO IR AMINO GRUPĖMIS FUNKCIONALIZUOTUOSE NANODEIMANTUOSE: GLOBALIOSIOS OPTIMIZACIJOS ALGORITMO TAIKYMAS
Šarūnas Masys^a, Valdas Jonauskas^a, Žilvinas Rinkevičius^b

^aVilniaus universiteto Fizikos fakulteto Teorinės fizikos ir astronomijos institutas, Vilnius, Lietuva
^bKarališkojo technologijos instituto Chemijos, biotechnologijos ir sveikatos inžinerijos mokslų mokyklos Teorinės chemijos ir biologijos departamentas, Stokholmas, Švedija

Nanodeimantai (ND) yra deimanto nanodalelės, kurių dydis siekia nuo apytiksliai vieno iki keliolikos dešimčių nanometrų. Jos pasižymi nanomedicinai itin tinkamomis savybėmis: išskirtiniu biosuderinamumu, didele pernašos talpa bei nepaprastai gausia paviršiaus funkcinių grupių įvairove. Tačiau vienas iš ND panaudojimo trūkumų – sudėtinga sekti jų lokalizaciją ir judėjimą in vivo, todėl tai apriboja galimybę stebėti ilgalaikio gydymo eigą. Vis dėlto tiek magnetinio rezonanso, tiek fluorescencijos pagrindo ND vizualizacija yra įmanoma, bet tam būtini paramagnetiniai defektai. Kadangi nekompensuotieji ryšiai (NR) yra vieni iš dažniausiai ND susidarančių paramagnetinių defektų, šiame darbe tiriama jų geometrinė konfigūracija hidroksilo ir amino grupėmis funkcionalizuotuose ND. Atsižvelgus į tokių ND paviršiaus geometrinį sudėtingumą, tyrimams taikytas globaliosios optimizacijos algoritmas, kuris, priešingai nei standartinė geometrijos optimizacijos procedūra, užtikrina visuotinai žemiausios sistemos būsenos paiešką. Optimizuotos NR struktūros buvo panaudotos įvertinant elektroninį g-tenzorių – vieną svarbiausių elektronų paramagnetinio rezonanso parametrų. Gauti rezultatai rodo, kad oktaedrinės formos C₃₅(OH)₃₆ ir C₃₅(NH₂)₃₆ nanodalelėse egzistuota tik trys unikalūs NR, o tai suteikia vertingos informacijos ateities ND tyrimams ir leidžia reikšmingai sutaupyti skaičiavimo laiko ir išteklių.

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