Temperature-dependent photoluminescence and decay times of different phases of grown TiO2 nanoparticles: Carrier dynamics and trap states

Three different phases, namely anatase, mixed and rutile phases of TiO₂ nanoparticles (NPs) were developed with varying temperatures from 400 to 900 °C and confirmed using various characterization techniques. The XRD analysis of TiO₂ NPs in temperature range of 290 to 77 K with no significant changes predict the thermally stable NPs. Photoinduced carrier dynamics of TiO₂ NPs were investigated by the temperature dependence (TD) photoluminescence (PL) and TD time-resolved PL (TRPL) decays. With varying temperatures from 290 to 77 K, the anatase phase exhibits an additional and dominant 530 nm PL band. However, the mixed and rutile phases show three well-resolved PL bands, including 420 nm, 530 nm and near-infrared (NIR) bands at 820 nm at a lower temperature. Again, 530 nm band dominated for mixed-phase.In contrast, for the rutile phase, the 820 nm band dominated at <100 K. The PL lifetime of the 420 nm band is nearly a single exponential for all the phases. And is also true for the 530 and 820 nm PL bands, but bi-exponential for ≤100 K. Both the PL and TRPL results predict the presence of trap states in TiO₂ NPs for anatase and rutile phases. The PL is originated due to donor-acceptor recombination, whereas oxygen vacancies served as donor and hydroxyl groups serve as accepter sites. The NIR band is attributed to the trapped electrons in rutile TiO₂, which recombine with free holes and intrinsic defects. Also, the trapped electrons were generated in one of two ways: direct trapping or trap-to-trap hopping. The carrier dynamic in NPs depends on the trap states as the photoexcited carriers transfer into surface sites which competes with non-radiative and radiative recombinations during the relaxation process. Thus, the findings show that the trap states in TiO₂ can significantly influence TiO₂ photocatalytic activity when exposed to appropriate light.     

The effect of Ag nanoparticles content on dielectric and microwave absorption properties of β-SiC

In the present work, high purity cubic silicon carbide (β-SiC) was synthesized by using resorcinol-formaldehyde aerogel coated silica as precursor at high temperature. Subsequently, β-SiC was coated with various concentrations of silver nanoparticles (Ag NPs) by tin sensitization electroless plating. Thereafter, the effect of various Ag NPs contents on the dielectric and microwave absorption properties of β-SiC was investigated in detailed. It is found that the Ag NPs can significantly increase the overall complex permittivity, reduce the thickness of the absorber and increase the absorption bandwidth to some extent. Despite, the improvement of the attenuation ability of electromagnetic wave with increasing contents of Ag NPs also has an adverse effect on impedance matching. The improvement in the microwave absorption of β-SiC coated with Ag NPs mainly comes from the enhancement of dipole polarization, interface polarization and conductivity loss. In the 2–18 GHz band, Ag@SiC (1.0 g/L) can achieve an effective bandwidth of 4.99 GHz at a thickness of 1.6 mm, and it is a kind of lightweight, high-temperature microwave absorbent with excellent performance.     

Functionalization of manganite nanoparticles and their interaction with biologically relevant small ligands: picosecond time-resolved FRET studies

We report molecular functionalization of the promising manganite nanoparticles La0.67Sr0.33MnO3 (LSMO) for their solubilization in aqueous environments. The functionalization of individual NPs with the biocompatible citrate ligand, as confirmed by Fourier transform infrared (FTIR) spectroscopy, reveals that citrates are covalently attached to the surface of the NPs. UV-VIS spectroscopic studies on the citrate functionalized NPs reveals an optical band in the visible region. Uniform size selectivity (2.6 nm) of the functionalization process is confirmed from high resolution transmission electron microscope (HRTEM). In the present study we have used the optical band of the functionalized NPs to monitor their interaction with other biologically important ligands. F?rster resonance energy transfer (FRET) of a covalently attached probe 4-nitrophenylanthranilate (NPA) with the capped NPs confirm the attachment of the NPA ligands to the surface functional group (-OH) of the citrate ligand. The FRET of a DNA base mimic, 2-aminopurine (2AP), with the NPs confirms the surface adsorption of 2AP. Our study may find relevance in the study of the interaction of individual manganite NPs with drug/ligand molecules.     

Synthesis of cubic and monoclinic hafnia nanoparticles by pulsed plasma in liquid method

Hafnia (HfO₂, hafnium dioxide) is a wide band gap and high-κ material, and the metastable cubic hafnia has a much higher permittivity compared with the normal monoclinic hafnia. Here, we employ a one-step process, the pulsed plasma in liquid (PPL) method to synthesize two types of hafnia nanoparticles (NPs): one which is mainly in cubic phase (cubic: 81.7 at%, monoclinic: 18.3 at%) and the other which is in monoclinic phase. High-resolution transmission electron microscopy images showed that the particles were small (particle size ~3 nm). X-ray absorption fine structure analysis showed no chemical shifts, indicating that the synthetic hafnia NPs contained no oxygen vacancy. The synthetic hafnia NPs mainly in cubic phase showed a much higher relative permittivity than that of the commercial hafnia (monoclinic), and have a larger band gap than the synthetic monoclinic hafnia NPs.     

Study of Photoinduced Electron Transfer Process in Ruthenium Complex Modified Zinc Oxide Nanoparticles by Ultrafast Time-Resolved Transient Absorption Spectroscopy

We report the preparation of ruthenium complex functionalized zinc oxide nanoparticles and the studies of the photophysical properties by ultrafast time-resolved transient absorption spectroscopy. Diazonium group was used as the anchoring unit on ZnO surface and covalent linkage was formed between the ruthenium complex and ZnO upon UV irradiation. The morphological and electron transfer properties of the ruthenium complex modified ZnO were studied. XPS and EDX results confirmed the presence of covalent linkage. The charge generation and the transport dynamics of this light harvesting system were probed by ultrafast transient absorption (TA) spectroscopy. No positive TA absorption band was observed, which suggested an ultrafast direct electron injection from the singlet ¹MLCT excited state of the ruthenium complex to the conduction band of ZnO without going via the triplet ³MLCT excited state. The time constants for the ground states bleaching of the complex modified ZnO are 8.1 and 167 ps, both of which are shorter than those of the pure ruthenium complex (21.7 and 360 ps). This further suggests a strong electronic coupling between the ruthenium complex and ZnO.     

Structural,optical and magnetic behavior of (Pr,Fe) co-doped ZnO based dilute magnetic semiconducting nanocrystals

The development of ZnO-based dilute magnetic semiconductor nanostructures co-doped with rare-earth and transition metals has attracted substantial attention for spintronics application. In this work, Pr (1%) and Fe (1%, 3%, and 5%) co-doped ZnO nanoparticles (NPs) were synthesized via co-precipitation method, and their structural, morphological, optical, photoluminescence, and magnetic properties were investigated. The single-phase wurtzite hexagonal crystal structure of all samples was detected via X-ray diffraction. Morphological analysis revealed spherical shape of the NPs with an average size in 20–50 nm range. The ultraviolet (UV)–visible measurements showed a redshift in the UV band and a slight change in the bandgap of the co-doped NPs. Fourier transform infrared analysis proved the existence of different functional groups in all synthesized NPs. X-ray photoelectron spectroscopy confirmed that Pr and Fe ions incorporated in the host ZnO lattice exhibit Pr³⁺ and Fe³⁺ oxidation states, respectively. Photoluminescence analysis showed that incorporated ions induce characteristic emission bands and structural defects in the synthesized NPs. Magnetic characterization indicated that the ZnO NPs exhibit a diamagnetic nature. However, the (Pr, Fe) co-doped NPs exhibit ferromagnetism at room temperature because of the interactions between Pr³⁺ and Fe³⁺ ions and trapped electrons mediated by bound magnetic polarons. Excellent optical and magnetic properties of synthesized samples may render them promising candidates for spintronics applications.     

Preparation and electrooptic study of reverse mode polymer dispersed liquid crystal: Performance augmentation with the doping of nanoparticles and dichroic dye

Reported herein, the preparation, morphological, and electrooptic (EO) characterization of reverse mode polymer dispersed liquid crystals (PDLCs) with nematic liquid crystal (LC) and UV curable polymer optical adhesive using polymerization induced phase separation method. The PDLCs are switchable between transparent and opaque states due to the homeotropic and planar alignment of LC in their OFF and ON states of applied voltage, respectively. Further, effect of doping of a fixed concentration of azo dye and silica nanoparticles (NPs) on morphological, EO and response characteristics of same PDLC sample was also analyzed. Experimental results showed that doped reverse mode PDLCs have the higher OFF state optical transmission and boost up in the scattering ON state compared with pristine reverse mode PDLC. The phenomenon is also supported by extinction coefficient and absorption study based on Beer's law. The threshold and operating voltages were found reduced ~1.56 and ~1.73 times for NPs and (NPs + dye) doped reverse mode PDLCs, respectively, along with better contrasts to the pristine reverse mode PDLC. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48745.     

Deposition of silver nanoparticles on single wall carbon nanotubes via a self assembled block copolymer micelles

We demonstrate a facile route to decorate the surface of networked single walled carbon nanotubes (SWNTs) with silver nanoparticles (Ag NPs). The method is based on utilization of either spherical poly(styrene-b-4vinylpyridine) (PS-b-P4VP) or cylindrical poly(styrene-b-acrylic acid) (PS-b-PAA) copolymer micelles capable of stabilizing nanotubes in solution and subsequently forming a thin and uniform block copolymer/SWNTs composite film upon spin coating. The selective doping of silver acetate into either P4VP or PAA domains in a thin composite film, followed by thermal treatment, results in the formation of Ag NPs in the cores of micelles. Further heat treatment at 500 °C sufficiently high for degrading both block copolymers allows us to fabricate a thin SWNTs network in which Ag NPs are efficiently deposited on the surface of nanotubes. A sharp surface plasmon absorption band around 400 nm of the networked SWNTs with Ag NPs confirms the presence of Ag NPs with narrow distribution in their size.     

Tunable surface plasmon resonance frequencies of monodisperse indium tin oxide nanoparticles by controlling composition,size, and morphology

Monodisperse indium tin oxide nanoparticles (ITO NPs) with high crystallinity have been synthesized by the rapid thermal injection method and the seed-mediated growth method. We demonstrate that the surface plasmon resonance (SPR) frequencies of ITO NPs can be manipulated from 1,600 to 1,993 nm in near-infrared band by controlling the composition, size, and morphology. The doping Sn concentration in ITO NPs could be controlled via changing the %Sn in the initial feed from 0% to 30%. The shortest SPR wavelength at 1,600 nm with 10% Sn doping concentration indicates highest free electron carrier concentration in ITO NPs, which has direct relationship with doping Sn⁴⁺ ions. Furthermore, we demonstrate that the SPR peaks can also be tuned by the size of ITO NPs in the case of uniform doping. Besides, compared with the ITO NPs, single crystalline ITO with nanoflower morphology synthesized through the one-pot method exhibit SPR absorption peak features of red-shifting and broadening.     

Enhancement of the optical properties of poly vinyl alcohol by doping with silver nanoparticles

Poly vinyl alcohol (PVA) incorporated with different weight percent of Silver nanoparticles (Ag NPs) were prepared. The enhancement factors for each band in the Raman spectra were calculated and the degree of enhancement were found to be increased as the percent of Ag NPs increases up to 0.3%, and thereafter it decreases. Some bands were red shifted while others were blue shifted. The overtones FTIR bands and photoacoustic spectra were recorded and show the same behavior as those bands. The X‐ray diffraction pattern and Raman and photoacoustic spectra showed that PVA has a high degree of crystallinity. The UV–vis spectra of the same samples were red shifted and increase in their intensities up to 0.3% Ag NPs, thereafter the band intensities of the peak corresponding to Ag NPs were diminished. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3608–3614, 2006     

Magnetic characteristics and optical band alignments of rare earth (Sm+3, Nd+3) doped garnet ferrite nanoparticles (NPs)

Yttrium iron garnet (YIG) nanoparticles (NPs) doped with rare earth (RE) metal ions (Y_2.5Sm_0.5Fe₅O₁₂, Y_2.5Nd_0.5Fe₅O₁₂) were successfully synthesized by sol-gel auto combustion approach. The cubic crystalline structure and morphology of the prepared garnet ferrite NPs were analyzed by X-ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM). The cubic crystalline garnet phase of the synthesized YIG, Sm-YIG and Nd-YIG samples was successfully achieved at 950 °C sintering temperature. The force constant and absorption bands were estimated by using Fourier transform infrared spectroscopy (FTIR). The doping effect of RE metal ions on the chemical states of YIG were examined by x-ray photoelectron microscopy (XPS). The valence band (from 12.63 eV to 13.22 eV), conduction band (from 10.89 eV to 11.34 eV) edges and optical bandgap values of RE doped YIG samples were calculated using UV–Vis spectroscopy and ultraviolet photo electron spectroscopy (UPS). The magnetic analysis of the prepared NPs was studied using vibrating sample magnetometer (VSM). The XPS analysis of RE doped YIG samples exhibit the existence of RE (Sm⁺³, Nd⁺³) contents on the surface of YIG ferrite by decreasing the oxygen lattice in garnet structure. The optical bandgap (from 1.74 eV to 1.88 eV) explains the semiconducting nature of the synthesized NPs. The UPS results confirm the valence band position of YIG doped samples. The saturation magnetization and remanence of RE doped garnet ferrite samples increased from 13.45 to 18.83 emu/g and 4.06–6.53 emu/g, respectively.     

Preparation and photocatalytic performance of Bi nanoparticles by microwave-assisted method using ascorbic acid as reducing agent

Bismuth nanoparticles (NPs) were prepared by using microwave (MW) as heating source and ascorbic acid as reducing agent. Pure phase of Bi NPs was obtained and the size was uniform with the mean value of 70 nm. The visible light absorption was good and the optical band gap was 1.77 eV. The photocatalytic efficiency was 2.7 times that of the sample by solvothermal method for degradation of methyl blue (MB) under visible light irradiation. The hydroxyl radicals during photocatalysis were detected due to the transition of Bi from semimetal to semiconductor. The small size effect was considered to contribute a lot to the efficient photocatalytic activity.     

Photoluminescence of Ag Nanoparticles and Tm3+ Ions in the Bismuth Germanate Glasses for the Blue Light‐Excited W‐LED

Materials containing rare‐earth ions and Ag nanoparticles (NPs) have been widely applied due to prior demonstration of increase in their luminescence properties. Here, Tm³⁺ ions‐doped bismuth germanate glasses were synthesized by a chemical reduction method based on the conventional melting‐quenching technique. The Ag NPs were facilely precipitated in the glass matrix by the chemical reduction method during the annealing process. TEM image shows that the Ag NPs are closely dispersed in the glass matrix. The luminescence properties and energy‐transfer mechanism were systematically investigated by means of absorption, emission, and excitation spectra. Significant enhancements of Tm³⁺ ions emission and a broad emission band centered at 568 nm caused by Ag NPs are observed upon 474‐nm excitation. Our research may illustrate the interactions between Tm³⁺ ions and Ag NPs and provide a simplified way to synthesize the high‐efficiency luminescent materials for the blue light‐excited W‐LEDs.     

Optical absorption of dilute nitride alloys using self-consistent Green’s function method

We have calculated the optical absorption for InGaNAs and GaNSb using the band anticrossing (BAC) model and a self-consistent Green’s function (SCGF) method. In the BAC model, we include the interaction of isolated and pair N levels with the host matrix conduction and valence bands. In the SCGF approach, we include a full distribution of N states, with non-parabolic conduction and light-hole bands, and parabolic heavy-hole and spin-split-off bands. The comparison with experiments shows that the first model accounts for many features of the absorption spectrum in InGaNAs; including the full distribution of N states improves this agreement. Our calculated absorption spectra for GaNSb alloys predict the band edges correctly but show more features than are seen experimentally. This suggests the presence of more disorder in GaNSb alloys in comparison with InGaNAs.     

Effects of Sb-doped SnO2–WO3 nanocomposite on electrochromic performance

With the increase in global challenges related to energy depletion, there is significant emphasis on studies involving next-generation optoelectronic applications such as smart windows and electronic displays. In particular, electrochromic devices (ECDs) have been identified as strategic innovations for energy-saving “smart windows” to address these challenges. Despite this increased level of attentions, ECDs have not yet attained broad commercial acceptance because of their limited electrochromic (EC) properties including coloration efficiency (CE,< 30.0 cm²/C) and switching speeds (> 10.0 s). To address these limitations, critical effort is required to enhance the EC properties by tuning the film structure and electronic structure of ECDs. In this study, we demonstrated the effect of nanocomposite structure of conductive metal oxides and WO₃ EC films. Antimony-doped tin oxide nanoparticles (ATO NPs) were utilized because of their superior electrical conductivity and large band gap. To achieve the optimum addition amount of ATO NPs in EC films, we adjusted the amount as 0, 0.6, 1.2, 2.4 wt%. WO₃ EC films with the optimum addition amount (1.2 wt%) of ATO NPs exhibited improved EC performance including both the switching speeds (5.4 s for the coloration speed and 2.4 s for the bleaching speed) and CE value (48.2 cm²/C). The enhancement of EC performance was attributed to the well-dispersed ATO NPs in the WO₃ films that can effectively improve electrical conductivity via the formation of by forming preferred electron pathway. In addition, the large band gap of ATO NPs broadens the transmittance modulation of the EC layer which contributed to the increment of the CE value. Therefore, our results suggest a strategy to obtain the enhanced WO₃ films with superior EC performances using conductive metal oxides nanocomposite structure.     

Synthesis of stable AuAg bimetallic nanoparticles encapsulated by diblock copolymer micelles

We present a facile method for the preparation of bimetallic AuAg nanoparticles (NPs) with controlled size and composition rendering them ideally suitable for optical and catalytic applications. In analogy to methods for the generation of monometallic Au and Ag NPs, AuAg NPs were prepared inside polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block-copolymer micelles formed in toluene, by loading the P4VP cores of the micelles first with AgNO(3) and then with HAuCl(4). In contrast to the reverse sequence of loading, homogenously bimetallic AuAg particle arrays were achieved after reduction carried out in solution with hydrazine monohydrate as the reducing agent. TEM reveals that stable and spherical NPs can be prepared well separated from one another and with a narrow size distribution with diameters of ～3 nm. The bimetallic NP composition was confirmed by energy-dispersive X-ray spectroscopy (EDX) of single NPs. The atomic ratio of Ag and Au contained in single particles is in good agreement with the relative concentrations of both metals used in the synthesis which was confirmed by atomic absorption spectroscopy. The atomic ratio Au?:?Ag was systematically varied between 3?:?1 and 1?:?3. For all ratios UV-vis spectra showed a single plasmon band. Its wavelength varied from 430 for Au?:?Ag = 1?:?3 to 515 nm for Au?:?Ag = 3?:?1, showing a linear dependence on the relative amount of gold within the range of plasmon wavelengths from monometallic gold (538 nm) to silver (415 nm).     

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A₂B₂O₇, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La₂Zr₂O₇ (LZO) and La₂Hf₂O₇ (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu³⁺ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O²⁻→Zr⁴⁺/Hf⁴⁺ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu³⁺-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu³⁺ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays.     

Stable water-dispersed organic nanoparticles: preparation, optical properties, and cell imaging application

Water-dispersed organic nanoparticles (NPs) constructed by the conjugated molecule 2,5,2',5'-tetra(4'-N,N-diphenylaminostyryl)biphenyl (DPA-TSB) with a high luminescence and large two-photon absorption (TPA) section were fabricated via the reprecipitation method. The average size of the NPs can be controlled from 40 nm to 80 nm by adjusting the reprecipitation conditions. The NPs in water dispersions showed high aggregative and optical stability, which were due to contributions from the special cruciform configuration and amorphous nature of DPA-TSB molecules. The cellular uptake behavior of DPA-TSB NPs was investigated to show their cell staining capabilities as nanoprobes using a confocal microscopy test in vitro. The results demonstrated that DPA-TSB NPs were readily internalized into cytoplasm with no apparent toxicity for up to 24 h, implying excellent imaging capabilities.     

In-Vitro Catalytic and Antibacterial Potential of Green Synthesized CuO Nanoparticles against Prevalent Multiple Drug Resistant Bovine Mastitogen Staphylococcus aureus

Nanoparticles prepared from bio-reduction agents are of keen interest to researchers around the globe due to their ability to mitigate the harmful effects of chemicals. In this regard, the present study aims to synthesize copper oxide nanoparticles (CuO NPs) by utilizing root extracts of ginger and garlic as reducing agents, followed by the characterization and evaluation of their antimicrobial properties against multiple drug resistant (MDR) S. aureus. In this study, UV-vis spectroscopy revealed a reduced degree of absorption with an increase in the extract amount present in CuO. The maximum absorbance for doped NPs was recorded around 250 nm accompanying redshift. X-ray diffraction analysis revealed the monoclinic crystal phase of the particles. The fabricated NPs exhibited spherical shapes with dense agglomeration when examined with FE-SEM and TEM. The crystallite size measured by using XRD was found to be within a range of 23.38–46.64 nm for ginger-doped CuO and 26–56 nm for garlic-doped CuO. Green synthesized NPs of ginger demonstrated higher bactericidal tendencies against MDR S. aureus. At minimum and maximum concentrations of ginger-doped CuO NPs, substantial inhibition areas for MDR S. aureus were (2.05–3.80 mm) and (3.15–5.65 mm), and they were measured as (1.1–3.55 mm) and (1.25–4.45 mm) for garlic-doped NPs. Conventionally available CuO and crude aqueous extract (CAE) of ginger and garlic roots reduced MB in 12, 21, and 38 min, respectively, in comparison with an efficient (100%) reduction of dye in 1 min and 15 s for ginger and garlic doped CuO NPs.     

Passivating ligand and solvent contributions to the electronic properties of semiconductor nanocrystals

We examine in detail the impact of passivating ligands (i.e., amines, phosphines, phosphine oxides and pyridines) on the electronic and optical spectra of Cd(33)Se(33) quantum dots (QDs) using density functional theory (DFT) and time-dependent DFT (TDDFT) quantum-chemical methodologies. Most ligand orbitals are found deep inside in the valence and conduction bands of the QD, with pyridine being an exception by introducing new states close to the conduction band edge. Importantly, all ligands contribute states which are highly delocalized over both the QD surface and ligands, forming hybridized orbitals rather than ligand-localized trap states. In contrast, the states close to the band gap are delocalized over the QD atoms only and define the lower energy absorption spectra. The random detachment of one of ligands from the QD surface results in the appearance of a highly localized unoccupied state inside the energy gap of the QD. Such changes in the electronic structure are correlated with the respective QD-ligand binding energy and steric ligand-ligand interactions. Polar solvent significantly reduces both effects leading to delocalization and stabilization of the surface states. Thus, trap and surface states are substantially eliminated by the solvent. Polar solvent also blue-shifts (e.g., 0.3-0.4 eV in acetonitrile) the calculated absorption spectra. This shift increases with an increase of the dielectric constant of the solvent. We also found that the approximate single-particle Kohn-Sham (KS) approach is adequate for calculating the absorption spectra of the ligated QDs. Besides a systematic blue-shift, the KS spectra are in very good agreement with their respective counterparts calculated with the more accurate TDDFT method.