Toward use of a nano layered double hydroxide/ammonium pyrrolidine dithiocarbamate in speciation analysis: One-step dispersive solid-phase extraction of chromium species in human biological samples

Chromium is a controversial element with an important essentiality and toxicity. Depending on its different species, its speciation analysis in bio-origin matrices is of utmost importance. Ammonium pyrrolidine dithiocarbamate (APDC) and layered double hydroxide (LDH) nanoparticles, with the purpose of combining their outstanding performances, were served to speciate chromium ions in human biological samples. The as-obtained sorbent (nano LDH-APDC) - after characterization by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) - was used as a novel pH-sensitive adsorbent in an integrated one-step dispersive solid-phase extraction (I-OS-DSPE), which combines the benefits of the air-assisted microextraction and dispersive solid-phase extraction methods. An interesting feature of the nano LDH-APDC sorbent is that it is dissolved in an aqueous solution when the pH of the solution is lower than 4. Thus the analyte elution step, as required in most of the sorbent-based extraction methods, was obviated by dissolving the sorbent in an acidic solution after extraction and separation from the sample solution. The Cr(VI) ions were first extracted, while the Cr(III) ions remained in the aqueous solution. The extract was then directly injected into a flame atomic absorption spectrometer with a micro-sampling introduction system, and the concentration of the Cr(III) ions was calculated by its subtraction from the total chromium ions present. Several variables including the pH (5), type and amount of the nanosorbent used (30 mg of nano (Zn-Al) LDH-APDC), number of extraction cycles (15 times), and elution conditions (200 µL of 6.0 mol L⁻¹ HNO₃) were investigated to achieve the maximum extraction efficiency. Under the optimum experimental conditions, the limit of detection, linear range, consumptive index, and enrichment factor for the Cr(VI) ions were 2.4 μg L⁻¹, 8.0–640 μg L⁻¹, 0.24, and 42.5 ± 1, respectively. These findings suggested that nano (Zn-Al) LDH-APDC could be regarded as a promising adsorbent for an efficient speciation of the chromium species in the human hair, nail, saliva, plasma, and urine samples.     

Electrothermal vaporization coupled with inductively coupled plasma array–detector mass spectrometry for the multielement analysis of Al2O3 ceramic powders

An electrothermal vaporization (ETV) system useful for the analysis of solutions and slurries has been coupled with a sector-field inductively coupled plasma mass spectrometer (ICP–MS) equipped with an array detector. The ability of this instrument to record the transient signals produced for a number of analytes in ETV–ICP–MS is demonstrated. Detection limits for Mn, Fe, Co, Ni, Cu, Zn and Ga are in the range of 4–60 pg μL^− 1 for aqueous solutions and in the low μg g^− 1 range for the analysis of 10 mg mL^− 1 slurries of Al₂O₃ powders. The dynamic ranges measured for Fe, Cu and Ga spanned 3–5 orders of magnitude when the detector was operated in the low-gain mode and appear to be limited by the ETV system. Trace amounts of Fe, Cu and Ga could be directly determined in Al₂O₃ powders at the 2–270 μg g^− 1 level without the use of thermochemical reagents. The results well agree with literature values for Fe and Cu, whereas deviations of 50% at the 90 μg g^− 1 level for Ga were found.     

Determination of inorganic and total mercury by vapor generation atomic absorption spectrometry using different temperatures of the measurement cell

A simple and inexpensive laboratory-built flow injection vapor generation system coupled to atomic absorption spectrometry (FI-VG AAS) for inorganic and total mercury determination has been developed. It is based on the vapor generation of total mercury and a selective detection of Hg^2 + or total mercury by varying the temperature of the measurement cell. Only the inorganic mercury is measured when the quartz cell is at room temperature, and when the cell is heated to 650 °C or higher the total Hg concentration is measured. The organic Hg concentration in the sample is calculated from the difference between the total Hg and Hg^2 + concentrations. Parameters such as the type of acid (HCl or HNO₃) and its concentration, reductant (NaBH₄) concentration, carrier solution (HCl) flow rate, carrier gas flow rate, sample volume and quartz cell temperature, which influence FI-VG AAS system performance, were systematically investigated. The optimized conditions for Hg^2 + and total Hg determinations were: 1.0 mol l^− 1 HCl as carrier solution, carrier flow rate of 3.5 ml min^− 1, 0.1% (m/v) NaBH₄, reductant flow rate of 1.0 ml min^− 1 and carrier gas flow rate of 200 ml min^− 1. The relative standard deviation (RSD) is lower than 5.0% for a 1.0 μg l^− 1 Hg solution and the limit of quantification (LOQ, 10 s) is 55 ng g^− 1. Certified samples of dogfish muscle (DORM-1 and DORM-2) and non-certified fish samples were analyzed, using a 6.0 mol l^− 1 HCl solution for analyte extraction. The Hg^2 + and CH₃Hg⁺ concentrations found were in agreement with certified ones.     

Laser ablation–inductively coupled plasma–dynamic reaction cell–mass spectrometry for the multi-element analysis of polymers

In this work, the potential of laser ablation–inductively coupled plasma–mass spectrometry for the fast analysis of polymers has been explored. Different real-life samples (polyethylene shopping bags, an acrylonitrile butadiene styrene material and various plastic bricks) as well as several reference materials (VDA 001 to 004, Cd in polyethylene) have been selected for the study. Two polyethylene reference materials (ERM-EC 680 and 681), for which a reference or indicative value for the most relevant metals is available, have proved their suitability as standards for calibration.Special attention has been paid to the difficulties expected for the determination of Cr at the μg g^− 1 level in this kind of materials, due to the interference of ArC⁺ ions on the most abundant isotopes of Cr. The use of ammonia as a reaction gas in a dynamic reaction cell is shown to alleviate this problem, resulting in a limit of detection of 0.15 μg g^− 1 for this element, while limiting only modestly the possibilities of the technique for simultaneous multi-element analysis. In this regard, As is the analyte most seriously affected by the use of ammonia, and its determination has to be carried out in vented mode, at the expense of measuring time.In all cases studied, accurate results could be obtained for elements ranging in content from the sub-μg g^− 1 level to tens of thousands of μg g^− 1. However, the use of an element of known concentration as internal standard may be needed for materials with a matrix significantly different from that of the standard (polyethylene in this work).Precision ranged between 5% and 10% RSD for elements found at the 10 μg g^− 1 level or higher, while this value could deteriorate to 20% for analytes found at the sub-μg g^− 1 level. Overall, the technique evaluated presents many advantages for the fast and accurate multi-element analysis of these materials, avoiding laborious digestion procedures and minimizing the risk of analyte losses due to the formation of volatile compounds.     

Internal standardization in graphite furnace atomic absorption spectrometry: Comparative use of As and Ge to minimize matrix effects on Se determination in milk

Arsenic and germanium have been evaluated as internal standards to minimize matrix effects on the direct determination of selenium in milk by graphite furnace atomic absorption spectrometry (GFAAS) using tubes with integrated platform, pre-treated with W together with Pd as chemical modifier. The efficiency of As and Ge as internal standards for 25 μg L^− 1 Se plus 500 μg L^− 1 As or Ge in diluted (1 + 9 v/v) milk plus 1.0% (v/v) HNO₃ was evaluated by means of correlation graphs plotted from the normalized absorbance signals (n = 20) of internal standard (axis y) versus analyte (axis x). The equations that describe the linear regression were: A^As = − 0.004 ± 0.019 + 1.02 ± 0.019 A^Se (r = 0.9967 ± 0.005); A^Ge = − 0.017 ± 0.015 + 1.01 ± 0.015 A^Se (r = 0.9978 ± 0.004). Samples and reference solutions were automatically spiked with 500 μg L^− 1 Ge or As and 1.0% (v/v) HNO₃ by the autosampler. For 20 μL of aqueous standard solutions, analytical curves in the 5.00–40.0 μg L^− 1 Se range were established using the ratio of Se absorbance to internal standard absorbance (A^Se / A^IS) versus analyte concentration, and good linear correlations were obtained. The characteristic mass was 40 pg Se. Limits of detection were 0.55 and 0.40 μg L^− 1 with As and Ge as the internal standard, respectively. Relative standard deviations (RSD) for a sample containing 25 μg L^− 1 Se were 1.2% and 1.0% (n = 12) using As and Ge, respectively. The RSD without internal standardization was about 6%. The accuracy of the proposed method was evaluated by an addition-recovery experiment and all recovered values were in the 99–105% range with IS and in the 70–80% range without IS. Using Ge as the internal standard, results of analysis of standard reference materials were in agreement with certified values at a 95% confidence level. The selenium concentration for 10 analyzed milk samples varied from 5.0 to 20 μg L^− 1.     

Evaluation of on-line desalter-inductively coupled plasma-mass spectrometry system for determination of Cr(III), Cr(VI), and total chromium concentrations in natural water and urine samples

We have developed a simple and convenient method for the determination of Cr(III), Cr(VI), and the total chromium concentrations in natural water and urine samples that use a flow injection on-line desalter-inductively coupled plasma-mass spectrometry system. When using aqueous ammonium chloride (pH 8) as the stripping solution, the severe interference from sodium in the matrix can be eliminated prior to inductively coupled plasma-mass spectrometry measurement, and the Cr(VI) level can be determined directly. To determine the total concentration of Cr in natural water and urine samples, we used H₂O₂ or HNO₃ to decompose the organic matter and convert all chromium species into the Cr(VI) oxidation state. To overcome the spectral interference caused by the matrix chloride ion in the resulting solutions, we employed cool plasma to successfully suppress chloride-based molecular ion interference during the inductively coupled plasma-mass spectrometry measurement. By significantly eliminating interference from the cationic and anionic components in the matrices prior to the inductively coupled plasma-mass spectrometry measurement, we found that the detection limit reached 0.18 μg L^− 1 (based on 3 sigma). We validated this method through the analysis of the total chromium content in two reference materials (NIST 1643c and 2670E) and through measuring the recovery in spiked samples.     

Adsorption of Cr(VI) using cellulose microsphere-based adsorbent prepared by radiation-induced grafting

Cellulose microsphere (CMS) adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto CMS followed by a protonation process. The FTIR spectra analysis proved that PDMAEMA was grafted successfully onto CMS. The adsorption of Cr(VI) onto the resulting adsorbent was very fast, the equilibrium adsorption could be achieved within 15 min. The adsorption capacity strongly depended on the pH of the solution, which was attributed to the change of both the existed forms of Cr(VI) and the tertiary-ammonium group of PDMAEMA grafted CMS with the pH. A maximum Cr(VI) uptake (ca. 78 mg g^?1) was obtained as the pH was in the range of 3.0–6.0. However, even in strong acid media (pH 1.3), the adsorbents still showed a Cr(VI) uptake of 30 mg g^?1. The adsorption behavior of the resultant absorbent could be described with the Langmuir mode. This adsorbent has potential application for removing heavy metal ion pollutants (e.g. Cr(VI)) from wastewater.     

Copper removal from aqueous solution using biochar: Effect of chemical activation

The main aim of this study was to test the efficiency of biochar for Cu removal from synthetic and soil solutions, respectively.The biochar was produced from brewers draff via pyrolysis. Additionally, the prepared biochar was also activated using 2 M KOH to enhance its sorption efficiency to remove Cu from both solutions. Two different aqueous solutions were prepared for these experiments: (i) a synthetic using Cu-nitrate salt with 0.01 M NaNO₃ and (ii) soil solution obtained from a Cu-contaminated soil using 0.01 M CaCl₂ leaching procedure. Batch sorption and column experiments were used to evaluate the efficiency of both biochar (BC) and activated biochar (BC_act) to remove Cu from the solutions.Results showed that both biochar samples are pure amorphous carbon and the Cu sorption is thus mainly a result of physical sorption on the biochar surface. Next, chemical activation, using 2 M KOH, significantly increased the total volume of all pores in biochar (from 0.01 ± 0.002 to 8.74 ± 0.18 mL g⁻¹). On the other hand, the BET surface area was similar for both sorbents (BC = 9.80 ± 0.62 m² g⁻¹ and BC_act = 11.6 ± 0.4 m² g⁻¹). Results also demonstrate enhanced sorption efficiency of the BC_act (10.3 mg g⁻¹) in comparison with the BC (8.77 mg g⁻¹). Additionally, enhanced Cu removal during column retention test was observed for the BC_act in both synthetic and soil solutions, respectively.In summary, the results showed that biochar prepared from brewers draff was able to remove Cu from both aqueous solutions.     

Thermodynamic analysis of sorption isotherms of chromium(VI) anionic species on reed biomass

A new sorbent material for removing Cr(VI) anionic species from aqueous solutions has been investigated. Adsorption equilibrium and thermodynamics of Cr(VI) anionic species onto reed biomass were studied at different initial concentrations, sorbent concentrations, pH levels, temperatures, and ionic strength. Equilibrium isotherm was analyzed by Langmuir model. The experimental sorption data fit the model very well. The maximum sorption capacity of Cr(VI) onto reed biomass was found to be 33 mg · g^?1. It was noted that the Cr(VI) adsorption by reed biomass decreased with increase in pH. An increase in temperature resulted in a higher Cr(VI) loading per unit weight of the adsorbent. Removal of Cr(VI) by reed biomass seems to be mainly by chemisorption. The change in entropy (ΔS^°) and heat of adsorption (ΔH^°) for Cr(VI) adsorption on reed biomass were estimated as 2205 kJ · kg^?1 · K^?1 and 822 kJ · kg^?1, respectively. The values of isosteric heat of adsorption varied with the surface loading of Cr(VI).     

Solvothermal synthesis,structure, and magnetic property for nano-‘chromic wheels’ [Cr10(μ-O2CMe)10(μ-OMe)10(μ-OEt)10]

Nano-decanuclear cyclic Cr(III) complex, [Cr₁₀(μ-O₂CMe)₁₀(μ-OMe)₁₀(μ-OEt)₁₀] (1), has been synthesized in high yield by solvothermal technique using trinuclear basic chromium acetate [Cr₃O(CO₂Me)₆(MeOH)₃]Cl in EtOH. Complex 1 crystallizes in the monoclinic space group P2₁/n. The Cr₁₀ rings are close to planar, with each pair of neighboring Cr(III) ions bridged by one μ-acetate, one μ-ethoxide, and one μ-methoxide groups. Magnetic susceptibility studies reveal very weak antiferromagnetic Cr⋯Cr exchange of J = 0.37 cm⁻¹ .     

Highly active PtRuFe/C catalyst for methanol electro-oxidation

High methanol electro-oxidation activity was obtained on novel PtRuFe/C (2:1:1 at.%) catalyst. Mass and specific activities were 5.67 A  g⁻¹ catal. and 177 mA m⁻² for the PtRuFe/C catalyst while those of the commercial PtRu/C catalyst were 2.28 A g⁻¹ catal. and 87.7 mA m⁻², respectively. CO stripping results showed that on-set voltage for CO electro-oxidation was lowered by incorporation of Fe. XRD and XPS results revealed that Fe₂O₃ was formed instead of Fe(0), which resulted in large electron deficiency in Pt and easy CO electro-oxidation. The electron deficiency of Pt was proved by XPS results of Pt4f peaks, which moved to higher binding energies in PtRuFe/C than PtRu/C.     

Electronic structure and Raman spectroscopy study of dibarium magnesium orthoborate,Ba2Mg(BO3)2

The samples of dibarium magnesium orthoborate Ba₂Mg(BO₃)₂ were synthesized by solid-state reaction. The X-ray diffraction (XRD) patterns and Raman spectra of the samples were collected. Electronic structure and vibrational spectroscopy of Ba₂Mg(BO₃)₂ were systematically investigated by first principle calculation. A direct band gap of 4.4 eV was obtained from the calculated electronic structure results. The top valence band is constructed from O 2p states and the low conduction band mainly consists of Ba 5d states. Raman spectra for Ba₂Mg(BO₃)₂ polycrystalline were obtained at ambient temperature. The factor group analysis results show the total lattice modes are 5E_u + 4A_2u + 5E_g + 4A_1g + 1A_2g + 1A_1u, of which 5E_g + 4A_1g are Raman-active. Furthermore, we obtained the Raman active vibrational modes as well as their eigenfrequencies using first-principle calculation. With the assistance of the first-principle calculation and factor group analysis results, Raman bands of Ba₂Mg(BO₃)₂ were assigned as E_g (42 cm⁻¹), A_1g (85 cm⁻¹), E_g (156 cm⁻¹), E_g (237 cm⁻¹), A_1g (286 cm⁻¹), E_g (564 cm⁻¹), A_1g (761 cm⁻¹), A_1g (909 cm⁻¹), E_g (1165 cm⁻¹). The strongest band at 928 cm⁻¹ in the experimental spectrum is assigned to totally symmetric stretching mode of the BO₃ units.     

1,2,4-Triazole as a reference material for combustion calorimetry of N-containing compounds

A micro-bomb combustion calorimeter recently designed for samples of mass  ≈ 80 mg has been improved and tested with m -methoxybenzoic acid in order to verify the chemistry of the combustion process and the accuracy of the energy corrections involved in the analysis of results. From measurements in this calorimeter, the standard massic energy of combustion of 1,2,4-triazole was determined to beΔ_cu^o =  − (19200.3  ±  3.4)J · g ^− 1. Some new measurements with our macro combustion calorimeter confirm an earlier result from this laboratory of  − (19203.1  ±  1.2)J · g ^− 1. Determination of the purity by d.s.c. of 1,2,4-triazole purified some 10 years ago reveals that samples of this compound remained unchanged and suggest that 1,2,4-triazole be used as a possible reference material for organic compounds with a high content of nitrogen. From the experimental results with the micro-bomb combustion calorimeter, the actual and earlier results from macro-bomb combustion calorimetry, and those obtained in other laboratories, the standard massic energy of combustion of 1,2,4-triazole was deduced to beΔ_cu^o =  − (19202.5  ±  1.7)J · g ^− 1.     

Highly mesoporous and high surface area carbon: A high capacitance electrode material for EDLCs with various electrolytes

Activated carbon fibers (ACFs) with high surface area and highly mesoporous structure for electrochemical double layer capacitors (EDLCs) have been prepared from polyacrylonitrile fibers by NaOH activation. Their unique microstructural features enable the ACFs to present outstanding high specific capacitance in aqueous, non-aqueous and novel ionic liquid electrolytes, i.e. 371 F g⁻¹ in 6 mol L⁻¹ KOH, 213 F g⁻¹ in 1 mol L⁻¹ LiClO₄/PC and 188 F g⁻¹ in ionic liquid composed of lithium bis(trifluoromethane sulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) and 2-oxazolidinone (C₃H₅NO₂, OZO), suggesting that the ACF is a promising electrode material for high performance EDLCs.     

A layered δ-MnO2 nanoflake cathode with high zinc-storage capacities for eco-friendly battery applications

This study reports the use of a layered-type birnessite δ-MnO₂ nano-flake cathode for eco-friendly zinc-ion battery (ZIB) applications. The present δ-MnO₂ was prepared via the simple low temperature thermal decomposition of KMnO₄. The X-ray diffraction (XRD) pattern of the samples was well indexed to the δ-MnO₂ phase. Field emission SEM and TEM images of the δ-MnO₂ revealed flake-like morphologies with an average diameter of 200 nm. The electrochemical properties, investigated by cyclic voltammetry and constant current charge-discharge measurements, revealed that the nano-flake cathode exhibited first discharge capacity of 122 mAh g^− 1 under a high current density of 83 mA g^− 1 versus zinc. The discharge capacity thereafter increased until it reached 252 mAh g^− 1 in the fourth cycle. On the hundredth cycle, the electrode registered a discharge capacity of 112 mAh g^− 1. Coulombic efficiencies of nearly 100% were maintained on prolonged cycling and thereby indicate the long cycle stability of the δ-MnO₂. Besides, the realization of specific capacities of 92 and 30 mAh/g at high current densities of 666 and 1333 mA g⁻¹, respectively, clearly demonstrates the decent rate capabilities of δ-MnO₂ nano-flake cathode. These results may facilitate the utilization of layered-type birnessite δ-MnO₂ in ZIB applications.     

The standard molar enthalpy of sublimation ofη5-bis-pentamethylcyclopentadienyl iron measured with an electrically calibrated vacuum-drop sublimation microcalorimetric apparatus

A heat-flow Calvet microcalorimeter was adapted for the measurement of sublimation enthalpies by the vacuum-drop method, with samples of masses in the range 1 mg to 5 mg. The electrically calibrated apparatus was tested by determining the enthalpies of sublimation of benzoic acid and ferrocene, at T =  298.15 K. The obtained results, Δ_cr^gH_m^o(C₇H₆O₂)  =  (88.3  ±  0.5)kJ · mol ^− 1and Δ_cr^gH_m^o(C₁₀H₁₀Fe) =  (73.3  ±  0.1)kJ · mol ^− 1, are in excellent agreement with the corresponding values recommended in the literature. Subsequent application of the apparatus to the determination of the enthalpy of sublimation of η⁵-bis-pentamethylcyclopentadyenyl iron, at T =  298.15 K, led to Δ_cr^gH_m^o(C₂₀H₃₀Fe)  =  (96.8  ±  0.6)kJ · mol ^− 1.     

Nano TiO2-based preconcentration for the speciation analysis of inorganic selenium by using ion chromatography with conductivity detection

A simple, sensitive, and cost-effective analytical method was developed for the speciation analysis of inorganic selenium by combining a nano-TiO₂ preconcentration with an ion chromatography-conductivity detection (IC-CD) system. The experimental conditions for the simultaneous adsorption and desorption of Se(IV) and Se(VI) were carefully investigated. Under the established optimum condition, the Se(IV) and Se(VI) ions could been simultaneously adsorbed onto the nano-TiO₂ surface at pH 4.0, and then effectively desorbed by 0.1 M sodium hydroxide eluent. The adsorption process was fast and reached adsorption equilibrium within 10 min. The nano-TiO₂ also exhibited high adsorption capacity with 11.3 mg g^? 1 for Se(IV) and 8.34 mg g^? 1 for Se(VI). The enrichment factors for Se(IV) and Se(VI) were calculated to be 39 and 30, respectively, with sample volume of 50 mL. The detection limits (3σ) were 0.8 μg L^? 1 for Se(IV) and 0.4 μg L^? 1 for Se(VI), which were sensitive enough for the routine analysis of water and drink samples. The relative standard deviation was calculated to be < 4% (n = 6) for detection of 30 μg L^? 1 Se(IV) and 30 μg L^? 1 Se(VI). The results of the present work confirmed that our developed nano-TiO₂-IC-CD method could be applied for the detection of inorganic selenium species in tap water and drink samples with good recoveries in the range of 82%–108%.     

Enhanced electrochemical performance of carbon-coated TiO2 nanobarbed fibers as anode material for lithium-ion batteries

We report the electrochemical performance of carbon-coated TiO₂ nanobarbed fibers (TiO₂@C NBFs) as anode material for lithium-ion batteries. The TiO₂@C NBFs are composed of TiO₂ nanorods grown on TiO₂ nanofibers as a core, coated with a carbon shell. These nanostructures form a conductive network showing high capacity and C-rate performance due to fast lithium-ion diffusion and effective electron transfer. The TiO₂@C NBFs show a specific reversible capacity of approximately 170 mAh g^− 1 after 200 cycles at a 0.5 A g^− 1 current density, and exhibit a discharge rate capability of 4 A g^− 1 while retaining a capacity of about 70 mAh g^− 1. The uniformly coated amorphous carbon layer plays an important role to improve the electrical conductivity during the lithiation–delithiation process.     

Mesoporous Fe2O3 nanoparticles as high performance anode materials for lithium-ion batteries

This work introduces an effective, inexpensive, and large-scale production approach to the synthesis of Fe₂O₃ nanoparticles with a favorable configuration that 5 nm iron oxide domains in diameter assembled into a mesoporous network. The phase structure, morphology, and pore nature were characterized systematically. When used as anode materials for lithium-ion batteries, the mesoporous Fe₂O₃ nanoparticles exhibit excellent cycling performance (1009 mA h g^− 1 at 100 mA g^− 1 up to 230 cycles) and rate capability (reversible charging capacity of 420 mA h g^− 1 at 1000 mA g^− 1 during 230 cycles). This research suggests that the mesoporous Fe₂O₃ nanoparticles could be suitable as a high rate performance anode material for lithium-ion batteries.     

Vibrational and electronic properties of single-walled and double-walled boron nitride nanotubes

We calculated IR, nonresonance Raman spectra and vertical electronic transitions of the zigzag single-walled and double-walled boron nitride nanotubes ((0,n)-SWBNNTs and (0,n)@(0,2n)-DWBNNTs). In the low frequency range below 600 cm⁻¹, the calculated Raman spectra of the nanotubes showed that RBMs (radial breathing modes) are strongly diameter-dependent, and in addition the RBMs of the DWBNNTs are blue-shifted reference to their corresponding one in the Raman spectra of the isolated (0,n)-SWBNNTs. In the high frequency range above ∼1200 cm⁻¹, two proximate Raman features with symmetries of the A_1g (∼1355 ± 10 cm⁻¹) and E_2g (∼1330 ± 25 cm⁻¹) first increase in frequency then approach a constant value of ∼1365 and ∼1356 cm⁻¹, respectively, with increasing tubes’ diameter, which is in excellent agreement with experimental observations. The calculated IR spectra exhibited IR features in the range of 1200–1550 cm⁻¹ and in mid-frequency region are consistent with experiments. The calculated dipole allowed singlet–singlet and triplet–triplet electronic transitions suggesting a charge transfer process between the outer- and inner-shells of the DWBNNTs as well as, upon irradiation, the possibility of a system that can undergo internal conversion (IC) and intersystem crossing (ISC) processes, besides the photochemical and other photophysical processes.