Band Intensity Ratio Research Articles

Subtype discrimination of acute myeloid leukemia based on plasma SERS technique

Acute myeloid leukemia (AML) is a common hematologic malignancy. To this day, diagnose of AML and its genetic mutation still rely on invasive and time-consuming methods. In this study, 222 plasma samples were collected to discuss the performance of surface-enhanced Raman spectroscopy (SERS) to discriminate AML subtype acute promyelocytic leukemia and acute monocytic leukemia based on plasma. The Ag nanoparticles-based SERS technique was used to explore the biochemical differences among different AML subtypes. With the help of powerful supervised and unsupervised algorithms, the performance using the whole spectra and band intensities was confirmed to identify different subtypes of AML. The results demonstrated the intensities of several bands and band-intensity ratios were significantly different between groups, thus related to the discrimination of several AML subtypes and control. Combining indexes of band-intensity ratios, the result of multi-indexes ROC has excellent performance in differentiating AML patient with healthy control. Our work demonstrated the great potential of SERS technique as a rapid and micro detection method in clinical laboratory field, it’s a new and powerful tool for analyzing human blood plasma.

A single-band ratiometric luminescent thermometer based on tetrafluorides operating entirely in the infrared region.

Luminescence thermometry is a remote temperature measurement technique that relies on thermally induced changes in spectroscopic properties. Because of its great application potential, even under very demanding conditions where other techniques fail, it has attracted the attention of many researchers in recent years. Unfortunately, most of the existing luminescence thermometers are fraught with large inaccuracies and thus are not reliable enough to be applied in real and demanding applications. However, there is one of the most recent and very promising but insufficiently studied approaches to luminescence thermometry quantification – single-band ratiometric luminescence thermometry. It is based on the analysis of the luminescence intensity ratio of a single emission band being photoexcited in two ways, i.e. by ground (GSA) and excited (ESA) state absorption. It is characterized by high relative sensitivity to temperature changes as well as high measurement precision. However, because ESA-excited luminescence intensity can depend on the type and concentration of dopant ions or the properties of the host material, further more-detailed studies must be conducted to understand the impact of numerous photophysical processes on the relative sensitivity, temperature resolution and useful temperature range of SBR LTs. In this work, the effect of interionic interactions occurring through cross-relaxation on the thermometric properties of single-band ratiometric luminescent thermometers in NaYF4:Nd3+ and NaGdF4:Nd3+ was investigated and discussed. In contrast to the disadvantageous concentration quenching phenomenon that is typically observed at an increased content of dopants, the beneficial role of cross-relaxation in the enhancement of the signal-to-noise ratio of the ESA-excited luminescence at high temperatures was demonstrated. The maximum relative temperature sensitivity reached was equal to SR = 16.9% K−1 at 223 K for NaYF4:50%Nd3+ nanocrystals and its value remained above 1% K−1 throughout the whole analyzed temperature range from 223 K to 473 K.

Measurement Electric Field in Atmospheric Hermstein’s Glow Corona Discharge using N2 Spectrum Intensity Ratio of N2 1st and 2nd Positive System Band

We experimentally estimate a reduced electric field (<inline-formula> <tex-math notation="LaTeX">${E}/{N}{)}$ </tex-math></inline-formula> of Hermstein&#x2019;s glow corona discharge from <inline-formula> <tex-math notation="LaTeX">$\text{N}_{{2}}$ </tex-math></inline-formula> intensity ratio: the intensity of the first positive system band (3, 1) [FPS(3, 1)] and the intensity of second positive system band (0, 0) [SPS(0, 0)] are used. The intensity ratio [FPS(3, 1)<inline-formula> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula>SPS(0, 0)] has the relation with the <inline-formula> <tex-math notation="LaTeX">${E}/{N}$ </tex-math></inline-formula>. First, we experimentally clarify the relationship between FPS(3, 1)<inline-formula> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula>SPS(0, 0) and <inline-formula> <tex-math notation="LaTeX">$\text {E}/\text {N}$ </tex-math></inline-formula> at atmospheric pressure. This relationship is acquired by generating the uniform light ionized emission in the parallel-plane gap with the YAG laser and measuring the intensity ratio of FPS(3, 1)/SPS (0, 0) in the range of <inline-formula> <tex-math notation="LaTeX">${E}/{N} =83.9\,\,\times \,\,10^{-{21}}$ </tex-math></inline-formula>&#x2013;95.9 <inline-formula> <tex-math notation="LaTeX">$\times \,\,10^{-{21}}$ </tex-math></inline-formula> Vm². This relationship is applied to Hermstein&#x2019;s glow corona discharge at atmospheric pressure. As a result, the <inline-formula> <tex-math notation="LaTeX">${E}/{N}$ </tex-math></inline-formula> of Hermstein&#x2019;s glow corona discharge is acquired in the range of <inline-formula> <tex-math notation="LaTeX">${E}/{N} =117.4\,\,\times \,\,10^{-{21}}$ </tex-math></inline-formula>&#x2013;125.1 <inline-formula> <tex-math notation="LaTeX">$\times \,\,10^{-{21}}$ </tex-math></inline-formula> Vm². We find the transition of the corona stabilization effect from the discharge occurrence to breakdown by measuring the <inline-formula> <tex-math notation="LaTeX">${E}/{N}$ </tex-math></inline-formula>. This work also considers the gas temperature rise of discharge. Considering the gas temperature rise of discharge has led to the universal method of acquiring the <inline-formula> <tex-math notation="LaTeX">${E}/{N}$ </tex-math></inline-formula> of discharge from the intensity ratio of FPS(3, 1)/SPS(0, 0).

Synthesis and Photoluminescence Properties of Alkylbromoporphyrin

&lt;p&gt;The usage of porphyrin as a light-harvesting chromophore is considered as one of the keys to obtaining low-cost and high-efficiency dye-sensitized solar cell (DSSC). In this paper, a novel porphyrin, 5,10,15-tris(nitrophenyl)-20-(p-(11-bromo)dodecoxyphenyl))porphyrin, having a long alkyl chain and three nitro groups was synthesized. The nitro groups serve as anchoring groups to TiO&lt;sub&gt;2&lt;/sub&gt; surfaces and long alkyl chain prevents unwanted dye aggregation. The porphyrin was synthesized by condensation of &lt;em&gt;p&lt;/em&gt;-(12-Bromododecoxy)benzaldehyde and pyrrole in propionic acid according to an adaptation of the general Rothemund method &lt;a href="https://doi.org/10.1021/ja01265a096"&gt;[1]&lt;/a&gt;. &lt;em&gt;p&lt;/em&gt;-(12-Bromododecoxy)benzaldehyde was synthesized by nucleophilic substitution reaction between 4-hydroxybenzaldehyde and 1,12-dibromododecane in acetone. The reaction products were analyzed by &lt;sup&gt;1&lt;/sup&gt;H-NMR and mass spectroscopy. The absorption and fluorescence spectra of the porphyrin were also recorded. As results, the absorption spectrum of the porphyrin consists of a strong Soret and four weak Q-band. Compared to 5,10,15-tris(nitrophenyl)-20-(p-(11-bromo)dodecoxyphenyl))porphyrin spectrum, there is no wavelength shifting because of the incorporation of the alkyl chain. The fluorescence spectrum of the porphyrin shows two characteristic emission bands and the intensity ratio of those emission bands is always constant when irradiated by different excitation wavelength related to Soret and Q-band.&lt;/p&gt;

Electrochemical investigation of free-standing reduced graphene oxide hydrogel

Free-standing reduced graphene oxide (RGO) hydrogel was synthesized through two-stepped hydrothermal reduction treatment of aqueous graphene oxide (GO) suspension. GO with high interface affinity for overlapping of cross-linking graphene sheets contributes to forming steady-state RGO hydrogel. RGO hydrogel shows higher B band/G band intensity ratio than GO suspension in Raman spectrum analysis, indicating well-restored hexagonal carbon rings with the enhanced crystal structure. Free-standing RGO hydrogel could be directly acted as supercapacitor electrode without using any substrate material. The specific capacitance decreases from 253.9 to 92.3 F g−1 in 1.0 M Na2SO4 electrolyte and from 275.3 to 125.9 F g−1 in 1.0 M KOH electrolyte when the current density increased from 0.3 to 4.0 A g−1, presenting the capacity retention of 36.4% and 45.7% respectively. Free-standing RGO hydrogel presents specific capacitance in alkaline KOH electrolyte rather than neutral Na2SO4 electrolyte. KOH electrolyte with superior ionic diffusion coefficient of hydroxyl ion leads to higher current response and electrical double-layer capacitance performance. The capacitance retention ratio of 97.8% at 4.0 A g−1 in 1.0 M KOH electrolyte after 1000 charge-discharge cycles presents superior cycling stability. Accordingly, free-standing RGO hydrogel applied well as superior supercapacitor electrode presents the promising energy storage application.

Luminescent lanthanide nanocomposites in thermometry: Chemistry of dopant ions and host matrices

• Current progress on luminescent lanthanide nanocomposites for thermal sensing. • Effect of host matrices on thermometry. • Impact of dopant ions and their emission transition on thermal sensitivity. • Modern challenges in nanothermometry development. Recently, there has been observed huge progress in the advancement of remote optical nanothermometry, as it plays a vital role in remote, noninvasive, and remote temperature sensing, which is especially important for various bio-applications, e.g., in theranostics and photodynamic therapy. This is because the luminescence thermometry technique can accurately identify the temperature distribution in the molecular objectives or the biological body. Especially, the use of temperature-induced change in the luminescence intensity ratio (LIR) of two thermally coupled emission bands of lanthanide (Ln 3+ ) ions, embedded in some inorganic nanoparticles (NPs), allows temperature representing of a single living cell. In this review, we comprehensively summarized the concept of luminescence optical thermometry, photophysical properties of Ln 3+ ions, synthesis process, and various hosts doped with different Ln 3+ ions, in which they act as either sensitizers or activators. Selecting a proper host matrix is an efficient route to achieve the high performance of optical nanothermometers since it takes an important role in determining the luminescent efficiency. Initially, we defined and compared various classes of optical thermometers based on diverse spectroscopic parameters, such as emission intensity, band intensity ratio, bandwidth, band shape, polarization, spectral shift, and luminescence lifetime. Furthermore, we emphasized the most common approach for temperature monitoring, which is based on the thermally coupled levels (TCLs) of Ln 3+ ions, by exploiting the LIR technique, since it can provide a fast response with high accuracy, precision, and resolution. Additionally, this review also discusses the recent progress in diverse strategies to boost thermometric performances, such as changing dopants and utilizing various energy transfer mechanisms. Ultimately, we summed up the recent research achievements through analyzing the current research strategies, discussing future guidelines, as well as exploring the major difficulties for further advancement in the area.

Tm2+ Activated SrB4O7 Bifunctional Sensor of Temperature and Pressure—Highly Sensitive, Multi‐Parameter Luminescence Thermometry and Manometry

AbstractNoninvasive sensing of temperature and pressure offers new and exciting opportunities to investigate and monitor the variation of physicochemical and spectroscopic properties of materials under extreme conditions. In this work, Tm2+‐doped SrB4O7 phosphor material—a novel, contactless bifunctional, and multimodal optical sensor for pressure and temperature is reported. A series of SrB4O7: xTm2+ samples are synthesized via a high‐temperature solid‐state method in air. The impact of high pressure (up to ≈13 GPa) and temperature (from 10 to 400 K) on spectroscopic properties of SrB4O7:Tm2+ is investigated. The emission band of Tm2+ demonstrates a significant spectral shift and a band broadening as a function of both pressure and temperature. Such a result is a consequence of a significant change of vibronic components of the Tm2+ 4f125d ↔ 4f13 zero‐phonon line. The emission bandwidth and its spectral position exhibit excellent sensitivities to pressure, that is, ≈23.17 and ≈−11.85 cm−1 GPa−1, respectively. Furthermore, for the first time, it is shown that temperature sensing can be realized via four different pathways in a single material: i) bandwidth, ii) band shift, iii) band intensity ratio, and iv) luminescence lifetime, with maximal sensitivities of ≈3.85 cm−1 K−1, 1.44 cm−1 K−1, 1.48% K−1 and 4.16% K−1, respectively.

Dual-center thermochromic Bi2MoO6:Yb3+, Er3+, Tm3+ phosphors for ultrasensitive luminescence thermometry

Optical thermometers are of great interest due to their non-contact, high-sensitivity and fast measurement characteristics. In this work, a series of dual-center Bi1.96−xMoO6: 0.02Er3+, 0.02Tm3+, xYb3+ (x = 0.10–0.35) upconverting materials were prepared by a sol-gel synthesis method. Upon 975 nm excitation, the prepared materials exhibit bright color-tunable (from yellow to orange) upconversion (UC) emissions, as the Yb3+ content increases. The thermometric properties of the synthesized materials associated with different thermally-coupled and non-thermally coupled levels of Tm3+ and Er3+ were systematically investigated. Based on the temperature-dependent emissions originating from the non-thermally coupled levels of Tm3+ (3F2,3) and Er3+ (4F9/2), i.e., their band intensity ratios 700/670 nm, the developed optical thermometers were found to exhibit an exceptional relative thermal sensitivity (Sr), up to 5.90% K−1 at 293 K. Importantly, in the whole T-range of 293–623 K, the Sr values are larger than 2% K−1. Furthermore, it is revealed that the position of the Tm3+ emission band, centered around 800 nm is highly dependent on temperature, and, so, it can be utilized as a second thermometric parameter, which is important for a multi-parameter temperature sensing in the T-range of 293–623 K. These results suggest that Er3+/Tm3+/Yb3+-doped Bi2MoO6 materials are promising candidates for ultra-sensitive, dual mode optical thermometers and safety sign applications.

Adenine shares the plane with G-quartet detected by surface-enhanced Raman spectroscopy

DNA G-quadruplexes (G4s) formed by guanine(G)-rich sequences show diversity of structural topologies. The detection of structural details is of great significance for understanding of their functions and for the target drug design, but is very challenging. Herein, we demonstrate that the surface-enhanced Raman spectroscopy (SERS) via Ag IANPs as substrates is able to identify the numbers of Adenine (A) located on the G-quartet of the G4s. Eight G4s are selected for SERS studies. Besides the detection of series of characteristic bands indicating the formation of G4s, the intensity of the band represented A base ring breath (νA, ~733 cm−1) is observed particularly enhanced when there are A bases coplanar with G-quartet, and which is higher than the intensity of the band corresponding to G base ring breath (νG, ~655 cm−1). Furthermore, the band intensity ratio of νA to νG versus the ratio of the numbers of A on the plane to the sum of numbers of A and G shows very good linear relationship. Thus, based on the band intensities of νA to νG and their ratio in the SERS spectrum, the G-quadruplexes with or without a coplanar A base and numbers of A bases on the plane of G-quartet can be facilely identified. The method is simple, fast, low cost and sensitive to provide particular details of the structure in aqueous solution, therefore, implies widespread applications.

Characterization of Drug Resistance in Chronic Myeloid Leukemia Cells Based on Laser Tweezers Raman Spectroscopy.

Multidrug resistance is highly associated with poor prognosis of chronic myeloid leukemia. This work aims to explore whether the laser tweezers Raman spectroscopy (LTRS) could be practical in separating adriamycin-resistant chronic myeloid leukemia cells K562/adriamycin from its parental cells K562, and to explore the potential mechanisms. Detection of LTRS initially reflected the spectral differences caused by chemoresistance including bands assigned to carbohydrates, amino acid, protein, lipids, and nucleic acid. In addition, principal components analysis as well as the classification and regression trees algorithms showed that the specificity and sensitivity were above 90%. Moreover, the band data-based classification and regression tree model and receiver operating characteristic curve further determined some important bands and band intensity ratios to be reliable indexes in discriminating K562 chemoresistance status. Finally, we highlighted three metabolism pathways correlated with chemoresistance. This work demonstrates that the label-free LTRS analysis combined with multivariate statistical analyses have great potential to be a novel analytical strategy at the single-cell level for rapid evaluation of the chemoresistance status of K562 cells.

Biomolecular changes and subsequent time-dependent recovery in hippocampal tissue after experimental mild traumatic brain injury

Traumatic brain injury (TBI) is the main cause of disability and mortality in individuals under the age of 45 years. Elucidation of the molecular and structural alterations in brain tissue due to TBI is crucial to understand secondary and long-term effects after traumatic brain injury, and to develop and apply the correct therapies. In the current study, the molecular effects of TBI were investigated in rat brain at 24 h and 1 month after the injury to determine acute and chronic effects, respectively by Fourier transform infrared imaging. This study reports the time-dependent contextual and structural effects of TBI on hippocampal brain tissue. A mild form of TBI was induced in 11-week old male Sprague Dawley rats by weight drop. Band area and intensity ratios, band frequency and bandwidth values of specific spectral bands showed that TBI causes significant structural and contextual global changes including decrease in carbonyl content, unsaturated lipid content, lipid acyl chain length, membrane lipid order, total protein content, lipid/protein ratio, besides increase in membrane fluidity with an altered protein secondary structure and metabolic activity in hippocampus 24 h after injury. However, improvement and/or recovery effects in these parameters were observed at one month after TBI.

Nonlinear Optical Thermometry—A Novel Temperature Sensing Strategy via Second Harmonic Generation (SHG) and Upconversion Luminescence in BaTiO3:Ho3+,Yb3+ Perovskite

AbstractNonlinear optical spectroscopy may be a powerful tool for sensing of various intrinsic properties of materials and different state functions of the system. This is due to the strong dependence of nonlinear phenomena on numerous physicochemical factors. The feasibility of simultaneously employing the second harmonic generation (SHG) and upconversion luminescence (UCL) processes in BaTiO3:Ho3+,Yb3+ for optical temperature sensing is demonstrated for the first time. Under 976 nm laser excitation, the evolution of the SHG and UCL band intensity ratio is correlated with temperature and calibrated within the temperature range of 25–305 °C. The band intensity ratio between SHG and UCL exhibits a sigmoidal dependence on temperature, and, hence, it can allow the detection of phase transitions from non‐centrosymmetric to centrosymmetric systems, and vice versa. Most importantly, from the perspective of optical temperature sensing, this work provides a novel and effective strategy for nonlinear optical thermometry, with high sensitivity of up to 2.78% °C–1.

The association of osteochemometrics and bone mineral density in humans.

Even though much is known about bone mineral and matrix composition, studies about their relationship with several bone properties and its alterations related to bone diseases such as osteoporosis are practically non-existent in humans. Thus, the development of methods to understand the effects of bone properties at a microscopic level is paramount. This research aimed to evaluate whether Fourier transform infrared-attenuated total reflectance (FTIR-ATR) band intensity ratios correlate with femoral bone mass, bone mineral content (BMC) (total and femoral neck), bone mineral per unit area (BMD) (total, femoral neck, greater trochanter, intertrochanteric region, and Ward's area) and the area (total and femoral neck). A sample of femora from the 21st Century Identified Skeleton Collection (N= 78, 42 females and 36 males) was employed and BMC, BMD, and the femoral areas were acquired by DXA. It was found that only females' BMD had a significant association with the femoral FTIR-ATR indices under study, whereas bone collagen (Am/P) and the content of carbonate Type A (API) in males correlated with the total proximal femur area of the regions of interest and the femoral neck area. Men and women showed different changes related to their chemical composition in BMD, BMC, and probed area, most likely due to differences in structure and physiology, as well as mechanical strength in the proximal femoral sites where BMD was analyzed.

Effects of light-ion low-fluence implantation on the pressure response of double-walled carbon nanotubes

Low-fluence light-ion $(^{11}\mathrm{B}^{+})$ medium-energy (150 keV/ion) implantation preprocessing of double-walled carbon nanotubes (DWCNTs) has been effected to ``decorate'' them with defects. These are intended to serve as nucleation sites for potential $s{p}^{3}$ interlinking between tube walls in close proximity, following on strong deformation of the tube cross sections under cold compression to 20--25 GPa in diamond anvil cells. The pressure response of such implanted DWCNTs has been monitored in situ using Raman spectroscopy, and compared with those of unimplanted reference DWCNTs. Pressure dependences of the ${G}^{+}$ mode frequency and D to ${G}^{+}$ band intensity ratio, and radial breathing modes, have been monitored. These Raman signatures show that some degree of mechanical softening occurs in the implanted tube bundles, without major disruption to tube integrity in both samples. Consequently, the collapse pressure to racetrack or peanut shaped cross-sectional profiles is lowered substantially, from ${P}_{\mathrm{c}}\ensuremath{\sim}18\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the reference tube bundles to ${P}_{\mathrm{c}}\ensuremath{\sim}11\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the implanted case. Defect structures also proliferate more readily in the implanted sample under pressure. Therefore, the light-ion low-fluence implantation lowers the threshold pressure for deformation of tube cross sections to high-curvature profiles decorated with defects. Considerations of whether irreversible $s{p}^{3}$ interlinking at low volume fractions is discerned in the Raman data from implanted tube bundles under compression, and the stability of such bonding is discussed.

Investigation into coals of different ranks using FTIR and Raman spectroscopy, X-ray diffraction and thermo-kinetic analyses

Two sub-bituminous (Onyeama mine, Nigeria and Powder River Basin, USA) and one bituminous (CNX Coal Resources, USA) coal samples were subjected to structural and chemical characterisation. The FTIR and Raman spectroscopy, X-ray diffraction and other physico-chemical techniques were deployed for this purpose. The coal ranking and aromaticity were evaluated from specific peaks on the XRD diffractogram. The coal samples were also subjected to thermo-kinetic analysis. The HHV for the coal samples ranged from 26.0 MJ/kg to 33.8 MJ/kg. Relatively, the Nigerian coal demonstrated an exceptionally high surface area, approximately 29.0 m2/g while Wyoming's and Pennsylvania's respectively recorded 0.4 m2/g and 3.9 m2/g. The ratio of band intensities, ID/IG was computed from Raman spectroscopy to be between 0.84 and 0.94 for the coal samples. Furthermore, the kinetics parameters deduced from TGA measurements revealed that thermal decomposition of coal is better modelled as a multi-step reaction mechanism. [Received: August 10, 2019; Accepted: January 13, 2020]

BaYb-=SUB=-2-x-=/SUB=-Er-=SUB=-x-=/SUB=-Ge-=SUB=-3-=/SUB=-O-=SUB=-10-=/SUB=- и BaY-=SUB=-2-10y-=/SUB=-Yb-=SUB=-9y-=/SUB=-Er-=SUB=-y-=/SUB=-Ge-=SUB=-3-=/SUB=-O-=SUB=-10-=/SUB=-: люминесцентные свойства, перспективы использования для бесконтактного определения температуры

Triorthogermanates BaYb2-xErxGe3O10 (x = 0.1–0.3) and BaY2-10yYb9yEryGe3O10 (y = 0.015–0.15) have been synthesized by the solid-state method. According to X-ray powder diffraction data, the compounds crystallize in the monoclinic system, S.G. P21/m, Z = 2. The concentration and power pump dependences studies have been carried out for the lines in the 510–720 nm spectral range under 980 nm excitation. The mechanisms of energy transfer between optical centers have been also proposed and the optimal composition of the phosphor has been determined. The influence of temperature on the intensity ratio of the luminescence bands with maxima at 521 nm and 552 nm (2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions in Er3+) has been investigated, and conclusions about the possibility of using the germanates as materials for optical temperature sensors have been drawn.

Interrelation between Colorimetric and Spectral Parameters of White Led Lamps

The interrelation between colorimetric (correlated color temperature) and spectral (intensity ratio of spectral emission bands) parameters of white LED lamps for general lighting has been established based on an analysis of test results for a set of lamps during aging. Deconvolution of the lamp radiation spectra is used to show that the change in color temperature is mainly due to a change in the intensity ratio of the 450-nm band originating from the diode heterostructure and the long-wavelength component of the nonelementary yellow band of the phosphor radiation with a maximum at 580 nm. However, the shorter-wavelength component with a maximum of 530 nm manifests itself mainly in the change of the total luminous flux. A possible cause of the change in the intensity of the spectral components of the nonelementary phosphor radiation band may be both thermal effects and structural changes in the phosphor material.

Graphene Oxides Derivatives Prepared by an Electrochemical Approach: Correlation between Structure and Properties.

Graphene oxide (GO) can be defined as a single monolayer of graphite with oxygen-containing functionalities such as epoxides, alcohols, and carboxylic acids. It is an interesting alternative to graphene for many applications due to its exceptional properties and feasibility of functionalization. In this study, electrochemically exfoliated graphene oxides (EGOs) with different amounts of surface groups, hence level of oxidation, were prepared by an electrochemical two-stage approach using graphite as raw material. A complete characterization of the EGOs was carried out in order to correlate their surface topography, interlayer spacing, defect content, and specific surface area (SSA) with their electrical, thermal, and mechanical properties. It has been found that the SSA has a direct relationship with the d-spacing. The EGOs electrical resistance decreases with increasing SSA while rises with increasing the D/G band intensity ratio in the Raman spectra, hence the defect content. Their thermal stability under both nitrogen and dry air atmospheres depends on both their oxidation level and defect content. Their macroscopic mechanical properties, namely the Young’s modulus and tensile strength, are influenced by the defect content, while no correlation was found with their SSA or interlayer spacing. Young moduli values as high as 54 GPa have been measured, which corroborates that the developed method preserves the integrity of the graphene flakes. Understanding the structure-property relationships in these materials is useful for the design of modified GOs with controllable morphologies and properties for a wide range of applications in electrical/electronic devices.

Chemometrics-Enabled Raman Spectrometric Qualitative Determination and Assessment of Biochemical Alterations during Early Prostate Cancer Proliferation in Model Tissue

The use of Raman spectroscopy combined with multivariate chemometrics for disease diagnosis has attracted great attention from researchers in recent years. This is because it is a noninvasive and nondestructive detection approach with enhanced sensitivity. However, a major challenge when analyzing spectra from biological samples has been the detection of subtle biochemical alterations buried in background and fluorescence noise. This work reports a qualitative chemometrics-assisted investigation of subtle biochemical alterations associated with prostate malignancy in model biological tissue (metastatic androgen insensitive (PC3) and immortalized normal (PNT1a) prostate cell lines). Raman spectra were acquired from PC3 and PNT1a cells at various stages of growth, and their biochemical alterations were determined from difference spectra between the two cell lines (for prominent alterations) and principal component analysis (PCA) (for subtle alterations). The Raman difference spectra were computed by subtracting the normalized mean spectral intensities of PNT1a cells from the normalized mean spectral intensities of PC3 cells. These difference spectra revealed prominent biochemical alterations associated with the malignant PC3 cells at 566 ± 0.70 cm−1, 630 cm−1, 1370 ± 0.86 cm−1, and 1618 ± 1.73 cm−1 bands. The band intensity ratios at 566 ± 0.70 cm−1 and 630 cm−1 suggested that prostate malignancy can be associated with an increase in relative amounts of nucleic acids and lipids, respectively, whereas those at 1370 ± 0.86 cm−1 and 1618 ± 1.73 cm−1 suggested that prostate malignancy can be associated with a decrease in relative amounts of saccharides and tryptophan, respectively. In the analysis using PCA, intermediate-order and high-order principal components (PCs) were used to extract the subtle biochemical fingerprints associated with the cell lines. This revealed subtle biochemical differences at 1076 cm−1, (1232, 1234 cm−1), (1276, 1278 cm−1), (1330, 1333 cm−1), (1434, 1442 cm−1), and (1471, 1479 cm−1). The band intensity ratios at 1076 cm−1 and 1232 cm−1 suggested that prostate malignancy can be associated with an increase in subtle amounts of nucleic acids and amide III components, respectively. The method reported here has demonstrated that subtle biochemical alterations can be extracted from Raman spectra of normal and malignant cell lines. The identified subtle bands could play an important role in quantitative monitoring of early biomarker alterations associated with prostate cancer proliferation.

Surface enhanced Raman scattering of brilliant green: Packing density and stabilizing effect of the cationic surfactant CTAB on the “hotspot” spacing

Surface-enhanced Raman scattering (SERS) has been applied utilizing colloidal suspensions of silver nanoparticles (AgNPs), for the detection of brilliant green (BG) at very low concentrations. Proper stimulated surface-enhanced resonance Raman scattering (SERRS) spectra collected from BG aqueous solutions at different low concentration ranges revealed a variation of the relative intensity ratio of certain BG bands attributed to a respective alteration of the molecular orientation of the analyte with respect to the AgNPs. This behavior is closely related to a different packing of the BG molecules on the nanoparticle surface when the concentration increases and the available space decreases. Additionally, the addition of suitable amounts of cetyl thrimethyl ammonium bromide (CTAB) to the BG aqueous solutions enhanced the detection limit of the analyte. This enlightens the role of the cationic surfactant in tuning the interparticle distances of AgNPs in the colloidal suspension; this presumably allows an optimization of the SERS enhancement factor. The concentration of CTAB that maximizes the SERS of BG is the same with the critical micelle concentration (CMC) of the surfactant. Most probably, CTAB at the CMC acts as a spacer keeping the AgNPs at a certain distance suitable for the generation of SE(R)RS hotspots.