A forensic investigation of single human hair fibres using FTIR-ATR spectroscopy and chemometrics

Human hair fibres are ubiquitous in nature and are found frequently at crime scenes often as a result of exchange between the perpetrator, victim and/or the surroundings according to Locard's Principle. Therefore, hair fibre evidence can provide important information for crime investigation. For human hair evidence, the current forensic methods of analysis rely on comparisons of either hair morphology by microscopic examination or nuclear and mitochondrial DNA analyses. Unfortunately in some instances the utilisation of microscopy and DNA analyses are difficult and often not feasible. This dissertation is arguably the first comprehensive investigation aimed to compare, classify and identify the single human scalp hair fibres with the aid of FTIR-ATR spectroscopy in a forensic context. Spectra were collected from the hair of 66 subjects of Asian, Caucasian and African (i.e. African-type). The fibres ranged from untreated to variously mildly and heavily cosmetically treated hairs. The collected spectra reflected the physical and chemical nature of a hair from the near-surface particularly, the cuticle layer. In total, 550 spectra were acquired and processed to construct a relatively large database. To assist with the interpretation of the complex spectra from various types of human hair, Derivative Spectroscopy and Chemometric methods such as Principal Component Analysis (PCA), Fuzzy Clustering (FC) and Multi-Criteria Decision Making (MCDM) program; Preference Ranking Organisation Method for Enrichment Evaluation (PROMETHEE) and Geometrical Analysis for Interactive Aid (GAIA); were utilised. FTIR-ATR spectroscopy had two important advantages over to previous methods: (i) sample throughput and spectral collection were significantly improved (no physical flattening or microscope manipulations), and (ii) given the recent advances in FTIR-ATR instrument portability, there is real potential to transfer this work.s findings seamlessly to on-field applications. The "raw" spectra, spectral subtractions and second derivative spectra were compared to demonstrate the subtle differences in human hair. SEM images were used as corroborative evidence to demonstrate the surface topography of hair. It indicated that the condition of the cuticle surface could be of three types: untreated, mildly treated and treated hair. Extensive studies of potential spectral band regions responsible for matching and discrimination of various types of hair samples suggested the 1690-1500 cm^-1 IR spectral region was to be preferred in comparison with the commonly used 1750-800 cm^-1. The principal reason was the presence of the highly variable spectral profiles of cystine oxidation products (1200-1000 cm^-1), which contributed significantly to spectral scatter and hence, poor hair sample matching. In the preferred 1690-1500 cm^-1 region, conformational changes in the keratin protein attributed to the α-helical to β-sheet transitions in the Amide I and Amide II vibrations and played a significant role in matching and discrimination of the spectra and hence, the hair fibre samples. For gender comparison, the Amide II band is significant for differentiation. The results illustrated that the male hair spectra exhibit a more intense β-sheet vibration in the Amide II band at approximately 1511 cm^-1 whilst the female hair spectra displayed more intense α-helical vibration at 1520-1515cm^-1. In terms of chemical composition, female hair spectra exhibit greater intensity of the amino acid tryptophan (1554 cm^-1), aspartic and glutamic acid (1577 cm^-1). It was also observed that for the separation of samples based on racial differences, untreated Caucasian hair was discriminated from Asian hair as a result of having higher levels of the amino acid cystine and cysteic acid. However, when mildly or chemically treated, Asian and Caucasian hair fibres are similar, whereas African-type hair fibres are different. In terms of the investigation's novel contribution to the field of forensic science, it has allowed for the development of a novel, multifaceted, methodical protocol where previously none had existed. The protocol is a systematic method to rapidly investigate unknown or questioned single human hair FTIR-ATR spectra from different genders and racial origin, including fibres of different cosmetic treatments. Unknown or questioned spectra are first separated on the basis of chemical treatment i.e. untreated, mildly treated or chemically treated, genders, and racial origin i.e. Asian, Caucasian and African-type. The methodology has the potential to complement the current forensic analysis methods of fibre evidence (i.e. Microscopy and DNA), providing information on the morphological, genetic and structural levels.

FTIR-ATR study of self-assembled thiol monolayers on gold

Self-assembled monolayers of 1-teradecanethiol on gold were characterized by means of FTIR-ATR measurements, XPS and contact angle measurements. Linear dichroism measurements using FTIR-ATR are used to estimate the orientation of the alkyl chains. An equation for calculating the orientation angles of the alkyls chains was deduced. (C) 1998 Elsevier Science Limited. All rights reserved.

Intra-population variation and geographic correlation in Canthon humectus hidalgoensis using FTIR-ATR spectroscopy

In some cases external morphology is not sufficient to discern between populations of a species, as occurs in the dung beetle Canthon humectus hidalgoensis Bates; and much less to determine phenotypic distances between them. FTIR-ATR spectroscopy show several advantages over other identification techniques (e.g. morphological, genetic, and cuticular hydrocarbons analysis) due to the non-invasive manner of the sample preparation, the relative speed of sample analysis and the low-cost of this technology. The infrared spectrum obtained is recognized to give a unique ‘fingerprint’ because vibrational spectra are specific and unique to the molecular nature of the sample. In our study, results showed that proteins, amino acids and aromatic ethers of insect exocuticle have promising discriminative power to discern between different populations of C. h. hidalgoensis. Furthermore, the correlation between geographic distances between populations and the chemical distances obtained by proteins + amino acids + aromatic ethers was statistically significant, showing that the spectral and spatial information available of the taxa together with appropriated chemometric methods may help to a better understanding of the identity, structure, dynamics and diversity of insect populations.

Efeito da variação da suavização espectral na robustez de modelos de calibração de metanol e teor alcoólico em aguardentes por FTIR-ATR

No presente estudo pretendeu-se compreender o efeito da variação do número de pontos da suavização espectral (ou filtro digital) no desenvolvimento de modelos de calibração por FTIR-ATR utilizando técnicas PLS-R para determinações rápidas do teor em metanol e do teor alcoólico em aguardentes. De acordo com o descrito em ANJOS et al. (2016) as zonas espectrais identificadas foram 1607-977 cm-1 e 3057-2864 + 1292-663 cm-1 respetivamente para o teor em metanol e teor alcoólico, com coeficientes de determinação superiores a 96,3 %. O valor de RPD apresenta qualidade suficiente para utilização em laboratório de controlo de qualidade. Foi avaliada a robustez dos modelos para 5, 9, 13, 17, 21 e 25 pontos de suavização para o pré-processamento usando a Primeira Derivada (1stDer), aplicando o algoritmo de Savitzky-Golay.

Use of micro-ATR/FTIR imaging to study heterogeneous polymer oxidation by direct solvent casting onto the ATR IRE

A technique is described whereby micro-ATR/FTIR imaging can be used to follow polymer degradation reactions in situ in real time. The internal reflection element (IRE) assembly is removed from the ATR objective and polymer is solvent cast directly onto the IRE surface. The polymer is then subjected to degradation conditions and molecular structural changes monitored by periodically replacing the IRE assembly back in the ATR objective and collecting spectra which can be used to construct images. This approach has the benefit that the same part of the sample is always studied, and that contact by pressure which might damage the polymer surface is not required. The technique is demonstrated using the polymer Topas which was degraded by exposure to UVC light in air.

The relationship between charge density and polyelectrolyte brush profile using simultaneous neutron reflectivity and in situ attenuated total internal reflection FTIR

We report on a novel experimental study of a pH-responsive polyelectrolyte brush at the silicon/D2O interface. A poly[2-(diethylamino)ethyl methacrylate] brush was grown on a large silicon crystal which acted as both a substrate for a neutron reflectivity solid/liquid experiment but also as an FTIR-ATR spectroscopy crystal. This arrangement has allowed for both neutron reflectivities and FTIR spectroscopic information to be measured in parallel. The chosen polybase brush shows strong IR bands which can be assigned to the N-D+ stretch, D2O, and a carbonyl group. From such FTIR data, we are able to closely monitor the degree of protonation along the polymer chain as well as revealing information concerning the D2O concentration at the interface. The neutron reflectivity data allows us to determine the physical brush profile normal to the solid/liquid interface along with the corresponding degree of hydration. This combined approach makes it possible to quantify the charge on a polymer brush alongside the morphology adopted by the polymer chains. © 2013 American Chemical Society.

The encapsulation of gold nanoparticles using RAFT, ATRP and miniemulsion polymerisation techniques

The investigation into the encapsulation of gold nanoparticles (AuNPs) by poly(methyl methacrylate) (PMMA) was undertaken. This was performed by three polymerisation techniques including: grafting PMMA synthesised by reversible addition-fragmentation chain transfer (RAFT) polymerisation to AuNPs, grafting PMMA synthesised by atom transfer radical polymerisation (ATRP) from the surface of functionalised AuNPs and by encapsulation of AuNPs within PMMA latexes produced through photo-initiated oil-in-water (o/w) miniemulsion polymerisation. The grafting of RAFT PMMA to AuNPs was performed by the addition of the RAFT functionalised PMMA to citrate stabilised AuNPs. This was conducted with a range of PMMA of varying molecular weight distribution (MWD) as either the dithioester or thiol end-group functionalities. The RAFT PMMA polymers were characterised by gel permeation chromatography (GPC), ultraviolet-visible (UV-vis), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), Fourier transform Raman (FT-Raman) and proton nuclear magnetic resonance (1H NMR) spectroscopies. The attachment of PMMA to AuNPs showed a tendency for AuNPs to associate with the PMMA structures formed, though significant aggregation occurred. Interestingly, thiol functionalised end-group PMMA showed very little aggregation of AuNPs. The spherical polymer-AuNP structures did not vary in size with variations in PMMA MWD. The PMMA-AuNP structures were characterised using scanning electron microscopy (SEM), transition electron microscopy (TEM), energy dispersive X-ray analysis (EDAX) and UV-vis spectroscopy. The surface confined ATRP grafting of PMMA from initiator functionalised AuNPs was polymerised in both homogeneous and heterogeneous media. 11,11’- dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane] (DSBr) was used as the surface-confined initiator and was synthesised in a three step procedure from mercaptoundecanol (MUD). All compounds were characterised by 1H NMR, FTIR-ATR and Raman spectroscopies. The grafting in homogeneous media resulted in amorphous PMMA with significant AuNP aggregation. Individually grafted AuNPs were difficult to separate and characterise, though SEM, TEM, EDAX and UV-vis spectroscopy was used. The heterogeneous polymerisation did not produce grafted AuNPs as characterised by SEM and EDAX. The encapsulation of AuNPs within PMMA latexes through the process of photoinitiated miniemulsion polymerisation was successfully achieved. Initially, photoinitiated miniemulsion polymerisation was conducted as a viable low temperature method of miniemulsion initiation. This proved successful producing a stable PMMA with good conversion efficiency and narrow particle size distribution (PSD). This is the first report of such a system. The photo-initiated technique was further optimised and AuNPs were included into the miniemulsion. AuNP encapsulation was very effective, producing reproducible AuNP encapsulated PMMA latexes. Again, this is the first reported case of this. The latexes were characterised by TEM, SEM, GPC, gravimetric analysis and dynamic light scattering (DLS).

Preparação e Avaliação da Atividade Catalítica de Polímeros de Condensação de Metilpiridinas e Tereftalaldeído em Reações de Nitroaldol e Cicloadição Heterodipolar [3+2]

Nesse estudo, foram preparadas bases poliméricas derivadas de 2,6-dimetilpiridinas e tereftaladeído utilizando a 2,4,6-trimetilpiridina como agente de reticulação. As resinas foram sintetizadas sob aquecimento convencional e purificadas por precipitação em metanol, apresentando rendimentos variando de 59 a 95%. Os copolímeros produzidos foram caracterizados por análise termogravimétrica (TGA), ressonância nuclear magnética de núcleo de hidrogênio (RMN-1H) e espectroscopia na região do infravermelho com técnica de ATR (FTIR - ATR), além de sua atividade básica. A capacidade catalítica do material produzido foi avaliada em reações nitroaldólicas, do tipo Henry, tanto em aquecimento convencional quanto com o uso de reator de micro-ondas. Não sendo observada atividade catalítica significativa para as resinas testadas, nestas reações. O material polimérico produzido também foi testado como suporte para cobre na catálise de reações de cicloadição heterodipolar do tipo [3+2] com benzilazida e propiolato de etila, para a formação de triazóis, processadas em reator de micro-ondas e sob aquecimento convencional. A reação mostrou-se regiosseletiva e processos de reciclo do catalisador se mostrou eficiente em reações consecutivas

模拟生物膜的电化学研究

本文简要介绍了生物膜的组成、结构和一些基本性质，详细描述了各种生物膜模型（支撑磷脂双层膜、非支撑磷脂双层膜、泡囊等等）的制备方法。概要地总结了模拟生物膜的各个领域的研究情况，着重评述了模拟生物膜在电化学、生物传感器、膜片钳、图案化领域的研究进展。采用电化学、各种谱学以及扫描探针显微镜等方法对支撑双层磷脂膜、磷脂浇铸膜等不同的模拟生物膜体系进行了研究。主要结果如下：1．将一种支撑磷脂膜一杂化双层膜（Hbrid bilayerer membrane，HBM）首次用于钙离子与磷脂作用的研究，以Fe（CN）63-为探针，发现钙离子可诱导HBM产生离子通道，且通道的打开与关闭能反复运转，并用STM观察这一现象。2.Ru（bPy）32+的电化学发光法和电催化法被首先用于研究支持脂质双层膜（sBLM）的离子通道行为。高氯酸根可以诱导DODAB（dimethyldioctadecylammonium）产生离子通道行为。离子通道的产生存在着一个闺值，当高氯酸根阴离子的浓度超过0.1μM时离子通道打开，当浓度低于0.1μM时离子通道关闭。当高氯酸根离子浓度高于0.1μM时，被打开的离子通道的数量随着高氯酸根阴离子浓度的增加而增加，在1200μM时达到平衡。离子通道的打开和关闭行为是可逆的。在此基础上，研制了一种用于检测高氯酸根离子的传感器。3，用循环伏安法和交流阻抗法研究了稀土离子与支撑磷脂双层膜的相互作用．稀土离子可以影响支撑磷脂双层膜的结构，使之产生一些小孔，通过这些小孔Fe（CN）63/4可以到达电极表面，显示其电化学行为。Fe（CN）63／4-的氧化还原电流随着稀土离子的浓度的增加而变大，对于E矿＋当浓度达到1．2卿时，电流不再增加。发现三种稀土离子与膜作用的能力如下：Eu3+＞Th3＋＞La3＋。4．铁氰酸根离子通常被用来作离子通道传感器的标记物。在本项工作中，我们首次发现铁氰酸根离子本身也可以作为一种刺激物来控制玻碳电极上DDAB（一种合成磷脂）制备出的支撑双层磷脂膜的通透性。我们利用循环伏安、交流阻抗的方法来研究这种现象。支撑双层磷脂膜与铁氰化物的反应与时间有关。进一步地，我们研制了一种铁氰酸根离子传感器。这种离子通道响应灵敏度较高，它可以检测的铁氰化物的最小浓度为5μM。5．稳定的磷脂浇铸膜是通过把含磷脂的氯仿溶液浇铸到玻碳电极上制备的。我们把一种新的媒介质一去甲肾上腺素嵌入到这种磷脂浇铸膜中。磷脂浇铸膜可以被视为一种生物膜模型。用这个体系对抗坏血酸进行电催化氧化，与在裸玻碳电极上相比，阳极过电位降低了约250 mV。浇铸膜内去甲肾上腺素的电化学行为是受扩散控制的，其扩散系数是1.87×10-5cm2／s。在浓度为0.5-10 mmol／L的范围内，催化电流随抗坏血酸的浓度增大而呈线性增加。在同时含有抗坏血酸和尿酸的溶液中，我们用循环伏安法可以同时侧得两个峰，这两个峰之间的峰位差大约为147mV。6．卵磷脂泡囊和血红蛋白在热解石墨电极上制备的薄膜内，血红蛋白可以实现其直接电化学。血红蛋白在薄膜内表现出薄层电化学行为。其式电位E0在pH 3.5-7.0内随pH值直线变化，斜率为-46.4 mV/pH。磷脂膜内的血红蛋白对H2O2显示了很好的催化还原行为。基于此，研制了无媒介体的H2O2传感器。7．我们合成了一种人工磷脂（二甲基二（十二烷基）澳化钱，DDAB）保护的金纳米粒子。在这些金纳米粒子的促进下，血红蛋白可以表现出直接电子转移（DET）反应，其式电位位于-169mVvs Ag/AgCl参比电极。光谱数据表明电极上的血红蛋白没有变性。这种磷脂保护的金纳米粒子很稳定（至少8个月），它们的平均直径是6.42nm。这是首次应用单层膜保护的纳米粒子去实现蛋白质的直接电化学反应。8．我们在一种新的基底一碳电极上构建了杂化双层膜（HBM）。这是对其它基底上构建的HBM的一种扩展。首先，通过电化学扫描将烷基胺修饰在碳电极表面，使之在电极上形成单层膜。由于烷基链部分向外，因此所构筑的界面是疏水的。然后在碳电极的疏水表面铺展一层磷脂单层膜。所生成的HBM通过电化学和ATR-FTIR技术来表征。根据ATR-FTIR的结果，脂质的有序常数（S）为0.73。这种杂化膜具有磷脂／烷基硫醇HBM的优点。这种HBM在生物传感面具有潜在的应用。

Spectroscopic Study on Water Diffusion in Poly(ester urethane) Block Copolymer Matrix

The diffusion of water in a phase-separated biodegradable poly(ester urethane) shape-memory polymer with poly(E-caprolactone) (PCL) as the soft segment was investigated using time-resolved FTIR-ATR. On the basis of the band fitting and water ordering in drawn films, the broad water band in the 3800-2800 cm(-1) region was decomposed into four bands located at 3620, 3510, 3400, and 3260 cm(-1), and the first two components at 3620 and 35 10 cm(-1) were assigned to the vibrations of antisymmetric and symmetric stretching of water hydrogen bonded with the C=O group of the soft segment. The other two were associated with water bonded to the urethane hard segments in the forms of N-H:O-H:O=C bridge hydrogen bond and double hydrogen bonds with two C=O groups, respectively. Furthermore, band fitting and two-dimensional correlation analyses revealed that in the diffusion process, water first diffuses into the continuous soft-rich PCL phase and then into the hard-rich urethane domains, forming double hydrogen bonds with two C=O groups prior to the bridge hydrogen bond in the form of N-H:O-H:O=C.

Neodymium oxide co-catalyzed melt free radical grafting of maleic anhydride onto co-polypropylene by reactive extrusion

Rare earth oxide, neodymium oxide (Nd2O3), CO-catalyzed melt grafting of maleic anhydride (MAH) onto co-polypropylene (co-PP) in the presence of dicumyl peroxide (DCP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd2O3 as a coagent leads to an enhancement in both MFR and the grafting degree of MAH, along with a simultaneous decrease in the gel content. When the Nd2O3 concentration is 6.0 mmol%, the increment of the grafting degree of MAH maximally is up to about 20% compared with the related system without adding Nd2O3, and the gel content decreases simultaneously to a very low level of about 3%. Attenuated total reflection FTIR (ATR-FTIR) indicates that the gel in the graft copolymers mainly arise from the cross-linking reaction between ethylene units of co-PP. A reasonable reaction mechanism has been put forward on the basis of our experimental results and other mechanisms reported in the literature. We also tentatively explain above results by means of synergistic effect between DCP and Nd2O3, which causes a higher concentration of the macroradical, in particular the tertiary macroradical.

Paint-freeze method to form self-assembled alkanethiol/phospholipid bilayers on gold

A paint-freeze method for preparing self-assembled alkanethiol/phospholipid bilayers on a gold surface has been described (by cyclic voltammetry, a.c impedance, polarized FTIR-ATR) to be well-ordered and packed, stable, solvent-free bilayers. The lipid order parameter was 0.67, calculated from the dichroic ratio, consistent with a well-ordered lipid film in which the methylene groups have segmental flexibility and are disordered to a degree which is typical for a lipid bilayer in the liquid-crystalline phase. Such a supported membrane provides a useful way for studies in biophysics, physiology and electrochemistry.