Trace metal analysis by laser ablation-inductively coupled plasma-mass spectrometry and x-ray K-edge densitometry of forensic samples

This dissertation describes a variety of studies on the determination of trace elements in samples with forensic importance. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the trace element composition of numerous lipstick samples. Lipstick samples were determined to be homogeneous. Most lipstick samples of similar colors were readily distinguishable at a 95% confidence interval based on trace element composition. Numerous strands of a multi-strand speaker cable were analyzed by LA-ICP-MS. The strands in this study are spatially heterogeneous in trace element composition. In actual forensic applications, the possibility of spatial heterogeneity must be considered, especially in cases where only small samples (e.g., copper wire fragments after an explosion) are available. The effects of many unpredictable variables, such as weather, temperature, and human activity, on the retention of gunshot residue (GSR) around projectile wounds were assessed with LA-ICP-MS. Skin samples around gunshot and stab wounds and larvae feeding in and around the wounds on decomposing pig carcasses were analyzed for elements consistent with GSR (Sb, Pb, Ba, and Cu). These elements were detected at higher levels in skin and larvae samples around the gunshot wounds compared to the stab wounds for an extended period of time throughout decomposition in both a winter and summer study. After decomposition, radiographic images of the pig bones containing possible damage from bullets revealed metallic particles embedded within a number of bones. Metallic particles within the bones were analyzed with x-ray, K-edge densitometry and determined to contain lead, indicating that bullet residue can be retained throughout decomposition and detected within bones containing projectile trauma

Laser Spectroscopy for Atmospheric and Environmental Sensing

Lasers and laser spectroscopic techniques have been extensively used in several applications since their advent, and the subject has been reviewed extensively in the last several decades. This review is focused on three areas of laser spectroscopic applications in atmospheric and environmental sensing; namely laser-induced fluorescence (LIF), cavity ring-down spectroscopy (CRDS), and photoluminescence (PL) techniques used in the detection of solids, liquids, aerosols, trace gases, and volatile organic compounds (VOCs)

Three-dimensional reconstruction of the tissue-specific multielemental distribution within Ceriodaphnia dubia via multimodal registration using laser ablation ICP-mass spectrometry and X-ray spectroscopic techniques

In this work, the three-dimensional elemental, distribution profile within the freshwater crustacean Ceriodaphnia dubia was constructed at a spatial resolution down to S mu m via a data, fusion approach employing state-of-the-art laser ablation inductively coupled plasma-time-of-flight mass spectrometry (LAICP-TOFMS) and laboratory-based absorption microcomputed tomography (mu-CT). C. dubia was exposed to elevated Cu, Ni, and Zn concentrations, chemically fixed, dehydrated, stained, and embedded, prior to mu-CT analysis. Subsequently, the sample was cut into 5 pm thin sections that were subjected to LA-ICPTOFMS imaging. Multimodal image registration was performed to spatially align the 2D LA-ICP-TOFMS images relative to the Corresponding slices of the 3D mu-CT reconstruction. Mass channels corresponding to the isotopes of a single element were merged to improve the signal-to-noise ratios within the elemental images. In order to aid the visual interpretation of the data, LA-ICP-TOEMS data wete projected onto the mu-CT voxels representing tissue. Additionally, the image resolution and elemental sensitivity were compared to those obtained with synchrotron radiation based 3D confocal mu-X-ray fluorescence imaging upon a chemically fixed and air-dried C. dubia specimen

Laser induced breakdown spectroscopy for heavy metal detection in a sand matrix

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Spectrochimica Acta Part B: Atomic Spectroscopy 125 (2016):177-183, doi:10.1016/j.sab.2016.10.001.Sediments in many locations, including harbors and coastal areas, can become contaminated and polluted, for example, from anthropogenic inputs, shipping, human activities, and poor waste management. Sampling followed by laboratory analysis has been the traditional methodology for such analysis. In order to develop rapid methodologies for eld analysis of sediment samples, especially for metals analyses, we look to Laser Induced Breakdown Spectroscopy as an option. Here through laboratory experiments, we demonstrate that dry sand samples can be rapidly analyzed for the detection of the heavy metals chromium, zinc, lead, and copper. We also demonstrate that cadmium and nickel are detectable in sand matrices at high concentrations.This work is supported by funding from the National Science Foundation (OCE-RIG: 1322704) and the Woods Hole Oceanographic Institution by The Penzance Endowed Fund in Support of Assistant Scientists and The Reuben F. and Elizabeth B. Richards Endowed Fund in Support of Scienti c Sta .2018-10-0

Sunflower Plants as Bioindicators of Environmental Pollution with Lead (II) Ions

In this study, the influence of lead (II) ions on sunflower growth and biochemistry was investigated from various points of view. Sunflower plants were treated with 0, 10, 50, 100 and/or 500 μM Pb-EDTA for eight days. We observed alterations in growth in all experimental groups compared with non-treated control plants. Further we determined total content of proteins by a Bradford protein assay. By the eighth day of the experiment, total protein contents in all treated plants were much lower compared to control. Particularly noticeable was the loss of approx. 8 μg/mL or 15 μg/mL in shoots or roots of plants treated with 100 mM Pb-EDTA. We also focused our attention on the activity of alanine transaminase (ALT), aspartate transaminase (AST) and urease. Activity of the enzymes increased with increasing length of the treatment and applied concentration of lead (II) ions. This increase corresponds well with a higher metabolic activity of treated plants. Contents of cysteine, reduced glutathione (GSH), oxidized glutathione (GSSG) and phytochelatin 2 (PC2) were determined by high performance liquid chromatography with electrochemical detection. Cysteine content declined in roots of plants with the increasing time of treatment of plants with Pb-EDTA and the concentration of toxic substance. Moreover, we observed ten times higher content of cysteine in roots in comparison with shoots. The observed reduction of cysteine content probably relates with its utilization for biosynthesis of GSH and phytochelatins, because the content of GSH and PC2 was similar in roots and shoots and increased with increased treatment time and concentration of Pb-EDTA. Moreover, we observed oxidative stress caused by Pb-EDTA in roots where the GSSG/GSH ratio was about 0.66. In shoots, the oxidative stress was less distinctive, with a GSSG/GSH ratio 0.14. We also estimated the rate of phytochelatin biosynthesis from the slope of linear equations plotted with data measured in the particular experimental group. The highest rate was detected in roots treated with 100 μM of Pb-EDTA. To determine heavy metal ions many analytical instruments can be used, however, most of them are only able to quantify total content of the metals. This problem can be overcome using laser induced breakdown spectroscopy, because it is able to provide a high spatial-distribution of metal ions in different types of materials, including plant tissues. Data obtained were used to assemble 3D maps of Pb and Mg distribution. Distribution of these elements is concentrated around main vascular bundle of leaf, which means around midrib

Laser ablation-inductively coupled plasma-mass spectrometry: Examinations of the origins of polyatomic ions and advances in the sampling of particulates

Ongoing issues that affect the continued maturation of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) are studied. Spectral interferences in the form of polyatomic ions can hinder the analytical abilities of this method. Differences in the origins of polyatomic ions in solution nebulization ICP-MS versus LA-ICP-MS are investigated through observation of metal oxide (MO+) ions. Conditions responsible for the measured MO+ abundances are described via the measured gas kinetic temperature (Tgas). The effect of additional gases (nitrogen and helium) on the ICP and MO+ ion abundances is also studied using this method. Tgas measurements are also used to establish the origin of metal argide (MAr+) ions during LA-ICP-MS experiments and describe conditions during the ion extraction process. The fitness of femtosecond (fs)-LA-ICP-multicollector (MC)-MS for the determination of U isotope ratios from particulates is examined. Advantages of this method over sample dissolution techniques for environmental monitoring are discussed

플라즈모닉 귀금속 나노구조물의 합성 및 광학적 응용

학위논문 (박사) -- 서울대학교 대학원 : 자연과학대학 화학부, 2020. 8. 장두전.In this dissertation, synthesis and optical application of plasmonic noble metal nanostructures are mainly discussed. Various methods to fabricate core-shell, nanoshells, nanospike, and nanoparticle arrays structures have been investigated. The optical and morphological properties of as-prepared nanostructures have been also studied by using UV/vis spectroscopy, Raman spectroscopy, and electron microscopy. A brief overview on preparation methods and the plasmonic resonance of noble metal nanostructures are presented in Chapter 1. Chapter 2 presents the metal-enhanced fluorescence (MEF) of gold nanoclusters adsorbed onto Ag@SiO2 core-shell nanoparticle. The static and time-resolved MEF of Au25-adsorbed Ag@SiO2 core-shell nanoparticles (NPs) has been studied systematically with variation of shell thicknesses, core sizes, and excitation wavelengths. The emission of Au25-adsorbed Ag@SiO2 NPs is blue-shifted and highly enhanced compared with that of free Au25 clusters. The photoluminescence (PL) intensity of Au25-adsorbed Ag@SiO2 NPs is higher as much as 7.4 times than that of free Au25 clusters. The increase of the radiative decay rate constant with separation is identical to that of PL enhancement, suggesting that the MEF of Au25-adsorbed Ag@SiO2 NPs arises from the increase of the radiative decay rate constant induced by the near-field enhancement of plasmonic Ag NPs. Chapter 3 describes the fabrication of hollow and bumpy Au (HBA) NSs with rough surfaces using expanded silica mesopores as templates. Because some Au seeds were located at the inner surfaces of silica mesopores, produced Au NSs have inherent inward-grown nanobumps. During seven successive reduction steps, the LSPR peak of Au nanostructures shifted progressively toward a longer wavelength as the sizes of Au seeds increased gradually. Measuring the cross-sections of HBA NSs milled by a focused ion beam, we have found that hollow and bumpy nanostructures arose from the pore structures of mSiO2 NPs. HBA NSs confine Raman-probe molecules well owing to their hollow structures and have ragged surfaces due to their inward-bumpy morphologies, exhibiting highly efficient surface-enhanced Raman scattering activity. Chapter 4 presents the fabrication of genuinely hollow Au nanourchins (HANUs) using SiO2 NPs as hard templates. Ag-SiO2 NPs were fabricated via amine-assisted reduction. Then, Au nanourchins (ANUs) were synthesized by the galvanic replacement reaction of Ag-SiO2 NPs using L-3,4-dihydroxyphenylalanine (DOPA) as a reductant and a capping agent. The silica cores of ANUs were etched using HF(aq) to produce HANUs. Measuring cross sections, we have found that HANUs have well-defined hollow morphologies. Compared with nanourchins made via DOPA-mediated reduction, HANUs hardly contain residual silver because very tiny silver seeds were used as the initiation sites of galvanic replacement. HANUs have revealed large surface-enhanced Raman scattering enhancement and a significant photothermal effect under a weak illumination. Chapter 5 describes that highly dense plasmonic silver NP arrays have been fabricated by laser-induced dewetting of commercially available silver paste as a starting bulk material. The first laser-scan mode has produced unprecedented intermediate structures, so called laser-induced fine silver nanostructures (LIFSNs) while the second laser-scan mode has transformed LIFSNs into plasmonic silver NP arrays via the dewetting of the priorly formed nanostructures. The laser-induced fabrication of silver NP arrays has been found to be very sensitive to distance from secondly irradiated laser pulses, suggesting that the fine control of laser intensity is very important. As-prepared silver NP arrays have generated numerous hot spots to show highly strong surface-enhanced Raman scattering signals.독창적이고 기능적인 플라즈모닉 귀금속 나노입자의 합성과 광학적 특성에 대해 주로 연구하였다. 다양한 합성방식으로 코어쉘, 속이 빈 껍질, 나노스파이크 그리고 나노입자 어레이 구조를 합성해보았다. 분광광도계와 라만광도계, 전자현미경 등을 이용하여 제작된 나노구조물의 광학적, 구조적 특성을 연구해보았다. 귀금속 나노입자 합성방법과 플라즈모닉 공명현상을 Chapter 1에 간략히 소개하였다. Chapter 2에서는 금 클러스터가 흡착된 Ag@SiO2 코어쉘 나노입자의 금속-증강 형광 (Metal-enhanced fluorescence, MEF)에 대해 연구하였다. 금속나노입자는 입사 광에 의해서 표면의 자유전자들이 집단적인 진동하는 표면플라즈몬공명 (surface plasmon resonance, SPR)이라는 독특한 광학적 특성을 가진다. 이러한 현상을 통해 나노입자 표면에서는 입사되는 전자기장의 세기보다 수천~수만 배 더 큰 세기로 증폭될 수 있으며, 이러한 현상을 근접장증폭이라 불리고 있다. 이러한 광학적인 기능성을 가지는 금속나노입자에 실리카 껍질을 두르면, 금속입자 표면이 보호되거나 SPR 현상을 더욱 증강시킬 수 있다. 은 나노입자는 수용액상에서 은 이온의 화학적 환원을 통해 구 형태로 합성한 다음, 실리카 물질의 전구체를 이용한 Stober method를 통해 은 나노입자 표면에 실리카 껍질을 구현하였다. TEOS 양을 달리 함에 따라 실리카 쉘 두께를 변화시켜 각기 다른 Ag@SiO2 코어쉘 나노입자를 합성한 다음, 거리-의존적인 SPR 현상을 관찰하였습니다. 보통, 나노입자는 열역학적으로 가장 안정한 구(sphere) 형태로 합성된다. 열역학적의 한계를 넘어서 좀 더 고차원적이고 기능성을 가지는 나노입자 제작에 관한 연구가 국내외 연구진에서 활발하게 진행되고 있다. 나노쉘 (nanoshell) 형태의 입자란, 실리카 같은 유전물질이 중심에 존재하고, 그 표면을 금속물질로 껍질처럼 둘러싸인 구조를 말하는데, 나노쉘입자는 구 형태의 입자보다 SPR 현상을 더욱 강하게 발현시키고, 적외선 영역 쪽에서 광학적 활성을 보이는 고기능성 구조이다. Chapter 3에서는 이전에 보고되지 않았던 구조인, 속이 비어있고 그 안쪽에 표면에 거칠기가 있는 금 나노쉘 입자를 합성에 대해 설명하였다. 나노입자의 표면이 거칠다면, 나노미터 스케일에서 전자기장을 산란시킬 수 있으므로 SPR 효과를 더욱 증강시킬 수 있다. 속이 비어있고 안쪽의 표면이 거진 나노쉘 구조를 만들기 위해 메조포러스(mesoporous) 실리카 나노입자를 주형으로 이용했는데, 메조포러스 실리카는 입자 내에 CTAB 분자들의 자가조립에 의해서 만들어진 공동이 무수히 존재하는 실리카 입자를 말한다. 메조포러스 실리카 공동에 표면처리를 통해서 자그마한 금 나노입자를 부착시키고, 화학적 환원법을 통해 금 나노입자들을 성장시킨다. 성장되는 금 나노입자들은 입자가 커짐에 따라 실리카 공동구조를 부분적으로 채우게 되고, 추후 실리카를 HF로 에칭함으로서 속이 비어있고 안쪽에 거친 표면을 가지는 금 나노쉘 (hollow and bumpy gold nanoshell, HBA NS) 합성할 수 있었다. 어떠한 금속 나노구조물에 나노스케일의 거칠기나 나노팁 형태를 부여하면 더욱 향상된 플라즈모닉 성질을 보일 수 있다. 음의 유전율을 가지는 귀금속 나노구조물은 입사하는 전자기장을 국부적으로 구속하는 능력이 가지게 되고, 특히나 나노팁과 같이 구조체의 곡률이 심하게 변화하는 곳은 그 효과가 더욱 증폭됩니다. Chapter 4에서는 입자 안의 cavity가 확실히 존재하고 표면에 나노팁이 무수한 입자를 합성하고자 노력하였다. SH-로 표면개질된 실리카 나노입자를 합성한 다음, 아주 작은 크기의 은 나노입자를 실리카 표면에 합성한다. 이후, 점진적인 galvanic replacement 반응을 통해서 실리카 표면 위에 금 나노팁이 무수하게 존재하는 나노성게 입자(spiky Au nanourchins, SANUs) 를 합성한다. HAADF-STEM 측정방식을 통해서 SANUs 입자 중간에 실리카 입자가 확실히 보이며, galvanic replacement 반응으로 금 나노껍질이 환원된 모습이 관찰된다. 또한 EDX line-mapping과 원소분석을 통해서, SANUs 입자는 속이 비어있고 금 성분이 98 wt%로 관찰되는 데 반해, 은 성분은 0.2 wt% 아주 극미량으로 구성되어있음을 확인하였다. 최종적으로 합성된 SANUs 입자에 HF로 실리카 성분을 녹여서 속이 비어있고 나노팁이 무성한 금 나노성게 (hollow and spiky Au nanourchins, HSANUs)를 얻어보았다. FIB (focused-ion beam) 기법으로 그 단면을 조사하여 HSANUs 입자 안쪽에 확연한 cavity 형태를 확인하여, 중국의 연구진들에 의해 제안된 나노성게 입자의 cavity의 크기가 확연히 비교됨을 확인하였다. 레이저를 이용한 미세구조 가공기술은 레이저 빔의 고집속성 및 시공간적 정밀함으로 인해 반도체, 전자, 메카트로닉스 등의 첨단산업 분야에서 필수적인 기술로서, 신 공정 개발에 기여해왔습니다. 광열적 부작용이 적어서 마이크로-나노 급의 형상 가공이 가능한 극초단파 레이저(ultrafast laser)의 도입과 연구가 활발히 진행되고 있는데, chapter 5에서는 극초단파 레이저 광원을 사용하여 금속 나노구조를 손쉽게 제작한 연구를 설명하였다. 나노세컨드 레이저는 연속파 레이저에 비해 강한 파워를 가짐과 동시에 비교적 열적 영역 (heat-affected zone)이 넓어서 벌크물질에 극심한 형태변화를 유도할 수 있기 때문에 top-down 방식의 제작에 유리하다 판단하였습니다. 1.3 J/cm2의 파워와 50 μm/s의 속도로 레이저를 십자가 형태로 스캔한 (cross-line scanning) 실버 페이스트 필름에서, 균일한 나노입자배열이 십자가의 왼쪽, 오른쪽 가지에 관찰되었고 위, 아래의 가지에서는 이전에 관찰되었던 미세하고 무수한 은 입자들이 제작되었다. 가로방향의 스캔으로 통해 미세하고 무수한 은 나노입자를 제작한 다음, 세로방향으로 스캔 할 때, 불균일한 에너지 분포 형태의 Gaussian form을 가지는 레이저 빔에 의해서 dewetting threshold를 넘어가는 공간적 영역에서는 dewetting 현상이 일어나 나노입자배열이 제작되는 것을 발견하였다. 십자가 레이저 스캔 모드 양식의 확장으로서, 그물모양의 레이저 스캔을 시행하면 센티미터급의 대면적의 플라즈모닉 나노구조배열을 얻을 수 있었고 강한 전자기장 증강으로 표면증강라만산란기법 (Surface-enhanced Raman scattering)을 통해서 하여금 분석하고자 하는 물질의 농도가 nM 수준으로 내려가도 충분히 검출 가능한 기능성 기판 제작에 성공하였다.Chapter 1. General introduction 1 1.1 Preparation of noble metal nanostructures 2 1.2 Surface plasmons on noble metal nanoparticles 6 1.3 Near-field enhancement on hotspot 8 1.4 References 10 Chapter 2. Metal-enhanced fluorescence of gold nanoclusters adsorbed onto Ag@SiO2 core-shell nanoparticle 12 2.1 Abstract 13 2.2 Introduction 14 2.3 Experimental section 17 2.4 Result and discussion 21 2.5 Conclusion 45 2.6 Acknowledgements 46 2.7 References 46 Chapter 3. Hollow and inward-bumpy gold nanoshells fabricated using expanded silica mesopores as templates 50 3.1 Abstract 51 3.2 Introduction 52 3.3 Experimental section 54 3.4 Result and discussion 59 3.5 Conclusion 81 3.6 Acknowledgements 81 3.7 References 82 Chapter 4. Surface-enhanced Raman scattering and photothermal effect of hollow Au nanourchins with well-defined cavities 85 4.1 Abstract 86 4.2 Introduction 87 4.3 Experimental section 90 4.4 Result and discussion 93 4.5 Conclusion 112 4.6 Acknowledgements 113 4.7 References 113 Chapter 5. Fabrication of plasmonic silver nanoparticle arrays by laser-induced dewetting of commercial silver paste 116 5.1 Abstract 117 5.2 Introduction 118 5.3 Experimental section 122 5.4 Result and discussion 125 5.5 Conclusion 148 5.6 Acknowledgements 149 5.7 References 149 Appendices 153 A.1. List of publications 154 A.2. List of presentations 155 A.2.1. International presentations 155 A.2.2. Domestic presentations 155 Abstract (Korean) 157Docto

Synthesis and Applications of Organic-Based Fluorescent Carbon Dots: Technical Review

New ways of synthesizing organic-based fluorescent carbon dots (CDs) are required in environmental application. This is crucial for mitigation and control of pollutants without increasing the risk of releasing byproduct pollutants as the case with non-organic (metallic) quantum based substrate. Notably, this study provides current research on sustainable synthesis of CDs and their applications through analytical concept of recent and advance techniques for efficient and optimized processes. New scrutinized methods of synthesis and applications of CDs are beneficial and essential to optimize the state-of-art practices. The value distilled in this study adds to the field of sustainable production and application of CDs