Fabrication of Nanostructured Mesoporous Germanium for Application

Subscriber access provided by UB + Fachbibliothek Chemie | (FU-Bibliothekssystem)

Article

Fabrication of Nanostructured Mesoporous Germanium for Applications in Laser Desorption Ionization Mass Spectrometry Hazem H. Abdelmaksoud, Taryn M Guinan, and Nicolas H. Voelcker ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b14362 • Publication Date (Web): 20 Jan 2017 Downloaded from http://pubs.acs.org on January 31, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

1

Fabrication of Nanostructured Mesoporous

2

Germanium for Application in Laser Desorption

3

Ionization Mass Spectrometry

4

Hazem H. Abdelmaksoud1,2, Taryn M. Guinan1 and Nicolas H. Voelcker1,2*

5

1.

Future Industries Institute, University of South Australia. South Australia, 5095 Mawson Lakes,

6 7

University Boulevard 2.

ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Future Industries

8

Institute, University of South Australia. *

9

E-mails of corresponding authors: [email protected]

10 11

KEYWORDS:

Germanium, Mesoporous germanium, SALDI-MS, Bipolar electrochemical

12

etching, Cocaine, Illicit drugs, Laser desorption ionization.

13 14 15 16

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 29

1

ABSTRACT

2

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is a high-

3

throughput analytical technique ideally suited for small molecule detection from different bodily

4

fluids (e.g. saliva, urine, and blood plasma). Many SALDI-MS substrates require complex

5

fabrication processes and further surface modifications. Furthermore, some substrates show

6

instability upon exposure to ambient conditions and need to be kept under special inert

7

conditions. We have successfully optimized mesoporous germanium (meso-pGe) using bipolar

8

electrochemical etching (BEE) and efficiently applied meso-pGe as a SALDI-MS substrate for

9

the detection of cocaine in the context of workplace, roadside, and anti-addictive drug

10

compliance. Argon plasma treatment improved the meso-pGe efficiency as a SALDI-MS

11

substrate and eliminated the need for surface functionalization. The resulting substrate showed a

12

precise surface geometry tuning by altering the etching parameters, and an outstanding

13

performance for cocaine detection with a limit of detection (LOD) in milliQ water of 1.7 ng/mL

14

and in spiked saliva as low as 5.3 ng/mL. The meso-pGe substrate had a demonstrated stability

15

over 56 days stored in ambient conditions. This proof-of-principle study demonstrates, that

16

meso-pGe can be reproducibly fabricated and applied as an analytical SALDI-MS substrate

17

which opens the door for further analytical and forensic high throughput applications.

18 19 20 21


2

Page 3 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1


1. INTRODUCTION

2

Roadside and workplace drug testing has been introduced on a global scale due to the

3

increased abuse of illicit compounds. In 2004, Australia introduced roadside drug screening for

4

methamphetamine, 3,4-methylenedioxymethamphetamine and tetrahydrocannabinol.1-3 Even

5

more recently the United Kingdom has introduced cocaine screening from saliva at roadside

6

testing events. Furthermore, cocaine has been reliably detected from urine4 and plasma5 and even

7

more recently from hair6 and fingermark sweat.7 However, the accessibility of saliva for rapid

8

and non-invasive sampling makes it an attractive biological fluid for detecting illicit drugs.

9

Recent studies have shown that cocaine levels in saliva correlate with blood levels and with

10

pharmacologic effects following intravenous administration.8 Cocaine is recognized as one of

11

the most dangerous illicit drugs with powerful addictive, psychoactive and stimulant properties.

12

Statistics confirmed that 7.3% of Australians aged 14 years and over have used cocaine one or

13

more times in their lifetime.9 Cocaine and its metabolites have been detected in saliva after oral

14

and intravenous administration using immunoassay screening devices with a cut-off limit of 150

15

ng/mL.10 However, these tests are presumptive, requiring further confirmatory testing using gas

16

chromatography-mass spectrometry (GC-MS) or liquid chromatography mass spectroscopy (LC-

17

MS). Furthermore, most commercial immunoassay screening tests for oral fluids can cross react

18

with licit drugs, which reduces test specificity and increases the possibility of false positives.11

19

Whilst GC-MS and LC-MS are sensitive and accurate for the detection of many illicit drugs,

20

sample preparation is time-consuming, requiring extraction and (for GC-MS) derivatization steps

21

using costly analytical reagents.12

22

Matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-ToF-

23

MS) is a well-established analytical technique used for the analysis of a wide range of large


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 29

1

molecular weight compounds.13 In 1985, Karas and Hillenkamp adapted laser desorption

2

ionization mass spectrometry (LDI-MS) using an aromatic acid as a matrix to absorb the incident

3

laser energy and transfer it to the analyte of interest facilitating the desorption/ionization

4

process.14-16 In the low molecular weight range, MALDI mass spectra are convoluted due to the

5

matrix related fragment and adduct peaks, making the MALDI-MS based detection and

6

interpretation of small molecules ( 0.999) was observed demonstrating quantification of cocaine

10

using meso-pGe. The LOD for cocaine in water on meso-pGe SALDI substrates was comparable

11

to the reported LOD for DIOS substrates (0.86 ng/mL)28 despite the WCA being considerably

12

lower in comparison to both DIOS (WCA≈124o) and the commercially available NALDI

13

substrates (WCA≈138o). For DIOS and NALDI, a hydrophobic surface is required as it promotes

14

the concentration and extraction of hydrophobic drug molecules.24

15

compare the S/N observed for cocaine (303 pmol) for meso-pGe substrates with NALDI and

16

DIOS.

ANOVA was used to

17

Despite the surface hydrophilicity of our meso-pGe SALDI substrate (WCA 62o), the average

18

S/N ratio for cocaine (303 pmol) was higher (p< 0.01) compared to both NALDI and DIOS

19

substrates (Figure S8, Table S2).

20


20

Page 21 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1 2

Figure 6. A) Meso-pGe SALDI mass spectrum of cocaine (MH+ 304, 200 ng/mL) on meso-pGe

3

(2000 shots of spectra). The star represents the cocaine protonated peak and the pentagon

4

corresponds to a cocaine fragment observed at an ion of m/z 182. B). Linear regression curve for

5

cocaine in water for concentrations ranging from 1–200 ng/mL. Error bars correspond to the

6

standard deviation for n = 3, (2000 shots of spectra).

7


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 29

1

Following the successful determination for the LOD and LOQ of cocaine in water, cocaine in

2

spiked saliva at clinically relevant concentrations ranging from 1-200 ng/mL was investigated in

3

order to test the performance of meso-pGe SALDI-MS using a real sample matrix (Figure 7).

4

5 6

Figure 7. A) Meso-pGe SALDI mass spectrum for cocaine (200 ng/mL) spiked in saliva in the

7

presence of 50 ng/mL of cocaine–d3. The star indicates the protonated mass for cocaine (MH+

8

304), the circle represents cocaine fragment and the pentagon is the deuterated cocaine-d3 (MH+

9

307). B). Linear regression curve for cocaine in saliva for concentrations ranging from 1–200

10

ng/mL. Error bars correspond to the standard deviation for n = 3, (2000 shots of spectra).


22

Page 23 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

A representative meso-pGe SALDI mass spectrum for cocaine at 200 ng/mL in the presence of

2

cocaine-d3 (50 ng/mL), as the internal standard is presented in Figure 7A. The star represents the

3

abundant ion for cocaine, whilst additional peaks at an ion of m/z 182, are characteristic cocaine

4

fragment peaks, and the pentagon represents the peak for cocaine-d3 (m/z 307). In principle, the

5

simultaneous detection of both cocaine and cocaine-d3 demonstrates that SALDI-MS can be

6

used for the detection of multiple small molecules at the same time. A high S/N base peak for

7

cocaine was observed, with a LOD and LOQ of 5.3 ng/mL and 12.1 ng/mL, respectively, and

8

good linearity (R2=0.995, Figure 7B) which demonstrates the prospect of quantitative detection

9

of cocaine in saliva. Indeed, the observed LOD for cocaine in saliva using plasma-treated

10

hydrophilic meso-pGe substrates is comparable to the LOD for perfluorinated hydrophobic

11

DIOS substrates (3.9 ng/mL).28 Furthermore, the LOD for cocaine in saliva using confirmatory

12

meso-pGe SALDI-MS analysis is approximately 30 times lower than the current cut-off limit

13

defined for the RapiScan salivary immunoassay, which is used for screening at roadside and

14

workplace testing events.40

15 16

4. CONCLUSIONS

17

This manuscript details the reproducible fabrication of meso-pGe substrates for the sensitive

18

and consistent detection of cocaine using SALDI. HF concentration and current density were

19

specifically optimized and compared in terms of pore size to increase S/N for cocaine detection.

20

Facile plasma cleaning techniques produced a clean meso-pGe SALDI substrates. Furthermore,

21

we have achieved a LOD for cocaine in water and saliva of 1.7 ng/mL and 5.3 ng/mL,

22

respectively, and LOQ for cocaine in water of 3.5 ng/mL and in saliva of 12.1 ng/mL without

23

any surface chemistry treatments such as silanization and with comparable performance to


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 29

1

DIOS. This work opens new vistas for further investigations for Ge nanostructures as SALDI-

2

MS platform for analytical and forensic applications overcoming the multiple fabrication steps

3

required for DIOS substrates. We believe that the sensitivity of this hydrophilic surface may

4

engender this technology towards the detection of hydrophilic small molecules that are difficult

5

to detect on hydrophobic SALDI surfaces. Indeed, we believe that meso-pGe SALDI substrates

6

could be used for high throughput drug detection in the forensic field and beyond. While, in this

7

paper, meso-pGe substrates were used for proof-of-principle SALDI applications we believe the

8

concise and reproducible fabrication procedures outlined here will allow the further application

9

of meso-pGe in its intended fields for biosensing, photovoltaics, and optoelectronics, which will

10

be the subject of future experiments.

11 12 13

5. Associated content Supporting information:

14

The effect of varying current density at fixed hydrofluoric acid concentration on mesoporous germanium (meso-

15

pGe) average pore size; The effect of altering HF concentration ratio at a fixed current density on average pore size;

16

SEM of meso-pGe substrates fabricated using an electrolyte solution of 2:1 HF:EtOH at different current density;

17

SALDI MS detection of cocaine on all optimized meso-pGe substrates; contact angle for untreated meso-pGe;

18

contact angle measurements for plasma argon treated meso-pGe corresponding to the ageing test measurements;

19

XPS survey spectra for meso-pGe pre- and post- treatment; SALDI MS spectra of methadone, methamphetamine,

20

oxycodone and metformin on meso-pGe SALDI substrate; comparison of meso-pGe, DIOS and NALDI for cocaine

21

detection and the statistical analysis of the corresponding results.

22 23

Auther Information:

24

Corresponding Auther

25

Email: [email protected]


24

Page 25 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1 2 3

Acknowledgements

4

This research was conducted and funded by the Australian Research Centre of Excellence in

5

Convergent Bio-Nano Science and Technology (Project No. CE140100036) and an Australian

6

Research Council Linkage Project (LP110020044).

7 8

Table of Contents (TOC) Graphic

9 10

11 12 13 14 15 16 17 18 19 20 21


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 29

1 2 3

REFERENCE

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

1. Illicit Drug Data Report. https://www.crimecommission.gov.au/publications (accessed 30 June). 2. United Nation-World Drug Report. https://www.unodc.org/documents/wdr2014/World_Drug_Report_2014_web.pdf (accessed 30 June). 3. Cone, E. J., Saliva Testing for Drugs of Abuse. Annals of the New York Academy of Sciences 1993, 694, 91-127. 4. Cheng, Y.-C.; Chen, K.-H.; Wang, J.-S.; Hsu, W.-L.; Chien, C.-C.; Chen, W.-Y.; Tsao, C.-W., Rapid Analysis of Abused Drugs Using Nanostructured Silicon Surface Assisted Laser Desorption/Ionization Mass Spectrometry. Analyst 2012, 137 (3), 654-661. 5. Rook, E. J.; Hillebrand, M. J.; Rosing, H.; van Ree, J. M.; Beijnen, J. H., The Quantitative Analysis of Heroin, Methadone and Their Metabolites and the Simultaneous Detection of Cocaine, Acetylcodeine and Their Metabolites in Human Plasma by HighPerformance Liquid Chromatography Coupled with Tandem Mass Spectrometry. J. Chromatogr. B 2005, 824 (1), 213-221. 6. Brewer, W. E.; Galipo, R. C.; Sellers, K. W.; Morgan, S. L., Analysis of Cocaine, Benzoylecgonine, Codeine, and Morphine in Hair by Supercritical Fluid Extraction with Carbon Dioxide Modified with Methanol. Anal. Chem. 2001, 73 (11), 2371-2376. 7. Bailey, M. J.; Bradshaw, R.; Francese, S.; Salter, T. L.; Costa, C.; Ismail, M.; P. Webb, R.; Bosman, I.; Wolff, K.; De Puit, M., Rapid Detection of Cocaine, Benzoylecgonine and Methylecgonine in Fingerprints Using Surface Mass Spectrometry. Analyst 2015, 140 (18), 6254-6259. 8. Kato, K.; Hillsgrove, M.; Weinhold, L.; Gorelick, D. A.; Darwin, W. D.; Cone, E. J., Cocaine and Metabolite Excretion in Saliva under Stimulated and Nonstimulated Conditions. J. Anal. Toxicol. 1993, 17 (6), 338-341. 9. Gowing, L. R.; Ali, R. L.; Allsop, S.; Marsden, J.; Turf, E. E.; West, R.; Witton, J. Global Statistics on Addictive Behaviours: 2014 Status Report; 1360-0443; 2015; pp 904-919. 10. Dolan, K.; Rouen, D.; Kimber, J., An Overview of the Use of Urine, Hair, Sweat and Saliva to Detect Drug Use. Drug Alcohol Abuse Rev. 2004, 23 (2), 213-217. 11. Rouen, D.; Dolan, K. A.; Kimber, J., A Review of Drug Detection Testing and an Examination of Urine, Hair, Saliva and Sweat. National Drug and Alcohol Research Centre, University of New South Wales: 2001. 12. Makkai, T., Drug Use Monitoring in Australia (Duma): Drug Detection Testing. Australian Institute of Criminology: Australia, 2000. 13. Hillenkamp, F.; Jaskolla, T. W.; Karas, M., Maldi Ms: A Practical Guide to Instrumentation, Methods, and Applications. Wiley-VCH Verlag GmbH & Co. KGaA: GmbH, 2014.


26

Page 27 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44


14. Karas, M.; Bachmann, D.; Bahr, U. e.; Hillenkamp, F., Matrix-Assisted Ultraviolet Laser Desorption of Non-Volatile Compounds. Int. J. Mass Spectrom. Ion Processes 1987, 78, 53-68. 15. Karas, M.; Hillenkamp, F., Laser Desorption Ionization of Proteins with Molecular Masses Exceeding 10,000 Daltons. Anal. Chem. 1988, 60 (20), 2299-2301. 16. Karas, M.; Bachmann, D.; Hillenkamp, F., Influence of the Wavelength in HighIrradiance Ultraviolet Laser Desorption Mass Spectrometry of Organic Molecules. Anal. Chem. 1985, 57 (14), 2935-2939. 17. Wei, J.; Buriak, J. M.; Siuzdak, G., Desorption-Ionization Mass Spectrometry on Porous Silicon. Nature 1999, 399 (6733), 243-246. 18. Watanabe, T.; Kawasaki, H.; Yonezawa, T.; Arakawa, R., Surface‐Assisted Laser Desorption/Ionization Mass Spectrometry (Saldi‐Ms) of Low Molecular Weight Organic Compounds and Synthetic Polymers Using Zinc Oxide (Zno) Nanoparticles. J. Mass Spectrom. 2008, 43 (8), 1063-1071. 19. Lewis, W. G.; Shen, Z.; Finn, M. G.; Siuzdak, G., Desorption/Ionization on Silicon (Dios) Mass Spectrometry: Background and Applications. Int. J. Mass Spectrom. 2003, 226 (1), 107-116. 20. Najam-ul-Haq, M.; Rainer, M.; Szabó, Z.; Vallant, R.; Huck, C. W.; Bonn, G. K., Role of Carbon Nano-Materials in the Analysis of Biological Materials by Laser Desorption/IonizationMass Spectrometry. J. Biochem. Biophys. Methods 2007, 70 (2), 319-328. 21. Chih-Lin, S.; Wei-Lung, T., Gold Nanoparticles as Assisted Matrix for Determining Neutral Small Carbohydrates through Laser Desorption/Ionization Time-of-Flight Mass Spectrometry. Anal. Chem. 2007, 79 (4), 1626-1633. 22. Seino, T.; Sato, H.; Yamamoto, A.; Nemoto, A.; Torimura, M.; Tao, H., Matrix-Free Laser Desorption/Ionization-Mass Spectrometry Using Self-Assembled Germanium Nanodots. Analytical Chemistry 2007, 79 (13), 4827-4832. 23. Law, K. P., Laser Desorption/Ionization Mass Spectrometry on Nanostructured Semiconductor Substrates: Dios™ and Quickmass™. International Journal of Mass Spectrometry 2010, 290 (2–3), 72-84. 24. Guinan, T.; Ronci, M.; Vasani, R.; Kobus, H.; Voelcker, N. H., Comparison of the Performance of Different Silicon-Based Saldi Substrates for Illicit Drug Detection. Talanta 2015, 132 (0), 494-502. 25. Thomas, J. J.; Shen, Z.; Blackledge, R.; Siuzdak, G., Desorption–Ionization on Silicon Mass Spectrometry: An Application in Forensics. Anal. Chim. Acta 2001, 442 (2), 183-190. 26. Lowe, R. D.; Szili, E. J.; Kirkbride, P.; Thissen, H.; Siuzdak, G.; Voelcker, N. H., Combined Immunocapture and Laser Desorption/Ionization Mass Spectrometry on Porous Silicon. Anal. Chem. 2010, 82 (10), 4201-4208. 27. Trauger, S. A.; Go, E. P.; Shen, Z.; Apon, J. V.; Compton, B. J.; Bouvier, E. S. P.; Finn, M. G.; Siuzdak, G., High Sensitivity and Analyte Capture with Desorption/Ionization Mass Spectrometry on Silylated Porous Silicon. Anal. Chem. 2004, 76 (15), 4484-4489. 28. Guinan, T.; Ronci, M.; Kobus, H.; Voelcker, N. H., Rapid Detection of Illicit Drugs in Neat Saliva Using Desorption/Ionization on Porous Silicon. Talanta 2012, 99 (0), 791-798. 29. Shenar, N.; Cantel, S.; Martinez, J.; Enjalbal, C., Comparison of Inert Supports in Laser Desorption/Ionization Mass Spectrometry of Peptides: Pencil Lead, Porous Silica Gel, Dios‐Chip and Naldi™ Target. Rapid Commun. Mass Spectrom. 2009, 23 (15), 2371-2379.


27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

Page 28 of 29

30. Daniels, R. H.; Dikler, S.; Li, E.; Stacey, C., Break Free of the Matrix: Sensitive and Rapid Analysis of Small Molecules Using Nanostructured Surfaces and Ldi-Tof Mass Spectrometry. JALA 2008, 13 (6), 314-321. 31. Biosciences, P., Matrix-Free Small Molecule Analyses Using Redichip on a Maldi Platform. Protea Biosciences: 2015. 32. Fang, C.; Föll, H.; Carstensen, J., Electrochemical Pore Etching in Germanium. J. Electroanal. Chem. 2006, 589 (2), 259-288. 33. Caymax, M.; Houssa, M.; Pourtois, G.; Bellenger, F.; Martens, K.; Delabie, A.; Van Elshocht, S., Interface Control of High-K Gate Dielectrics on Ge. Appl. Surf. Sci. 2008, 254 (19), 6094-6099. 34. Ossicini, S.; Amato, M.; Guerra, R.; Palummo, M.; Pulci, O., Silicon and Germanium Nanostructures for Photovoltaic Applications: Ab-Initio Results. Nanoscale Res. Lett. 2010, 5 (10), 1637-1649. 35. Fang, C.; Föll, H.; Carstensen, J.; Langa, S., Electrochemical Pore Etching in Ge – an Overview. Phys. Status Solidi A 2007, 204 (5), 1292-1296. 36. Choi, H. C.; Buriak, J. M., Preparation and Functionalization of Hydride Terminated Porous Germanium. Chem. Commun. 2000, (17), 1669-1670. 37. Garralaga Rojas, E.; Hensen, J.; Carstensen, J.; Föll, H.; Brendel, R., Porous Germanium Multilayers. Phys. Status Solidi C 2011, 8 (6), 1731-1733. 38. Tutashkonko, S.; Alekseev, S.; Nychyporuk, T., Nanoscale Morphology Tuning of Mesoporous Ge: Electrochemical Mechanisms. Electrochim. Acta 2015, 180, 545-554. 39. Lin, L.; Wang, Q., Microplasma: A New Generation of Technology for Functional Nanomaterial Synthesis. Plasma Chem. Plasma Process. 2015, 35 (6), 925-962. 40. Spiehler, V.; Baldwin, D.; Hand, C. In Cut-Off Concentrations for Drugs of Abuse in Saliva for Dui, Dwi or Other Driving-Related Crimes, report presented at the Thirtyseventh Meeting of the International Association of Forensic Toxicologists, 1999. 41. Tutashkonko, S.; Boucherif, A.; Nychyporuk, T.; Kaminski-Cachopo, A.; Arès, R.; Lemiti, M.; Aimez, V., Mesoporous Germanium Formed by Bipolar Electrochemical Etching. Electrochimica Acta 2013, 88, 256-262. 42. Huang, C.-M., Comparative Proteomic Analysis of Human Whole Saliva. Arch. Oral Biol. 2004, 49 (12), 951-962. 43. Guinan, T. M.; Neldner, D.; Stockham, P.; Kobus, H.; Della Vedova, C. B.; Voelcker, N. H., Porous Silicon Mass Spectrometry as an Alternative Confirmatory Assay for Compliance Testing of Methadone. Drug Test. Anal. 2016. 44. European Guidelines for Workplace Drug Testing in Oral Fluid; European Workplace Drug Testing Society: 2015. 45. Xiao, Y.; Retterer, S. T.; Thomas, D. K.; Tao, J.-Y.; He, L., Impacts of Surface Morphology on Ion Desorption and Ionization in Desorption Ionization on Porous Silicon (Dios) Mass Spectrometry. J. Phys. Chem. C 2009, 113 (8), 3076-3083. 46. Elosta, S.; Gajdosova, D.; Hegrova, B.; Havel, J., Maldi Tof Mass Spectrometry of Selected Mycotoxins in Barley. J. Appl. Biomed 2007, 5, 39-47. 47. Knapp, D. Chemistry and Electronics of the Ge (111) Surface. California Institute of Technology, 2011. 48. Buriak, J. M., Organometallic Chemistry on Silicon and Germanium Surfaces. Chem. Rev. 2002, 102 (5), 1271-1308.


28

Page 29 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35


49. Sun, S. Germanium Surface Cleaning, Passivation, and Initial Oxidation. Ph.D., Stanford University, Ann Arbor, 2007. 50. Bodlaki, D.; Yamamoto, H.; Waldeck, D. H.; Borguet, E., Ambient Stability of Chemically Passivated Germanium Interfaces. Surf. Sci. 2003, 543 (1–3), 63-74. 51. Sato, H.; Nemoto, A.; Yamamoto, A.; Tao, H., Surface Cleaning of Germanium Nanodot Ionization Substrate for Surface‐Assisted Laser Desorption/Ionization Mass Spectrometry. Rapid Commun. Mass Spectrom. 2009, 23 (5), 603-610. 52. Law, K. P., Surface-Assisted Laser Desorption/Ionization Mass Spectrometry on Nanostructured Silicon Substrates Prepared by Iodine-Assisted Etching. Int. J. Mass Spectrom. 2010, 290 (1), 47-59. 53. Shoeb, J.; Kushner, M. J., Damage by Radicals and Photons During Plasma Cleaning of Porous Low-K Sioch. Ii. Water Uptake and Change in Dielectric Constant. J. Vac. Sci. Technol., A 2012, 30 (4), 041304. 54. Shoeb, J.; Wang, M. M.; Kushner, M. J., Damage by Radicals and Photons During Plasma Cleaning of Porous Low-K Sioch. I. Ar/O2 and He/H2 Plasmas. J. Vac. Sci. Technol., A 2012, 30 (4), 041303. 55. Krishnamurthy, V.; Kamel, I. L., Argon Plasma Treatment of Glass Surfaces. J. Mater. Sci. 1989, 24 (9), 3345-3352. 56. Van der Weide, J.; Nemanich, R., Argon and Hydrogen Plasma Interactions on Diamond (111) Surfaces: Electronic States and Structure. Appl. Phys. Lett. 1993, 62 (16), 1878-1880. 57. Yamamoto, T.; Okubo, M.; Imai, N.; Mori, Y., Improvement on Hydrophilic and Hydrophobic Properties of Glass Surface Treated by Nonthermal Plasma Induced by Silent Corona Discharge. Plasma Chem. Plasma Process. 2004, 24 (1), 1-12. 58. Aronsson, B. O.; Lausmaa, J.; Kasemo, B., Glow Discharge Plasma Treatment for Surface Cleaning and Modification of Metallic Biomaterials. J. Biomed. Mater. Res. 1997, 35 (1), 49-73. 59. Tabet, N.; Faiz, M.; Hamdan, N.; Hussain, Z., High Resolution Xps Study of Oxide Layers Grown on Ge Substrates. Surf. Sci. 2003, 523 (1), 68-72. 60. Chu, P. K.; Chen, J.; Wang, L.; Huang, N., Plasma-Surface Modification of Biomaterials. Mater. Sci. Eng., R 2002, 36 (5), 143-206. 61. Korotcenkov, G., Porous Silicon: From Formation to Application: Biomedical and Sensor Applications, Volume Two: Biomedical and Sensor Applications. CRC Press: 2016. 62. Jindal, S. P.; Lutz, T.; Vestergaard, P., Mass Spectrometric Determination of Cocaine and Its Biologically Active Metabolite, Norcocaine, in Human Urine. Biol. Mass Spectrom. 1978, 5 (12), 658-663.

36


29

Fabrication of Nanostructured Mesoporous Germanium for Application

Recommend Documents