Chapter Four · failure evidence
What Raman & Infrared Spectroscopy got wrong, from 63 dissertations
The records describe common limitations and operational failures encountered when applying Raman and infrared spectroscopy across biological, environmental, and materials characterization tasks. Analytical workflows frequently broke down due to weak optical scattering, intense background interference from fluorescence or water, sample matrix contamination, and inferior performance compared to established analytical baselines. These records come from PhD theses at 25 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Low analyte concentrations and weak optical scattering fall below spectroscopic detection limits
Target signals could not be detected when analyte concentrations were too dilute or when physical scattering cross-sections were inherently weak. Prolonged integration times, unenhanced measurements, and specialized detector configurations failed to resolve distinguishing spectral features for sub-nanometer defects, low-abundance minerals, and dilute biomolecules.
Tried and failed
Raman spectroscopy for defect detection applied to sub-nanometer defects in 2D materials. Outcome: no signal. Reason: optical measurement lacked sensitivity to detect sub-nanometer atomic defect formation across ion doses
Low-Dimensional Material Devices For Atomic Defect Engineering, Ionic And Molecular Transport · Penn
Tried and failed
unenhanced Raman spectroscopy with long acquisition times applied to low-concentration bacterial pathogen classification. Outcome: no signal. Reason: signal intensity at clinically relevant low concentrations was insufficient without enhancement despite prolonged integration
Raman spectroscopy for point of care urinary tract infection diagnosis · Imperial
Tried and failed
blind source separation on mixture spectra applied to low-intensity component identification. Outcome: no signal. Reason: low Raman scattering intensity prevented detection without artificial 100-fold amplification of its reference spectrum
Development of In Situ Monitoring and Data-Driven Modeling for Complex Systems: Case Study on Simulant Mixtures of Nuclear Waste · Georgia Tech
Tried and failed
low-power ambient Raman spectroscopy for phase detection applied to biphasic fluid inclusion density measurements. Outcome: no signal. Reason: low power and ambient temperature fail to detect small coexisting liquid volumes near the vapor boundary
Tried and failed
785 nm Raman spectroscopy applied to detecting high-wavenumber O-H stretching bands. Outcome: no signal. Reason: low quantum efficiency of silicon CCD detectors near the bandgap cutoff wavelength
Advanced applications of Raman spectroscopy and machine learning techniques · Iowa State
Tried and failed
Raman spectroscopy for organic detection applied to mineral precipitate coprecipitation samples. Outcome: no signal. Reason: Organic concentrations sufficient for mineral stabilization fell below the detection limit of Raman spectroscopy.
Organic influences on hydrated magnesium carbonate mineral formation · MIT
Considered and rejected
Considered and rejected: Dismissed solid-phase FTIR and Raman spectroscopy for detecting low-level auxotrophic UAA incorporation due to insufficient sensitivity and signal attenuation
An interdisciplinary approach for developing novel methods to study silks · Oxford
Tried and failed
visible-near-infrared spectroscopy with partial least squares regression applied to low-concentration iron compounds in soil. Outcome: no signal. Reason: insufficient spectral sensitivity and absorption feature definition at low analyte concentrations (0–5000 mg/kg)
Tried and failed
diffuse reflectance spectroscopy calibration applied to aged hydrocarbon contaminated soil. Outcome: no signal. Reason: Weathering and aging significantly reduced target analyte concentrations below spectroscopy detection sensitivity
Tried and failed
surface-enhanced Raman spectroscopy on precursor controls applied to isolated nanoparticle precursor mixtures. Outcome: no signal. Reason: isolated precursors or bare nanoparticles lacked sufficient cross-section or enhancement to produce detectable spectral signals
Tried and failed
surface-enhanced Raman spectroscopy single-peak detection applied to sub-nanomolar analyte concentration sensing. Outcome: no signal. Reason: insufficient spectral changes at low nanomolar concentration thresholds for single-peak spectral analysis
Polypyrrole-coated gold nanoflowers as multifunctional nanoparticles for cancer theranostics · Imperial
Tried and failed
Raman spectroscopy for localized stress characterization applied to laser-micromachined silicon surfaces. Outcome: no signal. Reason: laser-induced surface modifications and shallow stress depths produced undetectable Raman frequency shifts
Tried and failed
density separation and micro-FTIR spectroscopy applied to marine sediment core microplastic extraction. Outcome: no signal. Reason: Target particles were below detection limit or completely absent in specific sediment depth layers
Investigation of Microplastics from Deep-Sea Antarctic and West Coast North American Sediments · Harvard
Absence of distinct vibrational bands and spectral overlap hinder compound differentiation
Spectra frequently exhibited severe peak overlap or completely lacked diagnostic vibrational features required to distinguish chemical species, phases, or continuous ratio boundaries. Spectral deconvolution algorithms and frequency shift tracking failed when spectral responses were restricted to uniform amplitude variations or lacked sufficient degrees of freedom.
Tried and failed
Raman spectroscopy for tracking molecular doping levels applied to organic hole transport materials. Outcome: no signal. Reason: overlapping vibrational peaks between neutral molecules and polaronic charged states prevented distinction
Considered and rejected
Considered and rejected: Rejected direct femtosecond pulse excitation without spectral focusing due to inadequate spectral resolution for resolving narrow Raman fingerprint modes (<10 cm-1).
ADVANCEMENTS IN STIMULATED RAMAN SCATTERING MICROSCOPY · ResearchWorks
Tried and failed
partial least squares regression on infrared spectra applied to narrow continuous ratio class boundaries. Reason: prediction error exceeded the width of the target classification intervals
A soil organic carbon indexing and measurement system · Cranfield
Tried and failed
visible and near-infrared reflectance spectroscopy applied to subsurface sediment mobilization landforms. Outcome: no signal. Reason: Spectra lacked diagnostic absorption features required to identify expected alteration minerals like phyllosilicates, carbonates, or sulfates
Subsurface Sediment Mobilization on Mars: Insights Provided by Orbital Remote Sensing Datasets · Georgia Tech
Tried and failed
stimulated Raman scattering unmixing microscopy applied to organism digestive tract quantification. Outcome: no signal. Reason: ingested dietary material produced broad, highly variable interfering background signals
Chemical microscopy and image analysis for biomedical applications · Harvard
Considered and rejected
Considered and rejected: Rejected relying solely on FTIR spectroscopy for identifying polyethylene waste types due to lack of distinct absorption differences at 4 cm-1 resolution; adopted DSC second-heating analysis instead.
Tried and failed
ATR-FTIR spectroscopic imaging applied to identifying inorganic degradation products. Outcome: no signal. Reason: vibrational modes of these inorganic species lacked sufficient infrared activity or distinct absorption bands within measured range
Applications of advanced atr-ftir spectroscopic imaging to objects of cultural heritage · Imperial
Tried and failed
two-component spectral deconvolution modeling applied to mixed-phase infrared absorption spectra. Outcome: worse than baseline. Reason: two components lacked sufficient degrees of freedom to capture the observed multi-phase spectral variations
Infrared Spectroscopy at Three and Six Microns of Water Ices Mixtures of Astrochemical Interest · Georgia Tech
Tried and failed
infrared center-frequency shift spectroscopy applied to detecting biomolecular condensate desolvation. Outcome: no signal. Reason: vibrational lineshapes showed no appreciable frequency shifts between dilute and condensate phases despite phase separation
Gotta keep ‘em separated : probing phase separation with infrared spectroscopy · UT Austin
Tried and failed
multiphase spectral deconvolution applied to infrared vibrational absorption bands. Outcome: no signal. Reason: the spectral feature varied predominantly in amplitude rather than shape or position across phases
Infrared Spectroscopy at Three and Six Microns of Water Ices Mixtures of Astrochemical Interest · Georgia Tech
Tried and failed
polarized reflectance spectroscopy applied to interfacial water layer optical absorption. Outcome: no signal. Reason: No measurable interfacial absorption layer or predicted frequency-dependent absorption dips were observed under ambient conditions
Electron and Molecular Transport Induced by Light-Matter Interactions for Energy and Water Harvesting · Georgia Tech
Considered and rejected
Considered and rejected: Rejected infrared absorption as the detection mechanism for LPG phase change/bubbles (liquid propane did not absorb the IR wavelengths emitted, requiring a refractive scattering approach).
Development of a liquid-phase LPG MPI conversion system · Cranfield
Substrates, containers, and preparation matrices introduce optical interference and contamination
Sample vials, mounting slides, immersion media, and embedding agents introduced dominant optical bands that obscured subtle analyte signals. Adsorbed surface contaminants, displaced solvent backgrounds, and beam damage further distorted spectra and caused false compound identifications.
Tried and failed
membrane filtration surface-enhanced Raman spectroscopy applied to clinical biofluid pathogen detection. Outcome: no signal. Reason: detector saturation and spectral interference from background particulate matter in unpurified samples
Raman spectroscopy for point of care urinary tract infection diagnosis · Imperial
Tried and failed
Handheld Raman spectroscopy through glass containers applied to pharmaceutical powder in glass vials. Outcome: no signal. Reason: Container optical interference and dispersed powder prevented distinguishable spectral signal from empty vials
New Tools for Rapid Mass Spectrometric Screening · Georgia Tech
Tried and failed
Raman spectroscopy on thin exfoliated layers applied to few-layer metal oxychloride crystals. Outcome: no signal. Reason: low Raman scattering signal relative to substrate background at 1.58 eV excitation
Considered and rejected
Considered and rejected: Rejected paraffin embedding because paraffin-derived Raman bands interfered with subtle plasma-induced spectral alterations
Evaluierung der Raman-Mikrospektroskopie für das Monitoring und die Bestimmung der funktionellen Gewebeeindringtiefe der Behandlung mit physikalischem Niedertemperaturplasma basierend auf primärem und patientenspezifischem Gewebematerial · Publikationssystem UB Tuebingen
Considered and rejected
Considered and rejected: Rejected measuring optical properties (photoluminescence / Raman spectroscopy) after TEM imaging due to beam damage and carbon contamination
Structure and Properties of Moiré Interfaces in Two Dimensional Materials · Harvard
Considered and rejected
Considered and rejected: Rejected using oil immersion lenses to improve Raman depth resolution because immersion oils introduce interfering spectral peaks that mask weak protein signals.
Monitoring of biotherapeutic purification by vibrational spectroscopy · Imperial
Tried and failed
multiple linear regression spectral deconvolution applied to surface-enhanced infrared absorption spectra. Reason: displaced solvent background interference and optical grating-order shifts created false negative concentration signals
Considered and rejected
Considered and rejected: Rejected analyzing single-crystal Raman spectroscopy for bulk CoSb3 due to persistent surface Sb flux signals, choosing polycrystalline samples instead.
Considered and rejected
Considered and rejected: Rejected silicon and quartz substrates for Raman spectroscopy because substrate background signals obscured PVAL vibrational bands, adopting gold-sputtered glass SERS substrates instead.
Deciphering the influence of local chain order on thermal transport in macromolecular matter · Imperial
Tried and failed
single-point ATR-FTIR spectroscopy applied to surface-contaminated microplastics. Outcome: no signal. Reason: adsorbed chemical contaminants obscured surface spectra causing unmatchable spectra or false compound identifications
Microplastics in Wastewater Treatment Plant Sludges: Detection Methods, Seasonal Variation, and Effects on Anaerobic Digestion · Carleton University Institutional Repository
Tried and failed
infrared microspectroscopy on glass-mounted fixed samples applied to biological tissue sections. Outcome: no signal. Reason: standard glass slides and paraffin fixation cause strong infrared absorption and spectral blockage
Exploring Potential Applications of Fourier Transform Infrared Microspectroscopy Imaging · Texas Tech
Strong water absorption and moisture emissions obscure infrared spectral bands
Liquid water and ambient water vapor produced intense absorption and emission backgrounds that masked target vibrational modes across infrared regions. These aqueous interferences attenuated optical transmission, generated baseline correction artifacts, and distorted quantitative measurements in biological tissues and aqueous suspensions.
Considered and rejected
Considered and rejected: Mid-infrared (MIR) spectroscopy was rejected for in-field proximal NUE sensing due to requirement of sample preparation, spectral distortion, and strong masking by soil water.
Proximal sensing of soil properties for nitrogen use efficiency improvement · Research Repository UCD
Tried and failed
infrared spectroscopy detection using multi-pass absorption cell applied to trace volatile organic compound detection. Outcome: no signal. Reason: the analyte absorption peak overlapped with a dominant ambient water vapour absorption band
Nanoporous Silicon in Gas Preconcentration and Sensing · Cambridge
Tried and failed
thermal infrared imaging applied to in vivo gastrointestinal inflammation detection. Outcome: no signal. Reason: optical absorption and additive emission noise from luminal gases and water vapor obscured localized thermal features
Tried and failed
reflectance photoplethysmography at shortwave infrared wavelengths applied to optical haematocrit ratio estimation. Outcome: unstable. Reason: strong water absorption and small photodiode area caused severe optical attenuation and noisy ratios
Tried and failed
transmission mode FTIR spectroscopy applied to aqueous chromatographic resin beads. Outcome: no signal. Reason: strong water absorption and large bead dimensions prevented optical transmission
Monitoring of biotherapeutic purification by vibrational spectroscopy · Imperial
Considered and rejected
Considered and rejected: Rejected water baseline subtraction during IR/Raman preprocessing because IR water baseline is overly sensitive to probe position and agitation speed, introducing spectral artifacts.
Development of In Situ Monitoring and Data-Driven Modeling for Complex Systems: Case Study on Simulant Mixtures of Nuclear Waste · Georgia Tech
Considered and rejected
Considered and rejected: Rejected using reconstituted actin in standard H2O for 2D-IR spectroscopy due to the overwhelming background water OH vibrational band in the amide I region, substituting D2O.
In-vitro active gels: quantifying actin network interactions and morphologies · UT Austin
Considered and rejected
Considered and rejected: Decided against quantitatively interpreting the broad bridge-bound CO infrared feature due to its excessive breadth and convolution from water vapor evacuating from the catalyst layer.
The Electrochemical Nature of Non-Faradaic Catalysis at Interfaces · MIT
Considered and rejected
Considered and rejected: Rejected using mid-infrared absorption feature (~2900 cm⁻¹) for HCl CRDS due to strong water vapor interference and lower mirror reflectivity (<99.99%).
Discerning Trends in Wintertime Reactive Chlorine Chemistry and Air Quality · YorkSpace
Considered and rejected
Considered and rejected: Temperature measurements located in the gap areas between non-active and active chromium coatings were excluded/rejected from analysis due to infrared emission interference from water causing count discontinuities.
Inferencing Techniques for Enhanced Monitoring of Thermal-Fluid Systems · MIT
Fluorescence and photoluminescence backgrounds overwhelm Raman scattering signals
Excitation lasers induced intense fluorescence from organic constituents, carbon dot structures, and trace rare earth impurities that swamped weak Raman peaks. Reducing laser power left target peaks obscured by the background noise, whereas increasing power risked sample degradation without eliminating photoluminescence.
Tried and failed
visible laser Raman spectroscopy applied to ionic liquids. Reason: strong temperature-dependent fluorescence background obscured the Raman signal
Advanced applications of Raman spectroscopy and machine learning techniques · Iowa State
Tried and failed
near-infrared laser excitation Raman spectroscopy applied to narrow-bandgap semiconductor heterostructures. Outcome: no signal. Reason: laser wavelength proximity to material bandgap produced strong fluorescence background that overwhelmed Raman signal
Tried and failed
785 nm Raman spectroscopy applied to mineral phases in cementitious materials. Outcome: no signal. Reason: Photoluminescence from trace rare earth impurities overlapped and obscured characteristic Raman peaks
Assessing long-term carbonation resistance of blended concretes from short-term natural exposure · Imperial
Tried and failed
confocal Raman micro-spectroscopy applied to aged concrete binder phases. Outcome: no signal. Reason: impurity fluorescence overwhelmed and obscured weak characteristic Raman signals
Tried and failed
1H NMR and Raman spectroscopic characterization applied to purified carbon dots. Outcome: no signal. Reason: insolubility, strong fluorescence background interference, and low mass yields
Tried and failed
Raman spectroscopy applied to immature organic biological tissues. Outcome: no signal. Reason: Strong fluorescence background from high organic content overwhelmed the Raman signal
Tried and failed
direct unenhanced Raman spectroscopy applied to clinical urine specimens. Outcome: no signal. Reason: broad biochemical variability and high fluorescence background masked diagnostic spectra
Raman spectroscopy for point of care urinary tract infection diagnosis · Imperial
Considered and rejected
Considered and rejected: Rejected using 1H NMR and Raman spectroscopy for MCD characterization due to poor solvation signal, background fluorescence, and excessive required sample mass.
Considered and rejected
Considered and rejected: Selected a higher 4 mW laser power over a 0.8 mW setting for Raman spectroscopy because 0.8 mW yielded small, broad peaks obscured by strong fluorescence background, despite 4 mW inducing sample degradation upon repeat exposures.
Considered and rejected
Considered and rejected: Spatial Heterodyne Raman Spectroscopy (SHRS) rejected for biological and highly fluorescent samples due to excitation wavelength limitations and single-channel constraint
Chemical Sensing as a Utility using Swept-Source Raman Spectroscopy · MIT
Unprocessed spectral models and standalone spectroscopy underperform alternative analytical techniques
Spectroscopic classification models trained on raw spectral inputs were consistently beaten by principal component reductions and manual visual inspection. Handheld or single-modality vibrational spectrometers also produced higher error rates and false positive classifications compared to chromatographic baselines or fused multi-sensor data.
Lost to a baseline
Simulated in-line Raman DBC had 16.98% %CV relative to UV chromatograms, underperforming HPLC (1.25% %CV) and well-plate Raman (1.99% %CV).
Monitoring of biotherapeutic purification by vibrational spectroscopy · Imperial
Lost to a baseline
Visual spectral comparison correctly differentiated inkjet Raman spectra via 1-3 minor peaks where automated LDA classifiers (PCA-LDA, PLS-DA, Sparse LDA) produced concordant misclassifications.
DEVELOPMENT AND VALIDATION OF A TECHNIQUE FOR ANALYSIS OF TONER PRINTED DOCUMENTS USING MAGNETIC FLUX MEASUREMENTS · DSpace at SHSU
Lost to a baseline
Raw spectral data SVM (0.722 accuracy) performed worse than 10/50 PCs SVM (0.833) on tissue block samples with portable Raman spectroscopy
Characterization of cervid skin tissues with chronic wasting disease by Raman spectroscopy and machine learning · Iowa State
Lost to a baseline
HPLC was far more specific and accurate than handheld NIR and Raman spectroscopy, which produced false positive flags on authentic/compliant high-dose formulations.
RETROSPECTIVE DESCRIPTIVE STUDY ON POST-MARKET MEDICINE QUALITY-RELATED COMPLAINTS AND THE APPLICATION OF FIELD-BASED DETECTION OF POORQUALITY MEDICINES USING NEAR-INFRARED AND RAMAN SPECTROSCOPIC SCREENING METHODS · De Montfort Open Research Archive (DORA)
Lost to a baseline
Raw spectral data ANN (0.833 accuracy) performed worse than 10 PCs ANN (0.944) on tissue block samples with portable Raman spectroscopy
Characterization of cervid skin tissues with chronic wasting disease by Raman spectroscopy and machine learning · Iowa State
Lost to a baseline
Conventional Raman achieved lower RMSEC (0.00851 vs 0.0222 for SERS) and better signal stability for phenylalanine due to its strong aromatic ring peak.
Lost to a baseline
Raman spectral imaging was marginally less precise than FT-IR in recognizing dairy residue products (accuracy of 97.51% with 14 LVs vs 98.73% with 5 LVs, respectively).
Multiscale spectral imaging for food safety with relevance to dairy processing · Research Repository UCD
Considered and rejected
Considered and rejected: Rejected single-modality spectroscopy in favor of mid-level data fusion because individual Vis-NIR (85.8%) and Raman (87.3%) models yielded inferior classification compared to fused data (92.8%).
Signature of Irish grass-fed beef - Authentication of the dietary background and geographical origin of Irish grass-fed beef using chromatographic and rapid spectroscopic techniques integrated with chemometrics · Research Repository UCD
Lost to a baseline
Quantitative dispersion spectroscopy RMSEC for Glucose (0.17 g L-1) was beaten by direct absorption spectroscopy RMSEC (0.05 g L-1)
Advances in mid-infrared dispersion spectroscopy of liquids and photothermal gas sensing · DSpace-CRIS at TU Wien
Left open by the authors
Problems the authors named and did not get to.
Left open
Perform Raman thermography on III-V materials mitigating 785 nm fluorescence using polarization selection or anti-Stokes Raman spectroscopy. Blocker: Requires physical Raman microscopy apparatus, 785 nm laser setup, and physical III-V semiconductor samples
Left open
Compare data-preserving versus floor-valued baselining methods on Raman urinalysis spectra to assess false-positive rates from unrelated molecular signals. Blocker: Requires private Raman spectroscopy urine datasets or access to physical urinalysis samples and spectrometer
The Applications of Raman Spectroscopy Assisted Urinalysis: Hematuria and Bladder Cancer Detection · Virginia Tech
Left open
Spectrally filter the Raman laser using Echelle gratings to rectify anomalous Raman scattering rates. Blocker: Requires optical lab hardware, a physical Raman laser system, and trapped ion apparatus.
Multi-tone Mølmer-Sørensen interaction outside of the Lamb-Dicke regime · Imperial
Left open
Improve Raman spectroscopy sensitivity and disc triggering to measure spectra of lubricant films thinner than 1.5 µm. Blocker: Requires a physical experimental elastohydrodynamic lubrication rig and Raman spectroscopy hardware setup
Effect of polymers on lubricant rheology in an elastohydrodynamic contact · Imperial
Left open
Perform high-resolution characterisation to identify unidentified Raman peaks at 1456 cm^-1 in RR2450 and 1468/1601 cm^-1 in Stellite 20. Blocker: Requires physical access to alloy samples and advanced characterisation / Raman spectroscopy laboratory equipment.
Sliding wear tests and numerical modelling of Co- and Fe- based alloys · Imperial
Left open
Integrate in situ Raman spectroscopy into continuous-flow microreactors for monitoring nanoparticle synthesis kinetics. Blocker: Requires a wet chemistry laboratory, microfluidic setup, and Raman spectrometer hardware.
Left open
Synthesize bioorthogonal Raman probes functionalized with isotopes, azides, or triple bonds for intracellular Raman detection. Blocker: Requires a wet chemistry and cell culture lab to synthesize probes and perform intracellular Raman spectroscopy
Polypyrrole-coated gold nanoflowers as multifunctional nanoparticles for cancer theranostics · Imperial
Left open
Extend Loudon-Fleury Raman response calculations to incorporate crystalline topological defects in two- and three-dimensional quantum magnet models. Blocker: Lack of specified analytical models or tractable 2D/3D tensor network algorithms for defect-modulated Raman response
Dynamics and Transport in Strongly Correlated Quantum Magnets · Georgia Tech
Left open
Develop and evaluate multimodal optical sensing combining DRS with Raman spectroscopy, fluorescence spectroscopy, or hyperspectral DRS imaging. Blocker: Requires custom physical optical hardware, spectrometer instrumentation, and physical/biological tissue samples.
Sensing rectal cancer hypoxia for advanced prognostication and response monitoring · Imperial
Left open
Record simultaneous low- and high-dispersion Raman spectra to measure gas composition and temperature accounting for H2O and CO2 broadening. Blocker: Requires a physical experimental Raman spectroscopy lab apparatus and high-pressure gas setup
Thermometry in high pressure gases using spontaneous Raman scattering · UT Austin
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